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loaded, see 529 https://github.com/Khan/KaTeX/tree/master/contrib/auto-render --> 530<script> 531 document.addEventListener("DOMContentLoaded", function () { 532 renderMathInElement( 533 document.body, 534 { 535 delimiters: [ 536 { left: "$$", right: "$$", display: true}, 537 { left: "\\[", right: "\\]", display: true}, 538 { left: "$", right: "$", display: false}, 539 { left: "\\(", right: "\\)", display: false} 540 ] 541 } 542 ); 543 }); 544</script></head> 545<body class="book toc2 toc-left" style="max-width: 100;"> 546<div id="header"> 547<h1>The OpenGL<sup>®</sup> Shading Language, Version 4.60.7</h1> 548<div class="details"> 549<span id="author" class="author">John Kessenich, Google (Editor and Author) ; Dave Baldwin and Randi Rost (Version 1.1 Authors)</span><br> 550<span id="revnumber">version 4.60.7,</span> 551<span id="revdate">Wed, 10 Jul 2019 20:42:58 +0000</span> 552<br><span id="revremark">Git branch information not available</span> 553</div> 554<div id="toc" class="toc2"> 555<div id="toctitle">Table of Contents</div> 556<ul class="sectlevel1"> 557<li><a href="#introduction">1. Introduction</a> 558<ul class="sectlevel2"> 559<li><a href="#changes">1.1. Changes</a></li> 560<li><a href="#overview">1.2. Overview</a></li> 561<li><a href="#error-handling">1.3. Error Handling</a></li> 562<li><a href="#typographical-conventions">1.4. Typographical Conventions</a></li> 563<li><a href="#deprecation">1.5. Deprecation</a></li> 564</ul> 565</li> 566<li><a href="#overview-of-opengl-shading">2. Overview of Shading</a> 567<ul class="sectlevel2"> 568<li><a href="#vertex-processor">2.1. Vertex Processor</a></li> 569<li><a href="#tessellation-control-processor">2.2. Tessellation Control Processor</a></li> 570<li><a href="#tessellation-evaluation-processor">2.3. Tessellation Evaluation Processor</a></li> 571<li><a href="#geometry-processor">2.4. Geometry Processor</a></li> 572<li><a href="#fragment-processor">2.5. Fragment Processor</a></li> 573<li><a href="#compute-processor">2.6. Compute Processor</a></li> 574</ul> 575</li> 576<li><a href="#basics">3. Basics</a> 577<ul class="sectlevel2"> 578<li><a href="#character-set">3.1. Character Set and Phases of Compilation</a></li> 579<li><a href="#source-strings">3.2. Source Strings</a></li> 580<li><a href="#preprocessor">3.3. Preprocessor</a></li> 581<li><a href="#comments">3.4. Comments</a></li> 582<li><a href="#tokens">3.5. Tokens</a></li> 583<li><a href="#keywords">3.6. Keywords</a></li> 584<li><a href="#identifiers">3.7. Identifiers</a></li> 585<li><a href="#definitions">3.8. Definitions</a></li> 586</ul> 587</li> 588<li><a href="#variables-and-types">4. Variables and Types</a> 589<ul class="sectlevel2"> 590<li><a href="#basic-types">4.1. Basic Types</a></li> 591<li><a href="#scoping">4.2. Scoping</a></li> 592<li><a href="#storage-qualifiers">4.3. Storage Qualifiers</a></li> 593<li><a href="#layout-qualifiers">4.4. Layout Qualifiers</a></li> 594<li><a href="#interpolation-qualifiers">4.5. Interpolation Qualifiers</a></li> 595<li><a href="#parameter-qualifiers">4.6. Parameter Qualifiers</a></li> 596<li><a href="#precision-and-precision-qualifiers">4.7. Precision and Precision Qualifiers</a></li> 597<li><a href="#variance-and-the-invariant-qualifier">4.8. Variance and the Invariant Qualifier</a></li> 598<li><a href="#the-precise-qualifier">4.9. The Precise Qualifier</a></li> 599<li><a href="#memory-qualifiers">4.10. Memory Qualifiers</a></li> 600<li><a href="#specialization-constant-qualifier">4.11. Specialization-Constant Qualifier</a></li> 601<li><a href="#order-of-qualification">4.12. Order and Repetition of Qualification</a></li> 602<li><a href="#empty-declarations">4.13. Empty Declarations</a></li> 603</ul> 604</li> 605<li><a href="#operators-and-expressions">5. Operators and Expressions</a> 606<ul class="sectlevel2"> 607<li><a href="#operators">5.1. Operators</a></li> 608<li><a href="#array-operations">5.2. Array Operations</a></li> 609<li><a href="#function-calls">5.3. Function Calls</a></li> 610<li><a href="#constructors">5.4. Constructors</a></li> 611<li><a href="#vector-components">5.5. Vector and Scalar Components and Length</a></li> 612<li><a href="#matrix-components">5.6. Matrix Components</a></li> 613<li><a href="#structure-and-array-operations">5.7. Structure and Array Operations</a></li> 614<li><a href="#assignments">5.8. Assignments</a></li> 615<li><a href="#expressions">5.9. Expressions</a></li> 616<li><a href="#vector-and-matrix-operations">5.10. Vector and Matrix Operations</a></li> 617<li><a href="#out-of-bounds-accesses">5.11. Out-of-Bounds Accesses</a></li> 618<li><a href="#specialization-constant-operations">5.12. Specialization-Constant Operations</a></li> 619</ul> 620</li> 621<li><a href="#statements-and-structure">6. Statements and Structure</a> 622<ul class="sectlevel2"> 623<li><a href="#function-definitions">6.1. Function Definitions</a></li> 624<li><a href="#selection">6.2. Selection</a></li> 625<li><a href="#iteration">6.3. Iteration</a></li> 626<li><a href="#jumps">6.4. Jumps</a></li> 627</ul> 628</li> 629<li><a href="#built-in-variables">7. Built-In Variables</a> 630<ul class="sectlevel2"> 631<li><a href="#built-in-language-variables">7.1. Built-In Language Variables</a></li> 632<li><a href="#compatibility-profile-vertex-shader-built-in-inputs">7.2. Compatibility Profile Vertex Shader Built-In Inputs</a></li> 633<li><a href="#built-in-constants">7.3. Built-In Constants</a></li> 634<li><a href="#built-in-uniform-state">7.4. Built-In Uniform State</a></li> 635<li><a href="#redeclaring-built-in-blocks">7.5. Redeclaring Built-In Blocks</a></li> 636</ul> 637</li> 638<li><a href="#built-in-functions">8. Built-In Functions</a> 639<ul class="sectlevel2"> 640<li><a href="#angle-and-trigonometry-functions">8.1. Angle and Trigonometry Functions</a></li> 641<li><a href="#exponential-functions">8.2. Exponential Functions</a></li> 642<li><a href="#common-functions">8.3. Common Functions</a></li> 643<li><a href="#floating-point-pack-and-unpack-functions">8.4. Floating-Point Pack and Unpack Functions</a></li> 644<li><a href="#geometric-functions">8.5. Geometric Functions</a></li> 645<li><a href="#matrix-functions">8.6. Matrix Functions</a></li> 646<li><a href="#vector-relational-functions">8.7. Vector Relational Functions</a></li> 647<li><a href="#integer-functions">8.8. Integer Functions</a></li> 648<li><a href="#texture-functions">8.9. Texture Functions</a></li> 649<li><a href="#atomic-counter-functions">8.10. Atomic Counter Functions</a></li> 650<li><a href="#atomic-memory-functions">8.11. Atomic Memory Functions</a></li> 651<li><a href="#image-functions">8.12. Image Functions</a></li> 652<li><a href="#geometry-shader-functions">8.13. Geometry Shader Functions</a></li> 653<li><a href="#fragment-processing-functions">8.14. Fragment Processing Functions</a></li> 654<li><a href="#noise-functions">8.15. Noise Functions</a></li> 655<li><a href="#shader-invocation-control-functions">8.16. Shader Invocation Control Functions</a></li> 656<li><a href="#shader-memory-control-functions">8.17. Shader Memory Control Functions</a></li> 657<li><a href="#_subpass_input_functions">8.18. Subpass-Input Functions</a></li> 658<li><a href="#shader-invocation-group-functions">8.19. Shader Invocation Group Functions</a></li> 659</ul> 660</li> 661<li><a href="#shading-language-grammar">9. Shading Language Grammar</a></li> 662<li><a href="#acknowledgments">10. Acknowledgments</a></li> 663<li><a href="#references">11. Normative References</a></li> 664<li><a href="#_non_normative_spir_v_mappings">12. Non-Normative SPIR-V Mappings</a> 665<ul class="sectlevel2"> 666<li><a href="#_feature_comparisons">12.1. Feature Comparisons</a></li> 667<li><a href="#_mapping_from_glsl_to_spir_v">12.2. Mapping from GLSL to SPIR-V</a></li> 668</ul> 669</li> 670</ul> 671</div> 672</div> 673<div id="content"> 674<div id="preamble"> 675<div class="sectionbody"> 676<div style="page-break-after: always;"></div> 677<div class="paragraph"> 678<p>Copyright © 2008-2018 The Khronos Group Inc. All Rights Reserved.</p> 679</div> 680<div class="paragraph"> 681<p>This specification is protected by copyright laws and contains material 682proprietary to the Khronos Group, Inc. It or any components may not be 683reproduced, republished, distributed, transmitted, displayed, broadcast, 684or otherwise exploited in any manner without the express prior written 685permission of Khronos Group. You may use this specification for 686implementing the functionality therein, without altering or removing any 687trademark, copyright or other notice from the specification, but the 688receipt or possession of this specification does not convey any rights 689to reproduce, disclose, or distribute its contents, or to manufacture, 690use, or sell anything that it may describe, in whole or in part.</p> 691</div> 692<div class="paragraph"> 693<p>Khronos Group grants express permission to any current Promoter, 694Contributor or Adopter member of Khronos to copy and redistribute 695UNMODIFIED versions of this specification in any fashion, provided that 696NO CHARGE is made for the specification and the latest available update 697of the specification for any version of the API is used whenever 698possible. Such distributed specification may be reformatted AS LONG AS 699the contents of the specification are not changed in any way. The 700specification may be incorporated into a product that is sold as long as 701such product includes significant independent work developed by the 702seller. A link to the current version of this specification on the 703Khronos Group website should be included whenever possible with 704specification distributions.</p> 705</div> 706<div class="paragraph"> 707<p>Khronos Group makes no, and expressly disclaims any, representations or 708warranties, express or implied, regarding this specification, including, 709without limitation, any implied warranties of merchantability or fitness 710for a particular purpose or noninfringement of any intellectual 711property. Khronos Group makes no, and expressly disclaims any, 712warranties, express or implied, regarding the correctness, accuracy, 713completeness, timeliness, and reliability of the specification. Under no 714circumstances will the Khronos Group, or any of its Promoters, 715Contributors or Members or their respective partners, officers, 716directors, employees, agents, or representatives be liable for any 717damages, whether direct, indirect, special or consequential damages for 718lost revenues, lost profits, or otherwise, arising from or in connection 719with these materials.</p> 720</div> 721<div class="paragraph"> 722<p>Khronos, Vulkan, SYCL, SPIR, WebGL, EGL, COLLADA, StreamInput, OpenVX, 723OpenKCam, glTF, OpenKODE, OpenVG, OpenWF, OpenSL ES, OpenMAX, OpenMAX 724AL, OpenMAX IL and OpenMAX DL are trademarks and WebCL is a 725certification mark of the Khronos Group Inc. OpenCL is a trademark of 726Apple Inc. and OpenGL and OpenML are registered trademarks and the 727OpenGL ES and OpenGL SC logos are trademarks of Silicon Graphics 728International used under license by Khronos. All other product names, 729trademarks, and/or company names are used solely for identification and 730belong to their respective owners.</p> 731</div> 732<div style="page-break-after: always;"></div> 733<!-- toc disabled --> 734</div> 735</div> 736<div class="sect1"> 737<h2 id="introduction">1. Introduction</h2> 738<div class="sectionbody"> 739<div class="paragraph"> 740<p>This document specifies only version 4.60 of the OpenGL Shading Language (GLSL). 741It requires __VERSION__ to substitute 460, and requires 742<strong>#version</strong> to accept only 743<code>460</code>. 744If <strong>#version</strong> is declared with a smaller number, the language accepted is a 745previous version of the shading language, which will be supported depending 746on the version and type of context in the API. 747See the <a href="#references">normative references</a> for details on what language 748versions are supported.</p> 749</div> 750<div class="paragraph"> 751<p>Previous versions of the OpenGL Shading Language, as well as the OpenGL ES Shading Language, 752are not strict subsets of the version specified here, particularly with 753respect to precision, name-hiding rules, and treatment of interface 754variables. 755See the specification corresponding to a particular language version for 756details specific to that version of the language.</p> 757</div> 758<div class="paragraph"> 759<p>Throughout, when generating SPIR-V for consumption by the Vulkan API 760(see <a href="#references">normative references</a>), this will be said to be 761<em>targeting Vulkan</em>.</p> 762</div> 763<div class="paragraph"> 764<p>While this specification and the OpenGL Specification are normative for OpenGL Shading Language, for 765SPIR-V generation it is still the SPIR-V specification and the SPIR-V client 766API specification that are normative for the generated SPIR-V. 767See the <a href="#references">normative references</a> for further detail.</p> 768</div> 769<div class="paragraph"> 770<p>For SPIR-V generation, the SPIR-V client API specifies the commands used to 771manipulate SPIR-V shaders.</p> 772</div> 773<div class="paragraph"> 774<p>Independent offline tool chains will compile GLSL down to the SPIR-V 775intermediate language. 776SPIR-V generation is not enabled with a <strong>#extension</strong>, <strong>#version</strong>, or a 777profile. 778Instead, use of GLSL for SPIR-V is determined by offline tool-chain use. 779See the documentation of such tools to see how to request generation of 780SPIR-V for its client API.</p> 781</div> 782<div class="paragraph"> 783<p>GLSL → SPIR-V compilers must be directed as to what SPIR-V <strong>Capabilities</strong> 784are legal at run-time and give errors for GLSL feature use outside those 785capabilities. 786This is also true for implementation-dependent limits that can be error 787checked by the front-end against built-in constants present in the GLSL 788source: the front-end can be informed of such limits, and report errors when 789they are exceeded.</p> 790</div> 791<div class="paragraph"> 792<p>SPIR-V features that are not controlled by a SPIR-V capability, but do have an 793equivalent GLSL counterpart (stages, built-in functions, types, limits, etc.) 794are only expected to work on OpenGL drivers that support the GLSL counterpart.</p> 795</div> 796<div class="paragraph"> 797<p>All references in this specification to the <a href="#references">OpenGL Specification</a> are to 798the Core profile of version 4.6, unless a different profile is 799specified.</p> 800</div> 801<div class="sect2"> 802<h3 id="changes">1.1. Changes</h3> 803<div class="sect3"> 804<h4 id="_changes_from_revision_6_of_glsl_4_6">1.1.1. Changes from Revision 6 of GLSL 4.6</h4> 805<div class="ulist"> 806<ul> 807<li> 808<p>Incorporated the GL_KHR_vulkan_glsl specification.</p> 809</li> 810<li> 811<p>Add note in the introduction about presence in drivers of SPIR-V features, 812as they relate to GLSL features.</p> 813</li> 814<li> 815<p>Clarify it is same location that triggers default-uniform block matching 816rules. 817See <a href="#uniform-variable-layout-qualifiers">Uniform Variable Layout Qualifiers</a>.</p> 818</li> 819</ul> 820</div> 821</div> 822<div class="sect3"> 823<h4 id="_changes_from_revision_5_of_glsl_4_6">1.1.2. Changes from Revision 5 of GLSL 4.6</h4> 824<div class="ulist"> 825<ul> 826<li> 827<p>Private GLSL issue #34: Clarify/consolidate implicit conversion rules from int → uint 828to be the same as explicit construction.</p> 829</li> 830<li> 831<p>Private GLSL issue #24: Clarify that <strong>barrier</strong>() by itself is enough to synchronize 832both control flow and memory accesses to <strong>shared</strong> variables and tessellation 833control output variables. For other memory accesses an additional memory 834barrier is still required.</p> 835</li> 836<li> 837<p>Normatively reference IEEE-754 for definitions of floating-point formats.</p> 838</li> 839<li> 840<p>Private GLSL issue 36: <strong>refract</strong> function on <strong>double</strong> types requires eta 841argument to have type <strong>double</strong>.</p> 842</li> 843<li> 844<p>Clarify restrictions on input variables in tessellation and geometry stages.</p> 845</li> 846<li> 847<p>Private GLSL issue 15: Clarify the ordering of bindings for arrays of arrays.</p> 848</li> 849<li> 850<p>Private GLSL issue 14: Uniform variables need only match at link time if they 851are statically used.</p> 852</li> 853<li> 854<p>For <strong>precise</strong> computations, the controlling expressions for 855control flow and ternary operators (<strong>?:</strong>) are not included.</p> 856</li> 857</ul> 858</div> 859</div> 860<div class="sect3"> 861<h4 id="_changes_from_revision_4_of_glsl_4_6">1.1.3. Changes from Revision 4 of GLSL 4.6</h4> 862<div class="ulist"> 863<ul> 864<li> 865<p>Private bug 13012: Clarified that builtin uniform variables might only 866be available in the fragment stage.</p> 867</li> 868<li> 869<p>Private bug 13837: Ternary and sequence operators may operate on <strong>void</strong> types.</p> 870</li> 871<li> 872<p>Clarified that errors arising from preprocessing must be returned at compile time.</p> 873</li> 874<li> 875<p>Clarified that access to any part of a variable constitutes a static use.</p> 876</li> 877<li> 878<p>Private GLSL issue 19: A statement is required following any label at the end of a <strong>switch</strong>.</p> 879</li> 880<li> 881<p>Private GLSL issue 26: <strong>noise</strong> is not valid when compiling for SPIR-V.</p> 882</li> 883<li> 884<p>Private GLSL issue 20: <strong>length</strong>() expressions returning a constant value may not 885contain side effects.</p> 886</li> 887<li> 888<p>Public OpenGL-API issue 7: Variables can be declared as both <strong>readonly</strong> 889and <strong>writeonly</strong>.</p> 890</li> 891<li> 892<p>Private GLSL issue 16: Use of constant expressions within <strong>#line</strong> directives is undefined.</p> 893</li> 894<li> 895<p>Corrected return type of <strong>imageAtomicExchange</strong> on <strong>float</strong> images.</p> 896</li> 897<li> 898<p>Private GLSL issue 32: Remove <strong>length</strong>() method contradiction: 899Non runtime-sized arrays only support <strong>length</strong>() on explicitly 900sized arrays.</p> 901</li> 902<li> 903<p>Private GLSL issue 21: Clarified the l-value restriction on <strong>interpolateAt</strong>.</p> 904</li> 905<li> 906<p>Private OpenGL-API issue 53: Clarified bit-width requirements for location aliasing.</p> 907</li> 908<li> 909<p>Public GLSL issue 15: <strong>gl_in</strong> can be redeclared using unsized-array syntax.</p> 910</li> 911<li> 912<p>Clarification of the formats needed for DEPTH_COMPONENT and 913STENCIL_COMPONENT for depth/stencil textures.</p> 914</li> 915<li> 916<p>Added image formats to the layout-qualifier table in the 917<a href="#layout-qualifiers">Layout Qualifiers</a> section.</p> 918</li> 919</ul> 920</div> 921</div> 922<div class="sect3"> 923<h4 id="_changes_from_revision_3_of_glsl_4_6">1.1.4. Changes from Revision 3 of GLSL 4.6</h4> 924<div class="ulist"> 925<ul> 926<li> 927<p>Private GLSL issue 13: Fix misspelling of <strong>allInvocationsEqual</strong>(). 928(The one in the table was incorrectly listed as <strong>anyInvocationsEqual</strong>(), 929other spellings were correct.)</p> 930</li> 931</ul> 932</div> 933</div> 934<div class="sect3"> 935<h4 id="_summary_of_changes_from_revision_7_of_glsl_version_4_50">1.1.5. Summary of Changes from Revision 7 of GLSL Version 4.50</h4> 936<div class="ulist"> 937<ul> 938<li> 939<p>Incorporated the GL_ARB_shader_atomic_counter_ops extension.</p> 940</li> 941<li> 942<p>Incorporated the GL_ARB_shader_draw_parameters extension.</p> 943</li> 944<li> 945<p>Incorporated the GL_ARB_shader_group_vote extension.</p> 946</li> 947<li> 948<p>Incorporated the GL_ARB_gl_spirv extension.</p> 949</li> 950<li> 951<p>Private Bug 16070: Allow extra semi-colons at global scope.</p> 952</li> 953<li> 954<p>Private GLSL Issue 5: Be explicit that “fail to link” is really 955“compile-time or link-time error”, for some forms of error.</p> 956</li> 957<li> 958<p>Private GLSL Issue 7: Change <em>gl_MaxComputeUniformComponents</em> to 1024.</p> 959</li> 960<li> 961<p>Private OpenGL API Issue 35: Require location on transparent individual 962uniform variables for SPIR-V.</p> 963</li> 964<li> 965<p>Private GLSL Issue 8: Be more clear an <strong>interpolateAt</strong>() interpolant can 966be a structure member.</p> 967</li> 968<li> 969<p>Private GLSL Issue 9: Specify how <strong>xfb_buffer</strong> interacts with a block 970array: the capturing buffer increments for each block array element.</p> 971</li> 972</ul> 973</div> 974</div> 975</div> 976<div class="sect2"> 977<h3 id="overview">1.2. Overview</h3> 978<div class="paragraph"> 979<p>This document describes <em>The OpenGL Shading Language, version 4.60</em>.</p> 980</div> 981<div class="paragraph"> 982<p>Independent compilation units written in this language are called <em>shaders</em>. 983A <em>program</em> is a set of shaders that are compiled and linked 984together, 985completely creating one or more of the programmable stages of the 986API pipeline. 987All the shaders for a single programmable stage must be within the same 988program. 989A complete set of programmable stages can be put into a single program or 990the stages can be partitioned across multiple programs. 991The aim of this document is to thoroughly specify the programming language. 992The <a href="#references">normative references</a> will specify the API entry points 993used to manipulate and communicate with programs and shaders.</p> 994</div> 995</div> 996<div class="sect2"> 997<h3 id="error-handling">1.3. Error Handling</h3> 998<div class="paragraph"> 999<p>Compilers, in general, accept programs that are ill-formed, due to the 1000impossibility of detecting all ill-formed programs. 1001Portability is only ensured for well-formed programs, which this 1002specification describes. 1003Compilers are encouraged to detect ill-formed programs and issue diagnostic 1004messages, but are not required to do so for all cases. 1005Compile-time errors must be returned for lexically or grammatically 1006incorrect shaders. 1007Other errors are reported at compile time or link time as indicated. 1008Code that is “dead” must still be error checked. 1009For example:</p> 1010</div> 1011<div class="listingblock"> 1012<div class="content"> 1013<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">if</span> (<span class="predefined-constant">false</span>) <span class="comment">// changing false to true cannot uncover additional errors</span> 1014 statement; <span class="comment">// statement must be error checked regardless</span></code></pre> 1015</div> 1016</div> 1017</div> 1018<div class="sect2"> 1019<h3 id="typographical-conventions">1.4. Typographical Conventions</h3> 1020<div class="paragraph"> 1021<p>Italic, bold, and font choices have been used in this specification 1022primarily to improve readability. 1023Code fragments use a fixed width font. 1024Identifiers embedded in text are italicized. 1025Keywords embedded in text are bold. 1026Operators are called by their name, followed by their symbol in bold in 1027parentheses. 1028The clarifying grammar fragments in the text use bold for literals and 1029italics for non-terminals. 1030The official grammar in “<a href="#shading-language-grammar">Shading Language 1031Grammar</a>” uses all capitals for terminals and lower case for 1032non-terminals.</p> 1033</div> 1034</div> 1035<div class="sect2"> 1036<h3 id="deprecation">1.5. Deprecation</h3> 1037<div class="paragraph"> 1038<p>The OpenGL Shading Language has deprecated some features. 1039These are clearly called out in this specification as “deprecated”. 1040They are still present in this version of the language, but are targeted for 1041potential removal in a future version of the shading language. 1042The OpenGL API has a forward compatibility mode that will disallow use of 1043deprecated features. 1044If compiling in a mode where use of deprecated features is disallowed, their 1045use causes compile-time or link-time errors. 1046See the <a href="#references">OpenGL Specification</a> for details on what causes deprecated 1047language features to be accepted or to return an error.</p> 1048</div> 1049</div> 1050</div> 1051</div> 1052<div class="sect1"> 1053<h2 id="overview-of-opengl-shading">2. Overview of Shading</h2> 1054<div class="sectionbody"> 1055<div class="paragraph"> 1056<p>The OpenGL Shading Language is actually several closely related languages. 1057These languages are used to create shaders for each of the programmable 1058processors contained in the API’s processing pipeline. 1059Currently, these processors are the vertex, tessellation control, 1060tessellation evaluation, geometry, fragment, and compute processors.</p> 1061</div> 1062<div class="paragraph"> 1063<p>Unless otherwise noted in this paper, a language feature applies to all 1064languages, and common usage will refer to these languages as a single 1065language. 1066The specific languages will be referred to by the name of the processor they 1067target: vertex, tessellation control, tessellation evaluation, geometry, 1068fragment, or compute.</p> 1069</div> 1070<div class="paragraph"> 1071<p>Most API state is not tracked or made available to shaders. 1072Typically, user-defined variables will be used for communicating between 1073different stages of the API pipeline. 1074However, a small amount of state is still tracked and automatically made 1075available to shaders, and there are a few built-in variables for interfaces 1076between different stages of the API pipeline.</p> 1077</div> 1078<div class="sect2"> 1079<h3 id="vertex-processor">2.1. Vertex Processor</h3> 1080<div class="paragraph"> 1081<p>The <em>vertex processor</em> is a programmable unit that operates on incoming 1082vertices and their associated data. 1083Compilation units written in the OpenGL Shading Language to run on this processor are called 1084<em>vertex shaders</em>. 1085When a set of vertex shaders are successfully compiled and linked, they 1086result in a <em>vertex shader executable</em> that runs on the vertex processor.</p> 1087</div> 1088<div class="paragraph"> 1089<p>The vertex processor operates on one vertex at a time. 1090It does not replace graphics operations that require knowledge of several 1091vertices at a time.</p> 1092</div> 1093</div> 1094<div class="sect2"> 1095<h3 id="tessellation-control-processor">2.2. Tessellation Control Processor</h3> 1096<div class="paragraph"> 1097<p>The <em>tessellation control processor</em> is a programmable unit that operates on 1098a patch of incoming vertices and their associated data, emitting a new 1099output patch. 1100Compilation units written in the OpenGL Shading Language to run on this processor are called 1101tessellation control shaders. 1102When a set of tessellation control shaders are successfully compiled and 1103linked, they result in a <em>tessellation control shader executable</em> that runs 1104on the tessellation control processor.</p> 1105</div> 1106<div class="paragraph"> 1107<p>The tessellation control shader is invoked for each vertex of the output 1108patch. 1109Each invocation can read the attributes of any vertex in the input or output 1110patches, but can only write per-vertex attributes for the corresponding 1111output patch vertex. 1112The shader invocations collectively produce a set of per-patch attributes 1113for the output patch.</p> 1114</div> 1115<div class="paragraph"> 1116<p>After all tessellation control shader invocations have completed, the output 1117vertices and per-patch attributes are assembled to form a patch to be used 1118by subsequent pipeline stages.</p> 1119</div> 1120<div class="paragraph"> 1121<p>Tessellation control shader invocations run mostly independently, with 1122undefined relative execution order. 1123However, the built-in function <strong>barrier</strong>() can be used to control execution 1124order by synchronizing invocations, effectively dividing tessellation 1125control shader execution into a set of phases. 1126Tessellation control shaders will get undefined results if one invocation 1127reads from a per-vertex or per-patch attribute written by another invocation 1128at any point during the same phase, or if two invocations attempt to write 1129different values to the same per-patch output 113032-bit component 1131in a single phase.</p> 1132</div> 1133</div> 1134<div class="sect2"> 1135<h3 id="tessellation-evaluation-processor">2.3. Tessellation Evaluation Processor</h3> 1136<div class="paragraph"> 1137<p>The <em>tessellation evaluation processor</em> is a programmable unit that 1138evaluates the position and other attributes of a vertex generated by the 1139tessellation primitive generator, using a patch of incoming vertices and 1140their associated data. 1141Compilation units written in the OpenGL Shading Language to run on this processor are called 1142tessellation evaluation shaders. 1143When a set of tessellation evaluation shaders are successfully compiled and 1144linked, they result in a <em>tessellation evaluation shader executable</em> that 1145runs on the tessellation evaluation processor.</p> 1146</div> 1147<div class="paragraph"> 1148<p>Each invocation of the tessellation evaluation executable computes the 1149position and attributes of a single vertex generated by the tessellation 1150primitive generator. 1151The executable can read the attributes of any vertex in the input patch, 1152plus the tessellation coordinate, which is the relative location of the 1153vertex in the primitive being tessellated. 1154The executable writes the position and other attributes of the vertex.</p> 1155</div> 1156</div> 1157<div class="sect2"> 1158<h3 id="geometry-processor">2.4. Geometry Processor</h3> 1159<div class="paragraph"> 1160<p>The <em>geometry processor</em> is a programmable unit that operates on data for 1161incoming vertices for a primitive assembled after vertex processing and 1162outputs a sequence of vertices forming output primitives. 1163Compilation units written in the OpenGL Shading Language to run on this processor are called 1164<em>geometry shaders</em>. 1165When a set of geometry shaders are successfully compiled and linked, they 1166result in a <em>geometry shader executable</em> that runs on the geometry 1167processor.</p> 1168</div> 1169<div class="paragraph"> 1170<p>A single invocation of the geometry shader executable on the geometry 1171processor will operate on a declared input primitive with a fixed number of 1172vertices. 1173This single invocation can emit a variable number of vertices that are 1174assembled into primitives of a declared output primitive type and passed to 1175subsequent pipeline stages.</p> 1176</div> 1177</div> 1178<div class="sect2"> 1179<h3 id="fragment-processor">2.5. Fragment Processor</h3> 1180<div class="paragraph"> 1181<p>The <em>fragment processor</em> is a programmable unit that operates on fragment 1182values and their associated data. 1183Compilation units written in the OpenGL Shading Language to run on this processor are called 1184<em>fragment shaders</em>. 1185When a set of fragment shaders are successfully compiled and linked, they 1186result in a <em>fragment shader executable</em> that runs on the fragment 1187processor.</p> 1188</div> 1189<div class="paragraph"> 1190<p>A fragment shader cannot change a fragment’s (<em>x</em>, <em>y</em>) position. 1191Access to neighboring fragments is not allowed. 1192The values computed by the fragment shader are ultimately used to update 1193framebuffer memory or texture memory, depending on the current API 1194state and the API command that caused the fragments to be generated.</p> 1195</div> 1196</div> 1197<div class="sect2"> 1198<h3 id="compute-processor">2.6. Compute Processor</h3> 1199<div class="paragraph"> 1200<p>The <em>compute processor</em> is a programmable unit that operates independently 1201from the other shader processors. 1202Compilation units written in the OpenGL Shading Language to run on this processor are called 1203<em>compute shaders</em>. 1204When a set of compute shaders are successfully compiled and linked, they 1205result in a <em>compute shader executable</em> that runs on the compute processor.</p> 1206</div> 1207<div class="paragraph"> 1208<p>A compute shader has access to many of the same resources as fragment and 1209other shader processors, such as textures, buffers, image variables, and 1210atomic counters. 1211It does not have fixed-function outputs. 1212It is not part of the graphics pipeline and its visible side effects are 1213through changes to images, storage buffers, and atomic counters.</p> 1214</div> 1215<div class="paragraph"> 1216<p>A compute shader operates on a group of work items called a <em>workgroup</em>. 1217A workgroup is a collection of shader invocations that execute the same 1218code, potentially in parallel. 1219An invocation within a workgroup may share data with other members of the 1220same workgroup through shared variables and issue memory and control flow 1221barriers to synchronize with other members of the same workgroup.</p> 1222</div> 1223</div> 1224</div> 1225</div> 1226<div class="sect1"> 1227<h2 id="basics">3. Basics</h2> 1228<div class="sectionbody"> 1229<div class="sect2"> 1230<h3 id="character-set">3.1. Character Set and Phases of Compilation</h3> 1231<div class="paragraph"> 1232<p>The source character set used for the OpenGL Shading Language is Unicode in the UTF-8 1233encoding scheme.</p> 1234</div> 1235<div class="paragraph"> 1236<p>After preprocessing, only the following characters are allowed in the 1237resulting stream of GLSL tokens:</p> 1238</div> 1239<div class="ulist"> 1240<ul> 1241<li> 1242<p>The letters <strong>a-z</strong>, <strong>A-Z</strong>, and the underscore (<strong>_</strong>).</p> 1243</li> 1244<li> 1245<p>The numbers <strong>0-9</strong>.</p> 1246</li> 1247<li> 1248<p>The symbols period (<strong>.</strong>), plus (<strong>+</strong>), dash (<strong>-</strong>), slash (<strong>/</strong>), asterisk 1249(<strong>*</strong>), percent (<strong>%</strong>), angled brackets (<strong><</strong> and <strong>></strong>), square brackets 1250(<strong>[</strong> and <strong>]</strong>), parentheses (<strong>(</strong> and <strong>)</strong>), braces (<strong>{</strong> and <strong>}</strong>), caret 1251(<strong>^</strong>), vertical bar (<strong>|</strong>), ampersand (<strong>&</strong>), tilde (<strong>~</strong>), equals (<strong>=</strong>), 1252exclamation point (<strong>!</strong>), colon (<strong>:</strong>), semicolon (<strong>;</strong>), comma (<strong>,</strong>), and 1253question mark (<strong>?</strong>).</p> 1254</li> 1255</ul> 1256</div> 1257<div class="paragraph"> 1258<p>A compile-time error will be given if any other character is used in a GLSL 1259token.</p> 1260</div> 1261<div class="paragraph"> 1262<p>There are no digraphs or trigraphs. 1263There are no escape sequences or other uses of the backslash beyond use as 1264the line-continuation character.</p> 1265</div> 1266<div class="paragraph"> 1267<p>Lines are relevant for compiler diagnostic messages and the preprocessor. 1268They are terminated by carriage-return or line-feed. 1269If both are used together, it will count as only a single line termination. 1270For the remainder of this document, any of these combinations is simply 1271referred to as a new-line. 1272Lines may be of arbitrary length.</p> 1273</div> 1274<div class="paragraph"> 1275<p>In general, the language’s use of this character set is case sensitive.</p> 1276</div> 1277<div class="paragraph"> 1278<p>There are no character or string data types, so no quoting characters are 1279included.</p> 1280</div> 1281<div class="paragraph"> 1282<p>There is no end-of-file character.</p> 1283</div> 1284<div class="paragraph"> 1285<p>More formally, compilation happens as if the following logical phases were 1286executed in order:</p> 1287</div> 1288<div class="olist arabic"> 1289<ol class="arabic"> 1290<li> 1291<p>Source strings are concatenated to form a single input. 1292All provided new-lines are retained.</p> 1293</li> 1294<li> 1295<p>Line numbering is noted, based on all present new-lines, and does not 1296change when new-lines are later eliminated.</p> 1297</li> 1298<li> 1299<p>Wherever a backslash ('\') occurs immediately before a new-line, both 1300are eliminated. 1301(Note no white space is substituted, allowing a single token to span a 1302new-line.) Any newly formed backslash followed by a new-line is not 1303eliminated; only those pairs originally occurring after phase 1 are 1304eliminated.</p> 1305</li> 1306<li> 1307<p>All comments are replaced with a single space. 1308(Note that '//' style comments end before their terminating new-lines 1309and white space is generally relevant to preprocessing.)</p> 1310</li> 1311<li> 1312<p>Preprocessing is done, resulting in a sequence of GLSL tokens, formed 1313from the character set stated above.</p> 1314</li> 1315<li> 1316<p>GLSL processing is done on the sequence of GLSL tokens.</p> 1317</li> 1318</ol> 1319</div> 1320<div class="paragraph"> 1321<p>Details that fully define source strings, comments, line numbering, new-line 1322elimination, and preprocessing are all discussed in upcoming sections. 1323Sections beyond those describe GLSL processing.</p> 1324</div> 1325</div> 1326<div class="sect2"> 1327<h3 id="source-strings">3.2. Source Strings</h3> 1328<div class="paragraph"> 1329<p>The source for a single shader is an array of strings of characters from the 1330character set. 1331A single shader is made from the concatenation of these strings. 1332Each string can contain multiple lines, separated by new-lines. 1333No new-lines need be present in a string; a single line can be formed from 1334multiple strings. 1335No new-lines or other characters are inserted by the implementation when it 1336concatenates the strings to form a single shader. 1337Multiple shaders can be linked together to form a single program.</p> 1338</div> 1339<div class="paragraph"> 1340<p>Diagnostic messages returned from compiling a shader must identify both the 1341line number within a string and which source string the message applies to. 1342Source strings are counted sequentially with the first string being string 13430. 1344Line numbers are one more than the number of new-lines that have been 1345processed, including counting the new-lines that will be removed by the 1346line-continuation character (<strong>\</strong>).</p> 1347</div> 1348<div class="paragraph"> 1349<p>Lines separated by the line-continuation character preceding a new-line are 1350concatenated together before either comment processing or preprocessing. 1351This means that no white space is substituted for the line-continuation 1352character. 1353That is, a single token could be formed by the concatenation by taking the 1354characters at the end of one line concatenating them with the characters at 1355the beginning of the next line.</p> 1356</div> 1357<div class="listingblock"> 1358<div class="content"> 1359<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> f\ 1360oo; 1361<span class="comment">// forms a single line equivalent to "float foo;"</span> 1362<span class="comment">// (assuming '\' is the last character before the new-line and "oo" are</span> 1363<span class="comment">// the first two characters of the next line)</span></code></pre> 1364</div> 1365</div> 1366</div> 1367<div class="sect2"> 1368<h3 id="preprocessor">3.3. Preprocessor</h3> 1369<div class="paragraph"> 1370<p>There is a preprocessor that processes the source strings as part of the 1371compilation process. 1372Except as noted below, it behaves as the C++ standard preprocessor (see 1373“<a href="#references">Normative References</a>”).</p> 1374</div> 1375<div class="paragraph"> 1376<p>The complete list of preprocessor directives is as follows.</p> 1377</div> 1378<div class="dlist"> 1379<dl> 1380<dt class="hdlist1"></dt> 1381<dd> 1382<p>#<br> 1383#define<br> 1384#undef<br></p> 1385</dd> 1386<dt class="hdlist1"></dt> 1387<dd> 1388<p>#if<br> 1389#ifdef<br> 1390#ifndef<br> 1391#else<br> 1392#elif<br> 1393#endif<br></p> 1394</dd> 1395<dt class="hdlist1"></dt> 1396<dd> 1397<p>#error<br> 1398#pragma<br></p> 1399</dd> 1400<dt class="hdlist1"></dt> 1401<dd> 1402<p>#extension<br> 1403#version<br></p> 1404</dd> 1405<dt class="hdlist1"></dt> 1406<dd> 1407<p>#line</p> 1408</dd> 1409</dl> 1410</div> 1411<div class="paragraph"> 1412<p>The following 1413operators are 1414also available:</p> 1415</div> 1416<div class="dlist"> 1417<dl> 1418<dt class="hdlist1"></dt> 1419<dd> 1420<p>defined<br> 1421##</p> 1422</dd> 1423</dl> 1424</div> 1425<div class="paragraph"> 1426<p>Each number sign (<strong>#</strong>) can be preceded in its line only by spaces or 1427horizontal tabs. 1428It may also be followed by spaces and horizontal tabs, preceding the 1429directive. 1430Each directive is terminated by a new-line. 1431Preprocessing does not change the number or relative location of new-lines 1432in a source string. 1433Preprocessing takes places after new-lines have been removed by the 1434line-continuation character.</p> 1435</div> 1436<div class="paragraph"> 1437<p>The number sign (<strong>#</strong>) on a line by itself is ignored. 1438Any directive not listed above will cause a compile-time error.</p> 1439</div> 1440<div class="paragraph"> 1441<p><strong>#define</strong> and <strong>#undef</strong> functionality are defined as is standard for C++ 1442preprocessors for macro definitions both with and without macro parameters.</p> 1443</div> 1444<div class="paragraph"> 1445<p>The following predefined macros are available:</p> 1446</div> 1447<div class="dlist"> 1448<dl> 1449<dt class="hdlist1"></dt> 1450<dd> 1451<p>__LINE__<br> 1452__FILE__<br> 1453__VERSION__<br></p> 1454</dd> 1455</dl> 1456</div> 1457<div class="paragraph"> 1458<p>__LINE__ will substitute a decimal integer constant that is one more than 1459the number of preceding new-lines in the current source string.</p> 1460</div> 1461<div class="paragraph"> 1462<p>__FILE__ will substitute a decimal integer constant that says which source 1463string number is currently being processed.</p> 1464</div> 1465<div class="paragraph"> 1466<p>__VERSION__ will substitute a decimal integer reflecting the version 1467number of the OpenGL Shading Language. 1468The version of the shading language described in this document will have 1469__VERSION__ substitute the decimal integer 460.</p> 1470</div> 1471<div class="paragraph"> 1472<p>By convention, all macro names containing two consecutive underscores (__) 1473are reserved for use by underlying software layers. 1474Defining 1475or undefining 1476such a name in a shader does not itself result in an error, but may 1477result in unintended behaviors that stem from having multiple definitions of 1478the same name. 1479All macro names prefixed with “GL_” (“GL” followed by a single 1480underscore) are also reserved, and defining 1481or undefining 1482such a name results in a compile-time error.</p> 1483</div> 1484<div class="paragraph"> 1485<p>Implementations must support macro-name lengths of up to 1024 characters. 1486Implementations are allowed to generate an error for a macro name of length 1487greater than 1024 characters, but are also allowed to support lengths 1488greater than 1024.</p> 1489</div> 1490<div class="paragraph"> 1491<p><strong>#if</strong>, <strong>#ifdef</strong>, <strong>#ifndef</strong>, <strong>#else</strong>, <strong>#elif</strong>, and <strong>#endif</strong> are defined to 1492operate as is standard for C++ preprocessors except for the following:</p> 1493</div> 1494<div class="ulist"> 1495<ul> 1496<li> 1497<p>Expressions following <strong>#if</strong> and <strong>#elif</strong> are 1498further restricted to 1499expressions operating on literal integer constants, plus identifiers 1500consumed by the <strong>defined</strong> operator.</p> 1501</li> 1502<li> 1503<p>Character constants are not supported.</p> 1504</li> 1505</ul> 1506</div> 1507<div class="paragraph"> 1508<p>The operators available are as follows.</p> 1509</div> 1510<table class="tableblock frame-all grid-all stretch"> 1511<colgroup> 1512<col style="width: 25%;"> 1513<col style="width: 25%;"> 1514<col style="width: 25%;"> 1515<col style="width: 25%;"> 1516</colgroup> 1517<thead> 1518<tr> 1519<th class="tableblock halign-left valign-top">Precedence</th> 1520<th class="tableblock halign-left valign-top">Operator class</th> 1521<th class="tableblock halign-left valign-top">Operators</th> 1522<th class="tableblock halign-left valign-top">Associativity</th> 1523</tr> 1524</thead> 1525<tbody> 1526<tr> 1527<td class="tableblock halign-left valign-top"><p class="tableblock">1 (highest)</p></td> 1528<td class="tableblock halign-left valign-top"><p class="tableblock">parenthetical grouping</p></td> 1529<td class="tableblock halign-left valign-top"><p class="tableblock">( )</p></td> 1530<td class="tableblock halign-left valign-top"><p class="tableblock">NA</p></td> 1531</tr> 1532<tr> 1533<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td> 1534<td class="tableblock halign-left valign-top"><p class="tableblock">unary</p></td> 1535<td class="tableblock halign-left valign-top"><p class="tableblock">defined<br> 1536 + - ~ !</p></td> 1537<td class="tableblock halign-left valign-top"><p class="tableblock">Right to Left</p></td> 1538</tr> 1539<tr> 1540<td class="tableblock halign-left valign-top"><p class="tableblock">3</p></td> 1541<td class="tableblock halign-left valign-top"><p class="tableblock">multiplicative</p></td> 1542<td class="tableblock halign-left valign-top"><p class="tableblock">* / %</p></td> 1543<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1544</tr> 1545<tr> 1546<td class="tableblock halign-left valign-top"><p class="tableblock">4</p></td> 1547<td class="tableblock halign-left valign-top"><p class="tableblock">additive</p></td> 1548<td class="tableblock halign-left valign-top"><p class="tableblock">+ -</p></td> 1549<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1550</tr> 1551<tr> 1552<td class="tableblock halign-left valign-top"><p class="tableblock">5</p></td> 1553<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise shift</p></td> 1554<td class="tableblock halign-left valign-top"><p class="tableblock"><< >></p></td> 1555<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1556</tr> 1557<tr> 1558<td class="tableblock halign-left valign-top"><p class="tableblock">6</p></td> 1559<td class="tableblock halign-left valign-top"><p class="tableblock">relational</p></td> 1560<td class="tableblock halign-left valign-top"><p class="tableblock">< > <= >=</p></td> 1561<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1562</tr> 1563<tr> 1564<td class="tableblock halign-left valign-top"><p class="tableblock">7</p></td> 1565<td class="tableblock halign-left valign-top"><p class="tableblock">equality</p></td> 1566<td class="tableblock halign-left valign-top"><p class="tableblock">== !=</p></td> 1567<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1568</tr> 1569<tr> 1570<td class="tableblock halign-left valign-top"><p class="tableblock">8</p></td> 1571<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise and</p></td> 1572<td class="tableblock halign-left valign-top"><p class="tableblock">&</p></td> 1573<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1574</tr> 1575<tr> 1576<td class="tableblock halign-left valign-top"><p class="tableblock">9</p></td> 1577<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise exclusive or</p></td> 1578<td class="tableblock halign-left valign-top"><p class="tableblock">^</p></td> 1579<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1580</tr> 1581<tr> 1582<td class="tableblock halign-left valign-top"><p class="tableblock">10</p></td> 1583<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise inclusive or</p></td> 1584<td class="tableblock halign-left valign-top"><p class="tableblock">|</p></td> 1585<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1586</tr> 1587<tr> 1588<td class="tableblock halign-left valign-top"><p class="tableblock">11</p></td> 1589<td class="tableblock halign-left valign-top"><p class="tableblock">logical and</p></td> 1590<td class="tableblock halign-left valign-top"><p class="tableblock">&&</p></td> 1591<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1592</tr> 1593<tr> 1594<td class="tableblock halign-left valign-top"><p class="tableblock">12 (lowest)</p></td> 1595<td class="tableblock halign-left valign-top"><p class="tableblock">logical inclusive or</p></td> 1596<td class="tableblock halign-left valign-top"><p class="tableblock">||</p></td> 1597<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 1598</tr> 1599</tbody> 1600</table> 1601<div class="paragraph"> 1602<p>The <strong>defined</strong> operator can be used in either of the following ways:</p> 1603</div> 1604<div class="listingblock"> 1605<div class="content"> 1606<pre class="CodeRay highlight"><code data-lang="c++">defined identifier 1607defined ( identifier )</code></pre> 1608</div> 1609</div> 1610<div class="paragraph"> 1611<p>Two tokens in a macro can be concatenated into one token using the token 1612pasting (<strong>##</strong>) operator, as is standard for C++ preprocessors. 1613The result must be a valid single token, which will then be subject to macro 1614expansion. 1615That is, macro expansion happens only after token pasting. 1616There are no other number sign based operators (e.g. no <strong>#</strong> or <strong>#@</strong>), nor is 1617there a <strong>sizeof</strong> operator.</p> 1618</div> 1619<div class="paragraph"> 1620<p>The semantics of applying operators to integer literals in the preprocessor 1621match those standard in the C++ preprocessor, not those in the OpenGL Shading Language.</p> 1622</div> 1623<div class="paragraph"> 1624<p>Preprocessor expressions will be evaluated according to the behavior of the 1625host processor, not the processor targeted by the shader.</p> 1626</div> 1627<div class="paragraph"> 1628<p><strong>#error</strong> will cause the implementation to put a compile-time diagnostic message 1629into the shader object’s information log (see section 7.12 “Shader, Program 1630and Program Pipeline Queries” of the <a href="#references">OpenGL Specification</a> for how to 1631access a shader object’s information log). 1632The message will be the tokens following the <strong>#error</strong> directive, up to the 1633first new-line. 1634The implementation must treat the presence of a <strong>#error</strong> directive as a 1635compile-time error.</p> 1636</div> 1637<div class="paragraph"> 1638<p><strong>#pragma</strong> allows implementation-dependent compiler control. 1639Tokens following <strong>#pragma</strong> are not subject to preprocessor macro expansion. 1640If an implementation does not recognize the tokens following <strong>#pragma</strong>, then 1641it will ignore that pragma. 1642The following pragmas are defined as part of the language.</p> 1643</div> 1644<div class="listingblock"> 1645<div class="content"> 1646<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#pragma</span> STDGL</code></pre> 1647</div> 1648</div> 1649<div class="paragraph"> 1650<p>The <strong>STDGL</strong> pragma is used to reserve pragmas for use by future revisions of 1651this language. 1652No implementation may use a pragma whose first token is <strong>STDGL</strong>.</p> 1653</div> 1654<div class="listingblock"> 1655<div class="content"> 1656<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#pragma</span> optimize(on) 1657<span class="preprocessor">#pragma</span> optimize(off)</code></pre> 1658</div> 1659</div> 1660<div class="paragraph"> 1661<p>can be used to turn off optimizations as an aid in developing and debugging 1662shaders. 1663It can only be used outside function definitions. 1664By default, optimization is turned on for all shaders. 1665The debug pragma</p> 1666</div> 1667<div class="listingblock"> 1668<div class="content"> 1669<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#pragma</span> debug(on) 1670<span class="preprocessor">#pragma</span> debug(off)</code></pre> 1671</div> 1672</div> 1673<div class="paragraph"> 1674<p>can be used to enable compiling and annotating a shader with debug 1675information, so that it can be used with a debugger. 1676It can only be used outside function definitions. 1677By default, debug is turned off.</p> 1678</div> 1679<div class="paragraph"> 1680<p>Shaders should declare the version of the language they are written to. 1681The language version a shader is written to is specified by</p> 1682</div> 1683<div class="listingblock"> 1684<div class="content"> 1685<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#version</span> number profile_opt</code></pre> 1686</div> 1687</div> 1688<div class="paragraph"> 1689<p>where <em>number</em> must be a version of the language, following the same 1690convention as __VERSION__ above. 1691The directive “<strong>#version 460</strong>” is required in any shader that 1692uses version 4.60 of the language. 1693Any <em>number</em> representing a version of the language a compiler does not 1694support will cause a compile-time error to be generated. 1695Version 1.10 of the language does not require shaders to include this 1696directive, and shaders that do not include a <strong>#version</strong> directive will be 1697treated as targeting version 1.10. 1698Shaders that specify <strong>#version</strong> 100 will be treated as targeting version 16991.00 of the OpenGL ES Shading Language. 1700Shaders that specify <strong>#version</strong> 300 will be treated as targeting version 17013.00 of the OpenGL ES Shading Language. 1702Shaders that specify <strong>#version</strong> 310 will be treated as targeting version 17033.10 of the OpenGL ES Shading Language.</p> 1704</div> 1705<div class="paragraph"> 1706<p>If the optional <em>profile</em> argument is provided, it must be the name of an 1707OpenGL profile. 1708Currently, there are three choices:</p> 1709</div> 1710<div class="listingblock"> 1711<div class="content"> 1712<pre class="CodeRay highlight"><code data-lang="c++">core 1713compatibility 1714es</code></pre> 1715</div> 1716</div> 1717<div class="paragraph"> 1718<p>A <em>profile</em> argument can only be used with version 150 or greater. 1719If no profile argument is provided and the version is 150 or greater, the 1720default is <strong>core</strong>. 1721If version 300 or 310 is specified, the profile argument is not optional and 1722must be <strong>es</strong>, or a compile-time error results. 1723The Language Specification for the <strong>es</strong> profile is specified in The OpenGL 1724ES Shading Language specification.</p> 1725</div> 1726<div class="paragraph"> 1727<p>Shaders for the <strong>core</strong> or <strong>compatibility</strong> profiles that declare different 1728versions can be linked together. 1729However, <strong>es</strong> profile shaders cannot be linked with non-<strong>es</strong> profile shaders 1730or with <strong>es</strong> profile shaders of a different version, or a link-time error 1731will result. 1732When linking shaders of versions allowed by these rules, remaining link-time 1733errors will be given as per the linking rules in the GLSL version 1734corresponding to the version of the context the shaders are linked under. 1735Shader compile-time errors must still be given strictly based on the version 1736declared (or defaulted to) within each shader.</p> 1737</div> 1738<div class="paragraph"> 1739<p>Unless otherwise specified, this specification is documenting the core 1740profile, and everything specified for the core profile is also available in 1741the compatibility profile. 1742Features specified as belonging specifically to the compatibility profile 1743are not available in the core profile. 1744Compatibility-profile features are not available when generating SPIR-V.</p> 1745</div> 1746<div class="paragraph"> 1747<p>There is a built-in macro definition for each profile the implementation 1748supports. 1749All implementations provide the following macro:</p> 1750</div> 1751<div class="listingblock"> 1752<div class="content"> 1753<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#define</span> GL_core_profile <span class="integer">1</span></code></pre> 1754</div> 1755</div> 1756<div class="paragraph"> 1757<p>Implementations providing the <strong>compatibility</strong> profile provide the following 1758macro:</p> 1759</div> 1760<div class="listingblock"> 1761<div class="content"> 1762<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#define</span> GL_compatibility_profile <span class="integer">1</span></code></pre> 1763</div> 1764</div> 1765<div class="paragraph"> 1766<p>Implementations providing the <strong>es</strong> profile provide the following macro:</p> 1767</div> 1768<div class="listingblock"> 1769<div class="content"> 1770<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#define</span> GL_es_profile <span class="integer">1</span></code></pre> 1771</div> 1772</div> 1773<div class="paragraph"> 1774<p>The <strong>#version</strong> directive must occur in a shader before anything else, except 1775for comments and white space.</p> 1776</div> 1777<div class="paragraph"> 1778<p>By default, compilers of this language must issue compile-time 1779lexical 1780and 1781grammatical errors for shaders that do not conform to this specification. 1782Any extended behavior must first be enabled. 1783Directives to control the behavior of the compiler with respect to 1784extensions are declared with the <strong>#extension</strong> directive</p> 1785</div> 1786<div class="listingblock"> 1787<div class="content"> 1788<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#extension</span> extension_name : behavior 1789<span class="preprocessor">#extension</span> all : behavior</code></pre> 1790</div> 1791</div> 1792<div class="paragraph"> 1793<p>where <em>extension_name</em> is the name of an extension. 1794Extension names are not documented in this specification. 1795The token <strong>all</strong> means the behavior applies to all extensions supported by 1796the compiler. 1797The <em>behavior</em> can be one of the following:</p> 1798</div> 1799<table class="tableblock frame-all grid-all stretch"> 1800<colgroup> 1801<col style="width: 50%;"> 1802<col style="width: 50%;"> 1803</colgroup> 1804<thead> 1805<tr> 1806<th class="tableblock halign-left valign-top">Behavior</th> 1807<th class="tableblock halign-left valign-top">Effect</th> 1808</tr> 1809</thead> 1810<tbody> 1811<tr> 1812<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>require</strong></p></td> 1813<td class="tableblock halign-left valign-top"><p class="tableblock">Behave as specified by the extension <em>extension_name</em>.<br> 1814 Give a compile-time error on the <strong>#extension</strong> if the extension 1815 <em>extension_name</em> is not supported, or if <strong>all</strong> is specified.</p></td> 1816</tr> 1817<tr> 1818<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>enable</strong></p></td> 1819<td class="tableblock halign-left valign-top"><p class="tableblock">Behave as specified by the extension <em>extension_name</em>.<br> 1820 Warn on the <strong>#extension</strong> if the extension <em>extension_name</em> is 1821 not supported.<br> 1822 Give a compile-time error on the <strong>#extension</strong> if <strong>all</strong> is 1823 specified.</p></td> 1824</tr> 1825<tr> 1826<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>warn</strong></p></td> 1827<td class="tableblock halign-left valign-top"><p class="tableblock">Behave as specified by the extension <em>extension_name</em>, 1828 except issue warnings on any detectable use of that extension, 1829 unless such use is supported by other enabled or required 1830 extensions.<br> 1831 If <strong>all</strong> is specified, then warn on all detectable uses of any 1832 extension used.<br> 1833 Warn on the <strong>#extension</strong> if the extension <em>extension_name</em> is 1834 not supported.</p></td> 1835</tr> 1836<tr> 1837<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>disable</strong></p></td> 1838<td class="tableblock halign-left valign-top"><p class="tableblock">Behave (including issuing errors and warnings) as if the 1839 extension <em>extension_name</em> is not part of the language 1840 definition.<br> 1841 If <strong>all</strong> is specified, then behavior must revert back to that 1842 of the non-extended core version of the language being 1843 compiled to.<br> 1844 Warn on the <strong>#extension</strong> if the extension <em>extension_name</em> is 1845 not supported.</p></td> 1846</tr> 1847</tbody> 1848</table> 1849<div class="paragraph"> 1850<p>The <strong>extension</strong> directive is a simple, low-level mechanism to set the 1851behavior for each extension. 1852It does not define policies such as which combinations are appropriate, 1853those must be defined elsewhere. 1854Order of directives matters in setting the behavior for each extension: 1855Directives that occur later override those seen earlier. 1856The <strong>all</strong> variant sets the behavior for all extensions, overriding all 1857previously issued <strong>extension</strong> directives, but only for the <em>behaviors</em> 1858<strong>warn</strong> and <strong>disable</strong>.</p> 1859</div> 1860<div class="paragraph"> 1861<p>The initial state of the compiler is as if the directive</p> 1862</div> 1863<div class="listingblock"> 1864<div class="content"> 1865<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#extension</span> all : disable</code></pre> 1866</div> 1867</div> 1868<div class="paragraph"> 1869<p>was issued, telling the compiler that all error and warning reporting must 1870be done according to this specification, ignoring any extensions.</p> 1871</div> 1872<div class="paragraph"> 1873<p>Each extension can define its allowed granularity of scope. 1874If nothing is said, the granularity is a shader (that is, a single 1875compilation unit), and the extension directives must occur before any 1876non-preprocessor tokens. 1877If necessary, the linker can enforce granularities larger than a single 1878compilation unit, in which case each involved shader will have to contain 1879the necessary extension directive.</p> 1880</div> 1881<div class="paragraph"> 1882<p>Macro expansion is not done on lines containing <strong>#extension</strong> and <strong>#version</strong> 1883directives.</p> 1884</div> 1885<div class="paragraph"> 1886<p><strong>#line</strong> must have, after macro substitution, one of the following forms:</p> 1887</div> 1888<div class="listingblock"> 1889<div class="content"> 1890<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#line</span> line 1891<span class="preprocessor">#line</span> line source-<span class="predefined-type">string</span>-number</code></pre> 1892</div> 1893</div> 1894<div class="paragraph"> 1895<p>where <em>line</em> and <em>source-string-number</em> are 1896constant integer expressions. 1897If these constant expressions are not integer literals then behavior is undefined. 1898After processing this directive (including its new-line), the implementation 1899will behave as if it is compiling at line number <em>line</em> and source string 1900number <em>source-string-number</em>. 1901Subsequent source strings will be numbered sequentially, until another 1902<strong>#line</strong> directive overrides that numbering.</p> 1903</div> 1904<div class="admonitionblock note"> 1905<table> 1906<tr> 1907<td class="icon"> 1908<i class="fa icon-note" title="Note"></i> 1909</td> 1910<td class="content"> 1911<div class="title">Note</div> 1912<div class="paragraph"> 1913<p>Some implementations have allowed constant expressions in #line directives and 1914some have not. Even where expressions are supported the grammar is ambiguous and so 1915results are implementation dependent. For example, 1916+ #line +2 +2 // Line number set to 4, or file to 2 and line to 2</p> 1917</div> 1918</td> 1919</tr> 1920</table> 1921</div> 1922<div class="paragraph"> 1923<p>When shaders are compiled for OpenGL SPIR-V, the following predefined 1924macro is available:</p> 1925</div> 1926<div class="listingblock"> 1927<div class="content"> 1928<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#define</span> GL_SPIRV <span class="integer">100</span></code></pre> 1929</div> 1930</div> 1931<div class="paragraph"> 1932<p>When targeting Vulkan, the following predefined macro is available:</p> 1933</div> 1934<div class="listingblock"> 1935<div class="content"> 1936<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#define</span> VULKAN <span class="integer">100</span></code></pre> 1937</div> 1938</div> 1939</div> 1940<div class="sect2"> 1941<h3 id="comments">3.4. Comments</h3> 1942<div class="paragraph"> 1943<p>Comments are delimited by <strong>/*</strong> and <strong>*/</strong>, or by <strong>//</strong> and a new-line. 1944The begin comment delimiters (/* or //) are not recognized as comment 1945delimiters inside of a comment, hence comments cannot be nested. 1946A <strong>/*</strong> comment includes its terminating delimiter (*/). 1947However, a <strong>//</strong> comment does not include (or eliminate) its terminating new 1948line.</p> 1949</div> 1950<div class="paragraph"> 1951<p>Inside comments, any byte values may be used, except a byte whose value is 19520. 1953No errors will be given for the content of comments and no validation on the 1954content of comments need be done.</p> 1955</div> 1956<div class="paragraph"> 1957<p>Removal of new-lines by the line-continuation character (<strong>\</strong>) logically 1958occurs before comments are processed. 1959That is, a single-line comment ending in the line-continuation character 1960(<strong>\</strong>) includes the next line in the comment.</p> 1961</div> 1962<div class="listingblock"> 1963<div class="content"> 1964<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// a single-line comment containing the next line \ 1965a = b; // this is still in the first comment</span></code></pre> 1966</div> 1967</div> 1968</div> 1969<div class="sect2"> 1970<h3 id="tokens">3.5. Tokens</h3> 1971<div class="paragraph"> 1972<p>The language, after preprocessing, is a sequence of tokens. 1973A token can be</p> 1974</div> 1975<div class="openblock bnf"> 1976<div class="content"> 1977<div class="dlist"> 1978<dl> 1979<dt class="hdlist1"><em>token</em> : </dt> 1980<dd> 1981<p><em>keyword</em><br> 1982<em>identifier</em><br> 1983<em>integer-constant</em><br> 1984<em>floating-constant</em><br> 1985<em>operator</em><br> 1986<strong>;</strong> <strong>{</strong> <strong>}</strong></p> 1987</dd> 1988</dl> 1989</div> 1990</div> 1991</div> 1992</div> 1993<div class="sect2"> 1994<h3 id="keywords">3.6. Keywords</h3> 1995<div class="paragraph"> 1996<p>The following are the keywords in the language and (after 1997preprocessing) can only be used as described in this specification, 1998or a compile-time error results:</p> 1999</div> 2000<div class="dlist"> 2001<dl> 2002<dt class="hdlist1"></dt> 2003<dd> 2004<p><strong>const</strong> <strong>uniform</strong> <strong>buffer</strong> <strong>shared</strong> 2005<strong>attribute</strong> <strong>varying</strong></p> 2006</dd> 2007<dt class="hdlist1"></dt> 2008<dd> 2009<p><strong>coherent</strong> <strong>volatile</strong> <strong>restrict</strong> <strong>readonly</strong> <strong>writeonly</strong></p> 2010</dd> 2011<dt class="hdlist1"></dt> 2012<dd> 2013<p><strong>atomic_uint</strong></p> 2014</dd> 2015<dt class="hdlist1"></dt> 2016<dd> 2017<p><strong>layout</strong></p> 2018</dd> 2019<dt class="hdlist1"></dt> 2020<dd> 2021<p><strong>centroid</strong> <strong>flat</strong> <strong>smooth</strong> 2022<strong>noperspective</strong></p> 2023</dd> 2024<dt class="hdlist1"></dt> 2025<dd> 2026<p><strong>patch</strong> <strong>sample</strong></p> 2027</dd> 2028<dt class="hdlist1"></dt> 2029<dd> 2030<p><strong>invariant</strong> <strong>precise</strong></p> 2031</dd> 2032<dt class="hdlist1"></dt> 2033<dd> 2034<p><strong>break</strong> <strong>continue</strong> <strong>do</strong> <strong>for</strong> <strong>while</strong> <strong>switch</strong> <strong>case</strong> <strong>default</strong></p> 2035</dd> 2036<dt class="hdlist1"></dt> 2037<dd> 2038<p><strong>if</strong> <strong>else</strong></p> 2039</dd> 2040<dt class="hdlist1"></dt> 2041<dd> 2042<p><strong>subroutine</strong></p> 2043</dd> 2044<dt class="hdlist1"></dt> 2045<dd> 2046<p><strong>in</strong> <strong>out</strong> <strong>inout</strong></p> 2047</dd> 2048<dt class="hdlist1"></dt> 2049<dd> 2050<p><strong>int</strong> <strong>void</strong> <strong>bool</strong> <strong>true</strong> <strong>false</strong> <strong>float</strong> 2051<strong>double</strong></p> 2052</dd> 2053<dt class="hdlist1"></dt> 2054<dd> 2055<p><strong>discard</strong> <strong>return</strong></p> 2056</dd> 2057<dt class="hdlist1"></dt> 2058<dd> 2059<p><strong>vec2</strong> <strong>vec3</strong> <strong>vec4</strong> <strong>ivec2</strong> <strong>ivec3</strong> <strong>ivec4</strong> <strong>bvec2</strong> <strong>bvec3</strong> <strong>bvec4</strong></p> 2060</dd> 2061<dt class="hdlist1"></dt> 2062<dd> 2063<p><strong>uint</strong> <strong>uvec2</strong> <strong>uvec3</strong> <strong>uvec4</strong></p> 2064</dd> 2065<dt class="hdlist1"></dt> 2066<dd> 2067<p><strong>dvec2</strong> <strong>dvec3</strong> <strong>dvec4</strong></p> 2068</dd> 2069<dt class="hdlist1"></dt> 2070<dd> 2071<p><strong>mat2</strong> <strong>mat3</strong> <strong>mat4</strong></p> 2072</dd> 2073<dt class="hdlist1"></dt> 2074<dd> 2075<p><strong>mat2x2</strong> <strong>mat2x3</strong> <strong>mat2x4</strong></p> 2076</dd> 2077<dt class="hdlist1"></dt> 2078<dd> 2079<p><strong>mat3x2</strong> <strong>mat3x3</strong> <strong>mat3x4</strong></p> 2080</dd> 2081<dt class="hdlist1"></dt> 2082<dd> 2083<p><strong>mat4x2</strong> <strong>mat4x3</strong> <strong>mat4x4</strong></p> 2084</dd> 2085<dt class="hdlist1"></dt> 2086<dd> 2087<p><strong>dmat2</strong> <strong>dmat3</strong> <strong>dmat4</strong></p> 2088</dd> 2089<dt class="hdlist1"></dt> 2090<dd> 2091<p><strong>dmat2x2</strong> <strong>dmat2x3</strong> <strong>dmat2x4</strong></p> 2092</dd> 2093<dt class="hdlist1"></dt> 2094<dd> 2095<p><strong>dmat3x2</strong> <strong>dmat3x3</strong> <strong>dmat3x4</strong></p> 2096</dd> 2097<dt class="hdlist1"></dt> 2098<dd> 2099<p><strong>dmat4x2</strong> <strong>dmat4x3</strong> <strong>dmat4x4</strong></p> 2100</dd> 2101<dt class="hdlist1"></dt> 2102<dd> 2103<p><strong>lowp</strong> <strong>mediump</strong> <strong>highp</strong> <strong>precision</strong></p> 2104</dd> 2105<dt class="hdlist1"></dt> 2106<dd> 2107<p><strong>sampler1D</strong> <strong>sampler1DShadow</strong> <strong>sampler1DArray</strong> <strong>sampler1DArrayShadow</strong></p> 2108</dd> 2109<dt class="hdlist1"></dt> 2110<dd> 2111<p><strong>isampler1D</strong> <strong>isampler1DArray</strong> <strong>usampler1D</strong> <strong>usampler1DArray</strong></p> 2112</dd> 2113<dt class="hdlist1"></dt> 2114<dd> 2115<p><strong>sampler2D</strong> <strong>sampler2DShadow</strong> <strong>sampler2DArray</strong> <strong>sampler2DArrayShadow</strong></p> 2116</dd> 2117<dt class="hdlist1"></dt> 2118<dd> 2119<p><strong>isampler2D</strong> <strong>isampler2DArray</strong> <strong>usampler2D</strong> <strong>usampler2DArray</strong></p> 2120</dd> 2121<dt class="hdlist1"></dt> 2122<dd> 2123<p><strong>sampler2DRect</strong> <strong>sampler2DRectShadow</strong> <strong>isampler2DRect</strong> <strong>usampler2DRect</strong></p> 2124</dd> 2125<dt class="hdlist1"></dt> 2126<dd> 2127<p><strong>sampler2DMS</strong> <strong>isampler2DMS</strong> <strong>usampler2DMS</strong></p> 2128</dd> 2129<dt class="hdlist1"></dt> 2130<dd> 2131<p><strong>sampler2DMSArray</strong> <strong>isampler2DMSArray</strong> <strong>usampler2DMSArray</strong></p> 2132</dd> 2133<dt class="hdlist1"></dt> 2134<dd> 2135<p><strong>sampler3D</strong> <strong>isampler3D</strong> <strong>usampler3D</strong></p> 2136</dd> 2137<dt class="hdlist1"></dt> 2138<dd> 2139<p><strong>samplerCube</strong> <strong>samplerCubeShadow</strong> <strong>isamplerCube</strong> <strong>usamplerCube</strong></p> 2140</dd> 2141<dt class="hdlist1"></dt> 2142<dd> 2143<p><strong>samplerCubeArray</strong> <strong>samplerCubeArrayShadow</strong></p> 2144</dd> 2145<dt class="hdlist1"></dt> 2146<dd> 2147<p><strong>isamplerCubeArray</strong> <strong>usamplerCubeArray</strong></p> 2148</dd> 2149<dt class="hdlist1"></dt> 2150<dd> 2151<p><strong>samplerBuffer</strong> <strong>isamplerBuffer</strong> <strong>usamplerBuffer</strong></p> 2152</dd> 2153<dt class="hdlist1"></dt> 2154<dd> 2155<p><strong>image1D</strong> <strong>iimage1D</strong> <strong>uimage1D</strong></p> 2156</dd> 2157<dt class="hdlist1"></dt> 2158<dd> 2159<p><strong>image1DArray</strong> <strong>iimage1DArray</strong> <strong>uimage1DArray</strong></p> 2160</dd> 2161<dt class="hdlist1"></dt> 2162<dd> 2163<p><strong>image2D</strong> <strong>iimage2D</strong> <strong>uimage2D</strong></p> 2164</dd> 2165<dt class="hdlist1"></dt> 2166<dd> 2167<p><strong>image2DArray</strong> <strong>iimage2DArray</strong> <strong>uimage2DArray</strong></p> 2168</dd> 2169<dt class="hdlist1"></dt> 2170<dd> 2171<p><strong>image2DRect</strong> <strong>iimage2DRect</strong> <strong>uimage2DRect</strong></p> 2172</dd> 2173<dt class="hdlist1"></dt> 2174<dd> 2175<p><strong>image2DMS</strong> <strong>iimage2DMS</strong> <strong>uimage2DMS</strong></p> 2176</dd> 2177<dt class="hdlist1"></dt> 2178<dd> 2179<p><strong>image2DMSArray</strong> <strong>iimage2DMSArray</strong> <strong>uimage2DMSArray</strong></p> 2180</dd> 2181<dt class="hdlist1"></dt> 2182<dd> 2183<p><strong>image3D</strong> <strong>iimage3D</strong> <strong>uimage3D</strong></p> 2184</dd> 2185<dt class="hdlist1"></dt> 2186<dd> 2187<p><strong>imageCube</strong> <strong>iimageCube</strong> <strong>uimageCube</strong></p> 2188</dd> 2189<dt class="hdlist1"></dt> 2190<dd> 2191<p><strong>imageCubeArray</strong> <strong>iimageCubeArray</strong> <strong>uimageCubeArray</strong></p> 2192</dd> 2193<dt class="hdlist1"></dt> 2194<dd> 2195<p><strong>imageBuffer</strong> <strong>iimageBuffer</strong> <strong>uimageBuffer</strong></p> 2196</dd> 2197<dt class="hdlist1"></dt> 2198<dd> 2199<p><strong>struct</strong></p> 2200</dd> 2201</dl> 2202</div> 2203<div class="paragraph"> 2204<p>In addition, when targeting Vulkan, the following keywords also exist:</p> 2205</div> 2206<div class="dlist"> 2207<dl> 2208<dt class="hdlist1"></dt> 2209<dd> 2210<p><strong>texture1D</strong> <strong>texture1DArray</strong></p> 2211</dd> 2212<dt class="hdlist1"></dt> 2213<dd> 2214<p><strong>itexture1D</strong> <strong>itexture1DArray</strong> <strong>utexture1D</strong> <strong>utexture1DArray</strong></p> 2215</dd> 2216<dt class="hdlist1"></dt> 2217<dd> 2218<p><strong>texture2D</strong> <strong>texture2DArray</strong></p> 2219</dd> 2220<dt class="hdlist1"></dt> 2221<dd> 2222<p><strong>itexture2D</strong> <strong>itexture2DArray</strong> <strong>utexture2D</strong> <strong>utexture2DArray</strong></p> 2223</dd> 2224<dt class="hdlist1"></dt> 2225<dd> 2226<p><strong>texture2DRect</strong> <strong>itexture2DRect</strong> <strong>utexture2DRect</strong></p> 2227</dd> 2228<dt class="hdlist1"></dt> 2229<dd> 2230<p><strong>texture2DMS</strong> <strong>itexture2DMS</strong> <strong>utexture2DMS</strong></p> 2231</dd> 2232<dt class="hdlist1"></dt> 2233<dd> 2234<p><strong>texture2DMSArray</strong> <strong>itexture2DMSArray</strong> <strong>utexture2DMSArray</strong></p> 2235</dd> 2236<dt class="hdlist1"></dt> 2237<dd> 2238<p><strong>texture3D</strong> <strong>itexture3D</strong> <strong>utexture3D</strong></p> 2239</dd> 2240<dt class="hdlist1"></dt> 2241<dd> 2242<p><strong>textureCube</strong> <strong>itextureCube</strong> <strong>utextureCube</strong></p> 2243</dd> 2244<dt class="hdlist1"></dt> 2245<dd> 2246<p><strong>textureCubeArray</strong> <strong>itextureCubeArray</strong> <strong>utextureCubeArray</strong></p> 2247</dd> 2248<dt class="hdlist1"></dt> 2249<dd> 2250<p><strong>textureBuffer</strong> <strong>itextureBuffer</strong> <strong>utextureBuffer</strong></p> 2251</dd> 2252<dt class="hdlist1"></dt> 2253<dd> 2254<p><strong>sampler</strong> <strong>samplerShadow</strong></p> 2255</dd> 2256<dt class="hdlist1"></dt> 2257<dd> 2258<p><strong>subpassInput</strong> <strong>isubpassInput</strong> <strong>usubpassInput</strong></p> 2259</dd> 2260<dt class="hdlist1"></dt> 2261<dd> 2262<p><strong>subpassInputMS</strong> <strong>isubpassInputMS</strong> <strong>usubpassInputMS</strong></p> 2263</dd> 2264</dl> 2265</div> 2266<div class="paragraph"> 2267<p>The following are the keywords reserved for future use. 2268Using them will result in a compile-time error:</p> 2269</div> 2270<div class="dlist"> 2271<dl> 2272<dt class="hdlist1"></dt> 2273<dd> 2274<p><strong>common</strong> <strong>partition</strong> <strong>active</strong></p> 2275</dd> 2276<dt class="hdlist1"></dt> 2277<dd> 2278<p><strong>asm</strong></p> 2279</dd> 2280<dt class="hdlist1"></dt> 2281<dd> 2282<p><strong>class</strong> <strong>union</strong> <strong>enum</strong> <strong>typedef</strong> <strong>template</strong> <strong>this</strong></p> 2283</dd> 2284<dt class="hdlist1"></dt> 2285<dd> 2286<p><strong>resource</strong></p> 2287</dd> 2288<dt class="hdlist1"></dt> 2289<dd> 2290<p><strong>goto</strong></p> 2291</dd> 2292<dt class="hdlist1"></dt> 2293<dd> 2294<p><strong>inline</strong> <strong>noinline</strong> <strong>public</strong> <strong>static</strong> <strong>extern</strong> <strong>external</strong> <strong>interface</strong></p> 2295</dd> 2296<dt class="hdlist1"></dt> 2297<dd> 2298<p><strong>long</strong> <strong>short</strong> <strong>half</strong> <strong>fixed</strong> <strong>unsigned</strong> <strong>superp</strong></p> 2299</dd> 2300<dt class="hdlist1"></dt> 2301<dd> 2302<p><strong>input</strong> <strong>output</strong></p> 2303</dd> 2304<dt class="hdlist1"></dt> 2305<dd> 2306<p><strong>hvec2</strong> <strong>hvec3</strong> <strong>hvec4</strong> <strong>fvec2</strong> <strong>fvec3</strong> <strong>fvec4</strong></p> 2307</dd> 2308<dt class="hdlist1"></dt> 2309<dd> 2310<p><strong>filter</strong></p> 2311</dd> 2312<dt class="hdlist1"></dt> 2313<dd> 2314<p><strong>sizeof</strong> <strong>cast</strong></p> 2315</dd> 2316<dt class="hdlist1"></dt> 2317<dd> 2318<p><strong>namespace</strong> <strong>using</strong></p> 2319</dd> 2320<dt class="hdlist1"></dt> 2321<dd> 2322<p><strong>sampler3DRect</strong></p> 2323</dd> 2324</dl> 2325</div> 2326<div class="paragraph"> 2327<p>In addition, all identifiers containing two consecutive underscores (__) 2328are reserved for use by underlying software layers. 2329Defining such a name in a shader does not itself result in an error, but may 2330result in unintended behaviors that stem from having multiple definitions of 2331the same name.</p> 2332</div> 2333</div> 2334<div class="sect2"> 2335<h3 id="identifiers">3.7. Identifiers</h3> 2336<div class="paragraph"> 2337<p>Identifiers are used for variable names, function names, structure names, 2338and field selectors (field selectors select components of 2339<code><a href="#vector-components">vectors</a></code> and <code><a href="#matrix-components">matrices</a></code>, 2340similarly to structure members). 2341Identifiers have the form:</p> 2342</div> 2343<div class="openblock bnf"> 2344<div class="content"> 2345<div class="dlist"> 2346<dl> 2347<dt class="hdlist1"><em>identifier</em> : </dt> 2348<dd> 2349<p><em>nondigit</em><br> 2350<em>identifier</em> <em>nondigit</em><br> 2351<em>identifier</em> <em>digit</em></p> 2352</dd> 2353<dt class="hdlist1"><em>nondigit</em> : one of </dt> 2354<dd> 2355<p><strong>_</strong> <strong>a b c d e f g h i j k l m n o p q r s t u v w x y z</strong><br> 2356<strong>A B C D E F G H I J K L M N O P Q R S T U V W X Y Z</strong></p> 2357</dd> 2358<dt class="hdlist1"><em>digit</em> : one of </dt> 2359<dd> 2360<p><strong>0 1 2 3 4 5 6 7 8 9</strong></p> 2361</dd> 2362</dl> 2363</div> 2364</div> 2365</div> 2366<div class="paragraph"> 2367<p>Identifiers starting with “gl_” are reserved, and 2368in general, may not be declared in a shader; 2369this results in a compile-time error. 2370However, as noted in the specification, there are some cases where 2371previously declared variables can be redeclared, and predeclared “gl_” 2372names are allowed to be redeclared in a shader only for these specific 2373purposes.</p> 2374</div> 2375<div class="paragraph"> 2376<p>Implementations must support identifier lengths of up to 1024 characters. 2377Implementations are allowed to generate an error for an identifier of length 2378greater than 1024 characters, but are also allowed to support lengths 2379greater than 1024.</p> 2380</div> 2381</div> 2382<div class="sect2"> 2383<h3 id="definitions">3.8. Definitions</h3> 2384<div class="paragraph"> 2385<p>Some language rules described below depend on the following definitions.</p> 2386</div> 2387<div class="sect3"> 2388<h4 id="static-use">3.8.1. Static Use</h4> 2389<div class="paragraph"> 2390<p>A shader contains a <em>static use</em> of a variable <em>x</em> if, after preprocessing, 2391the shader contains a statement that would access any part of <em>x</em>, 2392whether or not flow of control will cause that statement to be executed. 2393Such a variable is referred to as being <em>statically used</em>. If the access is a 2394write then <em>x</em> is further said to be <em>statically assigned</em>.</p> 2395</div> 2396</div> 2397<div class="sect3"> 2398<h4 id="dynamically-uniform-expressions-and-uniform-control-flow">3.8.2. Dynamically Uniform Expressions and Uniform Control Flow</h4> 2399<div class="paragraph"> 2400<p>Some operations require an expression to be <em>dynamically uniform</em>, or that 2401it be located in <em>uniform control flow</em>. 2402These requirements are defined by the following set of definitions.</p> 2403</div> 2404<div class="paragraph"> 2405<p>An <em>invocation</em> is a single execution of <em>main()</em> for a particular stage, 2406operating only on the amount of data explicitly exposed within that stage’s 2407shaders. 2408(Any implicit operation on additional instances of data would comprise 2409additional invocations.) For example, in compute execution models, a single 2410invocation operates only on a single work item, or, in a vertex execution 2411model, a single invocation operates only on a single vertex.</p> 2412</div> 2413<div class="paragraph"> 2414<p>An <em>invocation group</em> is the complete set of invocations collectively 2415processing a particular compute workgroup or graphical operation, where the 2416scope of a "graphical operation" is implementation-dependent, but at least 2417as large as a single triangle or patch, and at most as large as a single 2418rendering command, as defined by the client API.</p> 2419</div> 2420<div class="paragraph"> 2421<p>Within a single invocation, a single shader statement can be executed 2422multiple times, giving multiple <em>dynamic instances</em> of that instruction. 2423This can happen when the instruction is executed in a loop, or in a function 2424called from multiple call sites, or combinations of multiple of these. 2425Different loop iterations and different dynamic function-call-site chains 2426yield different dynamic instances of such an instruction. 2427Dynamic instances are distinguished by their control-flow path within an 2428invocation, not by which invocation executed it. 2429That is, different invocations of <em>main()</em> execute the same dynamic 2430instances of an instruction when they follow the same control-flow path.</p> 2431</div> 2432<div class="paragraph"> 2433<p>An expression is <em>dynamically uniform</em> for a dynamic instance consuming it 2434when its value is the same for all invocations (in the invocation group) 2435that execute that dynamic instance.</p> 2436</div> 2437<div class="paragraph"> 2438<p><em>Uniform control flow</em> (or converged control flow) occurs when all 2439invocations in the invocation group execute the same control-flow path (and 2440hence the same sequence of dynamic instances of instructions). 2441Uniform control flow is the initial state at the entry into <em>main()</em>, and 2442lasts until a conditional branch takes different control paths for different 2443invocations (non-uniform or divergent control flow). 2444Such divergence can reconverge, with all the invocations once again 2445executing the same control-flow path, and this re-establishes the existence 2446of uniform control flow. 2447If control flow is uniform upon entry into a selection or loop, and all 2448invocations in the invocation group subsequently leave that selection or 2449loop, then control flow reconverges to be uniform.</p> 2450</div> 2451<div class="paragraph"> 2452<p>For example:</p> 2453</div> 2454<div class="listingblock"> 2455<div class="content"> 2456<pre class="CodeRay highlight"><code data-lang="c++">main() 2457{ 2458 <span class="predefined-type">float</span> a = ...; <span class="comment">// this is uniform control flow</span> 2459 <span class="keyword">if</span> (a < b) { <span class="comment">// this expression is true for some fragments, not all</span> 2460 ...; <span class="comment">// non-uniform control flow</span> 2461 } <span class="keyword">else</span> { 2462 ...; <span class="comment">// non-uniform control flow</span> 2463 } 2464 ...; <span class="comment">// uniform control flow again</span> 2465}</code></pre> 2466</div> 2467</div> 2468<div class="paragraph"> 2469<p>Note that constant expressions are trivially dynamically uniform. 2470It follows that typical loop counters based on these are also dynamically 2471uniform.</p> 2472</div> 2473</div> 2474</div> 2475</div> 2476</div> 2477<div class="sect1"> 2478<h2 id="variables-and-types">4. Variables and Types</h2> 2479<div class="sectionbody"> 2480<div class="paragraph"> 2481<p>All variables and functions must be declared before being used. 2482Variable and function names are identifiers.</p> 2483</div> 2484<div class="paragraph"> 2485<p>There are no default types. 2486All variable and function declarations must have a declared type, and 2487optionally qualifiers. 2488A variable is declared by specifying its type followed by one or more names 2489separated by commas. 2490In many cases, a variable can be initialized as part of its declaration by 2491using the assignment operator (<strong>=</strong>).</p> 2492</div> 2493<div class="paragraph"> 2494<p>User-defined types may be defined using <strong>struct</strong> to aggregate a list of 2495existing types into a single name.</p> 2496</div> 2497<div class="paragraph"> 2498<p>The OpenGL Shading Language is type safe. 2499There are some implicit conversions between types. 2500Exactly how and when this can occur is described in section 2501“<a href="#implicit-conversions">Implicit Conversions</a>” and as referenced by other 2502sections in this specification.</p> 2503</div> 2504<div class="sect2"> 2505<h3 id="basic-types">4.1. Basic Types</h3> 2506<div class="dlist"> 2507<dl> 2508<dt class="hdlist1">Definition</dt> 2509<dd> 2510<p>A <em>basic type</em> is a type defined by a keyword in the language.</p> 2511</dd> 2512</dl> 2513</div> 2514<div class="paragraph"> 2515<p>The OpenGL Shading Language supports the following basic data types, grouped as follows.</p> 2516</div> 2517<div class="paragraph"> 2518<p><strong>Transparent Types</strong></p> 2519</div> 2520<table class="tableblock frame-all grid-all stretch"> 2521<colgroup> 2522<col style="width: 50%;"> 2523<col style="width: 50%;"> 2524</colgroup> 2525<thead> 2526<tr> 2527<th class="tableblock halign-left valign-top">Type</th> 2528<th class="tableblock halign-left valign-top">Meaning</th> 2529</tr> 2530</thead> 2531<tbody> 2532<tr> 2533<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>void</strong></p></td> 2534<td class="tableblock halign-left valign-top"><p class="tableblock">for functions that do not return a value</p></td> 2535</tr> 2536<tr> 2537<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>bool</strong></p></td> 2538<td class="tableblock halign-left valign-top"><p class="tableblock">a conditional type, taking on values of true or false</p></td> 2539</tr> 2540<tr> 2541<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>int</strong></p></td> 2542<td class="tableblock halign-left valign-top"><p class="tableblock">a signed integer</p></td> 2543</tr> 2544<tr> 2545<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uint</strong></p></td> 2546<td class="tableblock halign-left valign-top"><p class="tableblock">an unsigned integer</p></td> 2547</tr> 2548<tr> 2549<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>float</strong></p></td> 2550<td class="tableblock halign-left valign-top"><p class="tableblock">a single-precision floating-point scalar</p></td> 2551</tr> 2552<tr> 2553<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>double</strong></p></td> 2554<td class="tableblock halign-left valign-top"><p class="tableblock">a double-precision floating-point scalar</p></td> 2555</tr> 2556<tr> 2557<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>vec2</strong></p></td> 2558<td class="tableblock halign-left valign-top"><p class="tableblock">a two-component single-precision floating-point vector</p></td> 2559</tr> 2560<tr> 2561<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>vec3</strong></p></td> 2562<td class="tableblock halign-left valign-top"><p class="tableblock">a three-component single-precision floating-point vector</p></td> 2563</tr> 2564<tr> 2565<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>vec4</strong></p></td> 2566<td class="tableblock halign-left valign-top"><p class="tableblock">a four-component single-precision floating-point vector</p></td> 2567</tr> 2568<tr> 2569<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dvec2</strong></p></td> 2570<td class="tableblock halign-left valign-top"><p class="tableblock">a two-component double-precision floating-point vector</p></td> 2571</tr> 2572<tr> 2573<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dvec3</strong></p></td> 2574<td class="tableblock halign-left valign-top"><p class="tableblock">a three-component double-precision floating-point vector</p></td> 2575</tr> 2576<tr> 2577<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dvec4</strong></p></td> 2578<td class="tableblock halign-left valign-top"><p class="tableblock">a four-component double-precision floating-point vector</p></td> 2579</tr> 2580<tr> 2581<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>bvec2</strong></p></td> 2582<td class="tableblock halign-left valign-top"><p class="tableblock">a two-component Boolean vector</p></td> 2583</tr> 2584<tr> 2585<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>bvec3</strong></p></td> 2586<td class="tableblock halign-left valign-top"><p class="tableblock">a three-component Boolean vector</p></td> 2587</tr> 2588<tr> 2589<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>bvec4</strong></p></td> 2590<td class="tableblock halign-left valign-top"><p class="tableblock">a four-component Boolean vector</p></td> 2591</tr> 2592<tr> 2593<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec2</strong></p></td> 2594<td class="tableblock halign-left valign-top"><p class="tableblock">a two-component signed integer vector</p></td> 2595</tr> 2596<tr> 2597<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec3</strong></p></td> 2598<td class="tableblock halign-left valign-top"><p class="tableblock">a three-component signed integer vector</p></td> 2599</tr> 2600<tr> 2601<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec4</strong></p></td> 2602<td class="tableblock halign-left valign-top"><p class="tableblock">a four-component signed integer vector</p></td> 2603</tr> 2604<tr> 2605<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uvec2</strong></p></td> 2606<td class="tableblock halign-left valign-top"><p class="tableblock">a two-component unsigned integer vector</p></td> 2607</tr> 2608<tr> 2609<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uvec3</strong></p></td> 2610<td class="tableblock halign-left valign-top"><p class="tableblock">a three-component unsigned integer vector</p></td> 2611</tr> 2612<tr> 2613<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uvec4</strong></p></td> 2614<td class="tableblock halign-left valign-top"><p class="tableblock">a four-component unsigned integer vector</p></td> 2615</tr> 2616<tr> 2617<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat2</strong></p></td> 2618<td class="tableblock halign-left valign-top"><p class="tableblock">a 2 × 2 single-precision floating-point matrix</p></td> 2619</tr> 2620<tr> 2621<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat3</strong></p></td> 2622<td class="tableblock halign-left valign-top"><p class="tableblock">a 3 × 3 single-precision floating-point matrix</p></td> 2623</tr> 2624<tr> 2625<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat4</strong></p></td> 2626<td class="tableblock halign-left valign-top"><p class="tableblock">a 4 × 4 single-precision floating-point matrix</p></td> 2627</tr> 2628<tr> 2629<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat2x2</strong></p></td> 2630<td class="tableblock halign-left valign-top"><p class="tableblock">same as a <strong>mat2</strong></p></td> 2631</tr> 2632<tr> 2633<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat2x3</strong></p></td> 2634<td class="tableblock halign-left valign-top"><p class="tableblock">a single-precision floating-point matrix with 2 columns and 3 rows</p></td> 2635</tr> 2636<tr> 2637<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat2x4</strong></p></td> 2638<td class="tableblock halign-left valign-top"><p class="tableblock">a single-precision floating-point matrix with 2 columns and 4 rows</p></td> 2639</tr> 2640<tr> 2641<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat3x2</strong></p></td> 2642<td class="tableblock halign-left valign-top"><p class="tableblock">a single-precision floating-point matrix with 3 columns and 2 rows</p></td> 2643</tr> 2644<tr> 2645<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat3x3</strong></p></td> 2646<td class="tableblock halign-left valign-top"><p class="tableblock">same as a <strong>mat3</strong></p></td> 2647</tr> 2648<tr> 2649<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat3x4</strong></p></td> 2650<td class="tableblock halign-left valign-top"><p class="tableblock">a single-precision floating-point matrix with 3 columns and 4 rows</p></td> 2651</tr> 2652<tr> 2653<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat4x2</strong></p></td> 2654<td class="tableblock halign-left valign-top"><p class="tableblock">a single-precision floating-point matrix with 4 columns and 2 rows</p></td> 2655</tr> 2656<tr> 2657<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat4x3</strong></p></td> 2658<td class="tableblock halign-left valign-top"><p class="tableblock">a single-precision floating-point matrix with 4 columns and 3 rows</p></td> 2659</tr> 2660<tr> 2661<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat4x4</strong></p></td> 2662<td class="tableblock halign-left valign-top"><p class="tableblock">same as a <strong>mat4</strong></p></td> 2663</tr> 2664<tr> 2665<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat2</strong></p></td> 2666<td class="tableblock halign-left valign-top"><p class="tableblock">a 2 × 2 double-precision floating-point matrix</p></td> 2667</tr> 2668<tr> 2669<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat3</strong></p></td> 2670<td class="tableblock halign-left valign-top"><p class="tableblock">a 3 × 3 double-precision floating-point matrix</p></td> 2671</tr> 2672<tr> 2673<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat4</strong></p></td> 2674<td class="tableblock halign-left valign-top"><p class="tableblock">a 4 × 4 double-precision floating-point matrix</p></td> 2675</tr> 2676<tr> 2677<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat2x2</strong></p></td> 2678<td class="tableblock halign-left valign-top"><p class="tableblock">same as a <strong>dmat2</strong></p></td> 2679</tr> 2680<tr> 2681<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat2x3</strong></p></td> 2682<td class="tableblock halign-left valign-top"><p class="tableblock">a double-precision floating-point matrix with 2 columns and 3 rows</p></td> 2683</tr> 2684<tr> 2685<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat2x4</strong></p></td> 2686<td class="tableblock halign-left valign-top"><p class="tableblock">a double-precision floating-point matrix with 2 columns and 4 rows</p></td> 2687</tr> 2688<tr> 2689<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat3x2</strong></p></td> 2690<td class="tableblock halign-left valign-top"><p class="tableblock">a double-precision floating-point matrix with 3 columns and 2 rows</p></td> 2691</tr> 2692<tr> 2693<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat3x3</strong></p></td> 2694<td class="tableblock halign-left valign-top"><p class="tableblock">same as a <strong>dmat3</strong></p></td> 2695</tr> 2696<tr> 2697<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat3x4</strong></p></td> 2698<td class="tableblock halign-left valign-top"><p class="tableblock">a double-precision floating-point matrix with 3 columns and 4 rows</p></td> 2699</tr> 2700<tr> 2701<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat4x2</strong></p></td> 2702<td class="tableblock halign-left valign-top"><p class="tableblock">a double-precision floating-point matrix with 4 columns and 2 rows</p></td> 2703</tr> 2704<tr> 2705<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat4x3</strong></p></td> 2706<td class="tableblock halign-left valign-top"><p class="tableblock">a double-precision floating-point matrix with 4 columns and 3 rows</p></td> 2707</tr> 2708<tr> 2709<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat4x4</strong></p></td> 2710<td class="tableblock halign-left valign-top"><p class="tableblock">same as a <strong>dmat4</strong></p></td> 2711</tr> 2712</tbody> 2713</table> 2714<div class="paragraph"> 2715<p>Note that where the following tables say “accessing a texture”, the 2716<strong>sampler*</strong> opaque types access textures, and the <strong>image*</strong> opaque types 2717access images, of a specified type.</p> 2718</div> 2719<div class="paragraph"> 2720<p><strong>Floating-Point Opaque Types</strong></p> 2721</div> 2722<table class="tableblock frame-all grid-all stretch"> 2723<colgroup> 2724<col style="width: 50%;"> 2725<col style="width: 50%;"> 2726</colgroup> 2727<thead> 2728<tr> 2729<th class="tableblock halign-left valign-top">Type</th> 2730<th class="tableblock halign-left valign-top">Meaning</th> 2731</tr> 2732</thead> 2733<tbody> 2734<tr> 2735<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler1D</strong><br> 2736 <strong>texture1D</strong><br> 2737 <strong>image1D</strong></p></td> 2738<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 1D texture</p></td> 2739</tr> 2740<tr> 2741<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler1DShadow</strong></p></td> 2742<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 1D depth texture with comparison</p></td> 2743</tr> 2744<tr> 2745<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler1DArray</strong><br> 2746 <strong>texture1DArray</strong><br> 2747 <strong>image1DArray</strong></p></td> 2748<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 1D array texture</p></td> 2749</tr> 2750<tr> 2751<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler1DArrayShadow</strong></p></td> 2752<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 1D array depth texture with comparison</p></td> 2753</tr> 2754<tr> 2755<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2D</strong><br> 2756 <strong>texture2D</strong><br> 2757 <strong>image2D</strong></p></td> 2758<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 2D texture</p></td> 2759</tr> 2760<tr> 2761<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2DShadow</strong></p></td> 2762<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 2D depth texture with comparison</p></td> 2763</tr> 2764<tr> 2765<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2DArray</strong><br> 2766 <strong>texture2DArray</strong><br> 2767 <strong>image2DArray</strong></p></td> 2768<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 2D array texture</p></td> 2769</tr> 2770<tr> 2771<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2DArrayShadow</strong></p></td> 2772<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 2D array depth texture with comparison</p></td> 2773</tr> 2774<tr> 2775<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2DMS</strong><br> 2776 <strong>texture2DMS</strong><br> 2777 <strong>image2DMS</strong></p></td> 2778<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 2D multisample texture</p></td> 2779</tr> 2780<tr> 2781<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2DMSArray</strong><br> 2782 <strong>texture2DMSArray</strong><br> 2783 <strong>image2DMSArray</strong></p></td> 2784<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 2D multisample array texture</p></td> 2785</tr> 2786<tr> 2787<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2DRect</strong><br> 2788 <strong>texture2DRect</strong><br> 2789 <strong>image2DRect</strong></p></td> 2790<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a rectangle texture</p></td> 2791</tr> 2792<tr> 2793<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler2DRectShadow</strong></p></td> 2794<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a rectangle texture with comparison</p></td> 2795</tr> 2796<tr> 2797<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler3D</strong><br> 2798 <strong>texture3D</strong><br> 2799 <strong>image3D</strong></p></td> 2800<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a 3D texture</p></td> 2801</tr> 2802<tr> 2803<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>samplerCube</strong><br> 2804 <strong>textureCube</strong><br> 2805 <strong>imageCube</strong></p></td> 2806<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a cube mapped texture</p></td> 2807</tr> 2808<tr> 2809<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>samplerCubeShadow</strong></p></td> 2810<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a cube map depth texture with comparison</p></td> 2811</tr> 2812<tr> 2813<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>samplerCubeArray</strong><br> 2814 <strong>textureCubeArray</strong><br> 2815 <strong>imageCubeArray</strong></p></td> 2816<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a cube map array texture</p></td> 2817</tr> 2818<tr> 2819<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>samplerCubeArrayShadow</strong></p></td> 2820<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a cube map array depth texture with comparison</p></td> 2821</tr> 2822<tr> 2823<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>samplerBuffer</strong><br> 2824 <strong>textureBuffer</strong><br> 2825 <strong>imageBuffer</strong></p></td> 2826<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a buffer texture</p></td> 2827</tr> 2828<tr> 2829<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>subpassInput</strong></p></td> 2830<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a floating-point subpass input</p></td> 2831</tr> 2832<tr> 2833<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>subpassInputMS</strong></p></td> 2834<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a multi-sampled floating-point subpass input</p></td> 2835</tr> 2836</tbody> 2837</table> 2838<div class="paragraph"> 2839<p><strong>Signed Integer Opaque Types</strong></p> 2840</div> 2841<table class="tableblock frame-all grid-all stretch"> 2842<colgroup> 2843<col style="width: 50%;"> 2844<col style="width: 50%;"> 2845</colgroup> 2846<thead> 2847<tr> 2848<th class="tableblock halign-left valign-top">Type</th> 2849<th class="tableblock halign-left valign-top">Meaning</th> 2850</tr> 2851</thead> 2852<tbody> 2853<tr> 2854<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler1D</strong><br> 2855 <strong>itexture1D</strong><br> 2856 <strong>iimage1D</strong></p></td> 2857<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 1D texture</p></td> 2858</tr> 2859<tr> 2860<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler1DArray</strong><br> 2861 <strong>itexture1DArray</strong><br> 2862 <strong>iimage1DArray</strong></p></td> 2863<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 1D array texture</p></td> 2864</tr> 2865<tr> 2866<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler2D</strong><br> 2867 <strong>itexture2D</strong><br> 2868 <strong>iimage2D</strong></p></td> 2869<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 2D texture</p></td> 2870</tr> 2871<tr> 2872<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler2DArray</strong><br> 2873 <strong>itexture2DArray</strong><br> 2874 <strong>iimage2DArray</strong></p></td> 2875<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 2D array texture</p></td> 2876</tr> 2877<tr> 2878<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler2DMS</strong><br> 2879 <strong>itexture2DMS</strong><br> 2880 <strong>iimage2DMS</strong></p></td> 2881<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 2D multisample texture</p></td> 2882</tr> 2883<tr> 2884<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler2DMSArray</strong><br> 2885 <strong>itexture2DMSArray</strong><br> 2886 <strong>iimage2DMSArray</strong></p></td> 2887<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 2D multisample array texture</p></td> 2888</tr> 2889<tr> 2890<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler2DRect</strong><br> 2891 <strong>itexture2DRect</strong><br> 2892 <strong>iimage2DRect</strong></p></td> 2893<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 2D rectangle texture</p></td> 2894</tr> 2895<tr> 2896<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isampler3D</strong><br> 2897 <strong>itexture3D</strong><br> 2898 <strong>iimage3D</strong></p></td> 2899<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer 3D texture</p></td> 2900</tr> 2901<tr> 2902<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isamplerCube</strong><br> 2903 <strong>itextureCube</strong><br> 2904 <strong>iimageCube</strong></p></td> 2905<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer cube mapped texture</p></td> 2906</tr> 2907<tr> 2908<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isamplerCubeArray</strong><br> 2909 <strong>itextureCubeArray</strong><br> 2910 <strong>iimageCubeArray</strong></p></td> 2911<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer cube map array texture</p></td> 2912</tr> 2913<tr> 2914<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isamplerBuffer</strong><br> 2915 <strong>itextureBuffer</strong><br> 2916 <strong>iimageBuffer</strong></p></td> 2917<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer buffer texture</p></td> 2918</tr> 2919<tr> 2920<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isubpassInput</strong></p></td> 2921<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an integer subpass input</p></td> 2922</tr> 2923<tr> 2924<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>isubpassInputMS</strong></p></td> 2925<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a multi-sampled integer subpass input</p></td> 2926</tr> 2927</tbody> 2928</table> 2929<div class="paragraph"> 2930<p><strong>Unsigned Integer Opaque Types</strong></p> 2931</div> 2932<table class="tableblock frame-all grid-all stretch"> 2933<colgroup> 2934<col style="width: 50%;"> 2935<col style="width: 50%;"> 2936</colgroup> 2937<thead> 2938<tr> 2939<th class="tableblock halign-left valign-top">Type</th> 2940<th class="tableblock halign-left valign-top">Meaning</th> 2941</tr> 2942</thead> 2943<tbody> 2944<tr> 2945<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler1D</strong><br> 2946 <strong>utexture1D</strong><br> 2947 <strong>uimage1D</strong></p></td> 2948<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer 1D texture</p></td> 2949</tr> 2950<tr> 2951<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler1DArray</strong><br> 2952 <strong>utexture1DArray</strong><br> 2953 <strong>uimage1DArray</strong></p></td> 2954<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer 1D array texture</p></td> 2955</tr> 2956<tr> 2957<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler2D</strong><br> 2958 <strong>utexture2D</strong><br> 2959 <strong>uimage2D</strong></p></td> 2960<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer 2D texture</p></td> 2961</tr> 2962<tr> 2963<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler2DArray</strong><br> 2964 <strong>utexture1DArray</strong><br> 2965 <strong>uimage2DArray</strong></p></td> 2966<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer 2D array texture</p></td> 2967</tr> 2968<tr> 2969<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler2DMS</strong><br> 2970 <strong>utexture2DMS</strong><br> 2971 <strong>uimage2DMS</strong></p></td> 2972<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer 2D multisample texture</p></td> 2973</tr> 2974<tr> 2975<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler2DMSArray</strong><br> 2976 <strong>utexture2DMSArray</strong><br> 2977 <strong>uimage2DMSArray</strong></p></td> 2978<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer 2D multisample array texture</p></td> 2979</tr> 2980<tr> 2981<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler2DRect</strong><br> 2982 <strong>utexture2DRect</strong><br> 2983 <strong>uimage2DRect</strong></p></td> 2984<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer rectangle texture</p></td> 2985</tr> 2986<tr> 2987<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usampler3D</strong><br> 2988 <strong>utexture3D</strong><br> 2989 <strong>uimage3D</strong></p></td> 2990<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer 3D texture</p></td> 2991</tr> 2992<tr> 2993<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usamplerCube</strong><br> 2994 <strong>utextureCube</strong><br> 2995 <strong>uimageCube</strong></p></td> 2996<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer cube mapped texture</p></td> 2997</tr> 2998<tr> 2999<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usamplerCubeArray</strong><br> 3000 <strong>utextureCubeArray</strong><br> 3001 <strong>uimageCubeArray</strong></p></td> 3002<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer cube map array texture</p></td> 3003</tr> 3004<tr> 3005<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usamplerBuffer</strong><br> 3006 <strong>utextureBuffer</strong><br> 3007 <strong>uimageBuffer</strong></p></td> 3008<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer buffer texture</p></td> 3009</tr> 3010<tr> 3011<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>atomic_uint</strong></p></td> 3012<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned integer atomic counter</p></td> 3013</tr> 3014<tr> 3015<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usubpassInput</strong></p></td> 3016<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing an unsigned-integer subpass input</p></td> 3017</tr> 3018<tr> 3019<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>usubpassInputMS</strong></p></td> 3020<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing a multi-sampled unsigned-integer subpass input</p></td> 3021</tr> 3022</tbody> 3023</table> 3024<div class="paragraph"> 3025<p><strong>Sampler Opaque Types</strong></p> 3026</div> 3027<table class="tableblock frame-all grid-all stretch"> 3028<colgroup> 3029<col style="width: 50%;"> 3030<col style="width: 50%;"> 3031</colgroup> 3032<thead> 3033<tr> 3034<th class="tableblock halign-left valign-top">Type</th> 3035<th class="tableblock halign-left valign-top">Meaning</th> 3036</tr> 3037</thead> 3038<tbody> 3039<tr> 3040<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sampler</strong></p></td> 3041<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing state describing how to sample a texture</p></td> 3042</tr> 3043<tr> 3044<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>samplerShadow</strong></p></td> 3045<td class="tableblock halign-left valign-top"><p class="tableblock">a handle for accessing state describing how to sample a depth 3046 texture with comparison</p></td> 3047</tr> 3048</tbody> 3049</table> 3050<div class="paragraph"> 3051<p>In addition, a shader can aggregate these basic types using arrays and 3052structures to build more complex types.</p> 3053</div> 3054<div class="paragraph"> 3055<p>There are no pointer types.</p> 3056</div> 3057<div class="paragraph"> 3058<p>In this specification, an <em>aggregate</em> will mean a structure or array. 3059(Matrices and vectors are not by themselves aggregates.) Aggregates, 3060matrices, and vectors will collectively be referred to as <em>composites</em>.</p> 3061</div> 3062<div class="sect3"> 3063<h4 id="void">4.1.1. Void</h4> 3064<div class="paragraph"> 3065<p>Functions that do not return a value must be declared as <strong>void</strong>. 3066There is no default function return type. 3067The keyword <strong>void</strong> cannot be used in any other declarations (except for 3068empty formal or actual parameter lists), or a compile-time error results.</p> 3069</div> 3070</div> 3071<div class="sect3"> 3072<h4 id="booleans">4.1.2. Booleans</h4> 3073<div class="dlist"> 3074<dl> 3075<dt class="hdlist1">Definition</dt> 3076<dd> 3077<p>A <em>boolean type</em> is any boolean scalar or vector type (<strong>bool</strong>, <strong>bvec2</strong>, 3078<strong>bvec3</strong>, <strong>bvec4</strong>)</p> 3079</dd> 3080</dl> 3081</div> 3082<div class="paragraph"> 3083<p>To make conditional execution of code easier to express, the type <strong>bool</strong> is 3084supported. 3085There is no expectation that hardware directly supports variables of this 3086type. 3087It is a genuine Boolean type, holding only one of two values meaning either 3088true or false. 3089Two keywords <strong>true</strong> and <strong>false</strong> can be used as literal Boolean constants. 3090Booleans are declared and optionally initialized as in the follow example:</p> 3091</div> 3092<div class="listingblock"> 3093<div class="content"> 3094<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">bool</span> success; <span class="comment">// declare "success" to be a Boolean</span> 3095<span class="predefined-type">bool</span> done = <span class="predefined-constant">false</span>; <span class="comment">// declare and initialize "done"</span></code></pre> 3096</div> 3097</div> 3098<div class="paragraph"> 3099<p>Expressions used for conditional jumps (<strong>if</strong>, <strong>for</strong>, <strong>?:</strong>, <strong>while</strong>, 3100<strong>do</strong>-<strong>while</strong>) must evaluate to the type <strong>bool</strong>.</p> 3101</div> 3102</div> 3103<div class="sect3"> 3104<h4 id="integers">4.1.3. Integers</h4> 3105<div class="dlist"> 3106<dl> 3107<dt class="hdlist1">Definitions</dt> 3108<dd> 3109<p>An <em>integral type</em> is any signed or unsigned, scalar or vector integer type. 3110It excludes arrays and structures.</p> 3111</dd> 3112<dt class="hdlist1"></dt> 3113<dd> 3114<p>A <em>scalar integral type</em> is a scalar signed or unsigned integer type:</p> 3115</dd> 3116<dt class="hdlist1"></dt> 3117<dd> 3118<p>A <em>vector integral type</em> is a vector of signed or unsigned integers:</p> 3119</dd> 3120</dl> 3121</div> 3122<div class="paragraph"> 3123<p>Signed and unsigned integer variables are fully supported. 3124In this document, the term <em>integer</em> is meant to generally include both 3125signed and unsigned integers.</p> 3126</div> 3127<div class="paragraph"> 3128<p>For OpenGL, unsigned integers have exactly 32 bits of precision. 3129When targeting Vulkan, <strong>highp</strong> 3130unsigned integers have exactly 32 bits of precision.</p> 3131</div> 3132<div class="paragraph"> 3133<p>For OpenGL, signed integers use 32 bits, including a sign bit, in two’s complement form. 3134When targeting Vulkan, <strong>highp</strong> 3135signed integers use 32 bits, including a sign bit, in two’s complement form.</p> 3136</div> 3137<div class="paragraph"> 3138<p>When targeting Vulkan, <strong>mediump</strong> and <strong>lowp</strong> integers are as defined by the 3139SPIR-V <strong>RelaxedPrecision</strong> decoration.</p> 3140</div> 3141<div class="paragraph"> 3142<p>Addition, 3143subtraction and multiplication resulting in overflow or 3144underflow will result in the low-order 314532 3146bits of the correct result R, where 3147R is computed with enough precision to avoid overflow or underflow. 3148Division resulting in overflow will result in an undefined value.</p> 3149</div> 3150<div class="paragraph"> 3151<p>Integers are declared and optionally initialized with integer expressions, 3152as in the following example:</p> 3153</div> 3154<div class="listingblock"> 3155<div class="content"> 3156<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">int</span> i, j = <span class="integer">42</span>; <span class="comment">// default integer literal type is int</span> 3157uint k = <span class="integer">3</span>u; <span class="comment">// "u" establishes the type as uint</span></code></pre> 3158</div> 3159</div> 3160<div class="paragraph"> 3161<p>Literal integer constants can be expressed in decimal (base 10), octal (base 31628), or hexadecimal (base 16) as follows.</p> 3163</div> 3164<div class="openblock bnf"> 3165<div class="content"> 3166<div class="dlist"> 3167<dl> 3168<dt class="hdlist1"><em>integer-constant</em> : </dt> 3169<dd> 3170<p><em>decimal-constant</em> <em>integer-suffix<sub>opt</sub></em><br> 3171<em>octal-constant</em> <em>integer-suffix<sub>opt</sub></em><br> 3172<em>hexadecimal-constant</em> <em>integer-suffix<sub>opt</sub></em></p> 3173</dd> 3174<dt class="hdlist1"><em>integer-suffix</em> : one of </dt> 3175<dd> 3176<p><strong>u</strong> <strong>U</strong></p> 3177</dd> 3178<dt class="hdlist1"><em>decimal-constant</em> : </dt> 3179<dd> 3180<p><em>nonzero-digit</em><br> 3181<em>decimal-constant</em> <em>digit</em></p> 3182</dd> 3183<dt class="hdlist1"><em>octal-constant</em> : </dt> 3184<dd> 3185<p><strong>0</strong><br> 3186<em>octal-constant</em> <em>octal-digit</em></p> 3187</dd> 3188<dt class="hdlist1"><em>hexadecimal-constant</em> : </dt> 3189<dd> 3190<p><strong>0x</strong> <em>hexadecimal-digit</em><br> 3191<strong>0X</strong> <em>hexadecimal-digit</em><br> 3192<em>hexadecimal-constant</em> <em>hexadecimal-digit</em></p> 3193</dd> 3194<dt class="hdlist1"><em>digit</em> : </dt> 3195<dd> 3196<p><strong>0</strong><br> 3197<em>nonzero-digit</em></p> 3198</dd> 3199<dt class="hdlist1"><em>nonzero-digit</em> : one of </dt> 3200<dd> 3201<p><strong>1 2 3 4 5 6 7 8 9</strong></p> 3202</dd> 3203<dt class="hdlist1"><em>octal-digit</em> : one of </dt> 3204<dd> 3205<p><strong>0 1 2 3 4 5 6 7</strong></p> 3206</dd> 3207<dt class="hdlist1"><em>hexadecimal-digit</em> : one of </dt> 3208<dd> 3209<p><strong>0 1 2 3 4 5 6 7 8 9<br> 3210a b c d e f<br> 3211A B C D E F</strong></p> 3212</dd> 3213</dl> 3214</div> 3215</div> 3216</div> 3217<div class="paragraph"> 3218<p>No white space is allowed between the digits of an integer constant, 3219including after the leading <strong>0</strong> or after the leading <strong>0x</strong> or <strong>0X</strong> of a 3220constant, or before the suffix <strong>u</strong> or <strong>U</strong>. 3221When tokenizing, the maximal token matching the above will be recognized 3222before a new token is started. 3223When the suffix <strong>u</strong> or <strong>U</strong> is present, the literal has type <strong>uint</strong>, 3224otherwise the type is <strong>int</strong>. 3225A leading unary minus sign (-) is interpreted as an arithmetic unary 3226negation, not as part of the constant. 3227Hence, literals themselves are always expressed with non-negative syntax, 3228though they could result in a negative value.</p> 3229</div> 3230<div class="paragraph"> 3231<p>It is a compile-time error to provide a literal integer whose bit pattern 3232cannot fit in 32 bits. 3233The bit pattern of the literal is always used unmodified. 3234So a signed literal whose bit pattern includes a set sign bit creates a 3235negative value.</p> 3236</div> 3237<div class="paragraph"> 3238<p>For example,</p> 3239</div> 3240<div class="listingblock"> 3241<div class="content"> 3242<pre class="CodeRay highlight"><code data-lang="c++"><span class="integer">1</span> <span class="comment">// OK. Signed integer, value 1</span> 3243<span class="integer">1</span>u <span class="comment">// OK. Unsigned integer, value 1</span> 3244-<span class="integer">1</span> <span class="comment">// OK. Unary minus applied to signed integer.</span> 3245 <span class="comment">// result is a signed integer, value -1</span> 3246-<span class="integer">1</span>u <span class="comment">// OK. Unary minus applies to unsigned integer.</span> 3247 <span class="comment">// Result is an unsigned integer, value 0xffffffff</span> 3248<span class="hex">0xA0000000</span> <span class="comment">// OK. 32-bit signed hexadecimal</span> 3249<span class="hex">0xABcdEF00</span>u <span class="comment">// OK. 32-bit unsigned hexadecimal</span> 3250<span class="hex">0xffffffff</span> <span class="comment">// OK. Signed integer, value -1</span> 3251<span class="hex">0x80000000</span> <span class="comment">// OK. Evaluates to -2147483648</span> 3252<span class="hex">0xffffffff</span>u <span class="comment">// OK. Unsigned integer, value 0xffffffff</span> 3253<span class="hex">0xfffffffff</span> <span class="comment">// Error: needs more than 32 bits</span> 3254<span class="integer">3000000000</span> <span class="comment">// OK. A signed decimal literal taking 32 bits.</span> 3255 <span class="comment">// It evaluates to -1294967296</span> 3256<span class="integer">2147483648</span> <span class="comment">// OK. Evaluates to -2147483648 (the literal set the sign bit)</span> 3257<span class="integer">5000000000</span> <span class="comment">// Error: needs more than 32 bits</span></code></pre> 3258</div> 3259</div> 3260</div> 3261<div class="sect3"> 3262<h4 id="floats">4.1.4. Floats</h4> 3263<div class="paragraph"> 3264<p>Single-precision and double-precision floating-point variables are available 3265for use in a variety of scalar calculations. 3266Generally, the term <em>floating-point</em> will refer to both single- and 3267double-precision floating-point. 3268Floating-point variables are defined as in the following examples:</p> 3269</div> 3270<div class="listingblock"> 3271<div class="content"> 3272<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> a, b = <span class="float">1</span><span class="float">.5</span>; <span class="comment">// single-precision floating-point</span> 3273<span class="predefined-type">double</span> c, d = <span class="float">2</span><span class="float">.0</span>LF; <span class="comment">// double-precision floating-point</span></code></pre> 3274</div> 3275</div> 3276<div class="paragraph"> 3277<p>As an input value to one of the processing units, a single-precision or 3278double-precision floating-point variable is expected to match the 3279corresponding IEEE 754 floating-point definition for precision and dynamic 3280range. 3281Floating-point variables within a shader are also encoded according to the 3282IEEE 754 specification for single-precision floating-point values</p> 3283</div> 3284<div class="paragraph"> 3285<p>(logically, not necessarily physically). 3286While encodings are logically IEEE 754, operations (addition, 3287multiplication, etc.) are not necessarily performed as required by IEEE 754. 3288See “<a href="#range-and-precision">Range and Precision</a>” for more details on 3289precision and usage of NaNs (Not a Number) and Infs (positive or negative 3290infinities).</p> 3291</div> 3292<div class="paragraph"> 3293<p>Floating-point constants are defined as follows.</p> 3294</div> 3295<div class="openblock bnf"> 3296<div class="content"> 3297<div class="dlist"> 3298<dl> 3299<dt class="hdlist1"><em>floating-constant</em> : </dt> 3300<dd> 3301<p><em>fractional-constant</em> <em>exponent-part<sub>opt</sub></em> <em>floating-suffix<sub>opt</sub></em><br> 3302<em>digit-sequence</em> <em>exponent-part</em> <em>floating-suffix<sub>opt</sub></em></p> 3303</dd> 3304<dt class="hdlist1"><em>fractional-constant</em> : </dt> 3305<dd> 3306<p><em>digit-sequence</em> <strong>.</strong> <em>digit-sequence</em><br> 3307<em>digit-sequence</em> <strong>.</strong><br> 3308<strong>.</strong> <em>digit-sequence</em></p> 3309</dd> 3310<dt class="hdlist1"><em>exponent-part</em> : </dt> 3311<dd> 3312<p><strong>e</strong> <em>sign<sub>opt</sub></em> <em>digit-sequence</em><br> 3313<strong>E</strong> <em>sign<sub>opt</sub></em> <em>digit-sequence</em></p> 3314</dd> 3315<dt class="hdlist1"><em>sign</em> : one of </dt> 3316<dd> 3317<p><strong>+</strong> <strong>-</strong></p> 3318</dd> 3319<dt class="hdlist1"><em>digit-sequence</em> : </dt> 3320<dd> 3321<p><em>digit</em><br> 3322<em>digit-sequence</em> <em>digit</em></p> 3323</dd> 3324<dt class="hdlist1"><em>floating-suffix</em> : one of </dt> 3325<dd> 3326<p> <strong>f</strong> <strong>F</strong> 3327<strong>lf</strong> <strong>LF</strong></p> 3328</dd> 3329</dl> 3330</div> 3331</div> 3332</div> 3333<div class="paragraph"> 3334<p>A decimal point (<strong>.</strong>) is not needed if the exponent part is present. 3335No white space may appear anywhere within a floating-point constant, 3336including before a suffix. 3337When tokenizing, the maximal token matching the above will be recognized 3338before a new token is started. 3339When the suffix "lf" or "LF" is present, the literal has type <strong>double</strong>. 3340Otherwise, the literal has type <strong>float</strong>. 3341A leading unary minus sign (<strong>-</strong>) is interpreted as a unary operator and is 3342not part of the floating-point constant.</p> 3343</div> 3344</div> 3345<div class="sect3"> 3346<h4 id="vectors">4.1.5. Vectors</h4> 3347<div class="paragraph"> 3348<p>The OpenGL Shading Language includes data types for generic 2-, 3-, and 4-component vectors 3349of floating-point values, integers, and Booleans. 3350Floating-point vector variables can be used to store colors, normals, 3351positions, texture coordinates, texture lookup results and the like. 3352Boolean vectors can be used for component-wise comparisons of numeric 3353vectors. 3354Some examples of vector declarations are:</p> 3355</div> 3356<div class="listingblock"> 3357<div class="content"> 3358<pre class="CodeRay highlight"><code data-lang="c++">vec2 texcoord1, texcoord2; 3359vec3 position; 3360vec4 myRGBA; 3361ivec2 textureLookup; 3362bvec3 less;</code></pre> 3363</div> 3364</div> 3365<div class="paragraph"> 3366<p>Initialization of vectors can be done with constructors. 3367See “<a href="#vector-and-matrix-constructors">Vector and Matrix Constructors</a>”.</p> 3368</div> 3369</div> 3370<div class="sect3"> 3371<h4 id="matrices">4.1.6. Matrices</h4> 3372<div class="paragraph"> 3373<p>The OpenGL Shading Language has built-in types for 2 × 2, 2 × 3, 2 × 4, 3 3374× 2, 3 × 3, 3 × 4, 4 × 2, 4 × 3, and 4 × 33754 matrices of floating-point numbers. 3376Matrix types beginning with "<strong>mat</strong>" have single-precision components while 3377matrix types beginning with "<strong>dmat</strong>" have double-precision components. 3378The first number in the type is the number of columns, the second is the 3379number of rows. 3380If there is only one number, the matrix is square. 3381Example matrix declarations:</p> 3382</div> 3383<div class="listingblock"> 3384<div class="content"> 3385<pre class="CodeRay highlight"><code data-lang="c++">mat2 mat2D; 3386mat3 optMatrix; 3387mat4 view, projection; 3388mat4x4 view; <span class="comment">// an alternate way of declaring a mat4</span> 3389mat3x2 m; <span class="comment">// a matrix with 3 columns and 2 rows</span> 3390dmat4 highPrecisionMVP; 3391dmat2x4 dm;</code></pre> 3392</div> 3393</div> 3394<div class="paragraph"> 3395<p>Initialization of matrix values is done with constructors (described in 3396“<a href="#vector-and-matrix-constructors">Vector and Matrix Constructors</a>”) in 3397column-major order.</p> 3398</div> 3399</div> 3400<div class="sect3"> 3401<h4 id="opaque-types">4.1.7. Opaque Types</h4> 3402<div class="dlist"> 3403<dl> 3404<dt class="hdlist1">Definition</dt> 3405<dd> 3406<p>An <em>opaque type</em> is a type where the internal structure of the type is 3407hidden from the language.</p> 3408</dd> 3409</dl> 3410</div> 3411<div class="paragraph"> 3412<p>The opaque types, as listed in the following sections, declare variables 3413that are effectively opaque handles to other objects. 3414These objects are accessed through built-in functions, not through direct 3415reading or writing of the declared variable. 3416They can only be declared as function parameters or in <strong>uniform</strong>-qualified 3417variables (see “<a href="#uniform-variables">Uniform Variables</a>”). 3418The only opaque types that take memory qualifiers are the image types. 3419Except for array indexing, structure member selection, and parentheses, 3420opaque variables are not allowed to be operands in expressions; such use 3421results in a compile-time error.</p> 3422</div> 3423<div class="paragraph"> 3424<p>Opaque variables cannot be treated as l-values; hence cannot be used as 3425<strong>out</strong> or <strong>inout</strong> function parameters, nor can they be assigned into. 3426Any such use results in a compile-time error. 3427However, they can be passed as <strong>in</strong> parameters with matching types and 3428memory qualifiers. 3429They cannot be declared with an initializer.</p> 3430</div> 3431<div class="paragraph"> 3432<p>Because a single opaque type declaration effectively declares two objects, 3433the opaque handle itself and the object it is a handle to, there is room for 3434both a storage qualifier and a memory qualifier. 3435The storage qualifier will qualify the opaque handle, while the memory 3436qualifier will qualify the object it is a handle to.</p> 3437</div> 3438<div class="sect4"> 3439<h5 id="samplers">Texture-Combined Samplers</h5> 3440<div class="paragraph"> 3441<p>Texture-combined sampler types (e.g. <strong>sampler2D</strong>) are the sampler types 3442described in the Basic Types tables as handles for accessing textures. 3443(They do not include <strong>sampler</strong> and <strong>samplerShadow</strong>.) 3444There are distinct texture-combined sampler types for each texture target, 3445and for each of float, integer, and unsigned integer data types. 3446Texture accesses are done through built-in texture functions (described in 3447“<a href="#texture-functions">Texture Functions</a>”) and texture-combined samplers 3448are used to specify which texture to access and how it is to be filtered.</p> 3449</div> 3450<div class="paragraph"> 3451<p>Texture-combined sampler types are opaque types, 3452declared and behaving as described above for opaque types. 3453When aggregated into arrays within a shader, they can only be indexed 3454with a dynamically uniform integral expression, otherwise results are 3455undefined.</p> 3456</div> 3457</div> 3458<div class="sect4"> 3459<h5 id="images">Images</h5> 3460<div class="paragraph"> 3461<p>Image types are opaque types, declared and behaving as described above for 3462opaque types. 3463They can be further qualified with memory qualifiers. 3464When aggregated into arrays within a shader, images can only be indexed with 3465a dynamically uniform integral expression, otherwise results are undefined.</p> 3466</div> 3467<div class="paragraph"> 3468<p>Image variables are handles to 3469one-, 3470two-, or three-dimensional images 3471corresponding to all or a portion of a single level of a texture image bound 3472to an image unit. 3473There are distinct image variable types for each texture target, and for 3474each of float, integer, and unsigned integer data types. 3475Image accesses should use an image type that matches the target of the 3476texture whose level is bound to the image unit, or for non-layered bindings 3477of 3D or array images should use the image type that matches the 3478dimensionality of the layer of the image (i.e., a layer of 3D, 2DArray, 3479Cube, or CubeArray should use 3480<strong>image2D</strong>, a layer of 1DArray should use <strong>image1D</strong>, and a layer of 2DMSArray 3481should use <strong>image2DMS</strong>). 3482If the image target type does not match the bound image in this manner, if 3483the data type does not match the bound image, or if the format layout 3484qualifier does not match the image unit format as described in section 34858.25 3486“Texture Image Loads and Stores” of the <a href="#references">OpenGL Specification</a>, the 3487results of image accesses are undefined but cannot include program 3488termination.</p> 3489</div> 3490<div class="paragraph"> 3491<p>Image variables are used in the image load, store, and atomic functions 3492described in “<a href="#image-functions">Image Functions</a>” to specify an image to 3493access.</p> 3494</div> 3495</div> 3496<div class="sect4"> 3497<h5 id="atomic-counters">Atomic Counters</h5> 3498<div class="paragraph"> 3499<p>Atomic counter types (e.g. <strong>atomic_uint</strong>) are opaque handles to counters, 3500declared and behaving as described above for opaque types. 3501The variables they declare specify which counter to access when using the 3502built-in atomic counter functions as described in 3503“<a href="#atomic-counter-functions">Atomic Counter Functions</a>”. 3504They are bound to buffers as described in 3505“<a href="#atomic-counter-layout-qualifiers">Atomic Counter Layout Qualifiers</a>”.</p> 3506</div> 3507<div class="paragraph"> 3508<p>Atomic counters aggregated into arrays within a shader can only be indexed 3509with dynamically uniform integral expressions, otherwise results are 3510undefined.</p> 3511</div> 3512<div class="paragraph"> 3513<p>Members of structures cannot be declared as atomic counter types.</p> 3514</div> 3515<div class="paragraph"> 3516<p>Atomic counter types are not available when targeting Vulkan.</p> 3517</div> 3518</div> 3519<div class="sect4"> 3520<h5 id="_texture_sampler_and_samplershadow_types">Texture, <strong>sampler</strong>, and <strong>samplerShadow</strong> Types</h5> 3521<div class="paragraph"> 3522<p>Texture (e.g., <strong>texture2D</strong>), <strong>sampler</strong>, and <strong>samplerShadow</strong> types are opaque 3523types, declared and behaving as described above for opaque types. 3524These types are only available when targeting Vulkan. 3525When aggregated into arrays within a shader, these types can only be indexed 3526with a dynamically uniform expression, or texture lookup will result in 3527undefined values. 3528Texture variables are handles to one-, two-, and three-dimensional textures, 3529cube maps, etc., as enumerated in the basic types tables. 3530There are distinct texture types for each texture target, and for each of 3531float, integer, and unsigned integer data types. 3532Textures can be combined with a variable of type <strong>sampler</strong> or <strong>samplerShadow</strong> 3533to create a texture-combined sampler type (e.g., sampler2D, or sampler2DShadow). 3534This is done with a constructor, e.g., <code>sampler2D(texture2D, sampler)</code>, 3535<code>sampler2DShadow(texture2D, sampler)</code>, <code>sampler2DShadow(texture2D, samplerShadow)</code>, 3536or <code>sampler2D(texture2D, samplerShadow)</code> and is described in more detail 3537in section 5.4 "Constructors".</p> 3538</div> 3539</div> 3540<div class="sect4"> 3541<h5 id="_subpass_inputs">Subpass Inputs</h5> 3542<div class="paragraph"> 3543<p>Subpass-input types are only available when targeting Vulkan.</p> 3544</div> 3545<div class="paragraph"> 3546<p>Subpass-input types (e.g., <strong>subpassInput</strong>) are opaque types, declared 3547and behaving as described above for opaque types. 3548When aggregated into arrays within a shader, they can only be indexed with a 3549dynamically uniform integral expression, otherwise results are undefined.</p> 3550</div> 3551<div class="paragraph"> 3552<p>Subpass-input types are handles to two-dimensional single sampled or 3553multi-sampled images, with distinct types for each of float, integer, 3554and unsigned integer data types.</p> 3555</div> 3556<div class="paragraph"> 3557<p>Subpass-input types are only available in fragment shaders. It is 3558a compile-time error to use them in any other stage.</p> 3559</div> 3560</div> 3561</div> 3562<div class="sect3"> 3563<h4 id="structures">4.1.8. Structures</h4> 3564<div class="paragraph"> 3565<p>User-defined types can be created by aggregating other already defined types 3566into a structure using the <strong>struct</strong> keyword. 3567For example,</p> 3568</div> 3569<div class="listingblock"> 3570<div class="content"> 3571<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">struct</span> light { 3572 <span class="predefined-type">float</span> intensity; 3573 vec3 position; 3574} lightVar;</code></pre> 3575</div> 3576</div> 3577<div class="paragraph"> 3578<p>In this example, <em>light</em> becomes the name of the new type, and <em>lightVar</em> 3579becomes a variable of type <em>light</em>. 3580To declare variables of the new type, use its name (without the keyword 3581<strong>struct</strong>).</p> 3582</div> 3583<div class="listingblock"> 3584<div class="content"> 3585<pre class="CodeRay highlight"><code data-lang="c++">light lightVar2;</code></pre> 3586</div> 3587</div> 3588<div class="paragraph"> 3589<p>More formally, structures are declared as follows. 3590However, the definitive grammar is as given in 3591“<a href="#shading-language-grammar">Shading Language Grammar</a>”.</p> 3592</div> 3593<div class="openblock bnf"> 3594<div class="content"> 3595<div class="dlist"> 3596<dl> 3597<dt class="hdlist1"><em>struct-definition</em> : </dt> 3598<dd> 3599<p><em>qualifier<sub>opt</sub></em> <strong>struct</strong> name<sub>opt</sub>_ <strong>{</strong> <em>member-list</em> <strong>}</strong> 3600<em>declarators<sub>opt</sub></em> <strong>;</strong></p> 3601</dd> 3602<dt class="hdlist1"><em>member-list</em> : </dt> 3603<dd> 3604<p><em>member-declaration</em> <strong>;</strong><br> 3605<em>member-declaration</em> <em>member-list</em> <strong>;</strong></p> 3606</dd> 3607<dt class="hdlist1"><em>member-declaration</em> : </dt> 3608<dd> 3609<p><em>basic-type</em> <em>declarators</em> <strong>;</strong></p> 3610</dd> 3611</dl> 3612</div> 3613</div> 3614</div> 3615<div class="paragraph"> 3616<p>where <em>name</em> becomes the user-defined type, and can be used to declare 3617variables to be of this new type. 3618The <em>name</em> shares the same name space as other variables, types, and 3619functions. 3620All previously visible variables, types, constructors, or functions with 3621that name are hidden. 3622The optional <em>qualifier</em> only applies to any <em>declarators</em>, and is not part 3623of the type being defined for <em>name</em>.</p> 3624</div> 3625<div class="paragraph"> 3626<p>Structures must have at least one member declaration. 3627Member declarators may contain precision qualifiers, but use of any other 3628qualifier results in a compile-time error. 3629Bit fields are not supported. 3630Member types must be already defined (there are no forward references). 3631A compile-time error results if a member declaration contains an 3632initializer. 3633Member declarators can contain arrays. 3634Such arrays must have a size specified, and the size must be a constant 3635integral expression that’s greater than zero (see 3636“<a href="#constant-expressions">Constant Expressions</a>”). 3637Each level of structure has its own name space for names given in member 3638declarators; such names need only be unique within that name space.</p> 3639</div> 3640<div class="paragraph"> 3641<p>Anonymous structures are not supported. 3642Embedded structure definitions are not supported. 3643These result in compile-time errors.</p> 3644</div> 3645<div class="listingblock"> 3646<div class="content"> 3647<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">struct</span> S { <span class="predefined-type">float</span> f; }; <span class="comment">// Allowed: S is defined as a structure.</span> 3648 3649<span class="keyword">struct</span> T { 3650 S; <span class="comment">// Error: anonymous structures disallowed</span> 3651 <span class="keyword">struct</span> { ... }; <span class="comment">// Error: embedded structures disallowed</span> 3652 S s; <span class="comment">// Allowed: nested structure with a name.</span> 3653};</code></pre> 3654</div> 3655</div> 3656<div class="paragraph"> 3657<p>Structures can be initialized at declaration time using constructors, as 3658discussed in “<a href="#structure-constructors">Structure Constructors</a>”.</p> 3659</div> 3660<div class="paragraph"> 3661<p>Any restrictions on the usage of a type or qualifier also apply to any 3662structure that contains a member of that type or qualifier. 3663This also applies to structure members that are structures, recursively.</p> 3664</div> 3665</div> 3666<div class="sect3"> 3667<h4 id="arrays">4.1.9. Arrays</h4> 3668<div class="paragraph"> 3669<p>Variables of the same type can be aggregated into arrays by declaring a name 3670followed by brackets (<strong>[ ]</strong>) enclosing an optional size. 3671When an array size is specified in a declaration, it must be an integral 3672constant expression (see “<a href="#constant-expressions">Constant Expressions</a>”) 3673greater than zero. 3674Except for the last declared member of a shader storage block (see section 3675“<a href="#interface-blocks">Interface Blocks</a>”), the size of an array must be 3676declared (<em>explicitly sized</em>) before it is indexed with anything other than 3677a constant integral expression. 3678The size of any array must be declared before passing it as an argument to a 3679function. 3680Violation of any of these rules result in compile-time errors. 3681It is legal to declare an array without a size (<em>unsized</em>) and then later 3682redeclare the same name as an array of the same type and specify a size, or 3683index it only with constant integral expressions (<em>implicitly sized</em>). 3684However, unless noted otherwise, blocks cannot be redeclared; an unsized 3685array member in a user-declared block cannot be sized by a block redeclaration. 3686It is a compile-time error to declare an array with a size, and then later 3687(in the same shader) index the same array with a constant integral 3688expression greater than or equal to the declared size. 3689It is a compile-time error to redeclare an unsized array with a size equal 3690to or smaller than any index used earlier in the shader to index the array. 3691It is also a compile-time error to index an array with a negative constant 3692expression. 3693Arrays declared as formal parameters in a function declaration must specify 3694a size. 3695Undefined behavior results from indexing an array with a non-constant 3696expression that’s greater than or equal to the array’s size or less than 0. 3697Arrays only have a single dimension (a single entry within "[ ]"), however, 3698arrays of arrays can be declared. 3699All types (basic types, structures, arrays) can be formed into an array.</p> 3700</div> 3701<div class="paragraph"> 3702<p>All arrays are inherently homogeneous; made of elements all having the same 3703type and size, with one exception. 3704The exception is a shader storage block having an unsized array as its last 3705member (<em>run-time sized</em>); an array can be formed from such a shader storage 3706block, even if the storage blocks have differing lengths for their last 3707member.</p> 3708</div> 3709<div class="paragraph"> 3710<p>Some examples are:</p> 3711</div> 3712<div class="listingblock"> 3713<div class="content"> 3714<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> frequencies[<span class="integer">3</span>]; 3715uniform vec4 lightPosition[<span class="integer">4</span>]; 3716light lights[]; 3717<span class="directive">const</span> <span class="predefined-type">int</span> numLights = <span class="integer">2</span>; 3718light lights[numLights]; 3719 3720<span class="comment">// a shader storage block, introduced in section 4.3.7 "Buffer Variables"</span> 3721buffer b { 3722 <span class="predefined-type">float</span> u[]; <span class="comment">// an error, unless u gets statically sized by link time</span> 3723 vec4 v[]; <span class="comment">// okay, v will be sized dynamically, if not statically</span> 3724} name[<span class="integer">3</span>]; <span class="comment">// when the block is arrayed, all u will be the same size,</span> 3725 <span class="comment">// but not necessarily all v, if sized dynamically</span></code></pre> 3726</div> 3727</div> 3728<div class="paragraph"> 3729<p>An array type can be formed by specifying non-array type followed by an 3730array specifier. 3731All dimensions of such an array specifier must include a size.</p> 3732</div> 3733<div class="listingblock"> 3734<div class="content"> 3735<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span>[<span class="integer">5</span>] <span class="comment">// an array of size [5] of float</span> 3736<span class="predefined-type">float</span>[<span class="integer">2</span>][<span class="integer">3</span>] <span class="comment">// an array of size [2][3] of float, not size [3] of float[2]</span></code></pre> 3737</div> 3738</div> 3739<div class="paragraph"> 3740<p>This type can be used anywhere any other type can be used, including as the 3741return value from a function</p> 3742</div> 3743<div class="listingblock"> 3744<div class="content"> 3745<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span>[<span class="integer">5</span>] foo() { }</code></pre> 3746</div> 3747</div> 3748<div class="paragraph"> 3749<p>as a constructor of an array:</p> 3750</div> 3751<div class="listingblock"> 3752<div class="content"> 3753<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span>[<span class="integer">5</span>](<span class="float">3</span><span class="float">.4</span>, <span class="float">4</span><span class="float">.2</span>, <span class="float">5</span><span class="float">.0</span>, <span class="float">5</span><span class="float">.2</span>, <span class="float">1</span><span class="float">.1</span>)</code></pre> 3754</div> 3755</div> 3756<div class="paragraph"> 3757<p>as an unnamed parameter:</p> 3758</div> 3759<div class="listingblock"> 3760<div class="content"> 3761<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">void</span> foo(<span class="predefined-type">float</span>[<span class="integer">5</span>])</code></pre> 3762</div> 3763</div> 3764<div class="paragraph"> 3765<p>and as an alternate way of declaring a variable or function parameter:</p> 3766</div> 3767<div class="listingblock"> 3768<div class="content"> 3769<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span>[<span class="integer">5</span>] a;</code></pre> 3770</div> 3771</div> 3772<div class="paragraph"> 3773<p>Arrays can have initializers formed from array constructors:</p> 3774</div> 3775<div class="listingblock"> 3776<div class="content"> 3777<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> a[<span class="integer">5</span>] = <span class="predefined-type">float</span>[<span class="integer">5</span>](<span class="float">3</span><span class="float">.4</span>, <span class="float">4</span><span class="float">.2</span>, <span class="float">5</span><span class="float">.0</span>, <span class="float">5</span><span class="float">.2</span>, <span class="float">1</span><span class="float">.1</span>); 3778<span class="predefined-type">float</span> a[<span class="integer">5</span>] = <span class="predefined-type">float</span>[](<span class="float">3</span><span class="float">.4</span>, <span class="float">4</span><span class="float">.2</span>, <span class="float">5</span><span class="float">.0</span>, <span class="float">5</span><span class="float">.2</span>, <span class="float">1</span><span class="float">.1</span>); <span class="comment">// same thing</span></code></pre> 3779</div> 3780</div> 3781<div class="paragraph"> 3782<p>An array of arrays can be declared as:</p> 3783</div> 3784<div class="listingblock"> 3785<div class="content"> 3786<pre class="CodeRay highlight"><code data-lang="c++">vec4 a[<span class="integer">3</span>][<span class="integer">2</span>]; <span class="comment">// size-3 array of size-2 array of vec4</span></code></pre> 3787</div> 3788</div> 3789<div class="paragraph"> 3790<p>which declares a one-dimensional array of size 3 of one-dimensional arrays 3791of size 2 of <strong>vec4</strong>. 3792The following declarations do the same thing:</p> 3793</div> 3794<div class="listingblock"> 3795<div class="content"> 3796<pre class="CodeRay highlight"><code data-lang="c++">vec4[<span class="integer">2</span>] a[<span class="integer">3</span>]; <span class="comment">// size-3 array of size-2 array of vec4</span> 3797vec4[<span class="integer">3</span>][<span class="integer">2</span>] a; <span class="comment">// size-3 array of size-2 array of vec4</span></code></pre> 3798</div> 3799</div> 3800<div class="paragraph"> 3801<p>When in transparent memory (like in a uniform block), the layout is that the 3802inner-most (right-most in declaration) dimensions iterate faster than the 3803outer dimensions. 3804That is, for the above, the order in memory would be:</p> 3805</div> 3806<div class="dlist"> 3807<dl> 3808<dt class="hdlist1"></dt> 3809<dd> 3810<p>Low address : a[0][0] : a[0][1] : a[1][0] : a[1][1] : a[2][0] : a[2][1] 3811: High address</p> 3812</dd> 3813</dl> 3814</div> 3815<div class="paragraph"> 3816<p>The type of <em>a</em> needed for both constructors and nameless parameters is 3817“vec4[3][2]”:</p> 3818</div> 3819<div class="listingblock"> 3820<div class="content"> 3821<pre class="CodeRay highlight"><code data-lang="c++">vec4 b[<span class="integer">2</span>] = vec4[<span class="integer">2</span>](vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">0</span><span class="float">.1</span>)); 3822vec4[<span class="integer">3</span>][<span class="integer">2</span>] a = vec4[<span class="integer">3</span>][<span class="integer">2</span>](b, b, b); <span class="comment">// constructor</span> 3823<span class="directive">void</span> foo(vec4[<span class="integer">3</span>][<span class="integer">2</span>]); <span class="comment">// prototype with unnamed parameter</span></code></pre> 3824</div> 3825</div> 3826<div class="paragraph"> 3827<p>Alternatively, the initializer-list syntax can be used to initialize an 3828array of arrays:</p> 3829</div> 3830<div class="listingblock"> 3831<div class="content"> 3832<pre class="CodeRay highlight"><code data-lang="c++">vec4 a[<span class="integer">3</span>][<span class="integer">2</span>] = { vec4[<span class="integer">2</span>](vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">1</span><span class="float">.0</span>)), 3833 vec4[<span class="integer">2</span>](vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">1</span><span class="float">.0</span>)), 3834 vec4[<span class="integer">2</span>](vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">1</span><span class="float">.0</span>)) };</code></pre> 3835</div> 3836</div> 3837<div class="paragraph"> 3838<p>Unsized arrays can be explicitly sized by an initializer at declaration 3839time:</p> 3840</div> 3841<div class="listingblock"> 3842<div class="content"> 3843<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> a[<span class="integer">5</span>]; 3844... 3845<span class="predefined-type">float</span> b[] = a; <span class="comment">// b is explicitly size 5</span> 3846<span class="predefined-type">float</span> b[<span class="integer">5</span>] = a; <span class="comment">// means the same thing</span> 3847<span class="predefined-type">float</span> b[] = <span class="predefined-type">float</span>[](<span class="integer">1</span>,<span class="integer">2</span>,<span class="integer">3</span>,<span class="integer">4</span>,<span class="integer">5</span>); <span class="comment">// also explicitly sizes to 5</span></code></pre> 3848</div> 3849</div> 3850<div class="paragraph"> 3851<p>However, it is a compile-time error to assign to an unsized array. 3852Note, this is a rare case that initializers and assignments appear to have 3853different semantics. 3854For arrays of arrays, any unsized dimension is explicitly sized by the 3855initializer:</p> 3856</div> 3857<div class="listingblock"> 3858<div class="content"> 3859<pre class="CodeRay highlight"><code data-lang="c++">vec4 a[][] = { vec4[<span class="integer">2</span>](vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">1</span><span class="float">.0</span>)), <span class="comment">// okay, size to a[3][2]</span> 3860 vec4[<span class="integer">2</span>](vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">1</span><span class="float">.0</span>)), 3861 vec4[<span class="integer">2</span>](vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">1</span><span class="float">.0</span>)) };</code></pre> 3862</div> 3863</div> 3864<div class="paragraph"> 3865<p>Arrays know the number of elements they contain. 3866This can be obtained by using the <strong>length</strong>() method:</p> 3867</div> 3868<div class="listingblock"> 3869<div class="content"> 3870<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> a[<span class="integer">5</span>]; 3871a.length(); <span class="comment">// returns 5</span></code></pre> 3872</div> 3873</div> 3874<div class="paragraph"> 3875<p>This returns a type <strong>int</strong>. 3876If an array has been explicitly sized, the value returned by the <strong>length</strong>() 3877method is a constant expression. 3878If an array has not been explicitly sized and is the last declared member of 3879a shader storage block, the value returned will not be a constant expression 3880and will be determined at runtime based on the size of the buffer object 3881providing storage for the block. 3882Such arrays are runtime sized. 3883For runtime-sized arrays, the value returned by the <strong>length</strong>() method will be 3884undefined if the array is contained in an array of shader storage blocks 3885that is indexed with a non-constant expression less than zero or greater 3886than or equal to the number of blocks in the array.</p> 3887</div> 3888<div class="paragraph"> 3889<p>The <strong>length</strong>() method cannot be called on an array that is not runtime sized 3890and also has not yet been explicitly sized; 3891this results in a compile-time error.</p> 3892</div> 3893<div class="paragraph"> 3894<p>When the <strong>length</strong>() method returns a compile-time constant, the expression the 3895<strong>length</strong>() method is applied to cannot contain any side effects, such as writes 3896to l-values within the expression, or function calls that themselves have side 3897effects: only the compile-time constant length itself need be computed. 3898Behavior and results, including any compile-time error reporting, 3899are undefined if the expression contains other effects.</p> 3900</div> 3901<div class="listingblock"> 3902<div class="content"> 3903<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> a, b; 3904<span class="directive">const</span> <span class="predefined-type">int</span> s = <span class="predefined-type">float</span>[<span class="integer">2</span>](a=<span class="float">3</span><span class="float">.0</span>, ++b).length(); <span class="comment">// illegal side effects</span></code></pre> 3905</div> 3906</div> 3907<div class="paragraph"> 3908<p>The <strong>length</strong>() method works equally well for arrays of arrays:</p> 3909</div> 3910<div class="listingblock"> 3911<div class="content"> 3912<pre class="CodeRay highlight"><code data-lang="c++">vec4 a[<span class="integer">3</span>][<span class="integer">2</span>]; 3913a.length() <span class="comment">// this is 3</span> 3914a[x].length() <span class="comment">// this is 2</span></code></pre> 3915</div> 3916</div> 3917<div class="paragraph"> 3918<p>When the <strong>length</strong>() method returns a compile-time constant, the expression 3919in brackets (<em>x</em> above) will be parsed and subjected to the rules required for 3920array indices, but the array will not be dereferenced. 3921Thus, behavior is well defined even if the run-time value of the expression 3922is out of bounds, as long as the expression contains no side effects.</p> 3923</div> 3924<div class="paragraph"> 3925<p>When the <strong>length</strong>() method returns a run-time value 3926(not a compile-time constant), the array will be 3927dereferenced. 3928E.g., if <em>x</em> is not a compile-time constant and is out of range, an undefined 3929value results. 3930More generally, all involved expressions are fully evaluated and executed.</p> 3931</div> 3932<div class="listingblock"> 3933<div class="content"> 3934<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// for a compile time-sized array b containing a member array a:</span> 3935b[x+<span class="integer">3</span>].a.length(); <span class="comment">// b is never dereferenced, x+3 is evaluated and checked</span> 3936b[++x].a.length(); <span class="comment">// not allowed; results are undefined</span> 3937 3938<span class="comment">// for an array s of a shader storage object (run-time sized) containing a member array a:</span> 3939s[++x].a.length(); <span class="comment">// s is dereferenced; ++x needs to be a valid index</span></code></pre> 3940</div> 3941</div> 3942<div class="paragraph"> 3943<p>For implicitly-sized or run-time-sized arrays, only the outer-most dimension 3944can be lacking a size. 3945A type that includes an unknown array size cannot be formed into an array 3946until it gets an explicit size, except for shader storage blocks where the 3947only unsized array member is the last member of the block.</p> 3948</div> 3949<div class="paragraph"> 3950<p>In a shader storage block, the last member may be declared without an 3951explicit size. 3952In this case, the effective array size is inferred at run-time from the size 3953of the data store backing the interface block. 3954Such run-time-sized arrays may be indexed with general integer expressions. 3955However, it is a compile-time error to pass them as an argument to a 3956function or index them with a negative constant expression.</p> 3957</div> 3958</div> 3959<div class="sect3"> 3960<h4 id="implicit-conversions">4.1.10. Implicit Conversions</h4> 3961<div class="paragraph"> 3962<p>In some situations, an expression and its type will be implicitly converted 3963to a different type. 3964The following table shows all allowed implicit conversions:</p> 3965</div> 3966<table class="tableblock frame-all grid-all stretch"> 3967<colgroup> 3968<col style="width: 50%;"> 3969<col style="width: 50%;"> 3970</colgroup> 3971<thead> 3972<tr> 3973<th class="tableblock halign-left valign-top">Type of expression</th> 3974<th class="tableblock halign-left valign-top">Can be implicitly converted to</th> 3975</tr> 3976</thead> 3977<tbody> 3978<tr> 3979<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>int</strong></p></td> 3980<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uint</strong></p></td> 3981</tr> 3982<tr> 3983<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>int</strong><br> 3984 <strong>uint</strong></p></td> 3985<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>float</strong></p></td> 3986</tr> 3987<tr> 3988<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>int</strong><br> 3989 <strong>uint</strong><br> 3990 <strong>float</strong></p></td> 3991<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>double</strong></p></td> 3992</tr> 3993<tr> 3994<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec2</strong></p></td> 3995<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uvec2</strong></p></td> 3996</tr> 3997<tr> 3998<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec3</strong></p></td> 3999<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uvec3</strong></p></td> 4000</tr> 4001<tr> 4002<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec4</strong></p></td> 4003<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uvec4</strong></p></td> 4004</tr> 4005<tr> 4006<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec2</strong><br> 4007 <strong>uvec2</strong></p></td> 4008<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>vec2</strong></p></td> 4009</tr> 4010<tr> 4011<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec3</strong><br> 4012 <strong>uvec3</strong></p></td> 4013<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>vec3</strong></p></td> 4014</tr> 4015<tr> 4016<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec4</strong><br> 4017 <strong>uvec4</strong></p></td> 4018<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>vec4</strong></p></td> 4019</tr> 4020<tr> 4021<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec2</strong><br> 4022 <strong>uvec2</strong><br> 4023 <strong>vec2</strong></p></td> 4024<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dvec2</strong></p></td> 4025</tr> 4026<tr> 4027<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec3</strong><br> 4028 <strong>uvec3</strong><br> 4029 <strong>vec3</strong></p></td> 4030<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dvec3</strong></p></td> 4031</tr> 4032<tr> 4033<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>ivec4</strong><br> 4034 <strong>uvec4</strong><br> 4035 <strong>vec4</strong></p></td> 4036<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dvec4</strong></p></td> 4037</tr> 4038<tr> 4039<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat2</strong></p></td> 4040<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat2</strong></p></td> 4041</tr> 4042<tr> 4043<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat3</strong></p></td> 4044<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat3</strong></p></td> 4045</tr> 4046<tr> 4047<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat4</strong></p></td> 4048<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat4</strong></p></td> 4049</tr> 4050<tr> 4051<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat2x3</strong></p></td> 4052<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat2x3</strong></p></td> 4053</tr> 4054<tr> 4055<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat2x4</strong></p></td> 4056<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat2x4</strong></p></td> 4057</tr> 4058<tr> 4059<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat3x2</strong></p></td> 4060<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat3x2</strong></p></td> 4061</tr> 4062<tr> 4063<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat3x4</strong></p></td> 4064<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat3x4</strong></p></td> 4065</tr> 4066<tr> 4067<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat4x2</strong></p></td> 4068<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat4x2</strong></p></td> 4069</tr> 4070<tr> 4071<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mat4x3</strong></p></td> 4072<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>dmat4x3</strong></p></td> 4073</tr> 4074</tbody> 4075</table> 4076<div class="paragraph"> 4077<p>There are no implicit array or structure conversions. 4078For example, an array of <strong>int</strong> cannot be implicitly converted to an array of 4079<strong>float</strong>.</p> 4080</div> 4081<div class="paragraph"> 4082<p>When an implicit conversion is done, it is the same conversion that would be 4083done under explicit conversion, using a constructor. 4084The explicit conversions via constructors are described in 4085<a href="#conversion-and-scalar-constructors">Conversion and Scalar Constructors</a>.</p> 4086</div> 4087<div class="paragraph"> 4088<p>When performing implicit conversion for binary operators, there may be 4089multiple data types to which the two operands can be converted. 4090For example, when adding an <strong>int</strong> value to a <strong>uint</strong> value, both values can 4091be implicitly converted to <strong>uint</strong>, <strong>float</strong>, and <strong>double</strong>. 4092In such cases, a floating-point type is chosen if either operand has a 4093floating-point type. 4094Otherwise, an unsigned integer type is chosen if either operand has an 4095unsigned integer type. 4096Otherwise, a signed integer type is chosen. 4097If operands can be implicitly converted to multiple data types deriving from 4098the same base data type, the type with the smallest component size is used.</p> 4099</div> 4100<div class="paragraph"> 4101<p>The conversions in the table above are done only as indicated by other 4102sections of this specification.</p> 4103</div> 4104</div> 4105<div class="sect3"> 4106<h4 id="initializers">4.1.11. Initializers</h4> 4107<div class="paragraph"> 4108<p>At declaration, an initial value for a variable may be provided, specified 4109as an equals (=) followed by an initializer. 4110The initializer is either an <em>assignment-expression</em> or a list of 4111initializers enclosed in curly braces. 4112The grammar for the initializer is:</p> 4113</div> 4114<div class="openblock bnf"> 4115<div class="content"> 4116<div class="dlist"> 4117<dl> 4118<dt class="hdlist1"><em>initializer</em> : </dt> 4119<dd> 4120<p><em>assignment-expression</em><br> 4121<strong>{</strong> <em>initializer-list</em> <strong>}</strong><br> 4122<strong>{</strong> <em>initializer-list</em> <strong>,</strong> <strong>}</strong></p> 4123</dd> 4124<dt class="hdlist1"><em>initializer-list</em> : </dt> 4125<dd> 4126<p><em>initializer</em><br> 4127<em>initializer-list</em> , <em>initializer</em></p> 4128</dd> 4129</dl> 4130</div> 4131</div> 4132</div> 4133<div class="paragraph"> 4134<p>The <em>assignment-expression</em> is a normal expression except that a comma (<strong>,</strong>) 4135outside parentheses is interpreted as the end of the initializer, not as the 4136sequence operator. 4137As explained in more detail below, this allows creation of nested 4138initializers: The variable type and its initializer must exactly match in 4139terms of nesting, number of components/elements/members present at each 4140level, and types of components/elements/members. 4141An <em>assignment-expression</em> at global scope can include calls to user-defined 4142functions.</p> 4143</div> 4144<div class="paragraph"> 4145<p>An <em>assignment-expression</em> in an initializer must be either the same type as 4146the object it initializes or be a type that can be converted to the object’s 4147type according to “<a href="#implicit-conversions">Implicit Conversions</a>”. 4148Since these include constructors, a composite variable can be initialized by 4149either a constructor or an initializer list; and an element in an 4150initializer list can be a constructor.</p> 4151</div> 4152<div class="paragraph"> 4153<p>If an initializer is a list of initializers enclosed in curly braces, the 4154variable being declared must be a vector, a matrix, an array, or a 4155structure.</p> 4156</div> 4157<div class="listingblock"> 4158<div class="content"> 4159<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">int</span> i = { <span class="integer">1</span> }; <span class="comment">// illegal, i is not a composite</span></code></pre> 4160</div> 4161</div> 4162<div class="paragraph"> 4163<p>A list of initializers enclosed in a matching set of curly braces is applied 4164to one composite. 4165This may be the variable being declared or a composite contained in the 4166variable being declared. 4167Individual initializers from the initializer list are applied to the 4168elements/members of the composite, in order.</p> 4169</div> 4170<div class="paragraph"> 4171<p>If the composite has a vector type, initializers from the list are applied 4172to the components of the vector, in order, starting with component 0. 4173The number of initializers must match the number of components.</p> 4174</div> 4175<div class="paragraph"> 4176<p>If the composite has a matrix type, initializers from the list must be 4177vector initializers and are applied to the columns of the matrix, in order, 4178starting with column 0. 4179The number of initializers must match the number of columns.</p> 4180</div> 4181<div class="paragraph"> 4182<p>If the composite has a structure type, initializers from the list are 4183applied to the members of the structure, in the order declared in the 4184structure, starting with the first member. 4185The number of initializers must match the number of members.</p> 4186</div> 4187<div class="paragraph"> 4188<p>Applying these rules, the following matrix declarations are equivalent:</p> 4189</div> 4190<div class="listingblock"> 4191<div class="content"> 4192<pre class="CodeRay highlight"><code data-lang="c++">mat2x2 a = mat2( vec2( <span class="float">1</span><span class="float">.0</span>, <span class="float">0</span><span class="float">.0</span> ), vec2( <span class="float">0</span><span class="float">.0</span>, <span class="float">1</span><span class="float">.0</span> ) ); 4193mat2x2 b = { vec2( <span class="float">1</span><span class="float">.0</span>, <span class="float">0</span><span class="float">.0</span> ), vec2( <span class="float">0</span><span class="float">.0</span>, <span class="float">1</span><span class="float">.0</span> ) }; 4194mat2x2 c = { { <span class="float">1</span><span class="float">.0</span>, <span class="float">0</span><span class="float">.0</span> }, { <span class="float">0</span><span class="float">.0</span>, <span class="float">1</span><span class="float">.0</span> } };</code></pre> 4195</div> 4196</div> 4197<div class="paragraph"> 4198<p>All of the following declarations result in a compile-time error.</p> 4199</div> 4200<div class="listingblock"> 4201<div class="content"> 4202<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> a[<span class="integer">2</span>] = { <span class="float">3</span><span class="float">.4</span>, <span class="float">4</span><span class="float">.2</span>, <span class="float">5</span><span class="float">.0</span> }; <span class="comment">// illegal</span> 4203vec2 b = { <span class="float">1</span><span class="float">.0</span>, <span class="float">2</span><span class="float">.0</span>, <span class="float">3</span><span class="float">.0</span> }; <span class="comment">// illegal</span> 4204mat3x3 c = { vec3(<span class="float">0</span><span class="float">.0</span>), vec3(<span class="float">1</span><span class="float">.0</span>), vec3(<span class="float">2</span><span class="float">.0</span>), vec3(<span class="float">3</span><span class="float">.0</span>) }; <span class="comment">// illegal</span> 4205mat2x2 d = { <span class="float">1</span><span class="float">.0</span>, <span class="float">0</span><span class="float">.0</span>, <span class="float">0</span><span class="float">.0</span>, <span class="float">1</span><span class="float">.0</span> }; <span class="comment">// illegal, can't flatten nesting</span> 4206<span class="keyword">struct</span> { 4207 <span class="predefined-type">float</span> a; 4208 <span class="predefined-type">int</span> b; 4209} e = { <span class="float">1</span><span class="float">.2</span>, <span class="integer">2</span>, <span class="integer">3</span> }; <span class="comment">// illegal</span></code></pre> 4210</div> 4211</div> 4212<div class="paragraph"> 4213<p>In all cases, the inner-most initializer (i.e., not a list of initializers 4214enclosed in curly braces) applied to an object must have the same type as 4215the object being initialized or be a type that can be converted to the 4216object’s type according to “<a href="#implicit-conversions">Implicit 4217Conversions</a>”. 4218In the latter case, an implicit conversion will be done on the initializer 4219before the assignment is done.</p> 4220</div> 4221<div class="listingblock"> 4222<div class="content"> 4223<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">struct</span> { 4224 <span class="predefined-type">float</span> a; 4225 <span class="predefined-type">int</span> b; 4226} e = { <span class="float">1</span><span class="float">.2</span>, <span class="integer">2</span> }; <span class="comment">// legal, all types match</span> 4227<span class="keyword">struct</span> { 4228 <span class="predefined-type">float</span> a; 4229 <span class="predefined-type">int</span> b; 4230} e = { <span class="integer">1</span>, <span class="integer">3</span> }; <span class="comment">// legal, first initializer is converted</span></code></pre> 4231</div> 4232</div> 4233<div class="paragraph"> 4234<p>All of the following declarations result in a compile-time error.</p> 4235</div> 4236<div class="listingblock"> 4237<div class="content"> 4238<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">int</span> a = <span class="predefined-constant">true</span>; <span class="comment">// illegal</span> 4239vec4 b[<span class="integer">2</span>] = { vec4(<span class="float">0</span><span class="float">.0</span>), <span class="float">1</span><span class="float">.0</span> }; <span class="comment">// illegal</span> 4240mat4x2 c = { vec3(<span class="float">0</span><span class="float">.0</span>), vec3(<span class="float">1</span><span class="float">.0</span>) }; <span class="comment">// illegal</span> 4241 4242<span class="keyword">struct</span> S1 { 4243 vec4 a; 4244 vec4 b; 4245}; 4246 4247<span class="keyword">struct</span> { 4248 <span class="predefined-type">float</span> s; 4249 <span class="predefined-type">float</span> t; 4250} d[] = { S1(vec4(<span class="float">0</span><span class="float">.0</span>), vec4(<span class="float">1</span><span class="float">.1</span>)) }; <span class="comment">// illegal</span></code></pre> 4251</div> 4252</div> 4253<div class="paragraph"> 4254<p>If an initializer (of either form) is provided for an unsized array, the 4255size of the array is determined by the number of top-level (non-nested) 4256initializers within the initializer. 4257All of the following declarations create arrays explicitly sized with five 4258elements:</p> 4259</div> 4260<div class="listingblock"> 4261<div class="content"> 4262<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> a[] = <span class="predefined-type">float</span>[](<span class="float">3</span><span class="float">.4</span>, <span class="float">4</span><span class="float">.2</span>, <span class="float">5</span><span class="float">.0</span>, <span class="float">5</span><span class="float">.2</span>, <span class="float">1</span><span class="float">.1</span>); 4263<span class="predefined-type">float</span> b[] = { <span class="float">3</span><span class="float">.4</span>, <span class="float">4</span><span class="float">.2</span>, <span class="float">5</span><span class="float">.0</span>, <span class="float">5</span><span class="float">.2</span>, <span class="float">1</span><span class="float">.1</span> }; 4264<span class="predefined-type">float</span> c[] = a; <span class="comment">// c is explicitly size 5</span> 4265<span class="predefined-type">float</span> d[<span class="integer">5</span>] = b; <span class="comment">// means the same thing</span></code></pre> 4266</div> 4267</div> 4268<div class="paragraph"> 4269<p>It is a compile-time error to have too few or too many initializers in an 4270initializer list for the composite being initialized. 4271That is, all elements of an array, all members of a structure, all columns 4272of a matrix, and all components of a vector must have exactly one 4273initializer expression present, with no unconsumed initializers.</p> 4274</div> 4275</div> 4276</div> 4277<div class="sect2"> 4278<h3 id="scoping">4.2. Scoping</h3> 4279<div class="paragraph"> 4280<p>The scope of a variable is determined by where it is declared. 4281If it is declared outside all function definitions, it has global scope, 4282which starts from where it is declared and persists to the end of the shader 4283it is declared in. 4284If it is declared in a <strong>while</strong> test or a <strong>for</strong> statement, then it is scoped 4285to the end of the following sub-statement. 4286If it is declared in an <strong>if</strong> or <strong>else</strong> statement, it is scoped to the end of 4287that statement. 4288(See “<a href="#selection">Selection</a>” and “<a href="#iteration">Iteration</a>” for the 4289location of statements and sub-statements.) Otherwise, if it is declared as 4290a statement within a compound statement, it is scoped to the end of that 4291compound statement. 4292If it is declared as a parameter in a function definition, it is scoped 4293until the end of that function definition. 4294A function’s parameter declarations and body together form a single scope 4295nested in the global scope. 4296The <strong>if</strong> statement’s expression does not allow new variables to be declared, 4297hence does not form a new scope.</p> 4298</div> 4299<div class="paragraph"> 4300<p>Within a declaration, the scope of a name starts immediately after the 4301initializer if present or immediately after the name being declared if not. 4302Several examples:</p> 4303</div> 4304<div class="listingblock"> 4305<div class="content"> 4306<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">int</span> x = <span class="integer">1</span>; 4307{ 4308 <span class="predefined-type">int</span> x = <span class="integer">2</span>, y = x; <span class="comment">// y is initialized to 2</span> 4309} 4310 4311<span class="keyword">struct</span> S 4312{ 4313 <span class="predefined-type">int</span> x; 4314}; 4315 4316{ 4317 S S = S(<span class="integer">0</span>); <span class="comment">// 'S' is only visible as a struct and constructor</span> 4318 S; <span class="comment">// 'S' is now visible as a variable</span> 4319} 4320 4321<span class="predefined-type">int</span> x = x; <span class="comment">// Error if x has not been previously defined.</span> 4322 <span class="comment">// If the previous definition of x was in this</span> 4323 <span class="comment">// same scope, this causes a redeclaration error.</span> 4324 4325<span class="predefined-type">int</span> f( <span class="comment">/* nested scope begins here */</span> <span class="predefined-type">int</span> k) 4326{ 4327 <span class="predefined-type">int</span> k = k + <span class="integer">3</span>; <span class="comment">// redeclaration error of the name k</span> 4328 ... 4329} 4330 4331<span class="predefined-type">int</span> f(<span class="predefined-type">int</span> k) 4332{ 4333 { 4334 <span class="predefined-type">int</span> k = k + <span class="integer">3</span>; <span class="comment">// 2nd k is parameter, initializing nested first k</span> 4335 <span class="predefined-type">int</span> m = k; <span class="comment">// use of new k, which is hiding the parameter</span> 4336 } 4337}</code></pre> 4338</div> 4339</div> 4340<div class="paragraph"> 4341<p>For both <strong>for</strong> and <strong>while</strong> loops, the sub-statement itself does not 4342introduce a new scope for variable names, so the following has a 4343redeclaration compile-time error:</p> 4344</div> 4345<div class="listingblock"> 4346<div class="content"> 4347<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">for</span> ( <span class="comment">/* nested scope begins here */</span> <span class="predefined-type">int</span> i = <span class="integer">0</span>; i < <span class="integer">10</span>; i++) { 4348 <span class="predefined-type">int</span> i; <span class="comment">// redeclaration error</span> 4349}</code></pre> 4350</div> 4351</div> 4352<div class="paragraph"> 4353<p>The body of a <strong>do</strong>-<strong>while</strong> loop introduces a new scope lasting only between 4354the <strong>do</strong> and <strong>while</strong> (not including the while test expression), whether or 4355not the body is simple or compound:</p> 4356</div> 4357<div class="listingblock"> 4358<div class="content"> 4359<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">int</span> i = <span class="integer">17</span>; 4360<span class="keyword">do</span> 4361 <span class="predefined-type">int</span> i = <span class="integer">4</span>; <span class="comment">// okay, in nested scope_</span> 4362<span class="keyword">while</span> (i == <span class="integer">0</span>); <span class="comment">// i is 17, scoped outside the do-while body</span></code></pre> 4363</div> 4364</div> 4365<div class="paragraph"> 4366<p>The statement following a <strong>switch</strong> (…​) forms a nested scope.</p> 4367</div> 4368<div class="paragraph"> 4369<p>All variable names, structure type names, and function names in a given 4370scope share the same name space. 4371Function names can be redeclared in the same scope, with the same or 4372different parameters, without error. 4373An implicitly-sized array can be redeclared in the same scope as an array of 4374the same base type. 4375Otherwise, within one compilation unit, a declared name cannot be redeclared 4376in the same scope; doing so results in a redeclaration compile-time error. 4377If a nested scope redeclares a name used in an outer scope, it hides all 4378existing uses of that name. 4379There is no way to access the hidden name or make it unhidden, without 4380exiting the scope that hid it.</p> 4381</div> 4382<div class="paragraph"> 4383<p>The built-in functions are scoped in a scope outside the global scope that 4384users declare global variables in. 4385That is, a shader’s global scope, available for user-defined functions and 4386global variables, is nested inside the scope containing the built-in 4387functions. 4388When a function name is redeclared in a nested scope, it hides all functions 4389declared with that name in the outer scope. 4390Function declarations (prototypes) cannot occur inside of functions; they 4391must be at global scope, or for the built-in functions, outside the global 4392scope, otherwise a compile-time error results.</p> 4393</div> 4394<div class="paragraph"> 4395<p>Shared globals are global variables declared with the same name in 4396independently compiled units (shaders) within the same language (i.e., same 4397stage, e.g. vertex) that are linked together when making a single program. 4398(Globals forming the interface between two different shader languages are 4399discussed in other sections.) Shared globals share the same name space, and 4400must be declared with the same type. 4401They will share the same storage.</p> 4402</div> 4403<div class="paragraph"> 4404<p>Shared global arrays must have the same base type and the same explicit 4405size. 4406An array implicitly sized in one shader can be explicitly sized by another 4407shader in the same stage. 4408If no shader in a stage has an explicit size for the array, the largest 4409implicit size (one more than the largest index used) in that stage is used. 4410There is no cross-stage array sizing. 4411If there is no static access to an implicitly sized array within the stage 4412declaring it, then the array is given a size of 1, which is relevant when 4413the array is declared within an interface block that is shared with other 4414stages or the application (other unused arrays might be eliminated by the 4415optimizer).</p> 4416</div> 4417<div class="paragraph"> 4418<p>Shared global scalars must have exactly the same type name and type 4419definition. 4420Structures must have the same name, sequence of type names, and type 4421definitions, and member names to be considered the same type. 4422This rule applies recursively for nested or embedded types. 4423If a shared global has multiple initializers, the initializers must all be 4424constant expressions, and they must all have the same value. 4425Otherwise, a link-time error will result. 4426(A shared global having only one initializer does not require that 4427initializer to be a constant expression.)</p> 4428</div> 4429</div> 4430<div class="sect2"> 4431<h3 id="storage-qualifiers">4.3. Storage Qualifiers</h3> 4432<div class="paragraph"> 4433<p>Variable declarations may have at most one storage qualifier specified in 4434front of the type. 4435These are summarized as</p> 4436</div> 4437<table class="tableblock frame-all grid-all stretch"> 4438<colgroup> 4439<col style="width: 50%;"> 4440<col style="width: 50%;"> 4441</colgroup> 4442<thead> 4443<tr> 4444<th class="tableblock halign-left valign-top">Storage Qualifier</th> 4445<th class="tableblock halign-left valign-top">Meaning</th> 4446</tr> 4447</thead> 4448<tbody> 4449<tr> 4450<td class="tableblock halign-left valign-top"><p class="tableblock"><none: default></p></td> 4451<td class="tableblock halign-left valign-top"><p class="tableblock">local read/write memory, or an input parameter to a 4452 function</p></td> 4453</tr> 4454<tr> 4455<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>const</strong></p></td> 4456<td class="tableblock halign-left valign-top"><p class="tableblock">a variable whose value cannot be changed</p></td> 4457</tr> 4458<tr> 4459<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>in</strong></p></td> 4460<td class="tableblock halign-left valign-top"><p class="tableblock">linkage into a shader from a previous stage, variable 4461 is copied in</p></td> 4462</tr> 4463<tr> 4464<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>out</strong></p></td> 4465<td class="tableblock halign-left valign-top"><p class="tableblock">linkage out of a shader to a subsequent stage, 4466 variable is copied out</p></td> 4467</tr> 4468<tr> 4469<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>attribute</strong></p></td> 4470<td class="tableblock halign-left valign-top"><p class="tableblock">compatibility profile only and vertex language only; 4471 same as <strong>in</strong> when in a vertex shader</p></td> 4472</tr> 4473<tr> 4474<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>uniform</strong></p></td> 4475<td class="tableblock halign-left valign-top"><p class="tableblock">value does not change across the primitive being 4476 processed, uniforms form the linkage between a shader, 4477 API, and the application</p></td> 4478</tr> 4479<tr> 4480<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>varying</strong></p></td> 4481<td class="tableblock halign-left valign-top"><p class="tableblock">compatibility profile only and vertex and fragment 4482 languages only; same as <strong>out</strong> when in a vertex shader 4483 and same as <strong>in</strong> when in a fragment shader</p></td> 4484</tr> 4485<tr> 4486<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>buffer</strong></p></td> 4487<td class="tableblock halign-left valign-top"><p class="tableblock">value is stored in a buffer object, and can be read or 4488 written both by shader invocations and the API</p></td> 4489</tr> 4490<tr> 4491<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>shared</strong></p></td> 4492<td class="tableblock halign-left valign-top"><p class="tableblock">compute shader only; variable storage is shared across 4493 all work items in a workgroup</p></td> 4494</tr> 4495</tbody> 4496</table> 4497<div class="paragraph"> 4498<p>Some input and output qualified variables can be qualified with at most one 4499additional auxiliary storage qualifier:</p> 4500</div> 4501<table class="tableblock frame-all grid-all stretch"> 4502<colgroup> 4503<col style="width: 50%;"> 4504<col style="width: 50%;"> 4505</colgroup> 4506<thead> 4507<tr> 4508<th class="tableblock halign-left valign-top">Auxiliary Storage Qualifier</th> 4509<th class="tableblock halign-left valign-top">Meaning</th> 4510</tr> 4511</thead> 4512<tbody> 4513<tr> 4514<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>centroid</strong></p></td> 4515<td class="tableblock halign-left valign-top"><p class="tableblock">centroid-based interpolation</p></td> 4516</tr> 4517<tr> 4518<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sample</strong></p></td> 4519<td class="tableblock halign-left valign-top"><p class="tableblock">per-sample interpolation</p></td> 4520</tr> 4521<tr> 4522<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>patch</strong></p></td> 4523<td class="tableblock halign-left valign-top"><p class="tableblock">per-tessellation-patch attributes</p></td> 4524</tr> 4525</tbody> 4526</table> 4527<div class="paragraph"> 4528<p>Not all combinations of qualification are allowed. 4529Auxiliary storage qualifiers can only be used with the <strong>in</strong> or <strong>out</strong> storage 4530qualifiers. 4531Additional qualifier rules are defined in upcoming sections.</p> 4532</div> 4533<div class="paragraph"> 4534<p>Local variables can only use the <strong>const</strong> storage qualifier (or use no 4535storage qualifier).</p> 4536</div> 4537<div class="paragraph"> 4538<p>Note that function parameters can use <strong>const</strong>, <strong>in</strong>, and <strong>out</strong> qualifiers, 4539but as <em>parameter qualifiers</em>. 4540Parameter qualifiers are discussed in 4541“<a href="#function-calling-conventions">Function Calling Conventions</a>”.</p> 4542</div> 4543<div class="paragraph"> 4544<p>Function return types and structure members do not use storage qualifiers.</p> 4545</div> 4546<div class="paragraph"> 4547<p>Initializers in global declarations may only be used in declarations of 4548global variables with no storage qualifier, with a <strong>const</strong> qualifier, or 4549with a <strong>uniform</strong> qualifier.</p> 4550</div> 4551<div class="paragraph"> 4552<p>Global variables without storage qualifiers that are not initialized in 4553their declaration or by the application will not be initialized, 4554but rather will enter <em>main()</em> with undefined values.</p> 4555</div> 4556<div class="paragraph"> 4557<p>When comparing an output from one shader stage to an input of a subsequent 4558shader stage, the input and output don’t match if their auxiliary qualifiers 4559(or lack thereof) are not the same.</p> 4560</div> 4561<div class="sect3"> 4562<h4 id="default-storage-qualifier">4.3.1. Default Storage Qualifier</h4> 4563<div class="paragraph"> 4564<p>If no qualifier is present on a global variable, then the variable has no 4565linkage to the application or shaders running on other pipeline stages. 4566For either global or local unqualified variables, the declaration will 4567appear to allocate memory associated with the processor it targets. 4568This variable will provide read/write access to this allocated memory.</p> 4569</div> 4570</div> 4571<div class="sect3"> 4572<h4 id="constant-qualifier">4.3.2. Constant Qualifier</h4> 4573<div class="paragraph"> 4574<p>Named compile-time constants 4575or read-only variables 4576can be declared using 4577the <strong>const</strong> qualifier. 4578The <strong>const</strong> qualifier can be used with any of the non-void transparent basic 4579data types, as well as with structures and arrays of these. 4580It is a compile-time error to write to a <strong>const</strong> variable outside of its 4581declaration, so they must be initialized when declared. 4582For example,</p> 4583</div> 4584<div class="listingblock"> 4585<div class="content"> 4586<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">const</span> vec3 zAxis = vec3 (<span class="float">0</span><span class="float">.0</span>, <span class="float">0</span><span class="float">.0</span>, <span class="float">1</span><span class="float">.0</span>); 4587<span class="directive">const</span> <span class="predefined-type">float</span> ceiling = a + b; <span class="comment">// a and b not necessarily constants</span></code></pre> 4588</div> 4589</div> 4590<div class="paragraph"> 4591<p>Structure members may not be qualified with <strong>const</strong>. 4592Structure variables can be declared as <strong>const</strong>, and initialized with a 4593structure 4594constructor or initializer.</p> 4595</div> 4596<div class="paragraph"> 4597<p>Initializers for <strong>const</strong> declarations 4598at global scope 4599must be constant expressions, as defined in 4600“<a href="#constant-expressions">Constant Expressions</a>”.</p> 4601</div> 4602</div> 4603<div class="sect3"> 4604<h4 id="constant-expressions">4.3.3. Constant Expressions</h4> 4605<div class="paragraph"> 4606<p>SPIR-V specialization constants are expressed in GLSL as <strong>const</strong> with the 4607layout qualifier <strong>constant_id</strong>, as described in 4608“<a href="#specialization-constant-qualifier">Specialization-Constant 4609Qualifier.</a>”</p> 4610</div> 4611<div class="paragraph"> 4612<p>A <em>constant expression</em> is one of</p> 4613</div> 4614<div class="ulist"> 4615<ul> 4616<li> 4617<p>A literal value (e.g. <strong>5</strong> or <strong>true</strong>).</p> 4618</li> 4619<li> 4620<p>A variable declared with the <strong>const</strong> qualifier and an initializer, where 4621the initializer is a constant expression. 4622This includes both <strong>const</strong> declared with a specialization-constant 4623layout qualifier, e.g. <strong>layout</strong>(<strong>constant_id</strong> = …​), and those declared 4624without a specialization-constant layout qualifier.</p> 4625</li> 4626<li> 4627<p>Built-in variables qualified as <strong>const</strong>.</p> 4628</li> 4629<li> 4630<p>An expression formed by an operator on operands that are all constant 4631expressions, including getting an element of a constant array, or a 4632member of a constant structure, or components of a constant vector. 4633However, the lowest precedence operators of the sequence operator (<strong>,</strong>) 4634and the assignment operators (<strong>=</strong>, <strong>+=</strong>, <strong>…​</strong>) are not included in the 4635operators that can create a constant expression. 4636Also, an array access with a specialization constant as an index does 4637not result in a constant expression.</p> 4638</li> 4639<li> 4640<p>Valid use of the <strong>length</strong>() method on an explicitly sized object, 4641whether or not the object itself is constant (implicitly sized or 4642run-time sized arrays do not return a constant expression).</p> 4643</li> 4644<li> 4645<p>A constructor whose arguments are all constant expressions.</p> 4646</li> 4647<li> 4648<p>For non-specialization constants only: The value returned by certain 4649built-in function calls whose arguments are all constant expressions, 4650including at least the list below. 4651Any other built-in function that does not access memory (not the texture 4652lookup functions, image access, atomic counter, etc.), that has a 4653non-<strong>void</strong> return type, that has no <strong>out</strong> parameter, and is not a noise 4654function might also be considered a constant. 4655When a function is called with an argument that is a specialization 4656constant, the result is not a constant expression.</p> 4657<div class="ulist"> 4658<ul> 4659<li> 4660<p>Angle and Trigonometric Functions</p> 4661<div class="ulist"> 4662<ul> 4663<li> 4664<p><strong>radians</strong></p> 4665</li> 4666<li> 4667<p><strong>degrees</strong></p> 4668</li> 4669<li> 4670<p><strong>sin</strong></p> 4671</li> 4672<li> 4673<p><strong>cos</strong></p> 4674</li> 4675<li> 4676<p><strong>asin</strong></p> 4677</li> 4678<li> 4679<p><strong>acos</strong></p> 4680</li> 4681</ul> 4682</div> 4683</li> 4684<li> 4685<p>Exponential Functions</p> 4686<div class="ulist"> 4687<ul> 4688<li> 4689<p><strong>pow</strong></p> 4690</li> 4691<li> 4692<p><strong>exp</strong></p> 4693</li> 4694<li> 4695<p><strong>log</strong></p> 4696</li> 4697<li> 4698<p><strong>exp2</strong></p> 4699</li> 4700<li> 4701<p><strong>log2</strong></p> 4702</li> 4703<li> 4704<p><strong>sqrt</strong></p> 4705</li> 4706<li> 4707<p><strong>inversesqrt</strong></p> 4708</li> 4709</ul> 4710</div> 4711</li> 4712<li> 4713<p>Common Functions</p> 4714<div class="ulist"> 4715<ul> 4716<li> 4717<p><strong>abs</strong></p> 4718</li> 4719<li> 4720<p><strong>sign</strong></p> 4721</li> 4722<li> 4723<p><strong>floor</strong></p> 4724</li> 4725<li> 4726<p><strong>trunc</strong></p> 4727</li> 4728<li> 4729<p><strong>round</strong></p> 4730</li> 4731<li> 4732<p><strong>ceil</strong></p> 4733</li> 4734<li> 4735<p><strong>mod</strong></p> 4736</li> 4737<li> 4738<p><strong>min</strong></p> 4739</li> 4740<li> 4741<p><strong>max</strong></p> 4742</li> 4743<li> 4744<p><strong>clamp</strong></p> 4745</li> 4746</ul> 4747</div> 4748</li> 4749<li> 4750<p>Geometric Functions</p> 4751<div class="ulist"> 4752<ul> 4753<li> 4754<p><strong>length</strong></p> 4755</li> 4756<li> 4757<p><strong>dot</strong></p> 4758</li> 4759<li> 4760<p><strong>normalize</strong></p> 4761</li> 4762</ul> 4763</div> 4764</li> 4765</ul> 4766</div> 4767</li> 4768<li> 4769<p>Function calls to user-defined functions (non-built-in functions) cannot 4770be used to form constant expressions.</p> 4771</li> 4772</ul> 4773</div> 4774<div class="paragraph"> 4775<p>A <em>constant integral expression</em> is a constant expression that evaluates to 4776a scalar signed or unsigned integer.</p> 4777</div> 4778<div class="paragraph"> 4779<p>Constant expressions will be evaluated in an invariant way so as to create 4780the same value in multiple shaders when the same constant expressions appear 4781in those shaders. 4782See “<a href="#the-invariant-qualifier">The Invariant Qualifier</a>” for more details 4783on how to create invariant expressions and 4784“<a href="#precision-qualifiers">Precision Qualifiers</a>” for detail on how 4785expressions are evaluated.</p> 4786</div> 4787<div class="paragraph"> 4788<p>Constant expressions respect the <strong>precise</strong> and <strong>invariant</strong> qualifiers but 4789will be always be evaluated in an invariant way, independent of the use of 4790such qualification, so as to create the same value in multiple shaders when 4791the same constant expressions appear in those shaders. 4792See “<a href="#the-invariant-qualifier">The Invariant Qualifier</a>” and 4793“<a href="#the-precise-qualifier">The Precise Qualifier</a>” for more details on how 4794to create invariant expressions.</p> 4795</div> 4796<div class="paragraph"> 4797<p>Constant-expressions may be evaluated by a 4798host platform, and are therefore not required to compute the same value that 4799the same expression would evaluate to on the shader execution target. 4800However, the host must use the same or greater precision than the target 4801would use. 4802When the precision qualification cannot be determined, the expression is 4803evaluated at <strong>highp</strong>. 4804See “<a href="#default-precision-qualifiers">Default Precision Qualifiers</a>”.</p> 4805</div> 4806<div class="paragraph"> 4807<p>Specialization-constant expressions are never evaluated by the compiler 4808front end, but instead retain the expression’s operations needed to evaluate 4809them later on the host.</p> 4810</div> 4811</div> 4812<div class="sect3"> 4813<h4 id="input-variables">4.3.4. Input Variables</h4> 4814<div class="paragraph"> 4815<p>Shader input variables are declared with the <strong>in</strong> storage qualifier. 4816They form the input interface between previous stages of the API 4817pipeline and the declaring shader. 4818Input variables must be declared at global scope. 4819Values from the previous pipeline stage are copied into input variables at 4820the beginning of shader execution. 4821It is a compile-time error to write to a variable declared as an input.</p> 4822</div> 4823<div class="paragraph"> 4824<p>Only the input variables that are 4825statically 4826read need to be written by the 4827previous stage; it is allowed to have superfluous declarations of input 4828variables. 4829This is shown in the following table.</p> 4830</div> 4831<table class="tableblock frame-all grid-all fit-content"> 4832<colgroup> 4833<col> 4834<col> 4835<col> 4836<col> 4837<col> 4838</colgroup> 4839<tbody> 4840<tr> 4841<td class="tableblock halign-left valign-top" colspan="2" rowspan="2"><p class="tableblock">Treatment of Mismatched Input Variables</p></td> 4842<td class="tableblock halign-left valign-top" colspan="3"><p class="tableblock">Consuming Shader (input variables)</p></td> 4843</tr> 4844<tr> 4845<td class="tableblock halign-left valign-top"><p class="tableblock">No Declaration</p></td> 4846<td class="tableblock halign-left valign-top"><p class="tableblock">Declared but no Static Use</p></td> 4847<td class="tableblock halign-left valign-top"><p class="tableblock">Declared and Static Use</p></td> 4848</tr> 4849<tr> 4850<td class="tableblock halign-left valign-top" rowspan="3"><p class="tableblock">Generating Shader (output variables)</p></td> 4851<td class="tableblock halign-left valign-top"><p class="tableblock">No Declaration</p></td> 4852<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed</p></td> 4853<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed</p></td> 4854<td class="tableblock halign-left valign-top"><p class="tableblock">Link-Time Error</p></td> 4855</tr> 4856<tr> 4857<td class="tableblock halign-left valign-top"><p class="tableblock">Declared but no Static Use</p></td> 4858<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed</p></td> 4859<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed</p></td> 4860<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed (values are undefined)</p></td> 4861</tr> 4862<tr> 4863<td class="tableblock halign-left valign-top"><p class="tableblock">Declared and Static Use</p></td> 4864<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed</p></td> 4865<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed</p></td> 4866<td class="tableblock halign-left valign-top"><p class="tableblock">Allowed (values are potentially undefined)</p></td> 4867</tr> 4868</tbody> 4869</table> 4870<div class="paragraph"> 4871<p>Consumption errors are based on static use only. 4872Compilation may generate a warning, but not an error, for any dynamic use 4873the compiler can deduce that might cause consumption of undefined values.</p> 4874</div> 4875<div class="paragraph"> 4876<p>See “<a href="#built-in-variables">Built-In Variables</a>” for a list of the built-in 4877input names.</p> 4878</div> 4879<div class="paragraph"> 4880<p>Vertex shader input variables (or attributes) receive per-vertex data. 4881It is a compile-time error to use auxiliary storage or interpolation qualifiers 4882on a vertex shader input. 4883The values copied in are established by the API or through the use 4884of the layout identifier <strong>location</strong>.</p> 4885</div> 4886<div class="paragraph"> 4887<p>It is a compile-time error to declare a vertex shader input with, or that 4888contains, any of the following types:</p> 4889</div> 4890<div class="ulist"> 4891<ul> 4892<li> 4893<p>A <a href="#booleans">boolean type</a></p> 4894</li> 4895<li> 4896<p>An <a href="#opaque-types">opaque type</a></p> 4897</li> 4898<li> 4899<p>A structure</p> 4900</li> 4901</ul> 4902</div> 4903<div class="paragraph"> 4904<p>Example declarations in a vertex shader:</p> 4905</div> 4906<div class="listingblock"> 4907<div class="content"> 4908<pre class="CodeRay highlight"><code data-lang="c++">in vec4 position; 4909in vec3 normal; 4910in vec2 texCoord[<span class="integer">4</span>];</code></pre> 4911</div> 4912</div> 4913<div class="paragraph"> 4914<p>It is expected that graphics hardware will have a small number of fixed 4915vector locations for passing vertex inputs. 4916Therefore, the OpenGL Shading Language defines each non-matrix input variable as taking up 4917one such vector location. 4918There is an implementation-dependent limit on the number of locations that 4919can be used, and if this is exceeded it will cause a link-time error. 4920(Declared input variables that are not statically used do not count against 4921this limit.) A scalar input counts the same amount against this limit as a 4922<strong>vec4</strong>, so applications may want to consider packing groups of four 4923unrelated float inputs together into a vector to better utilize the 4924capabilities of the underlying hardware. 4925A matrix input will use up multiple locations. 4926The number of locations used will equal the number of columns in the matrix.</p> 4927</div> 4928<div class="paragraph"> 4929<p>Tessellation control, evaluation, and geometry shader input variables get 4930the per-vertex values written out by output variables of the same names in 4931the previous active shader stage. 4932For these inputs, <strong>centroid</strong> and interpolation qualifiers are allowed, but 4933have no effect. 4934Since tessellation control, tessellation evaluation, and geometry shaders 4935operate on a set of vertices, each input variable (or input block, see 4936interface blocks below) needs to be declared as an array. 4937For example,</p> 4938</div> 4939<div class="listingblock"> 4940<div class="content"> 4941<pre class="CodeRay highlight"><code data-lang="c++">in <span class="predefined-type">float</span> foo[]; <span class="comment">// geometry shader input for vertex "out float foo"</span></code></pre> 4942</div> 4943</div> 4944<div class="paragraph"> 4945<p>Each element of such an array corresponds to one vertex of the primitive 4946being processed. 4947Each array can optionally have a size declared. 4948For geometry shaders, the array size will be set by, (or if provided must be 4949consistent with) the input <strong>layout</strong> declaration(s) establishing the type of 4950input primitive, as described later in “<a href="#input-layout-qualifiers">Input 4951Layout Qualifiers</a>”.</p> 4952</div> 4953<div class="paragraph"> 4954<p>Some inputs and outputs are <em>arrayed</em>, meaning that for an interface between 4955two shader stages either the input or output declaration requires an extra 4956level of array indexing for the declarations to match. 4957For example, with the interface between a vertex shader and a geometry 4958shader, vertex shader output variables and geometry shader input variables 4959of the same name must have matching types, except that the geometry shader 4960will have one more array dimension than the vertex shader, to allow for 4961vertex indexing. 4962If such an arrayed interface variable is not declared with the necessary 4963additional input or output array dimension, a link-time error will result. 4964Geometry shader inputs, tessellation control shader inputs and outputs, and 4965tessellation evaluation inputs all have an additional level of arrayness 4966relative to other shader inputs and outputs. 4967These inputs and outputs are known as <em>per-vertex-arrayed</em> inputs and 4968outputs. 4969Component limits for arrayed interfaces (e.g. 4970<em>gl_MaxTessControlInputComponents</em>) are limits per vertex, not limits for 4971the entire interface.</p> 4972</div> 4973<div class="paragraph"> 4974<p>For non-arrayed interfaces (meaning array dimensionally stays the same 4975between stages), it is a link-time error if the input variable is not 4976declared with the same type, including array dimensionality, as the matching 4977output variable.</p> 4978</div> 4979<div class="paragraph"> 4980<p>The link-time type-matching rules apply to all declared input and output 4981variables, whether or not they are used.</p> 4982</div> 4983<div class="paragraph"> 4984<p>Additionally, tessellation evaluation shaders support per-patch input 4985variables declared with the <strong>patch</strong> and <strong>in</strong> qualifiers. 4986Per-patch input variables are filled with the values of per-patch output 4987variables written by the tessellation control shader. 4988Per-patch inputs may be declared as one-dimensional arrays, but are not 4989indexed by vertex number. 4990Applying the <strong>patch</strong> qualifier to inputs can only be done in tessellation 4991evaluation shaders. 4992As with other input variables, per-patch inputs must be declared using the 4993same type and qualification as per-patch outputs from the previous 4994(tessellation control) shader stage. 4995It is a compile-time error to use <strong>patch</strong> with inputs in any other stage.</p> 4996</div> 4997<div class="paragraph"> 4998<p>It is a compile-time error to declare a tessellation control, tessellation 4999evaluation or geometry shader input with, or that contains, any of the 5000following types:</p> 5001</div> 5002<div class="ulist"> 5003<ul> 5004<li> 5005<p>A <a href="#booleans">boolean type</a></p> 5006</li> 5007<li> 5008<p>An <a href="#opaque-types">opaque type</a></p> 5009</li> 5010</ul> 5011</div> 5012<div class="paragraph"> 5013<p>Fragment shader inputs get per-fragment values, typically interpolated from 5014a previous stage’s outputs. 5015The auxiliary storage qualifiers <strong>centroid</strong> and <strong>sample</strong> can also be 5016applied, as well as the interpolation qualifiers <strong>flat</strong>, <strong>noperspective</strong>, 5017and <strong>smooth.</strong></p> 5018</div> 5019<div class="paragraph"> 5020<p>It is a compile-time error to declare a fragment shader input with, or that 5021contains, any of the following types:</p> 5022</div> 5023<div class="ulist"> 5024<ul> 5025<li> 5026<p>A <a href="#booleans">boolean type</a></p> 5027</li> 5028<li> 5029<p>An <a href="#opaque-types">opaque type</a></p> 5030</li> 5031</ul> 5032</div> 5033<div class="paragraph"> 5034<p>Fragment shader inputs that are, or contain, integral 5035or double-precision floating-point 5036types must be 5037qualified with the interpolation qualifier <strong>flat</strong>.</p> 5038</div> 5039<div class="paragraph"> 5040<p>Fragment inputs are declared as in the following examples:</p> 5041</div> 5042<div class="listingblock"> 5043<div class="content"> 5044<pre class="CodeRay highlight"><code data-lang="c++">in vec3 normal; 5045centroid in vec2 TexCoord; 5046invariant centroid in vec4 Color; 5047noperspective in <span class="predefined-type">float</span> temperature; 5048flat in vec3 myColor; 5049noperspective centroid in vec2 myTexCoord;</code></pre> 5050</div> 5051</div> 5052<div class="paragraph"> 5053<p>The fragment shader inputs form an interface with the last active shader in 5054the vertex processing pipeline. 5055For this interface, the last active shader stage output variables and 5056fragment shader input variables of the same name must match in type and 5057qualification, with a few exceptions: The storage qualifiers must, of 5058course, differ (one is <strong>in</strong> and one is <strong>out</strong>). 5059Also, 5060interpolation qualification (e.g. <strong>flat</strong>) and 5061auxiliary qualification (e.g. <strong>centroid</strong>) may differ. 5062These mismatches are allowed between any pair of stages. 5063When 5064interpolation or 5065auxiliary qualifiers do not match, those provided in 5066the fragment shader supersede those provided in previous stages. 5067If any such qualifiers are completely missing in the fragment shaders, then 5068the default is used, rather than any qualifiers that may have been declared 5069in previous stages. 5070That is, what matters is what is declared in the fragment shaders, not what 5071is declared in shaders in previous stages.</p> 5072</div> 5073<div class="paragraph"> 5074<p>When an interface between shader stages is formed using shaders from two 5075separate program objects, it is not possible to detect mismatches between 5076inputs and outputs when the programs are linked. 5077When there are mismatches between inputs and outputs on such interfaces, 5078the values passed across the interface will be partially or completely 5079undefined.</p> 5080</div> 5081<div class="paragraph"> 5082<p>Shaders can ensure matches across such interfaces either by using input and 5083output layout qualifiers (sections “<a href="#input-layout-qualifiers">Input Layout 5084Qualifiers</a>” and “<a href="#output-layout-qualifiers">Output Layout 5085Qualifiers</a>”) or by using identical input and output declarations of 5086blocks or variables. 5087Complete rules for interface matching are found in section 7.4.1 “Shader 5088Interface Matching” of the <a href="#references">OpenGL Specification</a>.</p> 5089</div> 5090<div class="paragraph"> 5091<p>Compute shaders do not permit user-defined input variables and do not form a 5092formal interface with any other shader stage. 5093See “<a href="#compute-shader-special-variables">Compute Shader Special 5094Variables</a>” for a description of built-in compute shader input variables. 5095All other input to a compute shader is retrieved explicitly through image 5096loads, texture fetches, loads from uniforms or uniform buffers, or other 5097user supplied code. 5098Redeclaration of built-in input variables in compute shaders is not 5099permitted.</p> 5100</div> 5101</div> 5102<div class="sect3"> 5103<h4 id="uniform-variables">4.3.5. Uniform Variables</h4> 5104<div class="paragraph"> 5105<p>The <strong>uniform</strong> qualifier is used to declare global variables whose values are 5106the same across the entire primitive being processed. 5107All <strong>uniform</strong> variables are read-only and are initialized externally either 5108at link time or through the API. 5109The link-time initial value is either the value of the variable’s 5110initializer, if present, or 0 if no initializer is present. 5111Opaque types cannot have initializers, or a compile-time error results. 5112When targeting Vulkan, it is a compile-time error to declare <strong>uniform</strong> 5113variables outside a block.</p> 5114</div> 5115<div class="paragraph"> 5116<p>Example declarations are:</p> 5117</div> 5118<div class="listingblock"> 5119<div class="content"> 5120<pre class="CodeRay highlight"><code data-lang="c++">uniform vec4 lightPosition; 5121uniform vec3 color = vec3(<span class="float">0</span><span class="float">.7</span>, <span class="float">0</span><span class="float">.7</span>, <span class="float">0</span><span class="float">.2</span>); <span class="comment">// value assigned at link time</span></code></pre> 5122</div> 5123</div> 5124<div class="paragraph"> 5125<p>The <strong>uniform</strong> qualifier can be used with any of the basic data types, or 5126when declaring a variable whose type is a structure, or an array of any of 5127these.</p> 5128</div> 5129<div class="paragraph"> 5130<p>There is an implementation-dependent limit on the amount of storage for 5131uniforms that can be used for each type of shader and if this is exceeded it 5132will cause a compile-time or link-time error. 5133Uniform variables that are declared but not 5134used do not count against this limit. 5135The number of user-defined uniform variables and the number of built-in 5136uniform variables that are used within a shader are added together to 5137determine whether available uniform storage has been exceeded.</p> 5138</div> 5139<div class="paragraph"> 5140<p>Uniforms in shaders all share a single global name space when linked into a 5141program or separable program. 5142Hence, the types, 5143initializers, 5144and any location specifiers of all statically used uniform variables with the 5145same name must match across all shaders that are linked into a single program. 5146However it is not required to repeat the 5147initializer or 5148location specifier in all the linked shaders. 5149While this single uniform name space is cross stage, a uniform variable 5150name’s scope is per stage: If a uniform variable name is declared in one 5151stage (e.g. a vertex shader) but not in another (e.g. a fragment shader), 5152then that name is still available in the other stage for a different use.</p> 5153</div> 5154</div> 5155<div class="sect3"> 5156<h4 id="output-variables">4.3.6. Output Variables</h4> 5157<div class="paragraph"> 5158<p>Shader output variables are declared with the <strong>out</strong> storage qualifier. 5159They form the output interface between the declaring shader and the 5160subsequent stages of the API pipeline. 5161Output variables must be declared at global scope. 5162During shader execution they will behave as normal unqualified global 5163variables. 5164Their values are copied out to the subsequent pipeline stage on shader exit. 5165Only output variables that are read by the subsequent pipeline stage need to 5166be written; it is allowed to have superfluous declarations of output 5167variables.</p> 5168</div> 5169<div class="paragraph"> 5170<p>There is <em>not</em> an <strong>inout</strong> storage qualifier for declaring a single variable 5171name as both input and output to a shader. 5172Also, a variable cannot be declared with both the <strong>in</strong> and the <strong>out</strong> 5173qualifiers, this will result in a compile-time or link-time error. 5174Output variables must be declared with different names than input variables. 5175However, nesting an input or output inside an interface block with an 5176instance name allows the same names with one referenced through a block 5177instance name.</p> 5178</div> 5179<div class="paragraph"> 5180<p>Vertex, tessellation evaluation, and geometry output variables output 5181per-vertex data and are declared using the <strong>out</strong> storage qualifier. 5182Applying <strong>patch</strong> to an output can only be done in a tessellation control 5183shader. 5184It is a compile-time error to use <strong>patch</strong> on outputs in any other stage.</p> 5185</div> 5186<div class="paragraph"> 5187<p>It is a compile-time error to declare a vertex, tessellation evaluation, 5188tessellation control, or geometry shader output with, or that contains, any 5189of the following types:</p> 5190</div> 5191<div class="ulist"> 5192<ul> 5193<li> 5194<p>A <a href="#booleans">boolean type</a></p> 5195</li> 5196<li> 5197<p>An <a href="#opaque-types">opaque type</a></p> 5198</li> 5199</ul> 5200</div> 5201<div class="paragraph"> 5202<p>Individual outputs are declared as in the following examples:</p> 5203</div> 5204<div class="listingblock"> 5205<div class="content"> 5206<pre class="CodeRay highlight"><code data-lang="c++">out vec3 normal; 5207centroid out vec2 TexCoord; 5208invariant centroid out vec4 Color; 5209flat out vec3 myColor; 5210sample out vec4 perSampleColor;</code></pre> 5211</div> 5212</div> 5213<div class="paragraph"> 5214<p>These can also appear in interface blocks, as described in 5215“<a href="#interface-blocks">Interface Blocks</a>”. 5216Interface blocks allow simpler addition of arrays to the interface from 5217vertex to geometry shader. 5218They also allow a fragment shader to have the same input interface as a 5219geometry shader for a given vertex shader.</p> 5220</div> 5221<div class="paragraph"> 5222<p>Tessellation control shader output variables are used to output 5223per-vertex and per-patch data. 5224Per-vertex output variables are arrayed (see <em>arrayed</em> under 5225“<a href="#input-variables">Input Variables</a>”) and declared using the <strong>out</strong> 5226qualifier without the <strong>patch</strong> qualifier. 5227Per-patch output variables are declared using the <strong>patch</strong> and <strong>out</strong> 5228qualifiers.</p> 5229</div> 5230<div class="paragraph"> 5231<p>Since tessellation control shaders produce an arrayed primitive comprising 5232multiple vertices, each per-vertex output variable (or output block, see 5233interface blocks below) needs to be declared as an array. 5234For example,</p> 5235</div> 5236<div class="listingblock"> 5237<div class="content"> 5238<pre class="CodeRay highlight"><code data-lang="c++">out <span class="predefined-type">float</span> foo[]; <span class="comment">// feeds next stage input "in float foo[]"</span></code></pre> 5239</div> 5240</div> 5241<div class="paragraph"> 5242<p>Each element of such an array corresponds to one vertex of the primitive 5243being produced. 5244Each array can optionally have a size declared. 5245The array size will be set by (or if provided must be consistent with) the 5246output layout declaration(s) establishing the number of vertices in the 5247output patch, as described later in 5248“<a href="#tessellation-control-outputs">Tessellation Control Outputs</a>”.</p> 5249</div> 5250<div class="paragraph"> 5251<p>Each tessellation control shader invocation has a corresponding output patch 5252vertex, and may assign values to per-vertex outputs only if they belong to 5253that corresponding vertex. 5254If a per-vertex output variable is used as an l-value, it is a compile-time 5255or link-time error if the expression indicating the vertex index is not the 5256identifier <em>gl_InvocationID</em>.</p> 5257</div> 5258<div class="paragraph"> 5259<p>The order of execution of a tessellation control shader invocation relative 5260to the other invocations for the same input patch is undefined unless the 5261built-in function <strong>barrier</strong>() is used. 5262This provides some control over relative execution order. 5263When a shader invocation calls <strong>barrier</strong>(), its execution pauses until all 5264other invocations have reached the same point of execution. 5265Output variable assignments performed by any invocation executed prior to 5266calling <strong>barrier</strong>() will be visible to any other invocation after the call 5267to <strong>barrier</strong>() returns.</p> 5268</div> 5269<div class="paragraph"> 5270<p>Because tessellation control shader invocations execute in undefined order 5271between barriers, the values of per-vertex or per-patch output variables 5272will sometimes be undefined. 5273Consider the beginning and end of shader execution and each call to 5274<strong>barrier</strong>() as synchronization points. 5275The value of an output variable will be undefined in any of the three 5276following cases:</p> 5277</div> 5278<div class="olist arabic"> 5279<ol class="arabic"> 5280<li> 5281<p>At the beginning of execution.</p> 5282</li> 5283<li> 5284<p>At each synchronization point, unless</p> 5285<div class="openblock"> 5286<div class="content"> 5287<div class="ulist"> 5288<ul> 5289<li> 5290<p>the value was well-defined after the previous synchronization point and 5291was not written by any invocation since, or</p> 5292</li> 5293<li> 5294<p>the value was written by exactly one shader invocation since the previous 5295synchronization point, or</p> 5296</li> 5297<li> 5298<p>the value was written by multiple shader invocations since the previous 5299synchronization point, and the last write performed by all such 5300invocations wrote the same value.</p> 5301</li> 5302</ul> 5303</div> 5304</div> 5305</div> 5306</li> 5307<li> 5308<p>When read by a shader invocation, if</p> 5309<div class="openblock"> 5310<div class="content"> 5311<div class="ulist"> 5312<ul> 5313<li> 5314<p>the value was undefined at the previous synchronization point and has not 5315been written by the same shader invocation since, or</p> 5316</li> 5317<li> 5318<p>the output variable is written to by any other shader invocation between 5319the previous and next synchronization points, even if that assignment 5320occurs in code following the read.</p> 5321</li> 5322</ul> 5323</div> 5324</div> 5325</div> 5326</li> 5327</ol> 5328</div> 5329<div class="paragraph"> 5330<p>Fragment outputs output per-fragment data and are declared using the <strong>out</strong> 5331storage qualifier. 5332It is a compile-time error to use auxiliary storage qualifiers or 5333interpolation qualifiers in a fragment shader output declaration. 5334It is a compile-time error to declare a fragment shader output with, or that 5335contains, any of the following types:</p> 5336</div> 5337<div class="ulist"> 5338<ul> 5339<li> 5340<p>A <a href="#booleans">boolean type</a></p> 5341</li> 5342<li> 5343<p>A double-precision scalar or vector (<strong>double</strong>, <strong>dvec2</strong>, <strong>dvec3</strong>, 5344<strong>dvec4</strong>)</p> 5345</li> 5346<li> 5347<p>An <a href="#opaque-types">opaque type</a></p> 5348</li> 5349<li> 5350<p>A matrix type</p> 5351</li> 5352<li> 5353<p>A structure</p> 5354</li> 5355</ul> 5356</div> 5357<div class="paragraph"> 5358<p>Fragment outputs are declared as in the following examples:</p> 5359</div> 5360<div class="listingblock"> 5361<div class="content"> 5362<pre class="CodeRay highlight"><code data-lang="c++">out vec4 FragmentColor; 5363out uint Luminosity;</code></pre> 5364</div> 5365</div> 5366<div class="paragraph"> 5367<p>Compute shaders have no built-in output variables, do not support 5368user-defined output variables and do not form a formal interface with any 5369other shader stage. 5370All outputs from a compute shader take the form of the side effects such as 5371image stores and operations on atomic counters.</p> 5372</div> 5373</div> 5374<div class="sect3"> 5375<h4 id="buffer-variables">4.3.7. Buffer Variables</h4> 5376<div class="paragraph"> 5377<p>The <strong>buffer</strong> qualifier is used to declare global variables whose values are 5378stored in the data store of a buffer object bound through the API. 5379Buffer variables can be read and written, with the underlying storage shared 5380among all active shader invocations. 5381Buffer variable memory reads and writes within a single shader invocation 5382are processed in order. 5383However, the order of reads and writes performed in one invocation relative 5384to those performed by another invocation is largely undefined. 5385Buffer variables may be qualified with memory qualifiers affecting how the 5386underlying memory is accessed, as described in “<a href="#memory-qualifiers">Memory 5387Qualifiers</a>”.</p> 5388</div> 5389<div class="paragraph"> 5390<p>The <strong>buffer</strong> qualifier can be used to declare interface blocks (see 5391“<a href="#interface-blocks">Interface Blocks</a>”), which are then referred to as 5392shader storage blocks. 5393It is a compile-time error to declare buffer variables outside a block.</p> 5394</div> 5395<div class="listingblock"> 5396<div class="content"> 5397<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// use buffer to create a buffer block (shader storage block)</span> 5398buffer BufferName { <span class="comment">// externally visible name of buffer</span> 5399 <span class="predefined-type">int</span> count; <span class="comment">// typed, shared memory...</span> 5400 ... <span class="comment">// ...</span> 5401 vec4 v[]; <span class="comment">// last member may be an array that is not sized</span> 5402 <span class="comment">// until after link time (dynamically sized)</span> 5403} Name; <span class="comment">// name of block within the shader</span></code></pre> 5404</div> 5405</div> 5406<div class="paragraph"> 5407<p>There are implementation-dependent limits on the number of shader storage 5408blocks used for each type of shader, the combined number of shader storage 5409blocks used for a program, and the amount of storage required by each 5410individual shader storage block. 5411If any of these limits are exceeded, it will cause a compile-time or 5412link-time error.</p> 5413</div> 5414<div class="paragraph"> 5415<p>If multiple shaders are linked together, then they will share a single 5416global buffer variable name space. 5417Hence, the types of all declared buffer variables with the same name must 5418match across all shaders that are linked into a single program.</p> 5419</div> 5420</div> 5421<div class="sect3"> 5422<h4 id="shared-variables">4.3.8. Shared Variables</h4> 5423<div class="paragraph"> 5424<p>The <strong>shared</strong> qualifier is used to declare global variables that have storage 5425shared between all work items in a compute shader workgroup. 5426Variables declared as <strong>shared</strong> may only be used in compute shaders (see 5427“<a href="#compute-processor">Compute Processor</a>”). 5428Any other declaration of a <strong>shared</strong> variable is a compile-time error. 5429Shared variables are implicitly coherent (see 5430“<a href="#memory-qualifiers">Memory Qualifiers</a>”).</p> 5431</div> 5432<div class="paragraph"> 5433<p>Variables declared as <strong>shared</strong> may not have initializers and their contents 5434are undefined at the beginning of shader execution. 5435Any data written to <strong>shared</strong> variables will be visible to other work items 5436(executing the same shader) within the same workgroup.</p> 5437</div> 5438<div class="paragraph"> 5439<p>In the absence of synchronization, the order of reads and writes to the same 5440<strong>shared</strong> variable by different invocations of a shader is not defined.</p> 5441</div> 5442<div class="paragraph"> 5443<p>In order to achieve ordering with respect to reads and writes to <strong>shared</strong> 5444variables, control flow barriers must be employed using the <strong>barrier</strong>() function 5445(see “<a href="#shader-invocation-control-functions">Shader Invocation Control 5446Functions</a>”).</p> 5447</div> 5448<div class="paragraph"> 5449<p>There is a limit to the total size of all variables declared as <strong>shared</strong> in a 5450single program. 5451This limit, expressed in units of basic machine units may be determined by 5452using the OpenGL API to query the value of 5453MAX_COMPUTE_SHARED_MEMORY_SIZE.</p> 5454</div> 5455</div> 5456<div class="sect3"> 5457<h4 id="interface-blocks">4.3.9. Interface Blocks</h4> 5458<div class="paragraph"> 5459<p>Input, output, uniform, and buffer variable declarations can be grouped into 5460named interface blocks to provide coarser granularity backing than is 5461achievable with individual declarations. 5462They can have an optional instance name, used in the shader to reference 5463their members. 5464An output block of one programmable stage is backed by a corresponding input 5465block in the subsequent programmable stage. 5466A <em>uniform block</em> is backed by the application with a buffer object. 5467A block of buffer variables, called a <em>shader storage block</em>, is also backed 5468by the application with a buffer object. 5469It is a compile-time error to have an input block in a vertex shader or an 5470output block in a fragment shader. 5471These uses are reserved for future use.</p> 5472</div> 5473<div class="paragraph"> 5474<p>An interface block is started by an <strong>in</strong>, <strong>out</strong>, <strong>uniform</strong>, or <strong>buffer</strong> 5475keyword, followed by a block name, followed by an open curly brace (<strong>{</strong>) as 5476follows:</p> 5477</div> 5478<div class="openblock bnf"> 5479<div class="content"> 5480<div class="dlist"> 5481<dl> 5482<dt class="hdlist1"><em>interface-block</em> : </dt> 5483<dd> 5484<p><em>layout-qualifier<sub>opt</sub></em> <em>interface-qualifier</em> <em>block-name</em> <strong>{</strong> 5485<em>member-list</em> <strong>}</strong> <em>instance-name<sub>opt</sub></em> <strong>;</strong></p> 5486</dd> 5487</dl> 5488</div> 5489<div class="dlist"> 5490<dl> 5491<dt class="hdlist1"><em>interface-qualifier</em> : </dt> 5492<dd> 5493<p><strong>in</strong><br> 5494<strong>out</strong><br> 5495<strong>patch</strong> <strong>in</strong> // Note: Qualifiers can be in any order.<br> 5496<strong>patch</strong> <strong>out</strong><br> 5497<strong>uniform</strong><br> 5498<strong>buffer</strong></p> 5499</dd> 5500</dl> 5501</div> 5502<div class="dlist"> 5503<dl> 5504<dt class="hdlist1"><em>member-list</em> : </dt> 5505<dd> 5506<p><em>member-declaration</em><br> 5507<em>member-declaration</em> <em>member-list</em></p> 5508</dd> 5509<dt class="hdlist1"><em>member-declaration</em> : </dt> 5510<dd> 5511<p><em>layout-qualifier<sub>opt</sub></em> <em>qualifiers<sub>opt</sub></em> <em>type</em> <em>declarators</em> <strong>;</strong></p> 5512</dd> 5513</dl> 5514</div> 5515<div class="dlist"> 5516<dl> 5517<dt class="hdlist1"><em>instance-name</em> : </dt> 5518<dd> 5519<p><em>identifier</em><br> 5520<em>identifier</em> <strong>[</strong> <strong>]</strong><br> 5521<em>identifier</em> <strong>[</strong> <em>constant-integral-expression</em> <strong>]</strong></p> 5522</dd> 5523</dl> 5524</div> 5525</div> 5526</div> 5527<div class="paragraph"> 5528<p>Each of the above elements is discussed below, with the exception of layout 5529qualifiers (<em>layout-qualifier</em>), which are defined in the next section.</p> 5530</div> 5531<div class="paragraph"> 5532<p>First, an example,</p> 5533</div> 5534<div class="listingblock"> 5535<div class="content"> 5536<pre class="CodeRay highlight"><code data-lang="c++">uniform Transform { 5537 mat4 ModelViewMatrix; 5538 mat4 ModelViewProjectionMatrix; 5539 uniform mat3 NormalMatrix; <span class="comment">// allowed restatement of qualifier</span> 5540 <span class="predefined-type">float</span> Deformation; 5541};</code></pre> 5542</div> 5543</div> 5544<div class="paragraph"> 5545<p>The above establishes a uniform block named “Transform” with four uniforms 5546grouped inside it.</p> 5547</div> 5548<div class="paragraph"> 5549<p>Types and declarators are the same as for other input, output, uniform, and 5550buffer variable declarations outside blocks, with these exceptions:</p> 5551</div> 5552<div class="ulist"> 5553<ul> 5554<li> 5555<p>Initializers are not allowed</p> 5556</li> 5557<li> 5558<p>Opaque types are not allowed</p> 5559</li> 5560<li> 5561<p>Structure definitions cannot be nested inside a block</p> 5562</li> 5563</ul> 5564</div> 5565<div class="paragraph"> 5566<p>Any of these would result in a compile-time error.</p> 5567</div> 5568<div class="paragraph"> 5569<p>If no optional qualifier is used in a member-declaration, the qualification 5570of the member includes all <strong>in</strong>, <strong>out</strong>, <strong>patch</strong>, <strong>uniform</strong>, or <strong>buffer</strong> as 5571determined by <em>interface-qualifier</em>. 5572If optional qualifiers are used, they can include interpolation qualifiers, 5573auxiliary storage qualifiers, 5574and storage qualifiers and they must declare 5575an input, output, or uniform member consistent with the interface qualifier 5576of the block: Input variables, output variables, uniform variables, and 5577<strong>buffer</strong> members can only be in <strong>in</strong> blocks, <strong>out</strong> blocks, <strong>uniform</strong> blocks, 5578and shader storage blocks, respectively.</p> 5579</div> 5580<div class="paragraph"> 5581<p>Repeating the <strong>in</strong>, <strong>out</strong>, <strong>patch</strong>, <strong>uniform</strong>, or <strong>buffer</strong> interface 5582qualifier for a member’s storage qualifier is optional. 5583For example,</p> 5584</div> 5585<div class="listingblock"> 5586<div class="content"> 5587<pre class="CodeRay highlight"><code data-lang="c++">in Material { 5588 smooth in vec4 Color1; <span class="comment">// legal, input inside in block</span> 5589 smooth vec4 Color2; <span class="comment">// legal, 'in' inherited from 'in Material'</span> 5590 vec2 TexCoord; <span class="comment">// legal, TexCoord is an input</span> 5591 uniform <span class="predefined-type">float</span> Atten; <span class="comment">// illegal, mismatched storage qualifier</span> 5592};</code></pre> 5593</div> 5594</div> 5595<div class="paragraph"> 5596<p>A <em>shader interface</em> is defined to be one of these:</p> 5597</div> 5598<div class="ulist"> 5599<ul> 5600<li> 5601<p>All the uniform variables and uniform blocks declared in a program. 5602This spans all compilation units linked together within one program.</p> 5603</li> 5604<li> 5605<p>All the <strong>buffer</strong> blocks declared in a program.</p> 5606</li> 5607<li> 5608<p>The boundary between adjacent programmable pipeline stages: This spans 5609all the outputs declared in all compilation units of the first stage and 5610all the inputs declared in all compilation units of the second stage. 5611Note that for the purposes of this definition, the fragment shader and 5612the preceding shader are considered to have a shared boundary even 5613though in practice, all values passed to the fragment shader first pass 5614through the rasterizer and interpolator.</p> 5615</li> 5616</ul> 5617</div> 5618<div class="paragraph"> 5619<p>The block name (<em>block-name</em>) is used to match within shader interfaces: an 5620output block of one pipeline stage will be matched to an input block with 5621the same name in the subsequent pipeline stage. 5622For uniform or shader storage blocks, the application uses the block name to 5623identify the block. 5624Block names have no other use within a shader beyond interface matching; it 5625is a compile-time error 5626to use a block name at global scope for anything other than as a 5627block name (e.g. use of a block name for a global variable name or function 5628name is currently reserved). 5629It is a compile-time error to use the same block name for more than one 5630block declaration in the same shader interface (as defined above) within one 5631shader, even if the block contents are identical.</p> 5632</div> 5633<div class="paragraph"> 5634<p>Matched block names within a shader interface (as defined above) must match 5635in terms of having the same number of declarations with the same sequence of 5636types and the same sequence of member names, as well as having matching 5637member-wise layout qualification 5638(see next section). 5639Matched uniform or shader storage block names (but not input or output block 5640names) must also either all be lacking an instance name or all having an 5641instance name, putting their members at the same scoping level. 5642When instance names are present on matched block names, it is allowed for 5643the instance names to differ; they need not match for the blocks to match. 5644Furthermore, if a matching block is declared as an array, then the array 5645sizes must also match (or follow array matching rules for the shader 5646interface between consecutive shader stages). 5647Any mismatch will generate a link-time error. 5648A block name is allowed to have different definitions in different shader 5649interfaces within the same shader, allowing, for example, an input block and 5650output block to have the same name.</p> 5651</div> 5652<div class="paragraph"> 5653<p>If an instance name (<em>instance-name</em>) is not used, the names declared inside 5654the block are scoped at the global level and accessed as if they were 5655declared outside the block. 5656If an instance name (<em>instance-name</em>) is used, then it puts all the members 5657inside a scope within its own name space, accessed with the field selector 5658(<strong>.</strong>) operator (analogously to structures). 5659For example,</p> 5660</div> 5661<div class="listingblock"> 5662<div class="content"> 5663<pre class="CodeRay highlight"><code data-lang="c++">in Light { 5664 vec4 LightPos; 5665 vec3 LightColor; 5666}; 5667in ColoredTexture { 5668 vec4 Color; 5669 vec2 TexCoord; 5670} Material; <span class="comment">// instance name</span> 5671vec3 Color; <span class="comment">// different Color than Material.Color</span> 5672vec4 LightPos; <span class="comment">// illegal, already defined</span> 5673... 5674... = LightPos; <span class="comment">// accessing LightPos</span> 5675... = Material.Color; <span class="comment">// accessing Color in ColoredTexture block</span></code></pre> 5676</div> 5677</div> 5678<div class="paragraph"> 5679<p>Outside the shading language (i.e., in the API), members are similarly 5680identified except the block name is always used in place of the instance 5681name (API accesses are to shader interfaces, not to shaders). 5682If there is no instance name, then the API does not use the block name to 5683access a member, just the member name.</p> 5684</div> 5685<div class="paragraph"> 5686<p>Within a shader interface, all declarations of the same global name must be 5687for the same object and must match in type and in whether they declare a 5688variable or member of a block with no instance name. 5689The API also needs this name to uniquely identify an object in the shader 5690interface. 5691It is a link-time error if any particular shader interface contains</p> 5692</div> 5693<div class="ulist"> 5694<ul> 5695<li> 5696<p>two different blocks, each having no instance name, and each having a 5697member of the same name, or</p> 5698</li> 5699<li> 5700<p>a variable outside a block, and a block with no instance name, where the 5701variable has the same name as a member in the block.</p> 5702</li> 5703</ul> 5704</div> 5705<div class="listingblock"> 5706<div class="content"> 5707<pre class="CodeRay highlight"><code data-lang="c++">out Vertex { 5708 vec4 Position; <span class="comment">// API transform/feedback will use "Vertex.Position"</span> 5709 vec2 Texture; 5710} Coords; <span class="comment">// shader will use "Coords.Position"</span> 5711out Vertex2 { 5712 vec4 Color; <span class="comment">// API will use "Color"</span> 5713 <span class="predefined-type">float</span> Color2; 5714}; 5715 5716<span class="comment">// in same program as Vertex2 above:</span> 5717out Vertex3 { 5718 <span class="predefined-type">float</span> Intensity; 5719 vec4 Color; <span class="comment">// ERROR, name collision with Color in Vertex2</span> 5720}; 5721<span class="predefined-type">float</span> Color2; <span class="comment">// ERROR, collides with Color2 in Vertex2</span></code></pre> 5722</div> 5723</div> 5724<div class="paragraph"> 5725<p>For blocks declared as arrays, the array index must also be included when 5726accessing members, as in this example</p> 5727</div> 5728<div class="listingblock"> 5729<div class="content"> 5730<pre class="CodeRay highlight"><code data-lang="c++">uniform Transform { <span class="comment">// API uses "Transform[2]" to refer to instance 2</span> 5731 mat4 ModelViewMatrix; 5732 mat4 ModelViewProjectionMatrix; 5733 vec4 a[]; <span class="comment">// array will get implicitly sized</span> 5734 <span class="predefined-type">float</span> Deformation; 5735} transforms[<span class="integer">4</span>]; 5736... 5737... = transforms[<span class="integer">2</span>].ModelViewMatrix; <span class="comment">// shader access of instance 2</span> 5738<span class="comment">// API uses "Transform.ModelViewMatrix" to query an offset or other query</span> 5739transforms[x].a.length(); <span class="comment">// same length for 'a' for all x</span> 5740Transform[x]; <span class="comment">// illegal, must use 'transforms'</span> 5741Transform.a.length(); <span class="comment">// illegal, must use 'transforms'</span> 5742...transforms[<span class="integer">2</span>].a[<span class="integer">3</span>]... <span class="comment">// if these are the only two dereferences of 'a',</span> 5743...transforms[<span class="integer">3</span>].a[<span class="integer">7</span>]... <span class="comment">// then 'a' must be size 8, for all</span> 5744transforms[x]</code></pre> 5745</div> 5746</div> 5747<div class="paragraph"> 5748<p>For uniform or shader storage blocks declared as an array, each individual 5749array element corresponds to a separate buffer object bind range, backing 5750one instance of the block. 5751As the array size indicates the number of buffer objects needed, uniform and 5752shader storage block array declarations must specify an array size. 5753A uniform or shader storage block array can only be indexed with a 5754dynamically uniform integral expression, otherwise results are undefined.</p> 5755</div> 5756<div class="paragraph"> 5757<p>When using OpenGL API entry points to identify the name of an individual 5758block in an array of blocks, the name string may include an array index 5759(e.g. <em>Transform[2]</em>). 5760When using OpenGL API entry points to refer to offsets or other 5761characteristics of a block member, an array index must not be specified 5762(e.g. <em>Transform.ModelViewMatrix</em>).</p> 5763</div> 5764<div class="paragraph"> 5765<p>Tessellation control, tessellation evaluation and geometry shader input 5766blocks must be declared as arrays and follow the array declaration and 5767linking rules for all shader inputs for the respective stages. 5768All other input and output block arrays must specify an array size.</p> 5769</div> 5770<div class="paragraph"> 5771<p>There are implementation-dependent limits on the number of uniform blocks 5772and the number of shader storage blocks that can be used per stage. 5773If either limit is exceeded, it will cause a link-time error.</p> 5774</div> 5775</div> 5776</div> 5777<div class="sect2"> 5778<h3 id="layout-qualifiers">4.4. Layout Qualifiers</h3> 5779<div class="paragraph"> 5780<p>Layout qualifiers can appear in several forms of declaration. 5781They can appear as part of an interface block definition or block member, as 5782shown in the grammar in the previous section. 5783They can also appear with just an <em>interface-qualifier</em> to establish layouts 5784of other declarations made with that qualifier:</p> 5785</div> 5786<div class="openblock bnf"> 5787<div class="content"> 5788<div class="paragraph"> 5789<p><em>layout-qualifier</em> <em>interface-qualifier</em> <strong>;</strong></p> 5790</div> 5791</div> 5792</div> 5793<div class="paragraph"> 5794<p>Or, they can appear with an individual variable declared with an interface 5795qualifier:</p> 5796</div> 5797<div class="openblock bnf"> 5798<div class="content"> 5799<div class="paragraph"> 5800<p><em>layout-qualifier</em> <em>interface-qualifier</em> <em>declaration</em> <strong>;</strong></p> 5801</div> 5802</div> 5803</div> 5804<div class="paragraph"> 5805<p>Declarations of layouts can only be made at global scope or block members, 5806and only where indicated in the following subsections; their details are 5807specific to what the interface qualifier is, and are discussed individually.</p> 5808</div> 5809<div class="paragraph"> 5810<p>The <em>layout-qualifier</em> expands to:</p> 5811</div> 5812<div class="openblock bnf"> 5813<div class="content"> 5814<div class="dlist"> 5815<dl> 5816<dt class="hdlist1"><em>layout-qualifier</em> : </dt> 5817<dd> 5818<p><strong>layout</strong> <strong>(</strong> <em>layout-qualifier-id-list</em> <strong>)</strong></p> 5819</dd> 5820<dt class="hdlist1"><em>layout-qualifier-id-list</em> : </dt> 5821<dd> 5822<p><em>layout-qualifier-id</em><br> 5823<em>layout-qualifier-id</em> <strong>,</strong> <em>layout-qualifier-id-list</em></p> 5824</dd> 5825<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 5826<dd> 5827<p><em>layout-qualifier-name</em><br> 5828<em>layout-qualifier-name</em> <strong>=</strong> <em>layout-qualifier-value</em><br> 5829<strong>shared</strong></p> 5830</dd> 5831</dl> 5832</div> 5833</div> 5834</div> 5835<div class="openblock bnf"> 5836<div class="content"> 5837<div class="dlist"> 5838<dl> 5839<dt class="hdlist1"><em>layout-qualifier-value</em> : </dt> 5840<dd> 5841<p><em>integer-constant-expression</em></p> 5842</dd> 5843</dl> 5844</div> 5845</div> 5846</div> 5847<div class="paragraph"> 5848<p>The tokens used for <em>layout-qualifier-name</em> are identifiers, not keywords, 5849however, the <strong>shared</strong> keyword is allowed as a <em>layout-qualifier-id</em>. 5850Generally, they can be listed in any order. 5851Order-dependent meanings exist only if explicitly called out below. 5852Similarly, these identifiers are not case sensitive, unless explicitly noted 5853otherwise.</p> 5854</div> 5855<div class="paragraph"> 5856<p>More than one layout qualifier may appear in a single declaration. 5857Additionally, the same <em>layout-qualifier-name</em> can occur multiple times 5858within a layout qualifier or across multiple layout qualifiers in the same 5859declaration. 5860When the same <em>layout-qualifier-name</em> occurs multiple times, in a single 5861declaration, the last occurrence overrides the former occurrence(s). 5862Further, if such a <em>layout-qualifier-name</em> will affect subsequent 5863declarations or other observable behavior, it is only the last occurrence 5864that will have any effect, behaving as if the earlier occurrence(s) within 5865the declaration are not present. 5866This is also true for overriding <em>layout-qualifier-name</em>, where one 5867overrides the other (e.g. <strong>row_major</strong> vs. 5868<strong>column_major</strong>); only the last occurrence has any effect.</p> 5869</div> 5870<div class="paragraph"> 5871<p><em>integer-constant-expression</em> is defined in 5872“<a href="#constant-expressions">Constant Expressions</a>” as <em>constant integral 5873expression</em>, with it being a compile-time error for 5874<em>integer-constant-expression</em> to be a specialization constant.</p> 5875</div> 5876<div class="paragraph"> 5877<p>The following table summarizes the use of layout qualifiers. 5878It shows for each one what kinds of declarations it may be applied to. 5879These are all discussed in detail in the following sections.</p> 5880</div> 5881<table class="tableblock frame-all grid-all stretch"> 5882<colgroup> 5883<col style="width: 16.6666%;"> 5884<col style="width: 16.6666%;"> 5885<col style="width: 16.6666%;"> 5886<col style="width: 16.6666%;"> 5887<col style="width: 16.6666%;"> 5888<col style="width: 16.667%;"> 5889</colgroup> 5890<thead> 5891<tr> 5892<th class="tableblock halign-left valign-middle">Layout Qualifier</th> 5893<th class="tableblock halign-center valign-middle">Qualifier Only</th> 5894<th class="tableblock halign-center valign-middle">Individual Variable</th> 5895<th class="tableblock halign-center valign-middle">Block</th> 5896<th class="tableblock halign-center valign-middle">Block Member</th> 5897<th class="tableblock halign-left valign-middle">Allowed Interfaces</th> 5898</tr> 5899</thead> 5900<tbody> 5901<tr> 5902<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>shared</strong><br> 5903 <strong>packed</strong><br> 5904 <strong>std140</strong><br> 5905 <strong>std430</strong></p></td> 5906<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5907<td class="tableblock halign-center valign-middle"></td> 5908<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5909<td class="tableblock halign-center valign-middle"></td> 5910<td class="tableblock halign-left valign-middle" rowspan="5"><p class="tableblock"><strong>uniform</strong> / <strong>buffer</strong></p></td> 5911</tr> 5912<tr> 5913<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>row_major</strong><br> 5914 <strong>column_major</strong></p></td> 5915<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5916<td class="tableblock halign-center valign-middle"></td> 5917<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5918<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5919</tr> 5920<tr> 5921<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>binding</strong> =</p></td> 5922<td class="tableblock halign-center valign-middle"></td> 5923<td class="tableblock halign-center valign-middle"><p class="tableblock">opaque types only</p></td> 5924<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5925<td class="tableblock halign-center valign-middle"></td> 5926</tr> 5927<tr> 5928<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>offset</strong> =</p></td> 5929<td class="tableblock halign-center valign-middle"></td> 5930<td class="tableblock halign-center valign-middle"><p class="tableblock">atomic counters only</p></td> 5931<td class="tableblock halign-center valign-middle"></td> 5932<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5933</tr> 5934<tr> 5935<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>align</strong> =</p></td> 5936<td class="tableblock halign-center valign-middle"></td> 5937<td class="tableblock halign-center valign-middle"></td> 5938<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5939<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5940</tr> 5941<tr> 5942<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>set</strong> =</p></td> 5943<td class="tableblock halign-center valign-middle"></td> 5944<td class="tableblock halign-center valign-middle"><p class="tableblock">opaque types only</p></td> 5945<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5946<td class="tableblock halign-center valign-middle"></td> 5947<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>uniform</strong> / <strong>buffer</strong> (Vulkan only)</p></td> 5948</tr> 5949<tr> 5950<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>push_constant</strong></p></td> 5951<td class="tableblock halign-center valign-middle"></td> 5952<td class="tableblock halign-center valign-middle"></td> 5953<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5954<td class="tableblock halign-center valign-middle"></td> 5955<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>uniform</strong> (Vulkan only)</p></td> 5956</tr> 5957<tr> 5958<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>input_attachment_index</strong> =</p></td> 5959<td class="tableblock halign-center valign-middle"></td> 5960<td class="tableblock halign-center valign-middle"><p class="tableblock">subpass types only</p></td> 5961<td class="tableblock halign-center valign-middle"></td> 5962<td class="tableblock halign-center valign-middle"></td> 5963<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>uniform</strong> (Vulkan only)</p></td> 5964</tr> 5965<tr> 5966<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>location</strong> =</p></td> 5967<td class="tableblock halign-center valign-middle"></td> 5968<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5969<td class="tableblock halign-center valign-middle"></td> 5970<td class="tableblock halign-center valign-middle"></td> 5971<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>uniform</strong> / <strong>buffer</strong> and subroutine variables</p></td> 5972</tr> 5973<tr> 5974<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>location</strong> =</p></td> 5975<td class="tableblock halign-center valign-middle"></td> 5976<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5977<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5978<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5979<td class="tableblock halign-left valign-middle" rowspan="2"><p class="tableblock">all <strong>in</strong> / <strong>out</strong>, except for compute</p></td> 5980</tr> 5981<tr> 5982<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>component</strong> =</p></td> 5983<td class="tableblock halign-center valign-middle"></td> 5984<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5985<td class="tableblock halign-center valign-middle"></td> 5986<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5987</tr> 5988<tr> 5989<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>index</strong> =</p></td> 5990<td class="tableblock halign-center valign-middle"></td> 5991<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 5992<td class="tableblock halign-center valign-middle"></td> 5993<td class="tableblock halign-center valign-middle"></td> 5994<td class="tableblock halign-left valign-middle"><p class="tableblock">fragment <strong>out</strong> and subroutine functions</p></td> 5995</tr> 5996<tr> 5997<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>triangles</strong><br> 5998 <strong>quads</strong><br> 5999 <strong>isolines</strong></p></td> 6000<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6001<td class="tableblock halign-center valign-middle"></td> 6002<td class="tableblock halign-center valign-middle"></td> 6003<td class="tableblock halign-center valign-middle"></td> 6004<td class="tableblock halign-left valign-middle"><p class="tableblock">tessellation evaluation <strong>in</strong></p></td> 6005</tr> 6006<tr> 6007<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>equal_spacing</strong><br> 6008 <strong>fractional_even_spacing</strong><br> 6009 <strong>fractional_odd_spacing</strong></p></td> 6010<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6011<td class="tableblock halign-center valign-middle"></td> 6012<td class="tableblock halign-center valign-middle"></td> 6013<td class="tableblock halign-center valign-middle"></td> 6014<td class="tableblock halign-left valign-middle"><p class="tableblock">tessellation evaluation <strong>in</strong></p></td> 6015</tr> 6016<tr> 6017<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>cw</strong><br> 6018 <strong>ccw</strong></p></td> 6019<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6020<td class="tableblock halign-center valign-middle"></td> 6021<td class="tableblock halign-center valign-middle"></td> 6022<td class="tableblock halign-center valign-middle"></td> 6023<td class="tableblock halign-left valign-middle"><p class="tableblock">tessellation evaluation <strong>in</strong></p></td> 6024</tr> 6025<tr> 6026<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>point_mode</strong></p></td> 6027<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6028<td class="tableblock halign-center valign-middle"></td> 6029<td class="tableblock halign-center valign-middle"></td> 6030<td class="tableblock halign-center valign-middle"></td> 6031<td class="tableblock halign-left valign-middle"><p class="tableblock">tessellation evaluation <strong>in</strong></p></td> 6032</tr> 6033<tr> 6034<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>points</strong></p></td> 6035<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6036<td class="tableblock halign-center valign-middle"></td> 6037<td class="tableblock halign-center valign-middle"></td> 6038<td class="tableblock halign-center valign-middle"></td> 6039<td class="tableblock halign-left valign-middle"><p class="tableblock">geometry <strong>in</strong>/<strong>out</strong></p></td> 6040</tr> 6041<tr> 6042<td class="tableblock halign-left valign-middle"><p class="tableblock">[ <strong>points</strong> ]<br> 6043 <strong>lines</strong><br> 6044 <strong>lines_adjacency</strong><br> 6045 <strong>triangles</strong><br> 6046 <strong>triangles_adjacency</strong></p></td> 6047<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6048<td class="tableblock halign-center valign-middle"></td> 6049<td class="tableblock halign-center valign-middle"></td> 6050<td class="tableblock halign-center valign-middle"></td> 6051<td class="tableblock halign-left valign-middle"><p class="tableblock">geometry <strong>in</strong></p></td> 6052</tr> 6053<tr> 6054<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>invocations</strong> =</p></td> 6055<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6056<td class="tableblock halign-center valign-middle"></td> 6057<td class="tableblock halign-center valign-middle"></td> 6058<td class="tableblock halign-center valign-middle"></td> 6059<td class="tableblock halign-left valign-middle"><p class="tableblock">geometry <strong>in</strong></p></td> 6060</tr> 6061<tr> 6062<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>origin_upper_left</strong><br> 6063 <strong>pixel_center_integer</strong></p></td> 6064<td class="tableblock halign-center valign-middle"></td> 6065<td class="tableblock halign-center valign-middle"><p class="tableblock"><em>gl_FragCoord</em> only</p></td> 6066<td class="tableblock halign-center valign-middle"></td> 6067<td class="tableblock halign-center valign-middle"></td> 6068<td class="tableblock halign-left valign-middle" rowspan="2"><p class="tableblock">fragment <strong>in</strong></p></td> 6069</tr> 6070<tr> 6071<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>early_fragment_tests</strong></p></td> 6072<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6073<td class="tableblock halign-center valign-middle"></td> 6074<td class="tableblock halign-center valign-middle"></td> 6075<td class="tableblock halign-center valign-middle"></td> 6076</tr> 6077<tr> 6078<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>local_size_x</strong> =<br> 6079 <strong>local_size_y</strong> =<br> 6080 <strong>local_size_z</strong> =</p></td> 6081<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6082<td class="tableblock halign-center valign-middle"></td> 6083<td class="tableblock halign-center valign-middle"></td> 6084<td class="tableblock halign-center valign-middle"></td> 6085<td class="tableblock halign-left valign-middle"><p class="tableblock">compute <strong>in</strong></p></td> 6086</tr> 6087<tr> 6088<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>local_size_x_id</strong> =<br> 6089 <strong>local_size_y_id</strong> =<br> 6090 <strong>local_size_z_id</strong> =</p></td> 6091<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6092<td class="tableblock halign-center valign-middle"></td> 6093<td class="tableblock halign-center valign-middle"></td> 6094<td class="tableblock halign-center valign-middle"></td> 6095<td class="tableblock halign-left valign-middle"><p class="tableblock">compute <strong>in</strong> (SPIR-V only)</p></td> 6096</tr> 6097<tr> 6098<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>xfb_buffer</strong> =<br> 6099 <strong>xfb_stride</strong> =</p></td> 6100<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6101<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6102<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6103<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6104<td class="tableblock halign-left valign-middle" rowspan="2"><p class="tableblock">vertex, tessellation, and geometry <strong>out</strong></p></td> 6105</tr> 6106<tr> 6107<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>xfb_offset</strong> =</p></td> 6108<td class="tableblock halign-center valign-middle"></td> 6109<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6110<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6111<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6112</tr> 6113<tr> 6114<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>vertices</strong> =</p></td> 6115<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6116<td class="tableblock halign-center valign-middle"></td> 6117<td class="tableblock halign-center valign-middle"></td> 6118<td class="tableblock halign-center valign-middle"></td> 6119<td class="tableblock halign-left valign-middle"><p class="tableblock">tessellation control <strong>out</strong></p></td> 6120</tr> 6121<tr> 6122<td class="tableblock halign-left valign-middle"><p class="tableblock">[ <strong>points</strong> ]<br> 6123 <strong>line_strip</strong><br> 6124 <strong>triangle_strip</strong></p></td> 6125<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6126<td class="tableblock halign-center valign-middle"></td> 6127<td class="tableblock halign-center valign-middle"></td> 6128<td class="tableblock halign-center valign-middle"></td> 6129<td class="tableblock halign-left valign-middle" rowspan="3"><p class="tableblock">geometry <strong>out</strong></p></td> 6130</tr> 6131<tr> 6132<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>max_vertices</strong> =</p></td> 6133<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6134<td class="tableblock halign-center valign-middle"></td> 6135<td class="tableblock halign-center valign-middle"></td> 6136<td class="tableblock halign-center valign-middle"></td> 6137</tr> 6138<tr> 6139<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>stream</strong> =</p></td> 6140<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6141<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6142<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6143<td class="tableblock halign-center valign-middle"><p class="tableblock">X</p></td> 6144</tr> 6145<tr> 6146<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>depth_any</strong><br> 6147 <strong>depth_greater</strong><br> 6148 <strong>depth_less</strong><br> 6149 <strong>depth_unchanged</strong></p></td> 6150<td class="tableblock halign-center valign-middle"></td> 6151<td class="tableblock halign-center valign-middle"><p class="tableblock"><em>gl_FragDepth</em> only</p></td> 6152<td class="tableblock halign-center valign-middle"></td> 6153<td class="tableblock halign-center valign-middle"></td> 6154<td class="tableblock halign-left valign-middle"><p class="tableblock">fragment <strong>out</strong></p></td> 6155</tr> 6156<tr> 6157<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>constant_id</strong> =</p></td> 6158<td class="tableblock halign-center valign-middle"></td> 6159<td class="tableblock halign-center valign-middle"><p class="tableblock">scalar only</p></td> 6160<td class="tableblock halign-center valign-middle"></td> 6161<td class="tableblock halign-center valign-middle"></td> 6162<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>const</strong> (SPIR-V only)</p></td> 6163</tr> 6164<tr> 6165<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>rgba32f</strong><br> 6166 <strong>rgba16f</strong><br> 6167 <strong>rg32f</strong><br> 6168 <strong>rg16f</strong><br> 6169 <strong>r11f_g11f_b10f</strong><br> 6170 <strong>r32f</strong><br> 6171 <strong>r16f</strong><br> 6172 <strong>rgba16</strong><br> 6173 <strong>rgb10_a2</strong><br> 6174 <strong>rgba8</strong><br> 6175 <strong>rg16</strong><br> 6176 <strong>rg8</strong><br> 6177 <strong>r16</strong><br> 6178 <strong>r8</strong><br> 6179 <strong>rgba16_snorm</strong><br> 6180 <strong>rgba8_snorm</strong><br> 6181 <strong>rg16_snorm</strong><br> 6182 <strong>rg8_snorm</strong><br> 6183 <strong>r16_snorm</strong><br> 6184 <strong>r8_snorm</strong><br> 6185 <strong>rgba32i</strong><br> 6186 <strong>rgba16i</strong><br> 6187 <strong>rgba8i</strong><br> 6188 <strong>rg32i</strong><br> 6189 <strong>rg16i</strong><br> 6190 <strong>rg8i</strong><br> 6191 <strong>r32i</strong><br> 6192 <strong>r16i</strong><br> 6193 <strong>r8i</strong><br> 6194 <strong>rgba32ui</strong><br> 6195 <strong>rgba16ui</strong><br> 6196<strong>rgb10_a2ui</strong><br> 6197 <strong>rgba8ui</strong><br> 6198 <strong>rg32ui</strong><br> 6199 <strong>rg16ui</strong><br> 6200 <strong>rg8ui</strong><br> 6201 <strong>r32ui</strong><br> 6202 <strong>r16ui</strong><br> 6203 <strong>r8ui</strong></p></td> 6204<td class="tableblock halign-center valign-middle"></td> 6205<td class="tableblock halign-center valign-middle"><p class="tableblock">image types only</p></td> 6206<td class="tableblock halign-center valign-middle"></td> 6207<td class="tableblock halign-center valign-middle"></td> 6208<td class="tableblock halign-left valign-middle"><p class="tableblock"><strong>uniform</strong></p></td> 6209</tr> 6210</tbody> 6211</table> 6212<div class="sect3"> 6213<h4 id="input-layout-qualifiers">4.4.1. Input Layout Qualifiers</h4> 6214<div class="paragraph"> 6215<p>Layout qualifiers specific to a particular shader language are discussed in 6216separate sections below.</p> 6217</div> 6218<div class="paragraph"> 6219<p>All shaders except compute shaders allow <strong>location</strong> layout qualifiers on 6220input variable declarations, input block declarations, and input block 6221member declarations. 6222Of these, variables and block members (but not blocks) additionally allow 6223the <strong>component</strong> layout qualifier.</p> 6224</div> 6225<div class="openblock bnf"> 6226<div class="content"> 6227<div class="dlist"> 6228<dl> 6229<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 6230<dd> 6231<p><strong>location</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 6232<strong>component</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 6233</dd> 6234</dl> 6235</div> 6236</div> 6237</div> 6238<div class="paragraph"> 6239<p>For example,</p> 6240</div> 6241<div class="listingblock"> 6242<div class="content"> 6243<pre class="CodeRay highlight"><code data-lang="c++">layout(location = <span class="integer">3</span>) in vec4 normal; 6244<span class="directive">const</span> <span class="predefined-type">int</span> start = <span class="integer">6</span>; 6245layout(location = start + <span class="integer">2</span>) <span class="predefined-type">int</span> vec4 v;</code></pre> 6246</div> 6247</div> 6248<div class="paragraph"> 6249<p>will establish that the shader input <em>normal</em> is assigned to vector location 6250number 62513 and <em>v</em> is assigned location number 8. 6252For vertex shader inputs, the location specifies the number of the 6253vertex attribute from which input values are taken. 6254For inputs of all other shader types, the location specifies a vector number 6255that can be used to match against outputs from a previous shader stage, even 6256if that shader is in a different program object.</p> 6257</div> 6258<div class="paragraph"> 6259<p>The following language describes how many locations are consumed by a given 6260type. 6261However, geometry shader inputs, tessellation control shader inputs and 6262outputs, and tessellation evaluation inputs all have an additional level of 6263arrayness relative to other shader inputs and outputs. 6264This outer array level is removed from the type before considering how many 6265locations the type consumes.</p> 6266</div> 6267<div class="paragraph"> 6268<p>Except when targeting Vulkan, 6269if a vertex shader input is any scalar or vector type, it will consume a 6270single location. 6271If a non-vertex shader input, or any stage input when targeting Vulkan, 6272is a scalar or vector type other than <strong>dvec3</strong> 6273or <strong>dvec4</strong>, it will consume a single location, while types <strong>dvec3</strong> or 6274<strong>dvec4</strong> will consume two consecutive locations. 6275Inputs of type <strong>double</strong> and <strong>dvec2</strong> will consume only a single location, in 6276all stages.</p> 6277</div> 6278<div class="paragraph"> 6279<p>If the declared input (after potentially removing an outer array level as 6280just described above) is an array of size <em>n</em> and each of the elements takes 6281<em>m</em> locations, it will be assigned <em>m</em> * <em>n</em> consecutive locations starting 6282with the location specified. 6283For example,</p> 6284</div> 6285<div class="listingblock"> 6286<div class="content"> 6287<pre class="CodeRay highlight"><code data-lang="c++">layout(location = <span class="integer">6</span>) in vec4 colors[<span class="integer">3</span>];</code></pre> 6288</div> 6289</div> 6290<div class="paragraph"> 6291<p>will establish that the shader input <em>colors</em> is assigned to vector location 6292numbers 6, 7, and 8.</p> 6293</div> 6294<div class="paragraph"> 6295<p>If the declared input is an <em>n</em> × <em>m</em> 6296matrix, it will be assigned multiple locations starting with the location 6297specified. 6298The number of locations assigned for each matrix will be the same as for an 6299<em>n</em>-element array of <em>m</em>-component vectors. 6300For example,</p> 6301</div> 6302<div class="listingblock"> 6303<div class="content"> 6304<pre class="CodeRay highlight"><code data-lang="c++">layout(location = <span class="integer">9</span>) in mat4 transforms[<span class="integer">2</span>];</code></pre> 6305</div> 6306</div> 6307<div class="paragraph"> 6308<p>will establish that shader input <em>transforms</em> is assigned to vector 6309locations 9-16, with <em>transforms[0]</em> being assigned to locations 9-12, and 6310<em>transforms[1]</em> being assigned to locations 13-16.</p> 6311</div> 6312<div class="paragraph"> 6313<p>If the declared input is a structure or block, its members will be assigned 6314consecutive locations in their order of declaration, with the first member 6315assigned the location provided in the layout qualifier. 6316For a structure, this process applies to the entire structure. 6317It is a compile-time error to use a <strong>location</strong> qualifier on a member of a 6318structure. 6319For a block, this process applies to the entire block, or until the first 6320member is reached that has a <strong>location</strong> layout qualifier.</p> 6321</div> 6322<div class="paragraph"> 6323<p>When a block member is declared with a <strong>location</strong> qualifier, its location 6324comes from that qualifier; the member’s <strong>location</strong> qualifier overrides the 6325block-level declaration. 6326Subsequent members are again assigned consecutive locations, based on the 6327newest location, until the next member declared with a <strong>location</strong> qualifier. 6328The values used for locations do not have to be declared in increasing 6329order.</p> 6330</div> 6331<div class="paragraph"> 6332<p>If a block has no block-level <strong>location</strong> layout qualifier, it is required 6333that either all or none of its members have a <strong>location</strong> layout qualifier, 6334or a compile-time error results. 6335For some blocks declared as arrays, the <strong>location</strong> can only be applied at 6336the block level: When a block is declared as an array where additional 6337locations are needed for each member for each block array element, it is a 6338compile-time error to specify locations on the block members. 6339That is, when locations would be under specified by applying them on block 6340members, they are not allowed on block members. 6341For <em>arrayed</em> interfaces (those generally having an extra level of arrayness 6342due to interface expansion), the outer array is stripped before applying 6343this rule.</p> 6344</div> 6345<div class="paragraph"> 6346<p>When generating SPIR-V, all <strong>in</strong> and <strong>out</strong> qualified user-declared (non 6347built-in) variables and blocks (or all their members) must have a 6348shader-specified <strong>location</strong>. 6349Otherwise, a compile-time error is generated.</p> 6350</div> 6351<div class="paragraph"> 6352<p>The locations consumed by block and structure members are determined by 6353applying the rules above recursively as though the structure member were 6354declared as an input variable of the same type. 6355For example:</p> 6356</div> 6357<div class="listingblock"> 6358<div class="content"> 6359<pre class="CodeRay highlight"><code data-lang="c++">layout(location = <span class="integer">3</span>) in <span class="keyword">struct</span> S 6360{ 6361 vec3 a; <span class="comment">// gets location 3</span> 6362 mat2 b; <span class="comment">// gets locations 4 and 5</span> 6363 vec4 c[<span class="integer">2</span>]; <span class="comment">// gets locations 6 and 7</span> 6364 layout(location = <span class="integer">8</span>) vec2 A; <span class="comment">// ERROR, can't use on struct member</span> 6365} s; 6366layout(location = <span class="integer">4</span>) in block 6367{ 6368 vec4 d; <span class="comment">// gets location 4</span> 6369 vec4 e; <span class="comment">// gets location 5</span> 6370 layout(location = <span class="integer">7</span>) vec4 f; <span class="comment">// gets location 7</span> 6371 vec4 g; <span class="comment">// gets location 8</span> 6372 layout(location = <span class="integer">1</span>) vec4 h; <span class="comment">// gets location 1</span> 6373 vec4 i; <span class="comment">// gets location 2</span> 6374 vec4 j; <span class="comment">// gets location 3</span> 6375 vec4 k; <span class="comment">// ERROR, location 4 already used</span> 6376};</code></pre> 6377</div> 6378</div> 6379<div class="paragraph"> 6380<p>The number of input locations available to a shader is limited. 6381For vertex shaders, the limit is the advertised number of vertex attributes. 6382For all other shaders, the limit is implementation-dependent and must be no 6383less than one fourth of the advertised maximum input component count.</p> 6384</div> 6385<div class="paragraph"> 6386<p>A program will fail to link if any attached shader uses a location greater 6387than or equal to the number of supported locations, unless device-dependent 6388optimizations are able to make the program fit within available hardware 6389resources.</p> 6390</div> 6391<div class="paragraph"> 6392<p>A program will fail to link if explicit location assignments leave the 6393linker unable to find space for other variables without explicit 6394assignments.</p> 6395</div> 6396<div class="paragraph"> 6397<p>For the purposes of determining if a non-vertex input matches an output from 6398a previous shader stage, the <strong>location</strong> layout qualifier (if any) must 6399match.</p> 6400</div> 6401<div class="paragraph"> 6402<p>If a vertex shader input variable with no location assigned in the shader 6403text has a location specified through the OpenGL API, the API-assigned 6404location will be used. 6405Otherwise, such variables will be assigned a location by the linker. 6406See section 11.1.1 “Vertex Attributes” of the <a href="#references">OpenGL Specification</a> for 6407more details. 6408A link-time error will occur if an input variable is declared in multiple 6409shaders of the same language with conflicting locations.</p> 6410</div> 6411<div class="paragraph"> 6412<p>The <strong>component</strong> qualifier allows the location to be more finely specified 6413for scalars and vectors, down to the individual components within a location 6414that are consumed. 6415It is a compile-time error to use <strong>component</strong> without also specifying the 6416<strong>location</strong> qualifier (order does not matter). 6417The components within a location are 0, 1, 2, and 3. 6418A variable or block member starting at component <em>N</em> will consume components 6419<em>N</em>, <em>N+1</em>, <em>N+2</em>, …​ 6420up through its size. 6421It is a compile-time error if this sequence of components gets larger than 64223. 6423A scalar <strong>double</strong> will consume two of these components, and a <strong>dvec2</strong> will 6424consume all four components available within a location. 6425A <strong>dvec3</strong> or <strong>dvec4</strong> can only be declared without specifying a <strong>component</strong>. 6426A <strong>dvec3</strong> will consume all four components of the first location and 6427components 0 and 1 of the second location. 6428This leaves components 2 and 3 available for other component-qualified 6429declarations.</p> 6430</div> 6431<div class="paragraph"> 6432<p>For example:</p> 6433</div> 6434<div class="listingblock"> 6435<div class="content"> 6436<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// a consumes components 2 and 3 of location 4</span> 6437layout(location = <span class="integer">4</span>, component = <span class="integer">2</span>) in vec2 a; 6438 6439<span class="comment">// b consumes component 1 of location 4</span> 6440layout(location = <span class="integer">4</span>, component = <span class="integer">1</span>) in <span class="predefined-type">float</span> b; 6441 6442<span class="comment">// ERROR: c overflows component 3</span> 6443layout(location = <span class="integer">3</span>, component = <span class="integer">2</span>) in vec3 c; 6444 6445<span class="comment">// d consumes components 2 and 3 of location 5</span> 6446layout(location = <span class="integer">5</span>, component = <span class="integer">2</span>) in <span class="predefined-type">double</span> d; 6447 6448<span class="comment">// ERROR: e overflows component 3 of location 6</span> 6449layout(location = <span class="integer">6</span>, component = <span class="integer">2</span>) in dvec2 e; 6450 6451<span class="comment">// ERROR: f overlaps with g</span> 6452layout(location = <span class="integer">7</span>, component = <span class="integer">0</span>) <span class="predefined-type">double</span> f; 6453layout(location = <span class="integer">7</span>, component = <span class="integer">1</span>) <span class="predefined-type">float</span> g; 6454 6455layout(location = <span class="integer">8</span>) in dvec3 h; <span class="comment">// components 0,1,2 and 3 of location 8</span> 6456 <span class="comment">// and components 0 and 1 of location 9</span> 6457layout(location = <span class="integer">9</span>, component = <span class="integer">2</span>) in <span class="predefined-type">float</span> i; <span class="comment">// okay, compts 2 and 3</span></code></pre> 6458</div> 6459</div> 6460<div class="paragraph"> 6461<p>If the variable is an array, each element of the array, in order, is 6462assigned to consecutive locations, but all at the same specified component 6463within each location. 6464For example:</p> 6465</div> 6466<div class="listingblock"> 6467<div class="content"> 6468<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// component 3 in 6 locations are consumed</span> 6469layout(location = <span class="integer">2</span>, component = <span class="integer">3</span>) in <span class="predefined-type">float</span> d[<span class="integer">6</span>];</code></pre> 6470</div> 6471</div> 6472<div class="paragraph"> 6473<p>That is, location 2 component 3 will hold <em>d[0]</em>, location 3 component 3 6474will hold <em>d[1]</em>, …​, up through location 7 component 3 holding <em>d[5]</em>.</p> 6475</div> 6476<div class="paragraph"> 6477<p>This allows packing of two arrays into the same set of locations:</p> 6478</div> 6479<div class="listingblock"> 6480<div class="content"> 6481<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// e consumes beginning (components 0, 1 and 2) of each of 6 slots</span> 6482layout(location = <span class="integer">0</span>, component = <span class="integer">0</span>) in vec3 e[<span class="integer">6</span>]; 6483 6484<span class="comment">// f consumes last component of the same 6 slots</span> 6485layout(location = <span class="integer">0</span>, component = <span class="integer">3</span>) in <span class="predefined-type">float</span> f[<span class="integer">6</span>];</code></pre> 6486</div> 6487</div> 6488<div class="paragraph"> 6489<p>If applying this to an array of arrays, all levels of arrayness are removed 6490to get to the elements that are assigned per location to the specified 6491component. 6492These non-arrayed elements will fill the locations in the order specified 6493for arrays of arrays in “<a href="#arrays">Arrays</a>”.</p> 6494</div> 6495<div class="paragraph"> 6496<p>It is a compile-time error to apply the <strong>component</strong> qualifier to a matrix, a 6497structure, a block, or an array containing any of these. 6498It is a compile-time error to use <strong>component</strong> 1 or 3 as the beginning of a 6499<strong>double</strong> or <strong>dvec2</strong>. 6500It is a link-time error to specify different components for the same 6501variable within a program.</p> 6502</div> 6503<div class="paragraph"> 6504<p><em>Location aliasing</em> is causing two variables or block members to have the 6505same location number. 6506<em>Component aliasing</em> is assigning the same (or overlapping) component 6507numbers for two location aliases. 6508(Recall if <strong>component</strong> is not used, components are assigned starting with 65090.) 6510With one exception, location aliasing is allowed only if it does not 6511cause component aliasing; it is a compile-time or link-time error to cause 6512component aliasing. 6513Further, when location aliasing, the aliases sharing the location must have 6514the same underlying numerical type and bit width (floating-point or integer, 651532-bit versus 64-bit, etc.) and the same 6516auxiliary storage and interpolation qualification. 6517The one exception where component aliasing is permitted is 6518when targeting OpenGL for two input 6519variables (not block members) to a vertex shader, which are allowed to have 6520component aliasing. 6521This vertex-variable component aliasing is intended only to support vertex 6522shaders where each execution path accesses at most one input per each 6523aliased component. 6524Implementations are permitted, but not required, to generate link-time 6525errors if they detect that every path through the vertex shader executable 6526accesses multiple inputs aliased to any single component.</p> 6527</div> 6528<div class="sect4"> 6529<h5 id="tessellation-evaluation-inputs">Tessellation Evaluation Inputs</h5> 6530<div class="paragraph"> 6531<p>Additional input layout qualifier identifiers allowed for tessellation 6532evaluation shaders are described below.</p> 6533</div> 6534<div class="openblock bnf"> 6535<div class="content"> 6536<div class="dlist"> 6537<dl> 6538<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 6539<dd> 6540<p><em>primitive_mode</em><br> 6541<em>vertex_spacing</em><br> 6542<em>ordering</em><br> 6543<em>point_mode</em></p> 6544</dd> 6545</dl> 6546</div> 6547</div> 6548</div> 6549<div class="paragraph"> 6550<p>The <strong>primitive-mode</strong> is used to specify a tessellation primitive mode to be 6551used by the tessellation primitive generator.</p> 6552</div> 6553<div class="openblock bnf"> 6554<div class="content"> 6555<div class="dlist"> 6556<dl> 6557<dt class="hdlist1"><em>primitive-mode</em>: </dt> 6558<dd> 6559<p><strong>triangles</strong><br> 6560<strong>quads</strong><br> 6561<strong>isolines</strong></p> 6562</dd> 6563</dl> 6564</div> 6565</div> 6566</div> 6567<div class="paragraph"> 6568<p>If present, the <em>primitive-mode</em> specifies that the tessellation primitive 6569generator should subdivide a triangle into smaller triangles, a quad into 6570triangles, or a quad into a collection of lines, respectively.</p> 6571</div> 6572<div class="paragraph"> 6573<p>A second group of layout identifiers, <em>vertex spacing</em>, is used to specify 6574the spacing used by the tessellation primitive generator when subdividing an 6575edge.</p> 6576</div> 6577<div class="openblock bnf"> 6578<div class="content"> 6579<div class="dlist"> 6580<dl> 6581<dt class="hdlist1"><em>vertex-spacing</em>: </dt> 6582<dd> 6583<p><strong>equal_spacing</strong><br> 6584<strong>fractional_even_spacing</strong><br> 6585<strong>fractional_odd_spacing</strong></p> 6586</dd> 6587</dl> 6588</div> 6589</div> 6590</div> 6591<div class="paragraph"> 6592<p><strong>equal_spacing</strong> specifies that edges should be divided into a collection of 6593equal-sized segments;</p> 6594</div> 6595<div class="paragraph"> 6596<p><strong>fractional_even_spacing</strong> specifies that edges should be divided into an 6597even number of equal-length segments plus two additional shorter 6598“fractional” segments; or</p> 6599</div> 6600<div class="paragraph"> 6601<p><strong>fractional_odd_spacing</strong> specifies that edges should be divided into an odd 6602number of equal-length segments plus two additional shorter “fractional” 6603segments.</p> 6604</div> 6605<div class="paragraph"> 6606<p>A third group of layout identifiers, <em>ordering</em>, specifies whether the 6607tessellation primitive generator produces triangles in clockwise or 6608counter-clockwise order, according to the coordinate system depicted in the 6609<a href="#references">OpenGL Specification</a>.</p> 6610</div> 6611<div class="openblock bnf"> 6612<div class="content"> 6613<div class="dlist"> 6614<dl> 6615<dt class="hdlist1"><em>ordering</em>: </dt> 6616<dd> 6617<p><strong>cw</strong><br> 6618<strong>ccw</strong></p> 6619</dd> 6620</dl> 6621</div> 6622</div> 6623</div> 6624<div class="paragraph"> 6625<p>The identifiers <strong>cw</strong> and <strong>ccw</strong> indicate clockwise and counter-clockwise 6626triangles, respectively. 6627If the tessellation primitive generator does not produce triangles, the 6628order is ignored.</p> 6629</div> 6630<div class="paragraph"> 6631<p>Finally, <em>point mode</em> indicates that the tessellation primitive generator 6632should produce one point for each distinct vertex in the subdivided 6633primitive, rather than generating lines or triangles.</p> 6634</div> 6635<div class="openblock bnf"> 6636<div class="content"> 6637<div class="dlist"> 6638<dl> 6639<dt class="hdlist1"><em>point-mode</em>: </dt> 6640<dd> 6641<p><strong>point_mode</strong></p> 6642</dd> 6643</dl> 6644</div> 6645</div> 6646</div> 6647<div class="paragraph"> 6648<p>Any or all of these identifiers may be specified one or more times in a 6649single input layout declaration. 6650If primitive mode, vertex spacing, or ordering is declared more than once in 6651the tessellation evaluation shaders of a program, all such declarations must 6652use the same identifier.</p> 6653</div> 6654<div class="paragraph"> 6655<p>At least one tessellation evaluation shader (compilation unit) in a program 6656must declare a primitive mode in its input layout. 6657Declaring vertex spacing, ordering, or point mode identifiers is optional. 6658It is not required that all tessellation evaluation shaders in a program 6659declare a primitive mode. 6660If spacing or vertex ordering declarations are omitted, the tessellation 6661primitive generator will use equal spacing or counter-clockwise vertex 6662ordering, respectively. 6663If a point mode declaration is omitted, the tessellation primitive generator 6664will produce lines or triangles according to the primitive mode.</p> 6665</div> 6666</div> 6667<div class="sect4"> 6668<h5 id="geometry-shader-inputs">Geometry Shader Inputs</h5> 6669<div class="paragraph"> 6670<p>Additional layout qualifier identifiers for geometry shader inputs include 6671<em>primitive</em> identifiers and an <em>invocation count</em> identifier:</p> 6672</div> 6673<div class="openblock bnf"> 6674<div class="content"> 6675<div class="dlist"> 6676<dl> 6677<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 6678<dd> 6679<p><strong>points</strong><br> 6680<strong>lines</strong><br> 6681<strong>lines_adjacency</strong><br> 6682<strong>triangles</strong><br> 6683<strong>triangles_adjacency</strong><br> 6684<strong>invocations</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 6685</dd> 6686</dl> 6687</div> 6688</div> 6689</div> 6690<div class="paragraph"> 6691<p>The identifiers <strong>points</strong>, <strong>lines</strong>, <strong>lines_adjacency</strong>, <strong>triangles</strong>, and 6692<strong>triangles_adjacency</strong> are used to specify the type of input primitive 6693accepted by the geometry shader, and only one of these is accepted. 6694At least one geometry shader (compilation unit) in a program must declare 6695this input primitive layout, and all geometry shader input layout 6696declarations in a program must declare the same layout. 6697It is not required that all geometry shaders in a program declare an input 6698primitive layout.</p> 6699</div> 6700<div class="paragraph"> 6701<p>The identifier <strong>invocations</strong> is used to specify the number of times the 6702geometry shader executable is invoked for each input primitive received. 6703Invocation count declarations are optional. 6704If no invocation count is declared in any geometry shader in a program, the 6705geometry shader will be run once for each input primitive. 6706If an invocation count is declared, all such declarations must specify the 6707same count. 6708If a shader specifies an invocation count greater than the 6709implementation-dependent maximum, or less than or equal to zero, 6710a compile-time error results.</p> 6711</div> 6712<div class="paragraph"> 6713<p>For example,</p> 6714</div> 6715<div class="listingblock"> 6716<div class="content"> 6717<pre class="CodeRay highlight"><code data-lang="c++">layout(triangles, invocations = <span class="integer">6</span>) in;</code></pre> 6718</div> 6719</div> 6720<div class="paragraph"> 6721<p>will establish that all inputs to the geometry shader are triangles and that 6722the geometry shader executable is run six times for each triangle processed.</p> 6723</div> 6724<div class="paragraph"> 6725<p>All geometry shader input unsized array declarations will be sized by an 6726earlier input primitive layout qualifier, when present, as per the following 6727table.</p> 6728</div> 6729<table class="tableblock frame-all grid-all stretch"> 6730<colgroup> 6731<col style="width: 50%;"> 6732<col style="width: 50%;"> 6733</colgroup> 6734<thead> 6735<tr> 6736<th class="tableblock halign-left valign-top">Layout</th> 6737<th class="tableblock halign-left valign-top">Size of Input Arrays</th> 6738</tr> 6739</thead> 6740<tbody> 6741<tr> 6742<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>points</strong></p></td> 6743<td class="tableblock halign-left valign-top"><p class="tableblock">1</p></td> 6744</tr> 6745<tr> 6746<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>lines</strong></p></td> 6747<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td> 6748</tr> 6749<tr> 6750<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>lines_adjacency</strong></p></td> 6751<td class="tableblock halign-left valign-top"><p class="tableblock">4</p></td> 6752</tr> 6753<tr> 6754<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>triangles</strong></p></td> 6755<td class="tableblock halign-left valign-top"><p class="tableblock">3</p></td> 6756</tr> 6757<tr> 6758<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>triangles_adjacency</strong></p></td> 6759<td class="tableblock halign-left valign-top"><p class="tableblock">6</p></td> 6760</tr> 6761</tbody> 6762</table> 6763<div class="paragraph"> 6764<p>The intrinsically declared input array <em>gl_in[]</em> will also be sized by any 6765input primitive-layout declaration. 6766Hence, the expression</p> 6767</div> 6768<div class="listingblock"> 6769<div class="content"> 6770<pre class="CodeRay highlight"><code data-lang="c++">gl_in.length()</code></pre> 6771</div> 6772</div> 6773<div class="paragraph"> 6774<p>will return the value from the table above.</p> 6775</div> 6776<div class="paragraph"> 6777<p>For inputs declared without an array size, including intrinsically declared 6778inputs (i.e., <em>gl_in</em>), a layout must be declared before any use of the 6779method <strong>length</strong>() or other any array use that requires the array size to be 6780known.</p> 6781</div> 6782<div class="paragraph"> 6783<p>It is a compile-time error if a layout declaration’s array size (from the 6784table above) does not match all the explicit array sizes specified in 6785declarations of an input variables in the same shader. 6786The following includes examples of compile-time errors:</p> 6787</div> 6788<div class="listingblock"> 6789<div class="content"> 6790<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// code sequence within one shader...</span> 6791in vec4 Color1[]; <span class="comment">// legal, size still unknown</span> 6792in vec4 Color2[<span class="integer">2</span>]; <span class="comment">// legal, size is 2</span> 6793in vec4 Color3[<span class="integer">3</span>]; <span class="comment">// illegal, input sizes are inconsistent</span> 6794layout(lines) in; <span class="comment">// legal for Color2, input size is 2, matching Color2</span> 6795in vec4 Color4[<span class="integer">3</span>]; <span class="comment">// illegal, contradicts layout of lines</span> 6796layout(lines) in; <span class="comment">// legal, matches other layout() declaration</span> 6797layout(triangles) in; <span class="comment">// illegal, does not match earlier layout() declaration</span></code></pre> 6798</div> 6799</div> 6800<div class="paragraph"> 6801<p>It is a link-time error if not all provided sizes (sized input arrays and 6802layout size) match across all geometry shaders in a program.</p> 6803</div> 6804</div> 6805<div class="sect4"> 6806<h5 id="fragment-shader-inputs">Fragment Shader Inputs</h5> 6807<div class="paragraph"> 6808<p>Additional fragment layout qualifier identifiers include the following for 6809<em>gl_FragCoord</em> :</p> 6810</div> 6811<div class="openblock bnf"> 6812<div class="content"> 6813<div class="dlist"> 6814<dl> 6815<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 6816<dd> 6817<p><strong>origin_upper_left</strong><br> 6818<strong>pixel_center_integer</strong></p> 6819</dd> 6820</dl> 6821</div> 6822</div> 6823</div> 6824<div class="paragraph"> 6825<p>By default, <em>gl_FragCoord</em> in OpenGL assumes a lower-left origin for window 6826coordinates and assumes pixel centers are located at half-pixel coordinates. 6827For example, the (<em>x, y</em>) location (0.5, 0.5) is returned for the 6828lower-left-most pixel in a window. 6829The origin can be changed by redeclaring <em>gl_FragCoord</em> with the 6830<strong>origin_upper_left</strong> qualifier, moving the origin of <em>gl_FragCoord</em> to the 6831upper left of the window, with <em>y</em> increasing in value toward the bottom of 6832the window. 6833The values returned can also be shifted by half a pixel in both <em>x</em> and <em>y</em> 6834by <strong>pixel_center_integer</strong> so it appears the pixels are centered at whole 6835number pixel offsets. 6836This moves the (<em>x</em>, <em>y</em>) value returned by <em>gl_FragCoord</em> of (0.5, 0.5) by 6837default, to (0.0, 0.0) with <strong>pixel_center_integer</strong>.</p> 6838</div> 6839<div class="paragraph"> 6840<p>Targeting Vulkan will assume and require an upper-left origin for <em>gl_FragCoord</em> 6841with pixel centers located at half-pixel coordinates. 6842This origin can be explicitly set by redeclaring <em>gl_FragCoord</em> with the 6843<strong>origin_upper_left</strong> identifier.</p> 6844</div> 6845<div class="paragraph"> 6846<p>Redeclarations are done as follows</p> 6847</div> 6848<div class="listingblock"> 6849<div class="content"> 6850<pre class="CodeRay highlight"><code data-lang="c++">in vec4 gl_FragCoord; <span class="comment">// redeclaration that changes nothing is allowed</span> 6851 6852<span class="comment">// All the following are allowed redeclaration that change behavior</span> 6853layout(origin_upper_left) in vec4 gl_FragCoord; 6854layout(pixel_center_integer) in vec4 gl_FragCoord; 6855layout(origin_upper_left, pixel_center_integer) in vec4 gl_FragCoord;</code></pre> 6856</div> 6857</div> 6858<div class="paragraph"> 6859<p>If <em>gl_FragCoord</em> is redeclared in any fragment shader in a program, it must 6860be redeclared in all the fragment shaders in that program that have a static 6861use <em>gl_FragCoord</em>. 6862All redeclarations of <em>gl_FragCoord in all fragment shaders in a single 6863program must have the same set of qualifiers. 6864Within any shader, the first redeclarations of _glFragCoord</em> must appear 6865before any use of <em>gl_FragCoord</em>. 6866The built-in <em>gl_FragCoord</em> is only predeclared in fragment shaders, so 6867redeclaring it in any other shader language results in a compile-time error.</p> 6868</div> 6869<div class="paragraph"> 6870<p>Redeclaring <em>glFragCoord</em> with <strong>origin_upper_left</strong> and/or 6871<strong>pixel_center_integer</strong> qualifiers only affects <em>gl_FragCoord.x</em> and 6872<em>gl_FragCoord.y</em>. 6873It has no effect on rasterization, transformation, or any other part of the 6874API pipeline or language features.</p> 6875</div> 6876<div class="paragraph"> 6877<p>Fragment shaders allow the following layout qualifier on <strong>in</strong> only (not with 6878variable declarations):</p> 6879</div> 6880<div class="openblock bnf"> 6881<div class="content"> 6882<div class="dlist"> 6883<dl> 6884<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 6885<dd> 6886<p><strong>early_fragment_tests</strong></p> 6887</dd> 6888</dl> 6889</div> 6890</div> 6891</div> 6892<div class="paragraph"> 6893<p>to request that fragment tests be performed before fragment shader 6894execution, as described in section 15.2.4 “Early Fragment Tests” of the 6895<a href="#references">OpenGL Specification</a>.</p> 6896</div> 6897<div class="paragraph"> 6898<p>For example,</p> 6899</div> 6900<div class="listingblock"> 6901<div class="content"> 6902<pre class="CodeRay highlight"><code data-lang="c++">layout(early_fragment_tests) in;</code></pre> 6903</div> 6904</div> 6905<div class="paragraph"> 6906<p>Specifying this will make per-fragment tests be performed before fragment 6907shader execution. 6908If this is not declared, per-fragment tests will be performed after fragment 6909shader execution. 6910Only one fragment shader (compilation unit) need declare this, though more 6911than one can. 6912If at least one declares this, then it is enabled.</p> 6913</div> 6914</div> 6915<div class="sect4"> 6916<h5 id="compute-shader-inputs">Compute Shader Inputs</h5> 6917<div class="paragraph"> 6918<p>There are no layout location qualifiers for compute shader inputs.</p> 6919</div> 6920<div class="paragraph"> 6921<p>Layout qualifier identifiers for compute shader inputs are the workgroup 6922size qualifiers:</p> 6923</div> 6924<div class="openblock bnf"> 6925<div class="content"> 6926<div class="dlist"> 6927<dl> 6928<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 6929<dd> 6930<p><strong>local_size_x</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 6931<strong>local_size_y</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 6932<strong>local_size_z</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 6933</dd> 6934</dl> 6935</div> 6936</div> 6937</div> 6938<div class="paragraph"> 6939<p>The <strong>local_size_x</strong>, <strong>local_size_y</strong>, and <strong>local_size_z</strong> qualifiers are used 6940to declare a fixed workgroup size by the compute shader in the first, 6941second, and third dimension, respectively. 6942If a shader does not specify a size for one of the dimensions, that 6943dimension will have a size of 1.</p> 6944</div> 6945<div class="paragraph"> 6946<p>For example, the following declaration in a compute shader</p> 6947</div> 6948<div class="listingblock"> 6949<div class="content"> 6950<pre class="CodeRay highlight"><code data-lang="c++">layout(local_size_x = <span class="integer">32</span>, local_size_y = <span class="integer">32</span>) in;</code></pre> 6951</div> 6952</div> 6953<div class="paragraph"> 6954<p>is used to declare a two-dimensional compute shader with a workgroup size of 32 6955X 32 elements, which is equivalent to a three-dimensional compute shader 6956where the third dimension has size one.</p> 6957</div> 6958<div class="paragraph"> 6959<p>As another example, the declaration</p> 6960</div> 6961<div class="listingblock"> 6962<div class="content"> 6963<pre class="CodeRay highlight"><code data-lang="c++">layout(local_size_x = <span class="integer">8</span>) in;</code></pre> 6964</div> 6965</div> 6966<div class="paragraph"> 6967<p>effectively specifies that a one-dimensional compute shader is being 6968compiled, and its size is 8 elements.</p> 6969</div> 6970<div class="paragraph"> 6971<p>If the fixed workgroup size of the shader in any dimension is less than 6972or equal to zero or greater than the maximum size supported by the 6973implementation for that dimension, a compile-time error results. 6974Also, if such a layout qualifier is declared more than once in the same 6975shader, all those declarations must set the same set of workgroup 6976sizes and set them to the same values; otherwise a compile-time error 6977results. 6978If multiple compute shaders attached to a single program object declare a 6979fixed workgroup size, the declarations must be identical; otherwise a 6980link-time error results.</p> 6981</div> 6982<div class="paragraph"> 6983<p>Furthermore, if a program object contains any compute shaders, at least one 6984must contain an input layout qualifier specifying a fixed workgroup size 6985for the program, or a link-time error will occur.</p> 6986</div> 6987</div> 6988</div> 6989<div class="sect3"> 6990<h4 id="output-layout-qualifiers">4.4.2. Output Layout Qualifiers</h4> 6991<div class="paragraph"> 6992<p>Some output layout qualifiers apply to all shader stages and some apply only 6993to specific stages. 6994The latter are discussed in separate sections below.</p> 6995</div> 6996<div class="paragraph"> 6997<p>As with input layout qualifiers, all shaders except compute shaders allow 6998<strong>location</strong> layout qualifiers on output variable declarations, output block 6999declarations, and output block member declarations. 7000Of these, variables and block members (but not blocks) additionally allow 7001the <strong>component</strong> layout qualifier.</p> 7002</div> 7003<div class="openblock bnf"> 7004<div class="content"> 7005<div class="dlist"> 7006<dl> 7007<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7008<dd> 7009<p><strong>location</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 7010<strong>component</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7011</dd> 7012</dl> 7013</div> 7014</div> 7015</div> 7016<div class="paragraph"> 7017<p>The usage and rules for applying the <strong>location</strong> qualifier 7018and the <strong>component</strong> qualifier 7019to blocks and structures are exactly as described in 7020“<a href="#input-layout-qualifiers">Input Layout Qualifiers</a>”. 7021Additionally, for fragment shader outputs, if two variables are placed 7022within the same location, they must have the same underlying type 7023(floating-point or integer). 7024No component aliasing of output variables or members is allowed.</p> 7025</div> 7026<div class="paragraph"> 7027<p>Fragment shaders allow an additional <strong>index</strong> output layout qualifier:</p> 7028</div> 7029<div class="openblock bnf"> 7030<div class="content"> 7031<div class="dlist"> 7032<dl> 7033<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7034<dd> 7035<p><strong>index</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7036</dd> 7037</dl> 7038</div> 7039</div> 7040</div> 7041<div class="paragraph"> 7042<p>Each of these qualifiers may appear at most once. 7043If <strong>index</strong> is specified, <strong>location</strong> must also be specified. 7044If <strong>index</strong> is not specified, the value 0 is used. 7045For example, in a fragment shader,</p> 7046</div> 7047<div class="listingblock"> 7048<div class="content"> 7049<pre class="CodeRay highlight"><code data-lang="c++">layout(location = <span class="integer">3</span>) out vec4 color;</code></pre> 7050</div> 7051</div> 7052<div class="paragraph"> 7053<p>will establish that the fragment shader output <em>color</em> is assigned to 7054fragment color 3 as the first (index zero) input to the blend equation. 7055And,</p> 7056</div> 7057<div class="listingblock"> 7058<div class="content"> 7059<pre class="CodeRay highlight"><code data-lang="c++">layout(location = <span class="integer">3</span>, index = <span class="integer">1</span>) out vec4 factor;</code></pre> 7060</div> 7061</div> 7062<div class="paragraph"> 7063<p>will establish that the fragment shader output <em>factor</em> is assigned to 7064fragment color 3 as the second (index one) input to the blend equation.</p> 7065</div> 7066<div class="paragraph"> 7067<p>For fragment shader outputs, the location 7068and index specify 7069the color output number 7070and index 7071receiving the values of the output. 7072For outputs of all other shader stages, the location specifies a vector 7073number that can be used to match against inputs in a subsequent shader 7074stage, even if that shader is in a different program object.</p> 7075</div> 7076<div class="paragraph"> 7077<p>If a declared output is a scalar or vector type other than <strong>dvec3</strong> or 7078<strong>dvec4</strong>, it will consume a single location. 7079Outputs of type <strong>dvec3</strong> or <strong>dvec4</strong> will consume two consecutive locations. 7080Outputs of type <strong>double</strong> and <strong>dvec2</strong> will consume only a single location, in 7081all stages.</p> 7082</div> 7083<div class="paragraph"> 7084<p>If the declared output is an array, it will be assigned consecutive 7085locations starting with the location specified. 7086For example,</p> 7087</div> 7088<div class="listingblock"> 7089<div class="content"> 7090<pre class="CodeRay highlight"><code data-lang="c++">layout(location = <span class="integer">2</span>) out vec4 colors[<span class="integer">3</span>];</code></pre> 7091</div> 7092</div> 7093<div class="paragraph"> 7094<p>will establish that <em>colors</em> is assigned to vector location numbers 2, 3, 7095and 4.</p> 7096</div> 7097<div class="paragraph"> 7098<p>If the declared output is an <em>n</em> × <em>m</em> 7099matrix, it will be assigned multiple locations starting with the location 7100specified. 7101The number of locations assigned will be the same as for an <em>n</em>-element 7102array of <em>m</em>-component vectors.</p> 7103</div> 7104<div class="paragraph"> 7105<p>If the declared output is a structure, its members will be assigned 7106consecutive locations in the order of declaration, with the first member 7107assigned the location specified for the structure. 7108The number of locations consumed by a structure member is determined by 7109applying the rules above recursively as though the structure member were 7110declared as an output variable of the same type.</p> 7111</div> 7112<div class="paragraph"> 7113<p><strong>location</strong> layout qualifiers may be used on output variables declared as 7114structures. 7115However, it is a compile-time error to use a <strong>location</strong> qualifier on a 7116structure member. 7117Location layout qualifiers may be used on output blocks and output block 7118members.</p> 7119</div> 7120<div class="paragraph"> 7121<p>The number of output locations available to a shader is limited. 7122For fragment shaders, the limit is the advertised number of draw buffers.</p> 7123</div> 7124<div class="paragraph"> 7125<p>For all other shaders, the limit is implementation-dependent and must be no 7126less than one fourth of the advertised maximum output component count 7127(compute shaders have no outputs). 7128A program will fail to link if any attached shader uses a location greater 7129than or equal to the number of supported locations, unless device-dependent 7130optimizations are able to make the program fit within available hardware 7131resources.</p> 7132</div> 7133<div class="paragraph"> 7134<p>Compile-time errors may also be given if at compile time it is known the 7135link will fail. 7136A negative output location will result in a compile-time error. 7137It is also a compile-time error if a fragment shader sets a layout index to 7138less than 0 or greater than 1.</p> 7139</div> 7140<div class="paragraph"> 7141<p>It is a compile-time or link-time error if any of the following occur:</p> 7142</div> 7143<div class="ulist"> 7144<ul> 7145<li> 7146<p>any two fragment shader output variables are assigned to the same 7147location and index.</p> 7148</li> 7149<li> 7150<p>if any two output variables from the same vertex, tessellation or 7151geometry shader stage are assigned to the same location.</p> 7152</li> 7153</ul> 7154</div> 7155<div class="paragraph"> 7156<p>For fragment shader outputs, locations can be assigned using either a 7157<strong>layout</strong> qualifier or via the OpenGL API.</p> 7158</div> 7159<div class="paragraph"> 7160<p>For all shader types, a program will fail to link if explicit location 7161assignments leave the linker unable to find space for other variables 7162without explicit assignments.</p> 7163</div> 7164<div class="paragraph"> 7165<p>If an output variable with no location or index assigned in the shader text 7166has a location specified through the OpenGL API, the API-assigned 7167location will be used. 7168Otherwise, such variables will be assigned a location by the linker. 7169All such assignments will have a color index of zero. 7170See section 15.2 “Shader Execution” of the <a href="#references">OpenGL Specification</a> for 7171more details. 7172A link-time error will occur if an output variable is declared in multiple 7173shaders of the same language with conflicting location or index values.</p> 7174</div> 7175<div class="paragraph"> 7176<p>For the purposes of determining if a non-fragment output matches an input 7177from a subsequent shader stage, the <strong>location</strong> layout qualifier (if any) 7178must match.</p> 7179</div> 7180<div class="sect4"> 7181<h5 id="transform-feedback-layout-qualifiers">Transform Feedback Layout Qualifiers</h5> 7182<div class="paragraph"> 7183<p>The vertex, tessellation, and geometry stages allow shaders to control 7184transform feedback. 7185When doing this, shaders will dictate which transform feedback buffers are 7186in use, which output variables will be written to which buffers, and how 7187each buffer is laid out. 7188To accomplish this, shaders allow the following layout qualifier identifiers 7189on output declarations:</p> 7190</div> 7191<div class="openblock bnf"> 7192<div class="content"> 7193<div class="dlist"> 7194<dl> 7195<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7196<dd> 7197<p><strong>xfb_buffer</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 7198<strong>xfb_offset</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 7199<strong>xfb_stride</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7200</dd> 7201</dl> 7202</div> 7203</div> 7204</div> 7205<div class="paragraph"> 7206<p>Any shader making any static use (after preprocessing) of any of these 7207<strong>xfb_</strong> qualifiers will cause the shader to be in a transform feedback 7208capturing mode and hence responsible for describing the transform feedback 7209setup. 7210This mode will capture any output selected by <strong>xfb_offset</strong>, directly or 7211indirectly, to a transform feedback buffer.</p> 7212</div> 7213<div class="paragraph"> 7214<p>The <strong>xfb_buffer</strong> qualifier specifies which transform feedback buffer will 7215capture outputs selected with <strong>xfb_offset</strong>. 7216The <strong>xfb_buffer</strong> qualifier can be applied to the qualifier <strong>out</strong>, to output 7217variables, to output blocks, and to output block members. 7218Shaders in the transform feedback capturing mode have an initial global 7219default of</p> 7220</div> 7221<div class="listingblock"> 7222<div class="content"> 7223<pre class="CodeRay highlight"><code data-lang="c++">layout(xfb_buffer = <span class="integer">0</span>) out;</code></pre> 7224</div> 7225</div> 7226<div class="paragraph"> 7227<p>This default can be changed by declaring a different buffer with 7228<strong>xfb_buffer</strong> on the interface qualifier <strong>out</strong>. 7229This is the only way the global default can be changed. 7230When a variable or output block is declared without an <strong>xfb_buffer</strong> 7231qualifier, it inherits the global default buffer. 7232When a variable or output block is declared with an <strong>xfb_buffer</strong> qualifier, 7233it has that declared buffer. 7234All members of a block inherit the block’s buffer. 7235A member is allowed to declare an <strong>xfb_buffer</strong>, but it must match the buffer 7236inherited from its block, or a compile-time error results.</p> 7237</div> 7238<div class="listingblock"> 7239<div class="content"> 7240<pre class="CodeRay highlight"><code data-lang="c++">layout(xfb_buffer=<span class="integer">2</span>, xfb_offset=<span class="integer">0</span>) out block { <span class="comment">// block's buffer is 2</span> 7241 layout(xfb_buffer = <span class="integer">2</span>) vec4 v; <span class="comment">// okay, matches the inherited 2</span> 7242 layout(xfb_buffer = <span class="integer">3</span>) vec4 u; <span class="comment">// ERROR, mismatched buffer</span> 7243 vec4 w; <span class="comment">// inherited</span> 7244}; 7245layout(xfb_offset=<span class="integer">16</span>) out vec4 t; <span class="comment">// initial default is buffer 0</span> 7246layout(xfb_buffer=<span class="integer">1</span>) out; <span class="comment">// new global default of 1</span> 7247out block { <span class="comment">// block has buffer 1</span> 7248 vec4 x; <span class="comment">// x has buffer 1 (not captured)</span> 7249 layout(xfb_buffer = <span class="integer">1</span>) vec4 y; <span class="comment">// okay (not captured)</span> 7250 layout(xfb_buffer = <span class="integer">0</span>) vec4 z; <span class="comment">// ERROR, mismatched buffer</span> 7251}; 7252layout(xfb_offset=<span class="integer">0</span>) out vec4 g; <span class="comment">// g has buffer 1</span> 7253layout(xfb_buffer=<span class="integer">2</span>) out vec4 h; <span class="comment">// does not change global default</span> 7254layout(xfb_offset=<span class="integer">16</span>) out vec4 j; <span class="comment">// j has buffer 1</span></code></pre> 7255</div> 7256</div> 7257<div class="paragraph"> 7258<p>Note this means all members of a block that go to a transform feedback 7259buffer will go to the same buffer.</p> 7260</div> 7261<div class="paragraph"> 7262<p>When a block is declared as an array, all members of block array-element 0 7263are captured, as previously described, by the declared or inherited 7264<strong>xfb_buffer</strong>. 7265Generally, an array of size <em>N</em> of blocks is captured by <em>N</em> consecutive 7266buffers, with all members of block array-element <em>E</em> captured by buffer <em>B</em>, 7267where <em>B</em> equals the declared or inherited <strong>xfb_buffer</strong> plus <em>E</em>.</p> 7268</div> 7269<div class="paragraph"> 7270<p>It is a compile-time or link-time error to specify an <strong>xfb_buffer</strong>, 7271including any additional buffers needed to capture an arrays of blocks, that 7272is less than zero or greater than or equal to the implementation-dependent 7273constant <em>gl_MaxTransformFeedbackBuffers</em>.</p> 7274</div> 7275<div class="paragraph"> 7276<p>The <strong>xfb_offset</strong> qualifier assigns a byte offset within a transform feedback 7277buffer. 7278Only variables, block members, or blocks can be qualified with <strong>xfb_offset</strong>. 7279If a block is qualified with <strong>xfb_offset</strong>, all its members are assigned 7280transform feedback buffer offsets. 7281If a block is not qualified with <strong>xfb_offset</strong>, any members of that block not 7282qualified with an <strong>xfb_offset</strong> will not be assigned transform feedback 7283buffer offsets. 7284Only variables and block members that are assigned offsets will be captured 7285(thus, a proper subset of a block can be captured). 7286Each time such a variable or block member is written in a shader, the 7287written value is captured at the assigned offset. 7288If such a block member or variable is not written during a shader 7289invocation, the buffer contents at the assigned offset will be undefined. 7290Even if there are no static writes to a variable or member that is assigned 7291a transform feedback offset, the space is still allocated in the buffer and 7292still affects the stride.</p> 7293</div> 7294<div class="paragraph"> 7295<p>Variables and block members qualified with <strong>xfb_offset</strong> can be scalars, 7296vectors, matrices, structures, and (sized) arrays of these. 7297The offset must be a multiple of the size of the first component of the 7298first qualified variable or block member, or a compile-time error results. 7299Further, if applied to an aggregate containing a <strong>double</strong>, the offset must 7300also be a multiple of 8, and the space taken in the buffer will be a 7301multiple of 8. 7302The given offset applies to the first component of the first member of the 7303qualified entity. 7304Then, within the qualified entity, subsequent components are each assigned, 7305in order, to the next available offset aligned to a multiple of that 7306component’s size. 7307Aggregate types are flattened down to the component level to get this 7308sequence of components. 7309It is a compile-time error to apply <strong>xfb_offset</strong> to the declaration of an 7310unsized array.</p> 7311</div> 7312<div class="paragraph"> 7313<p>No aliasing in output buffers is allowed: It is a compile-time or link-time 7314error to specify variables with overlapping transform feedback offsets.</p> 7315</div> 7316<div class="paragraph"> 7317<p>The <strong>xfb_stride</strong> qualifier specifies how many bytes are consumed by each 7318captured vertex. 7319It applies to the transform feedback buffer for that declaration, whether it 7320is inherited or explicitly declared. 7321It can be applied to variables, blocks, block members, or just the qualifier 7322<strong>out</strong>. 7323If the buffer is capturing any outputs with double-precision components, the 7324stride must be a multiple of 8, otherwise it must be a multiple of 4, or a 7325compile-time or link-time error results. 7326It is a compile-time or link-time error to have any <strong>xfb_offset</strong> that 7327overflows <strong>xfb_stride</strong>, whether stated on declarations before or after the 7328<strong>xfb_stride</strong>, or in different compilation units. 7329While <strong>xfb_stride</strong> can be declared multiple times for the same buffer, it is 7330a compile-time or link-time error to have different values specified for the 7331stride for the same buffer.</p> 7332</div> 7333<div class="paragraph"> 7334<p>For example:</p> 7335</div> 7336<div class="listingblock"> 7337<div class="content"> 7338<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// buffer 1 has 32-byte stride</span> 7339layout(xfb_buffer = <span class="integer">1</span>, xfb_stride = <span class="integer">32</span>) out; 7340 7341<span class="comment">// same as previous example; order within layout does not matter</span> 7342layout(xfb_stride = <span class="integer">32</span>, xfb_buffer = <span class="integer">1</span>) out; 7343 7344<span class="comment">// everything in this block goes to buffer 0</span> 7345layout(xfb_buffer = <span class="integer">0</span>, xfb_stride = <span class="integer">32</span>) out block1 { 7346 layout(xfb_offset = <span class="integer">0</span>) vec4 a; <span class="comment">// a goes to byte offset 0 of buffer 0</span> 7347 layout(xfb_offset = <span class="integer">16</span>) vec4 b; <span class="comment">// b goes to offset 16 of buffer 0</span> 7348}; 7349 7350layout(xfb_buffer = <span class="integer">3</span>, xfb_offset = <span class="integer">12</span>) out block2 { 7351 vec4 v; <span class="comment">// v will be written to byte offsets 12 through 27 of buffer</span> 7352 <span class="predefined-type">float</span> u; <span class="comment">// u will be written to offset 28</span> 7353 layout(xfb_offset = <span class="integer">40</span>) vec4 w; 7354 vec4 x; <span class="comment">// x will be written to offset 56, the next available offset</span> 7355}; 7356 7357layout(xfb_buffer = <span class="integer">2</span>, xfb_stride = <span class="integer">32</span>) out block3 { 7358 layout(xfb_offset = <span class="integer">12</span>) vec3 c; 7359 layout(xfb_offset = <span class="integer">24</span>) vec3 d; <span class="comment">// ERROR, requires stride of 36</span> 7360 layout(xfb_offset = <span class="integer">0</span>) vec3 g; <span class="comment">// okay, increasing order not required</span> 7361};</code></pre> 7362</div> 7363</div> 7364<div class="paragraph"> 7365<p>When no <strong>xfb_stride</strong> is specified for a buffer, the stride of the buffer 7366will be the smallest needed to hold the variable placed at the highest 7367offset, including any required padding. 7368For example:</p> 7369</div> 7370<div class="listingblock"> 7371<div class="content"> 7372<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// if there no other declarations for buffer 3, it has stride 32</span> 7373layout(xfb_buffer = <span class="integer">3</span>) out block4 { 7374 layout(xfb_offset = <span class="integer">0</span>) vec4 e; 7375 layout(xfb_offset = <span class="integer">16</span>) vec4 f; 7376};</code></pre> 7377</div> 7378</div> 7379<div class="paragraph"> 7380<p>The resulting stride (implicit or explicit), when divided by 4, must be less 7381than or equal to the implementation-dependent constant 7382<em>gl_MaxTransformFeedbackInterleavedComponents</em>.</p> 7383</div> 7384</div> 7385<div class="sect4"> 7386<h5 id="tessellation-control-outputs">Tessellation Control Outputs</h5> 7387<div class="paragraph"> 7388<p>Other than for the transform feedback layout qualifiers, tessellation 7389control shaders allow output layout qualifiers only on the interface 7390qualifier <strong>out</strong>, not on an output block, block member, or variable 7391declaration. 7392The output layout qualifier identifiers allowed for tessellation control 7393shaders are:</p> 7394</div> 7395<div class="openblock bnf"> 7396<div class="content"> 7397<div class="dlist"> 7398<dl> 7399<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7400<dd> 7401<p><strong>vertices</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7402</dd> 7403</dl> 7404</div> 7405</div> 7406</div> 7407<div class="paragraph"> 7408<p>The identifier <strong>vertices</strong> specifies the number of vertices in the output 7409patch produced by the tessellation control shader, which also specifies the 7410number of times the tessellation control shader is invoked. 7411It is a compile- or link-time error for the output vertex count to be less 7412than or equal to zero, or greater than the implementation-dependent maximum 7413patch size.</p> 7414</div> 7415<div class="paragraph"> 7416<p>The intrinsically declared tessellation control output array <em>gl_out[]</em> will 7417also be sized by any output layout declaration. 7418Hence, the expression</p> 7419</div> 7420<div class="listingblock"> 7421<div class="content"> 7422<pre class="CodeRay highlight"><code data-lang="c++">gl_out.length()</code></pre> 7423</div> 7424</div> 7425<div class="paragraph"> 7426<p>will return the output patch vertex count specified in a previous output 7427layout qualifier. 7428For outputs declared without an array size, including intrinsically declared 7429outputs (i.e., <em>gl_out</em>), a layout must be declared before any use of the 7430method <strong>length</strong>() or other array use that requires its size to be known.</p> 7431</div> 7432<div class="paragraph"> 7433<p>It is a compile-time error if the output patch vertex count specified in an 7434output layout qualifier does not match the array size specified in any 7435output variable declaration in the same shader.</p> 7436</div> 7437<div class="paragraph"> 7438<p>All tessellation control shader layout declarations in a program must 7439specify the same output patch vertex count. 7440There must be at least one layout qualifier specifying an output patch 7441vertex count in any program containing tessellation control shaders; 7442however, such a declaration is not required in all tessellation control 7443shaders.</p> 7444</div> 7445</div> 7446<div class="sect4"> 7447<h5 id="geometry-outputs">Geometry Outputs</h5> 7448<div class="paragraph"> 7449<p>Geometry shaders can have three additional types of output layout 7450identifiers: an output <em>primitive type</em>, a maximum output <em>vertex count</em>, 7451and per-output <em>stream</em> numbers. 7452The primitive type and vertex count identifiers are allowed only on the 7453interface qualifier <strong>out</strong>, not on an output block, block member, or variable 7454declaration. 7455The stream identifier is allowed on the interface qualifier <strong>out</strong>, on output 7456blocks, and on variable declarations.</p> 7457</div> 7458<div class="paragraph"> 7459<p>The layout qualifier identifiers for geometry shader outputs are</p> 7460</div> 7461<div class="openblock bnf"> 7462<div class="content"> 7463<div class="dlist"> 7464<dl> 7465<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7466<dd> 7467<p><strong>points</strong><br> 7468<strong>line_strip</strong><br> 7469<strong>triangle_strip</strong><br> 7470<strong>max_vertices</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 7471<strong>stream</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7472</dd> 7473</dl> 7474</div> 7475</div> 7476</div> 7477<div class="paragraph"> 7478<p>The primitive type identifiers <strong>points</strong>, <strong>line_strip</strong>, and <strong>triangle_strip</strong> 7479are used to specify the type of output primitive produced by the geometry 7480shader, and only one of these is accepted. 7481At least one geometry shader (compilation unit) in a program must declare an 7482output primitive type, and all geometry shader output primitive type 7483declarations in a program must declare the same primitive type. 7484It is not required that all geometry shaders in a program declare an output 7485primitive type.</p> 7486</div> 7487<div class="paragraph"> 7488<p>The vertex count identifier <strong>max_vertices</strong> is used to specify the maximum 7489number of vertices the shader will ever emit in a single invocation. 7490At least one geometry shader (compilation unit) in a program must declare a 7491maximum output vertex count, and all geometry shader output vertex count 7492declarations in a program must declare the same count. 7493It is not required that all geometry shaders in a program declare a count.</p> 7494</div> 7495<div class="paragraph"> 7496<p>In this example,</p> 7497</div> 7498<div class="listingblock"> 7499<div class="content"> 7500<pre class="CodeRay highlight"><code data-lang="c++">layout(triangle_strip, max_vertices = <span class="integer">60</span>) out; <span class="comment">// order does not matter</span> 7501layout(max_vertices = <span class="integer">60</span>) out; <span class="comment">// redeclaration okay</span> 7502layout(triangle_strip) out; <span class="comment">// redeclaration okay</span> 7503layout(points) out; <span class="comment">// error, contradicts triangle_strip</span> 7504layout(max_vertices = <span class="integer">30</span>) out; <span class="comment">// error, contradicts 60</span></code></pre> 7505</div> 7506</div> 7507<div class="paragraph"> 7508<p>all outputs from the geometry shader are triangles and at most 60 vertices 7509will be emitted by the shader. 7510It is an error for the maximum number of vertices to be greater than 7511<em>gl_MaxGeometryOutputVertices</em>.</p> 7512</div> 7513<div class="paragraph"> 7514<p>The identifier <strong>stream</strong> is used to specify that a geometry shader output 7515variable or block is associated with a particular vertex stream (numbered 7516beginning with zero). 7517A default stream number may be declared at global scope by qualifying 7518interface qualifier <strong>out</strong> as in this example:</p> 7519</div> 7520<div class="listingblock"> 7521<div class="content"> 7522<pre class="CodeRay highlight"><code data-lang="c++">layout(stream = <span class="integer">1</span>) out;</code></pre> 7523</div> 7524</div> 7525<div class="paragraph"> 7526<p>The stream number specified in such a declaration replaces any previous 7527default and applies to all subsequent block and variable declarations until 7528a new default is established. 7529The initial default stream number is zero.</p> 7530</div> 7531<div class="paragraph"> 7532<p>Each output block or non-block output variable is associated with a vertex 7533stream. 7534If the block or variable is declared with the stream identifier, it is 7535associated with the specified stream; otherwise, it is associated with the 7536current default stream. 7537A block member may be declared with a stream identifier, but the specified 7538stream must match the stream associated with the containing block. 7539One example:</p> 7540</div> 7541<div class="listingblock"> 7542<div class="content"> 7543<pre class="CodeRay highlight"><code data-lang="c++">layout(stream=<span class="integer">1</span>) out; <span class="comment">// default is now stream 1</span> 7544out vec4 var1; <span class="comment">// var1 gets default stream (1)</span> 7545layout(stream=<span class="integer">2</span>) out Block1 { <span class="comment">// "Block1" belongs to stream 2</span> 7546 layout(stream=<span class="integer">2</span>) vec4 var2; <span class="comment">// redundant block member stream decl</span> 7547 layout(stream=<span class="integer">3</span>) vec2 var3; <span class="comment">// ILLEGAL (must match block stream)</span> 7548 vec3 var4; <span class="comment">// belongs to stream 2</span> 7549}; 7550layout(stream=<span class="integer">0</span>) out; <span class="comment">// default is now stream 0</span> 7551out vec4 var5; <span class="comment">// var5 gets default stream (0)</span> 7552out Block2 { <span class="comment">// "Block2" gets default stream (0)</span> 7553 vec4 var6; 7554}; 7555layout(stream=<span class="integer">3</span>) out vec4 var7; <span class="comment">// var7 belongs to stream 3</span></code></pre> 7556</div> 7557</div> 7558<div class="paragraph"> 7559<p>Each vertex emitted by the geometry shader is assigned to a specific stream, 7560and the attributes of the emitted vertex are taken from the set of output 7561blocks and variables assigned to the targeted stream. 7562After each vertex is emitted, the values of all output variables become 7563undefined. 7564Additionally, the output variables associated with each vertex stream may 7565share storage. 7566Writing to an output variable associated with one stream may overwrite 7567output variables associated with any other stream. 7568When emitting each vertex, a geometry shader should write to all outputs 7569associated with the stream to which the vertex will be emitted and to no 7570outputs associated with any other stream.</p> 7571</div> 7572<div class="paragraph"> 7573<p>If a geometry shader output block or variable is declared more than once, 7574all such declarations must associate the variable with the same vertex 7575stream. 7576If any stream declaration specifies a non-existent stream number, the shader 7577will fail to compile.</p> 7578</div> 7579<div class="paragraph"> 7580<p>Built-in geometry shader outputs are always associated with vertex stream 7581zero.</p> 7582</div> 7583<div class="paragraph"> 7584<p>All geometry shader output layout declarations in a program must declare the 7585same layout and same value for <strong>max_vertices</strong>. 7586If geometry shaders are in a program, there must be at least one geometry 7587output layout declaration somewhere in that 7588program, but not all geometry 7589shaders (compilation units) are required to declare it.</p> 7590</div> 7591</div> 7592<div class="sect4"> 7593<h5 id="fragment-outputs">Fragment Outputs</h5> 7594<div class="paragraph"> 7595<p>The built-in fragment shader variable <em>gl_FragDepth</em> may be redeclared using 7596one of the following layout qualifiers.</p> 7597</div> 7598<div class="openblock bnf"> 7599<div class="content"> 7600<div class="dlist"> 7601<dl> 7602<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7603<dd> 7604<p><strong>depth_any</strong><br> 7605<strong>depth_greater</strong><br> 7606<strong>depth_less</strong><br> 7607<strong>depth_unchanged</strong></p> 7608</dd> 7609</dl> 7610</div> 7611</div> 7612</div> 7613<div class="paragraph"> 7614<p>The layout qualifier for <em>gl_FragDepth</em> constrains intentions of the final 7615value of <em>gl_FragDepth</em> written by any shader invocation. 7616GL implementations are allowed to perform optimizations assuming that the 7617depth test fails (or passes) for a given fragment if all values of 7618<em>gl_FragDepth</em> consistent with the layout qualifier would fail (or pass). 7619This potentially includes skipping shader execution if the fragment is 7620discarded because it is occluded and the shader has no side effects. 7621If the final value of <em>gl_FragDepth</em> is inconsistent with its layout 7622qualifier, the result of the depth test for the corresponding fragment is 7623undefined. 7624However, no error will be generated in this case. 7625If the depth test passes and depth writes are enabled, the value written to 7626the depth buffer is always the value of <em>gl_FragDepth</em>, whether or not it is 7627consistent with the layout qualifier.</p> 7628</div> 7629<div class="paragraph"> 7630<p>By default, <em>gl_FragDepth</em> is qualified as <em>depth_any</em>. 7631When the layout qualifier for <em>gl_FragDepth</em> is <em>depth_any</em>, the shader 7632compiler will note any assignment to <em>gl_FragDepth</em> modifying it in an 7633unknown way, and depth testing will always be performed after the shader has 7634executed. 7635When the layout qualifier is <em>depth_greater</em>, the GL can assume that the 7636final value of <em>gl_FragDepth</em> is greater than or equal to the fragment’s 7637interpolated depth value, as given by the <em>z</em> component of <em>gl_FragCoord</em>. 7638When the layout qualifier is <em>depth_less</em>, the GL can assume that any 7639modification of <em>gl_FragDepth</em> will only decrease its value. 7640When the layout qualifier is <em>depth_unchanged</em>, the shader compiler will 7641honor any modification to <em>gl_FragDepth</em>, but the rest of the GL can assume 7642that <em>gl_FragDepth</em> is not assigned a new value.</p> 7643</div> 7644<div class="paragraph"> 7645<p>Redeclarations of <em>gl_FragDepth</em> are performed as follows:</p> 7646</div> 7647<div class="listingblock"> 7648<div class="content"> 7649<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// redeclaration that changes nothing is allowed +</span> 7650out <span class="predefined-type">float</span> gl_FragDepth; 7651 7652<span class="comment">// assume it may be modified in any way</span> 7653layout(depth_any) out <span class="predefined-type">float</span> gl_FragDepth; 7654 7655<span class="comment">// assume it may be modified such that its value will only increase</span> 7656layout(depth_greater) out <span class="predefined-type">float</span> gl_FragDepth; 7657 7658<span class="comment">// assume it may be modified such that its value will only decrease</span> 7659layout(depth_less) out <span class="predefined-type">float</span> gl_FragDepth; 7660 7661<span class="comment">// assume it will not be modified</span> 7662layout(depth_unchanged) out <span class="predefined-type">float</span> gl_FragDepth;</code></pre> 7663</div> 7664</div> 7665<div class="paragraph"> 7666<p>If <em>gl_FragDepth</em> is redeclared in any fragment shader in a program, it must 7667be redeclared in all fragment shaders in that program that have static 7668assignments to <em>gl_FragDepth</em>. 7669All redeclarations of <em>gl_FragDepth</em> in all fragment shaders in a single 7670program must have the same set of qualifiers. 7671Within any shader, the first redeclarations of <em>gl_FragDepth</em> must appear 7672before any use of <em>gl_FragDepth</em>. 7673The built-in <em>gl_FragDepth</em> is only predeclared in fragment shaders, so 7674redeclaring it in any other shader language results in a compile-time error.</p> 7675</div> 7676</div> 7677</div> 7678<div class="sect3"> 7679<h4 id="uniform-variable-layout-qualifiers">4.4.3. Uniform Variable Layout Qualifiers</h4> 7680<div class="paragraph"> 7681<p>Layout qualifiers can be used for uniform variables and subroutine uniforms. 7682The layout qualifier identifiers for uniform variables and subroutine 7683uniforms are:</p> 7684</div> 7685<div class="openblock bnf"> 7686<div class="content"> 7687<div class="dlist"> 7688<dl> 7689<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7690<dd> 7691<p><strong>location</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7692</dd> 7693</dl> 7694</div> 7695</div> 7696</div> 7697<div class="paragraph"> 7698<p>The location identifier can be used with default-block uniform variables and 7699subroutine uniforms. 7700The location specifies the location by which the API can reference 7701the uniform and update its value. 7702Individual elements of a uniform array are assigned consecutive locations 7703with the first element taking location <strong>location</strong>. 7704Default-block uniform variable declarations sharing the same location 7705linked in the program have to match by name, type, qualifiers and arrayness. 7706For arrays their array dimensionality and array sizes must match. 7707For structs this rule applies recursively to all members. 7708No two subroutine uniform variables can have the same location in the same 7709shader stage, otherwise a compile-time or link-time error will be generated. 7710Valid locations for default-block uniform variable locations are in the 7711range of 0 to the implementation-defined maximum number of uniform locations 7712minus one. 7713Valid locations for subroutine uniforms are in the range of 0 to the 7714implementation-defined per-stage maximum number of subroutine uniform 7715locations minus one.</p> 7716</div> 7717<div class="paragraph"> 7718<p>Locations can be assigned to default-block uniform arrays and structures. 7719The first inner-most scalar, vector or matrix member or element takes the 7720specified <strong>location</strong> and the compiler assigns the next inner-most member or 7721element the next incremental location value. 7722Each subsequent inner-most member or element gets incremental locations for 7723the entire structure or array. 7724This rule applies to nested structures and arrays and gives each inner-most 7725scalar, vector, or matrix member a unique location. 7726For arrays without an explicit size, the size is calculated based on its 7727static usage. 7728When the linker generates locations for uniforms without an explicit 7729location, it assumes for all uniforms with an explicit location all their 7730array elements and structure members are used and the linker will not 7731generate a conflicting location, even if that element or member is deemed 7732unused.</p> 7733</div> 7734<div class="paragraph"> 7735<p>When generating SPIR-V for API’s that accept individual (default block) 7736non-opaque uniform variables, it is a compile-time error to not 7737include a location when declaring them.</p> 7738</div> 7739<div class="paragraph"> 7740<p>When targeting Vulkan, the <strong>push_constant</strong> qualifier is used to 7741declare an entire block, and represents a set of <em>push constants</em>, as defined 7742by the Vulkan API. 7743It is a compile-time error to apply this to anything other than a uniform block 7744declaration, or when not targeting Vulkan. 7745The values in the block will be initialized as per the Vulkan API specification. 7746A block declared with <code>layout(push_constant)</code> may optionally include an 7747<em>instance-name</em>. 7748There can be only one <strong>push_constant</strong> block per stage, or a compile-time or 7749link-time error will result. 7750A push-constant array can only be indexed with dynamically uniform indices. 7751Uniform blocks declared with <strong>push_constant</strong> use different resources 7752than those without; and are accounted for separately.</p> 7753</div> 7754</div> 7755<div class="sect3"> 7756<h4 id="subroutine-function-layout-qualifiers">4.4.4. Subroutine Function Layout Qualifiers</h4> 7757<div class="paragraph"> 7758<p>Layout qualifiers can be used for subroutine functions. 7759The layout qualifier identifiers for subroutine functions are:</p> 7760</div> 7761<div class="openblock bnf"> 7762<div class="content"> 7763<div class="dlist"> 7764<dl> 7765<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7766<dd> 7767<p><strong>index</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7768</dd> 7769</dl> 7770</div> 7771</div> 7772</div> 7773<div class="paragraph"> 7774<p>Each subroutine with an index qualifier in the shader must be given a unique 7775index, otherwise a compile- or link-time error will be generated. 7776The indices must be in the range of 0 to the implementation defined maximum 7777number of subroutines minus one. 7778It is recommended, but not required, that the shader assigns a range of 7779tightly packed <em>index</em> values starting from zero so that the OpenGL 7780subroutine function enumeration API returns a non-empty name for all active 7781indices.</p> 7782</div> 7783</div> 7784<div class="sect3"> 7785<h4 id="uniform-and-shader-storage-block-layout-qualifiers">4.4.5. Uniform and Shader Storage Block Layout Qualifiers</h4> 7786<div class="paragraph"> 7787<p>Layout qualifiers can be used for uniform and shader storage blocks, but not 7788for non-block uniform declarations. 7789The layout qualifier identifiers (and <strong>shared</strong> keyword) for uniform and 7790shader storage blocks are:</p> 7791</div> 7792<div class="openblock bnf"> 7793<div class="content"> 7794<div class="dlist"> 7795<dl> 7796<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 7797<dd> 7798<p><strong>shared</strong><br> 7799<strong>packed</strong><br> 7800<strong>std140</strong><br> 7801<strong>std430</strong><br> 7802<strong>row_major</strong><br> 7803<strong>column_major</strong><br> 7804<strong>binding</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 7805<strong>offset</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 7806<strong>align</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 7807</dd> 7808</dl> 7809</div> 7810</div> 7811</div> 7812<div class="paragraph"> 7813<p>None of these have any semantic effect at all on the usage of the variables 7814being declared; they only describe how data is laid out in memory. 7815For example, matrix semantics are always column-based, as described in the 7816rest of this specification, no matter what layout qualifiers are being used.</p> 7817</div> 7818<div class="paragraph"> 7819<p>Uniform and shader storage block layout qualifiers can be declared for 7820global scope, on a single uniform or shader storage block, or on a single 7821block member declaration.</p> 7822</div> 7823<div class="paragraph"> 7824<p>Default layouts are established at global scope for uniform blocks as:</p> 7825</div> 7826<div class="listingblock"> 7827<div class="content"> 7828<pre class="CodeRay highlight"><code data-lang="c++">layout(layout-qualifier-id-list) uniform;</code></pre> 7829</div> 7830</div> 7831<div class="paragraph"> 7832<p>and for shader storage blocks as:</p> 7833</div> 7834<div class="listingblock"> 7835<div class="content"> 7836<pre class="CodeRay highlight"><code data-lang="c++">layout(layout-qualifier-id-list) buffer;</code></pre> 7837</div> 7838</div> 7839<div class="paragraph"> 7840<p>When this is done, the previous default qualification is first inherited and 7841then overridden as per the override rules listed below for each qualifier 7842listed in the declaration. 7843The result becomes the new default qualification scoped to subsequent 7844uniform or shader storage block definitions.</p> 7845</div> 7846<div class="paragraph"> 7847<p>The initial state of compilation when generating SPIR-V is as if the 7848following were declared:</p> 7849</div> 7850<div class="listingblock"> 7851<div class="content"> 7852<pre class="CodeRay highlight"><code data-lang="c++">layout(std140, column_major) uniform; 7853layout(std430, column_major) buffer;</code></pre> 7854</div> 7855</div> 7856<div class="paragraph"> 7857<p>However, when <strong>push_constant</strong> is declared, the default layout of the 7858buffer will be <strong>std430</strong>. There is no method to globally set this default.</p> 7859</div> 7860<div class="paragraph"> 7861<p>The initial state of compilation when not generating SPIR-V is as if the 7862following were declared:</p> 7863</div> 7864<div class="listingblock"> 7865<div class="content"> 7866<pre class="CodeRay highlight"><code data-lang="c++">layout(shared, column_major) uniform; 7867layout(shared, column_major) buffer;</code></pre> 7868</div> 7869</div> 7870<div class="paragraph"> 7871<p>Uniform and shader storage blocks can be declared with optional layout 7872qualifiers, and so can their individual member declarations. 7873Such block layout qualification is scoped only to the content of the block. 7874As with global layout declarations, block layout qualification first 7875inherits from the current default qualification and then overrides it. 7876Similarly, individual member layout qualification is scoped just to the 7877member declaration, and inherits from and overrides the block’s 7878qualification.</p> 7879</div> 7880<div class="paragraph"> 7881<p>The <strong>shared</strong> qualifier overrides only the <strong>std140</strong>, <strong>std430</strong>, and <strong>packed</strong> 7882qualifiers; other qualifiers are inherited. 7883The compiler/linker will ensure that multiple programs and programmable 7884stages containing this definition will share the same memory layout for this 7885block, as long as all arrays are declared with explicit sizes and all 7886matrices have matching <strong>row_major</strong> and/or <strong>column_major</strong> qualifications 7887(which may come from a declaration outside the block definition). 7888This allows use of the same buffer to back the same block definition across 7889different programs. 7890It is a compile-time error to use the <strong>shared</strong> qualifier when generating 7891SPIR-V.</p> 7892</div> 7893<div class="paragraph"> 7894<p>The <strong>packed</strong> qualifier overrides only <strong>std140</strong>, <strong>std430</strong>, and <strong>shared</strong>; 7895other qualifiers are inherited. 7896When <strong>packed</strong> is used, no shareable layout is guaranteed. 7897The compiler and linker can optimize memory use based on what variables 7898actively get used and on other criteria. 7899Offsets must be queried, as there is no other way of guaranteeing where (and 7900which) variables reside within the block.</p> 7901</div> 7902<div class="paragraph"> 7903<p>It is a link-time error to access the same packed uniform or shader storage 7904block in multiple stages within a program. 7905Attempts to access the same packed uniform or shader storage block across 7906programs can result in conflicting member offsets and in undefined values 7907being read. 7908However, implementations may aid application management of packed blocks by 7909using canonical layouts for packed blocks. 7910It is a compile-time error to use the <strong>packed</strong> qualifier when generating 7911SPIR-V.</p> 7912</div> 7913<div class="paragraph"> 7914<p>The <strong>std140</strong> and <strong>std430</strong> qualifiers override only the <strong>packed</strong>, <strong>shared</strong>, 7915<strong>std140</strong>, and <strong>std430</strong> qualifiers; other qualifiers are inherited. 7916The <strong>std430</strong> qualifier is supported only for shader storage blocks; a shader 7917using the <strong>std430</strong> qualifier on a uniform block will result in 7918a compile-time error, unless it is also declared with <strong>push_constant</strong>.</p> 7919</div> 7920<div class="paragraph"> 7921<p>The layout is explicitly determined by this, as described in section 7.6.2.2 7922“Standard Uniform Block Layout” of the <a href="#references">OpenGL Specification</a>. 7923Hence, as in <strong>shared</strong> above, the resulting layout is shareable across 7924programs.</p> 7925</div> 7926<div class="paragraph"> 7927<p>Layout qualifiers on member declarations cannot use the <strong>shared</strong>, <strong>packed</strong>, 7928<strong>std140</strong>, or <strong>std430</strong> qualifiers. 7929These can only be used at global scope (without an object) or on a block 7930declaration, or a compile-time error results.</p> 7931</div> 7932<div class="paragraph"> 7933<p>The <strong>row_major</strong> and <strong>column_major</strong> qualifiers only affect the layout of 7934matrices, including all matrices contained in structures and arrays they are 7935applied to, to all depths of nesting. 7936These qualifiers can be applied to other types, but will have no effect.</p> 7937</div> 7938<div class="paragraph"> 7939<p>The <strong>row_major</strong> qualifier overrides only the <strong>column_major</strong> qualifier; other 7940qualifiers are inherited. 7941Elements within a matrix row will be contiguous in memory.</p> 7942</div> 7943<div class="paragraph"> 7944<p>The <strong>column_major</strong> qualifier overrides only the <strong>row_major</strong> qualifier; other 7945qualifiers are inherited. 7946Elements within a matrix column will be contiguous in memory.</p> 7947</div> 7948<div class="paragraph"> 7949<p>The <strong>binding</strong> qualifier specifies the uniform buffer binding point 7950corresponding to the uniform or shader storage block, which will be used to 7951obtain the values of the member variables of the block. 7952It is a compile-time error to specify the <strong>binding</strong> qualifier for the global 7953scope or for block member declarations. 7954Any uniform or shader storage block declared without a <strong>binding</strong> qualifier 7955is initially assigned to block binding point zero. 7956After a program is linked, the binding points used for uniform 7957and shader storage blocks 7958declared with or without a <strong>binding</strong> qualifier can be updated 7959by the API.</p> 7960</div> 7961<div class="paragraph"> 7962<p>When used with OpenGL, 7963if the <strong>binding</strong> qualifier is used with a uniform block or shader storage 7964block instanced as an array, the first element of the array takes the 7965specified block binding and each subsequent element takes the next 7966consecutive binding point. 7967For an array of arrays, each element (e.g. 6 elements for a[2][3]) gets a 7968binding point, and they are ordered per the array of array ordering 7969described in “<a href="#arrays">Arrays.</a>”</p> 7970</div> 7971<div class="paragraph"> 7972<p>When targeting Vulkan, 7973if the <strong>binding</strong> qualifier is used with a uniform block or buffer block 7974instanced as an array, the entire array takes only the provided binding 7975number. 7976The next consecutive binding number is available for a different 7977object. 7978For an array of arrays, descriptor set array element numbers used 7979in descriptor set accesses are ordered per the array-of-array ordering 7980described in “<a href="#arrays">Arrays.</a>”</p> 7981</div> 7982<div class="paragraph"> 7983<p>If the binding point for any uniform or shader storage block instance is 7984less than zero, or greater than or equal to the corresponding 7985implementation-dependent maximum number of buffer bindings, a compile-time 7986error will occur. 7987When the <strong>binding</strong> qualifier is used with a uniform or shader storage block 7988instanced as an array of size <em>N</em>, all elements of the array from <strong>binding</strong> 7989through <em>binding + N - 1</em> must be within this range. 7990It is a compile-time or link-time error to use the same binding number for 7991more than one uniform block or for more than one buffer block.</p> 7992</div> 7993<div class="paragraph"> 7994<p>The <strong>set</strong> qualifier is only available when targeting Vulkan. 7995It specifies the descriptor set this object belongs to. 7996It is a compile-time error to apply <strong>set</strong> to a standalone qualifier, to 7997a member of a block, or when not targeting an API that supports descriptor sets. 7998It is a compile-time error to apply <strong>set</strong> to a block qualified as <strong>push_constant</strong>. 7999By default, any non-push-constant uniform or shader storage block declared 8000without a <strong>set</strong> identifier is assigned to descriptor set 0. 8001Similarly, any sampler, texture, or subpass-input type declared as a uniform 8002without a <strong>set</strong> identifier is also assigned to descriptor set 0.</p> 8003</div> 8004<div class="paragraph"> 8005<p>If applied to an object declared as an array, all elements of the array 8006belong to the specified <strong>set</strong>.</p> 8007</div> 8008<div class="paragraph"> 8009<p>When generating SPIR-V, it is a compile-time error for either the <strong>set</strong> or 8010<strong>binding</strong> value to exceed a front-end-configuration supplied maximum value.</p> 8011</div> 8012<div class="paragraph"> 8013<p>When multiple arguments are listed in a <strong>layout</strong> declaration, the effect 8014will be the same as if they were declared one at a time, in order from left 8015to right, each in turn inheriting from and overriding the result from the 8016previous qualification.</p> 8017</div> 8018<div class="paragraph"> 8019<p>For example</p> 8020</div> 8021<div class="listingblock"> 8022<div class="content"> 8023<pre class="CodeRay highlight"><code data-lang="c++">layout(row_major, column_major)</code></pre> 8024</div> 8025</div> 8026<div class="paragraph"> 8027<p>results in the qualification being <strong>column_major</strong>. 8028Other examples:</p> 8029</div> 8030<div class="listingblock"> 8031<div class="content"> 8032<pre class="CodeRay highlight"><code data-lang="c++">layout(shared, row_major) uniform; <span class="comment">// default is now shared and row_major</span> 8033 8034layout(std140) uniform Transform { <span class="comment">// layout of this block is std140</span> 8035 mat4 M1; <span class="comment">// row major</span> 8036 layout(column_major) mat4 M2; <span class="comment">// column major</span> 8037 mat3 N1; <span class="comment">// row major</span> 8038}; 8039 8040uniform T2 { <span class="comment">// layout of this block is shared</span> 8041 ... 8042}; 8043 8044layout(column_major) uniform T3 { <span class="comment">// shared and column major</span> 8045 mat4 M3; <span class="comment">// column major</span> 8046 layout(row_major) mat4 m4; <span class="comment">// row major</span> 8047 mat3 N2; <span class="comment">// column major</span> 8048};</code></pre> 8049</div> 8050</div> 8051<div class="paragraph"> 8052<p>When targeting Vulkan, the <strong>offset</strong> and <strong>align</strong> qualifiers for blocks and 8053block members can only be used with <strong>uniform</strong> and <strong>buffer</strong> blocks. 8054When not targeting Vulkan, they can only be used with blocks declared with 8055<strong>std140</strong> or <strong>std430</strong> layouts.</p> 8056</div> 8057<div class="paragraph"> 8058<p>The <strong>offset</strong> qualifier can only be used on block members. 8059The <strong>offset</strong> qualifier forces the qualified member to start at or after the 8060specified <em>layout-qualifier-value</em>, which will be its byte offset from 8061the beginning of the buffer. 8062It is a compile-time error to have any offset, explicit or assigned, that 8063lies within another member of the block. 8064When not generating SPIR-V, it is a compile-time error to specify an offset 8065that is smaller than the offset of the previous member in the block. 8066Two blocks linked together in the same program with the same block name must 8067have the exact same set of members qualified with <strong>offset</strong> and their 8068<em>layout-qualifier-value</em> values must be the same, or a link-time error 8069results. 8070The specified offset must be a multiple of the base alignment of the type of 8071the block member it qualifies, or a compile-time error results.</p> 8072</div> 8073<div class="paragraph"> 8074<p>The <strong>align</strong> qualifier makes the start of each block member have a minimum 8075byte alignment. 8076It does not affect the internal layout within each member, which will still 8077follow the <strong>std140</strong> or <strong>std430</strong> rules. 8078The specified alignment must be greater than 0 and a power of 2, or a 8079compile-time error results.</p> 8080</div> 8081<div class="paragraph"> 8082<p>The <em>actual alignment</em> of a member will be the greater of the specified 8083<strong>align</strong> alignment and the standard (e.g. <strong>std140</strong>) base alignment for the 8084member’s type. 8085The <em>actual offset</em> of a member is computed as follows: If <strong>offset</strong> was 8086declared, start with that offset, otherwise start with the offset immediately 8087following the preceding member (in declaration order). 8088If the resulting offset is not a multiple of the <em>actual alignment</em>, 8089increase it to the first offset that is a multiple of the <em>actual 8090alignment</em>. 8091This results in the <em>actual offset</em> the member will have.</p> 8092</div> 8093<div class="paragraph"> 8094<p>When <strong>align</strong> is applied to an array, it affects only the start of the array, 8095not the array’s internal stride. 8096Both an <strong>offset</strong> and an <strong>align</strong> qualifier can be specified on a declaration.</p> 8097</div> 8098<div class="paragraph"> 8099<p>The <strong>align</strong> qualifier, when used on a block, has the same effect as 8100qualifying each member with the same <strong>align</strong> value as declared on the block, 8101and gets the same compile-time results and errors as if this had been done. 8102As described in general earlier, an individual member can specify its own 8103<strong>align</strong>, which overrides the block-level <strong>align</strong>, but just for that member.</p> 8104</div> 8105<div class="paragraph"> 8106<p>Examples:</p> 8107</div> 8108<div class="listingblock"> 8109<div class="content"> 8110<pre class="CodeRay highlight"><code data-lang="c++">layout(std140) uniform block { 8111 vec4 a; <span class="comment">// a takes offsets 0-15</span> 8112 layout(offset = <span class="integer">32</span>) vec3 b; <span class="comment">// b takes offsets 32-43</span> 8113 layout(offset = <span class="integer">40</span>) vec2 c; <span class="comment">// ERROR, lies within previous member</span> 8114 layout(offset = <span class="integer">48</span>) vec2 d; <span class="comment">// d takes offsets 48-55</span> 8115 layout(align = <span class="integer">16</span>) <span class="predefined-type">float</span> e; <span class="comment">// e takes offsets 64-67</span> 8116 layout(align = <span class="integer">2</span>) <span class="predefined-type">double</span> f; <span class="comment">// f takes offsets 72-79</span> 8117 layout(align = <span class="integer">6</span>) <span class="predefined-type">double</span> g; <span class="comment">// ERROR, 6 is not a power of 2</span> 8118 layout(offset = <span class="integer">80</span>) <span class="predefined-type">float</span> h; <span class="comment">// h takes offsets 80-83</span> 8119 layout(align = <span class="integer">64</span>) dvec3 i; <span class="comment">// i takes offsets 128-151</span> 8120 layout(offset = <span class="integer">164</span>, align = <span class="integer">8</span>) 8121 <span class="predefined-type">float</span> j; <span class="comment">// j takes offsets 168-171</span> 8122};</code></pre> 8123</div> 8124</div> 8125</div> 8126<div class="sect3"> 8127<h4 id="opaque-uniform-layout-qualifiers">4.4.6. Opaque Uniform Layout Qualifiers</h4> 8128<div class="paragraph"> 8129<p>Opaque uniform variables can take the uniform layout qualifier for binding:</p> 8130</div> 8131<div class="openblock bnf"> 8132<div class="content"> 8133<div class="dlist"> 8134<dl> 8135<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 8136<dd> 8137<p><strong>binding</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 8138</dd> 8139</dl> 8140</div> 8141</div> 8142</div> 8143<div class="paragraph"> 8144<p>The <strong>binding</strong> qualifier specifies the point where the variable will be bound. 8145Any opaque variable declared without a binding qualifier has a default binding 8146of zero.</p> 8147</div> 8148<div class="paragraph"> 8149<p>When used with OpenGL, 8150if the <strong>binding</strong> qualifier is used with an array, the first element of the 8151array takes the specified binding point and each subsequent element takes the 8152next consecutive binding point. 8153For an array of arrays, each element (e.g. 6 elements for a[2][3]) gets a 8154binding point, and they are ordered per the array of array ordering 8155described in “<a href="#arrays">Arrays.</a>”</p> 8156</div> 8157<div class="paragraph"> 8158<p>When targeting Vulkan, 8159if the <strong>binding</strong> qualifier is used with an array, the entire array 8160takes only the provided binding number. The next consecutive binding 8161number is available for a different object.</p> 8162</div> 8163<div class="paragraph"> 8164<p>If the <strong>binding</strong> is less than zero, or greater than or equal to the 8165implementation-dependent maximum supported number of binding points, 8166a compile-time error will occur. 8167When the <strong>binding</strong> qualifier is used with an array of size <em>N</em>, all elements 8168of the array from <strong>binding</strong> through <em>binding + N - 1</em> must be within this 8169range. 8170It is a compile-time or link-time error to use the same <strong>binding</strong> number for 8171more than one atomic counter, unless the <em>offset</em> for the atomic counters 8172sharing the same binding are all different.</p> 8173</div> 8174<div class="paragraph"> 8175<p>A link-time error will result if two shaders in a program specify different 8176<em>layout-qualifier-value</em> bindings for the same opaque-uniform name. 8177However, it is not an error to specify a binding on some but not all 8178declarations for the same name, as shown in the examples below.</p> 8179</div> 8180<div class="listingblock"> 8181<div class="content"> 8182<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// in one shader...</span> 8183layout(binding=<span class="integer">3</span>) uniform sampler2D s; <span class="comment">// s bound to point 3</span> 8184 8185<span class="comment">// in another shader...</span> 8186uniform sampler2D s; <span class="comment">// okay, s still bound at 3</span> 8187 8188<span class="comment">// in another shader...</span> 8189layout(binding=<span class="integer">4</span>) uniform sampler2D s; <span class="comment">// ERROR: contradictory bindings</span></code></pre> 8190</div> 8191</div> 8192</div> 8193<div class="sect3"> 8194<h4 id="atomic-counter-layout-qualifiers">4.4.7. Atomic Counter Layout Qualifiers</h4> 8195<div class="paragraph"> 8196<p>Atomic counters are not available when targeting Vulkan.</p> 8197</div> 8198<div class="paragraph"> 8199<p>Atomic counter layout qualifiers can be used on atomic counter declarations. 8200The atomic counter qualifiers are:</p> 8201</div> 8202<div class="openblock bnf"> 8203<div class="content"> 8204<div class="dlist"> 8205<dl> 8206<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 8207<dd> 8208<p><strong>binding</strong> <strong>=</strong> <em>layout-qualifier-value</em><br> 8209<strong>offset</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 8210</dd> 8211</dl> 8212</div> 8213</div> 8214</div> 8215<div class="paragraph"> 8216<p>For example,</p> 8217</div> 8218<div class="listingblock"> 8219<div class="content"> 8220<pre class="CodeRay highlight"><code data-lang="c++">layout(binding = <span class="integer">2</span>, offset = <span class="integer">4</span>) uniform atomic_uint a;</code></pre> 8221</div> 8222</div> 8223<div class="paragraph"> 8224<p>will establish that the opaque handle to the atomic counter <em>a</em> will be 8225bound to atomic counter buffer binding point 2 at an offset of 4 basic 8226machine units into that buffer. 8227The default <em>offset</em> for binding point 2 will be post incremented by 4 (the 8228size of an atomic counter).</p> 8229</div> 8230<div class="paragraph"> 8231<p>A subsequent atomic counter declaration will inherit the previous (post 8232incremented) offset. 8233For example, a subsequent declaration of</p> 8234</div> 8235<div class="listingblock"> 8236<div class="content"> 8237<pre class="CodeRay highlight"><code data-lang="c++">layout(binding = <span class="integer">2</span>) uniform atomic_uint bar;</code></pre> 8238</div> 8239</div> 8240<div class="paragraph"> 8241<p>will establish that the atomic counter <em>bar</em> has a binding to buffer binding 8242point 2 at an offset of 8 basic machine units into that buffer. 8243The offset for binding point 2 will again be post-incremented by 4 (the size 8244of an atomic counter).</p> 8245</div> 8246<div class="paragraph"> 8247<p>When multiple variables are listed in a layout declaration, the effect will 8248be the same as if they were declared one at a time, in order from left to 8249right.</p> 8250</div> 8251<div class="paragraph"> 8252<p>Binding points are not inherited, only offsets. 8253Each binding point tracks its own current default <em>offset</em> for inheritance 8254of subsequent variables using the same <strong>binding</strong>. 8255The initial state of compilation is that all <strong>binding</strong> points have an 8256<em>offset</em> of 0. 8257The <em>offset</em> can be set per binding point at global scope (without declaring 8258a variable). 8259For example,</p> 8260</div> 8261<div class="listingblock"> 8262<div class="content"> 8263<pre class="CodeRay highlight"><code data-lang="c++">layout(binding = <span class="integer">2</span>, offset = <span class="integer">4</span>) uniform atomic_uint;</code></pre> 8264</div> 8265</div> 8266<div class="paragraph"> 8267<p>Establishes that the next <strong>atomic_uint</strong> declaration for binding point 2 will 8268inherit <em>offset</em> 4 (but does not establish a default <strong>binding</strong>):</p> 8269</div> 8270<div class="listingblock"> 8271<div class="content"> 8272<pre class="CodeRay highlight"><code data-lang="c++">layout(binding = <span class="integer">2</span>) uniform atomic_uint bar; <span class="comment">// offset is 4</span> 8273layout(offset = <span class="integer">8</span>) uniform atomic_uint bar; <span class="comment">// error, no default binding</span></code></pre> 8274</div> 8275</div> 8276<div class="paragraph"> 8277<p>Atomic counters may share the same binding point, but if a binding is 8278shared, their offsets must be either explicitly or implicitly (from 8279inheritance) unique and non overlapping.</p> 8280</div> 8281<div class="paragraph"> 8282<p>Example valid uniform declarations, assuming top of shader:</p> 8283</div> 8284<div class="listingblock"> 8285<div class="content"> 8286<pre class="CodeRay highlight"><code data-lang="c++">layout(binding=<span class="integer">3</span>, offset=<span class="integer">4</span>) uniform atomic_uint a; <span class="comment">// offset = 4</span> 8287layout(binding=<span class="integer">2</span>) uniform atomic_uint b; <span class="comment">// offset = 0</span> 8288layout(binding=<span class="integer">3</span>) uniform atomic_uint c; <span class="comment">// offset = 8</span> 8289layout(binding=<span class="integer">2</span>) uniform atomic_uint d; <span class="comment">// offset = 4</span></code></pre> 8290</div> 8291</div> 8292<div class="paragraph"> 8293<p>Example of an invalid uniform declaration:</p> 8294</div> 8295<div class="listingblock"> 8296<div class="content"> 8297<pre class="CodeRay highlight"><code data-lang="c++">layout(offset=<span class="integer">4</span>) ... <span class="comment">// error, must include binding</span> 8298layout(binding=<span class="integer">1</span>, offset=<span class="integer">0</span>) ... a; <span class="comment">// okay</span> 8299layout(binding=<span class="integer">2</span>, offset=<span class="integer">0</span>) ... b; <span class="comment">// okay</span> 8300layout(binding=<span class="integer">1</span>, offset=<span class="integer">0</span>) ... c; <span class="comment">// error, offsets must not be shared</span> 8301 <span class="comment">// between a and c</span> 8302layout(binding=<span class="integer">1</span>, offset=<span class="integer">2</span>) ... d; <span class="comment">// error, overlaps offset 0 of a</span></code></pre> 8303</div> 8304</div> 8305<div class="paragraph"> 8306<p>It is a compile-time error to bind an atomic counter with a binding value 8307greater than or equal to <em>gl_MaxAtomicCounterBindings</em>. 8308It is a compile-time error to declare an unsized array of <strong>atomic_uint</strong>.</p> 8309</div> 8310</div> 8311<div class="sect3"> 8312<h4 id="format-layout-qualifiers">4.4.8. Format Layout Qualifiers</h4> 8313<div class="paragraph"> 8314<p>Format layout qualifiers can be used on image variable declarations (those 8315declared with a basic type having “<strong>image</strong>” in its keyword). 8316The format layout qualifier identifiers for image variable declarations are:</p> 8317</div> 8318<div class="openblock bnf"> 8319<div class="content"> 8320<div class="dlist"> 8321<dl> 8322<dt class="hdlist1"><em>layout-qualifier-id</em> : </dt> 8323<dd> 8324<p><em>float-image-format-qualifier</em><br> 8325<em>int-image-format-qualifier</em><br> 8326<em>uint-image-format-qualifier</em><br> 8327<strong>binding</strong> <strong>=</strong> <em>layout-qualifier-value</em></p> 8328</dd> 8329</dl> 8330</div> 8331</div> 8332</div> 8333<div class="openblock bnf"> 8334<div class="content"> 8335<div class="dlist"> 8336<dl> 8337<dt class="hdlist1"><em>float-image-format-qualifier</em> : </dt> 8338<dd> 8339<p><strong>rgba32f</strong><br> 8340<strong>rgba16f</strong><br> 8341<strong>rg32f</strong><br> 8342<strong>rg16f</strong><br> 8343<strong>r11f_g11f_b10f</strong><br> 8344<strong>r32f</strong><br> 8345<strong>r16f</strong><br> 8346<strong>rgba16</strong><br> 8347<strong>rgb10_a2</strong><br> 8348<strong>rgba8</strong><br> 8349<strong>rg16</strong><br> 8350<strong>rg8</strong><br> 8351<strong>r16</strong><br> 8352<strong>r8</strong><br> 8353<strong>rgba16_snorm</strong><br> 8354<strong>rgba8_snorm</strong><br> 8355<strong>rg16_snorm</strong><br> 8356<strong>rg8_snorm</strong><br> 8357<strong>r16_snorm</strong><br> 8358<strong>r8_snorm</strong></p> 8359</dd> 8360<dt class="hdlist1"><em>int-image-format-qualifier</em> : </dt> 8361<dd> 8362<p><strong>rgba32i</strong><br> 8363<strong>rgba16i</strong><br> 8364<strong>rgba8i</strong><br> 8365<strong>rg32i</strong><br> 8366<strong>rg16i</strong><br> 8367<strong>rg8i</strong><br> 8368<strong>r32i</strong><br> 8369<strong>r16i</strong><br> 8370<strong>r8i</strong></p> 8371</dd> 8372<dt class="hdlist1"><em>uint-image-format-qualifier</em> : </dt> 8373<dd> 8374<p><strong>rgba32ui</strong><br> 8375<strong>rgba16ui</strong><br> 8376<strong>rgb10_a2ui</strong><br> 8377<strong>rgba8ui</strong><br> 8378<strong>rg32ui</strong><br> 8379<strong>rg16ui</strong><br> 8380<strong>rg8ui</strong><br> 8381<strong>r32ui</strong><br> 8382<strong>r16ui</strong><br> 8383<strong>r8ui</strong></p> 8384</dd> 8385</dl> 8386</div> 8387</div> 8388</div> 8389<div class="paragraph"> 8390<p>A format layout qualifier specifies the image format associated with a 8391declared image variable. 8392Only one format qualifier may be specified for any image variable 8393declaration. 8394For image variables with floating-point component types (keywords starting 8395with “<strong>image</strong>”), signed integer component types (keywords starting with 8396“<strong>iimage</strong>”), or unsigned integer component types (keywords starting with 8397“<strong>uimage</strong>”), the format qualifier used must match the 8398<em>float-image-format-qualifier</em>, <em>int-image-format-qualifier</em>, or 8399<em>uint-image-format-qualifier</em> grammar rules, respectively. 8400It is a compile-time error to declare an image variable where the format 8401qualifier does not match the image variable type.</p> 8402</div> 8403<div class="paragraph"> 8404<p>Any image variable used for image loads or atomic operations must specify a 8405format layout qualifier; it is a compile-time error to pass an image uniform 8406variable or function parameter declared without a format layout qualifier to 8407an image load or atomic function.</p> 8408</div> 8409<div class="paragraph"> 8410<p>Uniforms not qualified with <strong>writeonly</strong> must have a format layout qualifier. 8411Note that an image variable passed to a function for read access cannot be 8412declared as <strong>writeonly</strong> and hence must have been declared with a format 8413layout qualifier.</p> 8414</div> 8415<div class="paragraph"> 8416<p>The <strong>binding</strong> qualifier was described in 8417“<a href="#opaque-uniform-layout-qualifiers">Opaque Uniform Layout Qualifiers</a>”.</p> 8418</div> 8419</div> 8420<div class="sect3"> 8421<h4 id="_subpass_input_qualifier">4.4.9. Subpass Input Qualifier</h4> 8422<div class="paragraph"> 8423<p>Subpass inputs are only available when targeting Vulkan.</p> 8424</div> 8425<div class="paragraph"> 8426<p>Subpass inputs are declared with the basic <strong>subpassInput</strong> types. 8427They must be declared with the layout qualifier 8428<strong>input_attachment_index</strong>, or a compile-time error results. 8429For example:</p> 8430</div> 8431<div class="listingblock"> 8432<div class="content"> 8433<pre class="CodeRay highlight"><code data-lang="c++">layout(input_attachment_index = <span class="integer">2</span>) uniform subpassInput t;</code></pre> 8434</div> 8435</div> 8436<div class="paragraph"> 8437<p>This selects which subpass input is being read from. The value assigned 8438to <strong>input_attachment_index</strong>, say <em>i</em> (<code>input_attachment_index = i</code>), selects 8439that entry (<em>i</em> th entry) in the input list for the pass. See the API 8440documentation for more detail about passes and the input list.</p> 8441</div> 8442<div class="paragraph"> 8443<p>If an array of size <em>N</em> is declared, it consumes <em>N</em> consecutive 8444<strong>input_attachment_index</strong> values, starting with the one provided.</p> 8445</div> 8446<div class="paragraph"> 8447<p>It is a compile-time or link-time error to have different variables 8448declared with the same <strong>input_attachment_index</strong>. 8449This includes any overlap in the implicit <strong>input_attachment_index</strong> consumed by 8450array declarations.</p> 8451</div> 8452<div class="paragraph"> 8453<p>It is a compile-time error if the value assigned to an <strong>input_attachment_index</strong> 8454is greater than or equal to <em>gl_MaxInputAttachments</em>.</p> 8455</div> 8456</div> 8457</div> 8458<div class="sect2"> 8459<h3 id="interpolation-qualifiers">4.5. Interpolation Qualifiers</h3> 8460<div class="paragraph"> 8461<p>Inputs and outputs that could be interpolated can be further qualified by at 8462most one of the following interpolation qualifiers:</p> 8463</div> 8464<table class="tableblock frame-all grid-all stretch"> 8465<colgroup> 8466<col style="width: 50%;"> 8467<col style="width: 50%;"> 8468</colgroup> 8469<thead> 8470<tr> 8471<th class="tableblock halign-left valign-top">Qualifier</th> 8472<th class="tableblock halign-left valign-top">Meaning</th> 8473</tr> 8474</thead> 8475<tbody> 8476<tr> 8477<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>smooth</strong></p></td> 8478<td class="tableblock halign-left valign-top"><p class="tableblock">perspective correct interpolation</p></td> 8479</tr> 8480<tr> 8481<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>flat</strong></p></td> 8482<td class="tableblock halign-left valign-top"><p class="tableblock">no interpolation</p></td> 8483</tr> 8484<tr> 8485<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>noperspective</strong></p></td> 8486<td class="tableblock halign-left valign-top"><p class="tableblock">linear interpolation</p></td> 8487</tr> 8488</tbody> 8489</table> 8490<div class="paragraph"> 8491<p>The presence of and type of interpolation is controlled by the above 8492interpolation qualifiers as well as the auxiliary storage qualifiers 8493<strong>centroid</strong> and <strong>sample</strong>. 8494When no interpolation qualifier is present, smooth interpolation is used. 8495It is a compile-time error to use more than one interpolation qualifier. 8496The auxiliary storage qualifier <strong>patch</strong> is not used for interpolation; it is 8497a compile-time error to use interpolation qualifiers with <strong>patch</strong>.</p> 8498</div> 8499<div class="paragraph"> 8500<p>A variable qualified as <strong>flat</strong> will not be interpolated. 8501Instead, it will have the same value for every fragment within a primitive. 8502This value will come from a single provoking vertex, as described by the 8503<a href="#references">API</a>. 8504A variable qualified as <strong>flat</strong> may also be qualified as <strong>centroid</strong> or 8505<strong>sample</strong>, which will mean the same thing as qualifying it only as <strong>flat</strong>.</p> 8506</div> 8507<div class="paragraph"> 8508<p>A variable qualified as <strong>smooth</strong> will be interpolated in a 8509perspective-correct manner over the primitive being rendered. 8510Interpolation in a perspective correct manner is specified in equation 14.7 8511of the <a href="#references">OpenGL Specification</a>, section 14.5 “Line Segments”.</p> 8512</div> 8513<div class="paragraph"> 8514<p>A variable qualified as <strong>noperspective</strong> must be interpolated linearly in 8515screen space, as described in equation 3.7 of the <a href="#references">OpenGL Specification</a>, 8516section 3.5 “Line Segments”.</p> 8517</div> 8518<div class="paragraph"> 8519<p>When multisample rasterization is disabled, or for fragment shader input 8520variables qualified with neither <strong>centroid</strong> nor <strong>sample</strong>, the value of the 8521assigned variable may be interpolated anywhere within the pixel and a single 8522value may be assigned to each sample within the pixel, to the extent 8523permitted by the <a href="#references">OpenGL Specification</a>.</p> 8524</div> 8525<div class="paragraph"> 8526<p>When multisample rasterization is enabled, <strong>centroid</strong> and <strong>sample</strong> may be 8527used to control the location and frequency of the sampling of the qualified 8528fragment shader input. 8529If a fragment shader input is qualified with <strong>centroid</strong>, a single value may 8530be assigned to that variable for all samples in the pixel, but that value 8531must be interpolated at a location that lies in both the pixel and in the 8532primitive being rendered, including any of the pixel’s samples covered by 8533the primitive. 8534Because the location at which the variable is interpolated may be different 8535in neighboring pixels, and derivatives may be computed by computing 8536differences between neighboring pixels, derivatives of centroid-sampled 8537inputs may be less accurate than those for non-centroid interpolated 8538variables. 8539If a fragment shader input is qualified with <strong>sample</strong>, a separate value must 8540be assigned to that variable for each covered sample in the pixel, and that 8541value must be sampled at the location of the individual sample.</p> 8542</div> 8543<div class="paragraph"> 8544<p>It is a link-time error if, within the same stage, the interpolation 8545qualifiers of variables of the same name do not match.</p> 8546</div> 8547<div class="sect3"> 8548<h4 id="redeclaring-built-in-interpolation-variables-in-the-compatibility-profile">4.5.1. Redeclaring Built-In Interpolation Variables in the Compatibility Profile</h4> 8549<div class="paragraph"> 8550<p>The following predeclared variables can be redeclared with an interpolation 8551qualifier when using the compatibility profile:</p> 8552</div> 8553<div class="paragraph"> 8554<p>Vertex, tessellation control, tessellation evaluation, and geometry 8555languages:</p> 8556</div> 8557<div class="listingblock"> 8558<div class="content"> 8559<pre class="CodeRay highlight"><code data-lang="c++">gl_FrontColor 8560gl_BackColor 8561gl_FrontSecondaryColor 8562gl_BackSecondaryColor</code></pre> 8563</div> 8564</div> 8565<div class="paragraph"> 8566<p>Fragment language:</p> 8567</div> 8568<div class="listingblock"> 8569<div class="content"> 8570<pre class="CodeRay highlight"><code data-lang="c++">gl_Color 8571gl_SecondaryColor</code></pre> 8572</div> 8573</div> 8574<div class="paragraph"> 8575<p>For example,</p> 8576</div> 8577<div class="listingblock"> 8578<div class="content"> 8579<pre class="CodeRay highlight"><code data-lang="c++">in vec4 gl_Color; <span class="comment">// predeclared by the fragment language</span> 8580flat in vec4 gl_Color; <span class="comment">// redeclared by user to be flat</span> 8581flat in vec4 gl_FrontColor; <span class="comment">// input to geometry shader, no "gl_in[]"</span> 8582flat out vec4 gl_FrontColor; <span class="comment">// output from geometry shader</span></code></pre> 8583</div> 8584</div> 8585<div class="paragraph"> 8586<p>Ideally, these are redeclared as part of the redeclaration of an interface 8587block, as described in 8588“<a href="#compatibility-profile-built-in-language-variables">Compatibility Profile 8589Built-In Language Variables</a>”. 8590However, for the above purpose, they can be redeclared as individual 8591variables at global scope, outside an interface block. 8592Such redeclarations also allow adding the transform-feedback qualifiers 8593<strong>xfb_buffer</strong>, <strong>xfb_stride</strong>, and <strong>xfb_offset</strong> to output variables. 8594(Using <strong>xfb_buffer</strong> on a variable does not change the global default 8595buffer.) A compile-time error will result if a shader has both an interface 8596block redeclaration and a separate redeclaration of a member of that 8597interface block outside the interface block redeclaration.</p> 8598</div> 8599<div class="paragraph"> 8600<p>If <em>gl_Color</em> is redeclared with an interpolation qualifier, then 8601<em>gl_FrontColor</em> and <em>gl_BackColor</em> (if they are written to) must also be 8602redeclared with the same interpolation qualifier, and vice versa. 8603If <em>gl_SecondaryColor</em> is redeclared with an interpolation qualifier, then 8604<em>gl_FrontSecondaryColor</em> and _gl_BackSecondaryColor _(if they are written 8605to) must also be redeclared with the same interpolation qualifier, and vice 8606versa. 8607This qualifier matching on predeclared variables is only required for 8608variables that are statically used within the shaders in a program.</p> 8609</div> 8610</div> 8611</div> 8612<div class="sect2"> 8613<h3 id="parameter-qualifiers">4.6. Parameter Qualifiers</h3> 8614<div class="paragraph"> 8615<p>In addition to precision qualifiers and memory qualifiers, parameters can 8616have these parameter qualifiers.</p> 8617</div> 8618<table class="tableblock frame-all grid-all stretch"> 8619<colgroup> 8620<col style="width: 50%;"> 8621<col style="width: 50%;"> 8622</colgroup> 8623<thead> 8624<tr> 8625<th class="tableblock halign-left valign-top">Qualifier</th> 8626<th class="tableblock halign-left valign-top">Meaning</th> 8627</tr> 8628</thead> 8629<tbody> 8630<tr> 8631<td class="tableblock halign-left valign-top"><p class="tableblock"><none: default></p></td> 8632<td class="tableblock halign-left valign-top"><p class="tableblock">same as <strong>in</strong></p></td> 8633</tr> 8634<tr> 8635<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>const</strong></p></td> 8636<td class="tableblock halign-left valign-top"><p class="tableblock">for function parameters that cannot be written to</p></td> 8637</tr> 8638<tr> 8639<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>in</strong></p></td> 8640<td class="tableblock halign-left valign-top"><p class="tableblock">for function parameters passed into a function</p></td> 8641</tr> 8642<tr> 8643<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>out</strong></p></td> 8644<td class="tableblock halign-left valign-top"><p class="tableblock">for function parameters passed back out of a function, 8645 but not initialized for use when passed in</p></td> 8646</tr> 8647<tr> 8648<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>inout</strong></p></td> 8649<td class="tableblock halign-left valign-top"><p class="tableblock">for function parameters passed both into and out of a 8650 function</p></td> 8651</tr> 8652</tbody> 8653</table> 8654<div class="paragraph"> 8655<p>Parameter qualifiers are discussed in more detail in 8656“<a href="#function-calling-conventions">Function Calling Conventions</a>”.</p> 8657</div> 8658</div> 8659<div class="sect2"> 8660<h3 id="precision-and-precision-qualifiers">4.7. Precision and Precision Qualifiers</h3> 8661<div class="paragraph"> 8662<p>When not targeting Vulkan: 8663Precision qualifiers are added for code portability with OpenGL ES, not for 8664functionality. 8665They have the same syntax as in OpenGL ES, as described below, but they have 8666no semantic meaning, which includes no effect on the precision used to store 8667or operate on variables. 8668If an extension adds in the same semantics and functionality in the OpenGL 8669ES 2.0 specification for precision qualifiers, then the extension is allowed 8670to reuse the keywords below for that purpose.</p> 8671</div> 8672<div class="paragraph"> 8673<p>When targeting Vulkan: 8674For interface matching, uniform variables and uniform and buffer block 8675members must have the same precision qualification. 8676Global variables declared in different compilation units linked into the 8677same shader stage must be declared with the same precision qualification.</p> 8678</div> 8679<div class="paragraph"> 8680<p>For the purposes of determining if an output from one shader stage matches 8681an input of the next stage, the precision qualifier need not match.</p> 8682</div> 8683<div class="sect3"> 8684<h4 id="range-and-precision">4.7.1. Range and Precision</h4> 8685<div class="paragraph"> 8686<p>The precision of <strong>highp</strong> 8687single- and double-precision 8688floating-point variables is defined by the IEEE 754 standard for 868932-bit 8690and 64-bit 8691floating-point numbers.</p> 8692</div> 8693<div class="paragraph"> 8694<p>This includes support for NaNs (Not a Number) and Infs (positive or negative 8695infinities) and positive and negative zeros.</p> 8696</div> 8697<div class="paragraph"> 8698<p>The following rules apply to <strong>highp</strong> 8699for both single and double-precision 8700operations: 8701Signed infinities and zeros are generated as dictated by IEEE, but subject 8702to the precisions allowed in the following table. 8703Any subnormal (denormalized) value input into a shader or potentially 8704generated by any operation in a shader can be flushed to 0. 8705The rounding mode cannot be set and is undefined but must not affect the 8706result by more than 1 ULP. 8707NaNs are not required to be generated. 8708Support for signaling NaNs is not required and exceptions are never raised. 8709Operations including built-in functions that operate on a NaN are not 8710required to return a NaN as the result. 8711However if NaNs are generated, <strong>isnan</strong>() must return the correct value.</p> 8712</div> 8713<div class="paragraph"> 8714<p>Precisions are expressed in terms of maximum relative error in units of ULP 8715(units in the last place), unless otherwise noted.</p> 8716</div> 8717<div class="paragraph"> 8718<p>For single precision operations, precisions are required as follows:</p> 8719</div> 8720<table class="tableblock frame-all grid-all stretch"> 8721<colgroup> 8722<col style="width: 50%;"> 8723<col style="width: 50%;"> 8724</colgroup> 8725<thead> 8726<tr> 8727<th class="tableblock halign-left valign-top">Operation</th> 8728<th class="tableblock halign-left valign-top">Precision</th> 8729</tr> 8730</thead> 8731<tbody> 8732<tr> 8733<td class="tableblock halign-left valign-top"><p class="tableblock"><em>a</em> + <em>b</em>, <em>a</em> - <em>b</em>, <em>a</em> * <em>b</em></p></td> 8734<td class="tableblock halign-left valign-top"><p class="tableblock">Correctly rounded.</p></td> 8735</tr> 8736<tr> 8737<td class="tableblock halign-left valign-top"><p class="tableblock"><, <=, ==, >, >=</p></td> 8738<td class="tableblock halign-left valign-top"><p class="tableblock">Correct result.</p></td> 8739</tr> 8740<tr> 8741<td class="tableblock halign-left valign-top"><p class="tableblock"><em>a</em> / <em>b</em>, 1.0 / <em>b</em></p></td> 8742<td class="tableblock halign-left valign-top"><p class="tableblock">2.5 ULP for <span class="eq">|b|</span> in the range <span class="eq">[2<sup>-126</sup>, 2<sup>126</sup>]</span>.</p></td> 8743</tr> 8744<tr> 8745<td class="tableblock halign-left valign-top"><p class="tableblock"><em>a</em> * <em>b</em> + <em>c</em></p></td> 8746<td class="tableblock halign-left valign-top"><p class="tableblock">Correctly rounded single operation or 8747 sequence of two correctly rounded operations.</p></td> 8748</tr> 8749<tr> 8750<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>fma</strong>()</p></td> 8751<td class="tableblock halign-left valign-top"><p class="tableblock">Inherited from <em>a</em> * <em>b</em> + <em>c</em>.</p></td> 8752</tr> 8753<tr> 8754<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>pow</strong>(<em>x</em>, <em>y</em>)</p></td> 8755<td class="tableblock halign-left valign-top"><p class="tableblock">Inherited from <strong>exp2</strong>(<em>y</em> * <strong>log2</strong>(<em>x</em>)).</p></td> 8756</tr> 8757<tr> 8758<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>exp</strong>(<em>x</em>), <strong>exp2</strong>(<em>x</em>)</p></td> 8759<td class="tableblock halign-left valign-top"><p class="tableblock"><span class="eq">(3 + 2 · |x|)</span> ULP.</p></td> 8760</tr> 8761<tr> 8762<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>log</strong>(), <strong>log2</strong>()</p></td> 8763<td class="tableblock halign-left valign-top"><p class="tableblock">3 ULP outside the range <span class="eq">[0.5,2.0]</span>.<br> 8764 Absolute error < 2<sup>-21</sup> inside the range 8765 <span class="eq">[0.5,2.0]</span>.</p></td> 8766</tr> 8767<tr> 8768<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>sqrt</strong>()</p></td> 8769<td class="tableblock halign-left valign-top"><p class="tableblock">Inherited from 1.0 / <strong>inversesqrt</strong>().</p></td> 8770</tr> 8771<tr> 8772<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>inversesqrt</strong>()</p></td> 8773<td class="tableblock halign-left valign-top"><p class="tableblock">2 ULP.</p></td> 8774</tr> 8775<tr> 8776<td class="tableblock halign-left valign-top"><p class="tableblock">implicit and explicit 8777 conversions between types</p></td> 8778<td class="tableblock halign-left valign-top"><p class="tableblock">Correctly rounded.</p></td> 8779</tr> 8780</tbody> 8781</table> 8782<div class="paragraph"> 8783<p>Built-in functions defined in the specification with an equation built from 8784the above operations inherit the above errors. 8785These include, for example, the geometric functions, the common functions, 8786and many of the matrix functions. 8787Built-in functions not listed above and not defined as equations of the 8788above have undefined precision. 8789These include, for example, the trigonometric functions and determinant.</p> 8790</div> 8791<div class="paragraph"> 8792<p>The precision of double-precision operations is at least that of single 8793precision.</p> 8794</div> 8795</div> 8796<div class="sect3"> 8797<h4 id="precision-qualifiers">4.7.2. Precision Qualifiers</h4> 8798<div class="paragraph"> 8799<p>Any 8800single-precision 8801floating-point, integer, or opaque-type declaration can have the type 8802preceded by one of these precision qualifiers:</p> 8803</div> 8804<table class="tableblock frame-all grid-all stretch"> 8805<colgroup> 8806<col style="width: 50%;"> 8807<col style="width: 50%;"> 8808</colgroup> 8809<thead> 8810<tr> 8811<th class="tableblock halign-left valign-top">Qualifier</th> 8812<th class="tableblock halign-left valign-top">Meaning</th> 8813</tr> 8814</thead> 8815<tbody> 8816<tr> 8817<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>highp</strong></p></td> 8818<td class="tableblock halign-left valign-top"><p class="tableblock">32-bit two’s complement for integers, 8819 32-bit IEEE 754 floating-point for <strong>float</strong></p></td> 8820</tr> 8821<tr> 8822<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>mediump</strong></p></td> 8823<td class="tableblock halign-left valign-top"><p class="tableblock">SPIR-V <strong>RelaxedPrecision</strong> when targeting Vulkan, otherwise none.</p></td> 8824</tr> 8825<tr> 8826<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>lowp</strong></p></td> 8827<td class="tableblock halign-left valign-top"><p class="tableblock">SPIR-V <strong>RelaxedPrecision</strong> when targeting Vulkan, otherwise none.</p></td> 8828</tr> 8829</tbody> 8830</table> 8831<div class="paragraph"> 8832<p>For example:</p> 8833</div> 8834<div class="listingblock"> 8835<div class="content"> 8836<pre class="CodeRay highlight"><code data-lang="c++">lowp <span class="predefined-type">float</span> color; 8837out mediump vec2 P; 8838lowp ivec2 foo(lowp mat3); 8839highp mat4 m;</code></pre> 8840</div> 8841</div> 8842<div class="paragraph"> 8843<p>Literal constants do not have precision qualifiers. 8844Neither do Boolean variables. 8845Neither do constructors.</p> 8846</div> 8847<div class="paragraph"> 8848<p>For this paragraph, “operation” includes operators, built-in functions, 8849and constructors, and “operand” includes function arguments and 8850constructor arguments. 8851The precision used to internally evaluate an operation, and the precision 8852qualification subsequently associated with any resulting intermediate 8853values, must be at least as high as the highest precision qualification of 8854the operands consumed by the operation.</p> 8855</div> 8856<div class="paragraph"> 8857<p>In cases where operands do not have a precision qualifier, the precision 8858qualification will come from the other operands. 8859If no operands have a precision qualifier, then the precision qualifications 8860of the operands of the next consuming operation in the expression will be 8861used. 8862This rule can be applied recursively until a precision qualified operand is 8863found. 8864If necessary, it will also include the precision qualification of l-values 8865for assignments, of the declared variable for initializers, of formal 8866parameters for function call arguments, or of function return types for 8867function return values. 8868If the precision cannot be determined by this method e.g. if an entire 8869expression is composed only of operands with no precision qualifier, and the 8870result is not assigned or passed as an argument, then it is evaluated at the 8871default precision of the type or greater. 8872When this occurs in the fragment shader, the default precision must be 8873defined.</p> 8874</div> 8875<div class="paragraph"> 8876<p>For example, consider the statements:</p> 8877</div> 8878<div class="listingblock"> 8879<div class="content"> 8880<pre class="CodeRay highlight"><code data-lang="c++">uniform highp <span class="predefined-type">float</span> h1; 8881highp <span class="predefined-type">float</span> h2 = <span class="float">2</span><span class="float">.3</span> * <span class="float">4</span><span class="float">.7</span>; <span class="comment">// operation and result are highp</span> 8882precision 8883mediump <span class="predefined-type">float</span> m; 8884m = <span class="float">3</span><span class="float">.7</span> * h1 * h2; <span class="comment">// all operations are highp precision</span> 8885h2 = m * h1; <span class="comment">// operation is highp precision</span> 8886m = h2 - h1; <span class="comment">// operation is highp precision</span> 8887h2 = m + m; <span class="comment">// addition and result at mediump precision</span> 8888<span class="directive">void</span> f(highp <span class="predefined-type">float</span> p); 8889f(<span class="float">3</span><span class="float">.3</span>); <span class="comment">// 3.3 will be passed in at highp precision</span></code></pre> 8890</div> 8891</div> 8892<div class="paragraph"> 8893<p>Precision qualifiers, as with other qualifiers, do not affect the basic type 8894of the variable. 8895In particular, there are no constructors for precision conversions; 8896constructors only convert types. 8897Similarly, precision qualifiers, as with other qualifiers, do not contribute 8898to function overloading based on parameter types. 8899As discussed in “<a href="#function-calling-conventions">Function Calling 8900Conventions</a>”, function input and output is done through copies, and 8901therefore qualifiers do not have to match.</p> 8902</div> 8903<div class="paragraph"> 8904<p>The precision of a variable is determined when the variable is declared and 8905cannot be subsequently changed.</p> 8906</div> 8907<div class="paragraph"> 8908<p>Where the precision of a constant integral or constant floating-point 8909expression is not specified, evaluation is performed at <strong>highp</strong>. 8910This rule does not affect the precision qualification of the expression.</p> 8911</div> 8912<div class="paragraph"> 8913<p>The evaluation of constant expressions must be invariant and will usually be 8914performed at compile time.</p> 8915</div> 8916</div> 8917<div class="sect3"> 8918<h4 id="default-precision-qualifiers">4.7.3. Default Precision Qualifiers</h4> 8919<div class="paragraph"> 8920<p>The precision statement</p> 8921</div> 8922<div class="listingblock"> 8923<div class="content"> 8924<pre class="CodeRay highlight"><code data-lang="c++">precision precision-qualifier type;</code></pre> 8925</div> 8926</div> 8927<div class="paragraph"> 8928<p>can be used to establish a default precision qualifier. 8929The <em>type</em> field can be either <strong>int</strong>, <strong>float</strong>, or any of the opaque types, 8930and the <em>precision-qualifier</em> can be <strong>lowp</strong>, <strong>mediump</strong>, or <strong>highp</strong>.</p> 8931</div> 8932<div class="paragraph"> 8933<p>Any other types or qualifiers will result in a compile-time error. 8934If <em>type</em> is <strong>float</strong>, the directive applies to non-precision-qualified 8935single-precision 8936floating-point type (scalar, vector, and matrix) declarations. 8937If <em>type</em> is <strong>int</strong>, the directive applies to all non-precision-qualified 8938integer type (scalar, vector, signed, and unsigned) declarations. 8939This includes global variable declarations, function return declarations, 8940function parameter declarations, and local variable declarations.</p> 8941</div> 8942<div class="paragraph"> 8943<p>Non-precision qualified declarations will use the precision qualifier 8944specified in the most recent <strong>precision</strong> statement that is still in scope. 8945The <strong>precision</strong> statement has the same scoping rules as variable 8946declarations. 8947If it is declared inside a compound statement, its effect stops at the end 8948of the inner-most statement it was declared in. 8949Precision statements in nested scopes override precision statements in outer 8950scopes. 8951Multiple precision statements for the same basic type can appear inside the 8952same scope, with later statements overriding earlier statements within that 8953scope.</p> 8954</div> 8955<div class="paragraph"> 8956<p>For any type that accepts a precision qualifier, 8957the default precision qualification will be <strong>highp</strong>. 8958Because all types requiring a precision qualifier have a default precision, 8959there are no errors for omission of a precision qualifier.</p> 8960</div> 8961</div> 8962<div class="sect3"> 8963<h4 id="available-precision-qualifiers">4.7.4. Available Precision Qualifiers</h4> 8964<div class="paragraph"> 8965<p>The built-in macro GL_FRAGMENT_PRECISION_HIGH is defined to one:</p> 8966</div> 8967<div class="listingblock"> 8968<div class="content"> 8969<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#define</span> GL_FRAGMENT_PRECISION_HIGH <span class="integer">1</span></code></pre> 8970</div> 8971</div> 8972<div class="paragraph"> 8973<p>This macro is available in all languages except compute.</p> 8974</div> 8975</div> 8976</div> 8977<div class="sect2"> 8978<h3 id="variance-and-the-invariant-qualifier">4.8. Variance and the Invariant Qualifier</h3> 8979<div class="paragraph"> 8980<p>In this section, <em>variance</em> refers to the possibility of getting different 8981values from the same expression in different programs. 8982For example, consider the situation where two vertex shaders, in different 8983programs, each set <em>gl_Position</em> with the same expression, and the input 8984values into that expression are the same when both shaders run. 8985It is possible, due to independent compilation of the two shaders, that the 8986values assigned to <em>gl_Position</em> are not exactly the same when the two 8987shaders run. 8988In this example, this can cause problems with alignment of geometry in a 8989multi-pass algorithm.</p> 8990</div> 8991<div class="paragraph"> 8992<p>In general, such variance between shaders is allowed. 8993When such variance does not exist for a particular output variable, that 8994variable is said to be <em>invariant</em>.</p> 8995</div> 8996<div class="sect3"> 8997<h4 id="the-invariant-qualifier">4.8.1. The Invariant Qualifier</h4> 8998<div class="paragraph"> 8999<p>To ensure that a particular output variable is invariant, it is necessary to 9000use the <strong>invariant</strong> qualifier. 9001It can either be used to qualify a previously declared variable as being 9002invariant:</p> 9003</div> 9004<div class="listingblock"> 9005<div class="content"> 9006<pre class="CodeRay highlight"><code data-lang="c++">invariant gl_Position; <span class="comment">// make existing gl_Position be invariant</span> 9007out vec3 Color; 9008invariant Color; <span class="comment">// make existing Color be invariant</span></code></pre> 9009</div> 9010</div> 9011<div class="paragraph"> 9012<p>or as part of a declaration when a variable is declared:</p> 9013</div> 9014<div class="listingblock"> 9015<div class="content"> 9016<pre class="CodeRay highlight"><code data-lang="c++">invariant centroid out vec3 Color;</code></pre> 9017</div> 9018</div> 9019<div class="paragraph"> 9020<p>Only variables output from a shader can be candidates for invariance. 9021This includes user-defined output variables and the built-in output 9022variables. 9023As only outputs can be declared as invariant, an output from one shader 9024stage will still match an input of a subsequent stage without the input 9025being declared as invariant.</p> 9026</div> 9027<div class="paragraph"> 9028<p>Input or output instance names on blocks are not used when redeclaring 9029built-in variables.</p> 9030</div> 9031<div class="paragraph"> 9032<p>The <strong>invariant</strong> keyword can be followed by a comma separated list of 9033previously declared identifiers. 9034All uses of <strong>invariant</strong> must be at global scope or on block 9035members, and before any use of the variables being declared as invariant.</p> 9036</div> 9037<div class="paragraph"> 9038<p>To guarantee invariance of a particular output variable across two programs, 9039the following must also be true:</p> 9040</div> 9041<div class="ulist"> 9042<ul> 9043<li> 9044<p>The output variable is declared as invariant in both programs.</p> 9045</li> 9046<li> 9047<p>The same values must be input to all shader input variables consumed by 9048expressions and control flow contributing to the value assigned to the 9049output variable.</p> 9050</li> 9051<li> 9052<p>The texture formats, texel values, and texture filtering are set the 9053same way for any texture function calls contributing to the value of the 9054output variable.</p> 9055</li> 9056<li> 9057<p>All input values are all operated on in the same way. 9058 All operations in the consuming expressions and any intermediate 9059 expressions must be the same, with the same order of operands and same 9060 associativity, to give the same order of evaluation. 9061 Intermediate variables and functions must be declared as the same type 9062 with the same explicit or implicit precision 9063qualifiers. 9064 Any control flow affecting the output value must be the same, and any 9065 expressions consumed to determine this control flow must also follow 9066 these invariance rules.</p> 9067</li> 9068<li> 9069<p>All the data flow and control flow leading to setting the invariant 9070output variable reside in a single compilation unit.</p> 9071</li> 9072</ul> 9073</div> 9074<div class="paragraph"> 9075<p>Essentially, all the data flow and control flow leading to an invariant 9076output must match.</p> 9077</div> 9078<div class="paragraph"> 9079<p>Initially, by default, all output variables are allowed to be variant. 9080To force all output variables to be invariant, use the pragma</p> 9081</div> 9082<div class="listingblock"> 9083<div class="content"> 9084<pre class="CodeRay highlight"><code data-lang="c++"><span class="preprocessor">#pragma</span> STDGL invariant(all)</code></pre> 9085</div> 9086</div> 9087<div class="paragraph"> 9088<p>before all declarations in a shader. 9089If this pragma is used after the declaration of any variables or functions, 9090then the set of outputs that behave as invariant is undefined.</p> 9091</div> 9092<div class="paragraph"> 9093<p>Generally, invariance is ensured at the cost of flexibility in optimization, 9094so performance can be degraded by use of invariance. 9095Hence, use of this pragma is intended as a debug aid, to avoid individually 9096declaring all output variables as invariant.</p> 9097</div> 9098</div> 9099<div class="sect3"> 9100<h4 id="invariance-of-constant-expressions">4.8.2. Invariance of Constant Expressions</h4> 9101<div class="paragraph"> 9102<p>Invariance must be guaranteed for constant expressions. 9103A particular constant expression must evaluate to the same result if it 9104appears again in the same shader or a different shader. 9105This includes the same expression appearing in two shaders of the same 9106language or shaders of two different languages.</p> 9107</div> 9108<div class="paragraph"> 9109<p>Constant expressions must evaluate to the same result when operated on as 9110already described above for invariant variables.</p> 9111</div> 9112</div> 9113</div> 9114<div class="sect2"> 9115<h3 id="the-precise-qualifier">4.9. The Precise Qualifier</h3> 9116<div class="paragraph"> 9117<p>Some algorithms require floating-point computations to exactly follow the 9118order of operations specified in the source code and to treat all operations 9119consistently, even if the implementation supports optimizations that could 9120produce nearly equivalent results with higher performance. 9121For example, many GL implementations support a “multiply-add” instruction 9122that can compute a floating-point expression such as</p> 9123</div> 9124<div class="listingblock"> 9125<div class="content"> 9126<pre class="CodeRay highlight"><code data-lang="c++">result = (a * b) + (c * d);</code></pre> 9127</div> 9128</div> 9129<div class="paragraph"> 9130<p>in two operations instead of three operations; one multiply and one 9131multiply-add instead of two multiplies and one add. 9132The result of a floating-point multiply-add might not always be identical to 9133first doing a multiply yielding a floating-point result and then doing a 9134floating-point add. 9135Hence, in this example, the two multiply operations would not be treated 9136consistently; the two multiplies could effectively appear to have differing 9137precisions.</p> 9138</div> 9139<div class="paragraph"> 9140<p>The key computation that needs to be made consistent appears when 9141tessellating, where intermediate points for subdivision are synthesized in 9142different directions, yet need to yield the same result, as shown in the 9143diagram below.</p> 9144</div> 9145<div id="img-precise" class="imageblock"> 9146<div class="content"> 9147<img src="data:image/svg+xml;base64,<?xml version="1.0" encoding="UTF-8"?>

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</svg>" alt="precise"> 9148</div> 9149</div> 9150<div class="paragraph"> 9151<p>Without any qualifiers, implementations are permitted to perform 9152optimizations that effectively modify the order or number of operations used 9153to evaluate an expression, even if those optimizations may produce slightly 9154different results relative to unoptimized code.</p> 9155</div> 9156<div class="paragraph"> 9157<p>The <strong>precise</strong> qualifier ensures that operations contributing to a 9158variable’s value are done in their stated order and with operator consistency. 9159The order is determined by operator precedence and parenthesis, as described in 9160“<a href="#operators">Operators</a>”. 9161Operator consistency means for each particular operator, for example the 9162multiply operator (<strong>*</strong>), its operation is always computed with the same 9163precision. 9164Specifically, values computed by compiler-generated code must adhere to the 9165following identities:</p> 9166</div> 9167<div class="olist arabic"> 9168<ol class="arabic"> 9169<li> 9170<p>a + b = b + a</p> 9171</li> 9172<li> 9173<p>a * b = b * a</p> 9174</li> 9175<li> 9176<p>a * b + c * d = b * a + c* d = d * c + b * a = <any other mathematically 9177valid combination></p> 9178</li> 9179</ol> 9180</div> 9181<div class="paragraph"> 9182<p>While the following are prevented:</p> 9183</div> 9184<div class="olist arabic"> 9185<ol class="arabic"> 9186<li> 9187<p>a + (b + c) is not allowed to become (a + b) + c</p> 9188</li> 9189<li> 9190<p>a * (b * c) is not allowed to become (a * b) * c</p> 9191</li> 9192<li> 9193<p>a * b + c is not allowed to become a single operation <strong>fma</strong>(a, b, c)</p> 9194</li> 9195</ol> 9196</div> 9197<div class="paragraph"> 9198<p>Where <em>a</em>, <em>b</em>, <em>c</em>, and <em>d</em>, are scalars or vectors, not matrices. 9199(Matrix multiplication generally does not commute.) It is the shader 9200writer’s responsibility to express the computation in terms of these rules 9201and the compiler’s responsibility to follow these rules. 9202See the description of <em>gl_TessCoord</em> for the rules the tessellation stages 9203are responsible for following, which in conjunction with the above allow 9204avoiding cracking when subdividing.</p> 9205</div> 9206<div class="paragraph"> 9207<p>For example,</p> 9208</div> 9209<div class="listingblock"> 9210<div class="content"> 9211<pre class="CodeRay highlight"><code data-lang="c++">precise out vec4 position;</code></pre> 9212</div> 9213</div> 9214<div class="paragraph"> 9215<p>declares that operations used to produce the value of <em>position</em> must be 9216performed in exactly the order specified in the source code and with all 9217operators being treated consistently. 9218As with the <strong>invariant</strong> qualifier (see “<a href="#the-invariant-qualifier">The 9219Invariant Qualifier</a>”), the <strong>precise</strong> qualifier may be used to qualify a 9220built-in or previously declared user-defined variable as being precise:</p> 9221</div> 9222<div class="listingblock"> 9223<div class="content"> 9224<pre class="CodeRay highlight"><code data-lang="c++">out vec3 Color; 9225precise Color; <span class="comment">// make existing Color be precise</span></code></pre> 9226</div> 9227</div> 9228<div class="paragraph"> 9229<p>When applied to a block, a structure type, or a variable of structure type, 9230<strong>precise</strong> applies to each contained member, recursively.</p> 9231</div> 9232<div class="paragraph"> 9233<p>This qualifier will affect the evaluation of an r-value in a particular 9234function if and only if the result is eventually consumed in the same 9235function by an l-value qualified as <strong>precise</strong>. 9236Any other expressions within a function are not affected, including return 9237values and output parameters not declared as <strong>precise</strong> but that are 9238eventually consumed outside the function by a variable qualified as 9239<strong>precise</strong>. Unaffected expressions also include the controlling expressions 9240in selection and iteration statements and the condition in ternary 9241operators (<strong>?:</strong>).</p> 9242</div> 9243<div class="paragraph"> 9244<p>Some examples of the use of <strong>precise</strong>:</p> 9245</div> 9246<div class="listingblock"> 9247<div class="content"> 9248<pre class="CodeRay highlight"><code data-lang="c++">in vec4 a, b, c, d; 9249precise out vec4 v; 9250 9251<span class="predefined-type">float</span> func(<span class="predefined-type">float</span> e, <span class="predefined-type">float</span> f, <span class="predefined-type">float</span> g, <span class="predefined-type">float</span> h) 9252{ 9253 <span class="keyword">return</span> (e*f) + (g*h); <span class="comment">// no constraint on order or operator consistency</span> 9254} 9255 9256<span class="predefined-type">float</span> func2(<span class="predefined-type">float</span> e, <span class="predefined-type">float</span> f, <span class="predefined-type">float</span> g, <span class="predefined-type">float</span> h) 9257{ 9258 precise <span class="predefined-type">float</span> result = (e*f) + (g*h); <span class="comment">// ensures same precision for the two multiplies</span> 9259 <span class="keyword">return</span> result; 9260} 9261 9262<span class="predefined-type">float</span> func3(<span class="predefined-type">float</span> i, <span class="predefined-type">float</span> j, precise out <span class="predefined-type">float</span> k) 9263{ 9264 k = i * i + j; <span class="comment">// precise, due to <k> declaration</span> 9265} 9266 9267<span class="directive">void</span> main() 9268{ 9269 vec3 r = vec3(a * b); <span class="comment">// precise, used to compute v.xyz</span> 9270 vec3 s = vec3(c * d); <span class="comment">// precise, used to compute v.xyz</span> 9271 v.xyz = r + s; <span class="comment">// precise</span> 9272 v.w = (a.w * b.w) + (c.w * d.w); <span class="comment">// precise</span> 9273 v.x = func(a.x, b.x, c.x, d.x); <span class="comment">// values computed in func() are NOT precise</span> 9274 v.x = func2(a.x, b.x, c.x, d.x); <span class="comment">// precise!</span> 9275 func3(a.x * b.x, c.x * d.x, v.x); <span class="comment">// precise!</span> 9276}</code></pre> 9277</div> 9278</div> 9279<div class="paragraph"> 9280<p>For the purposes of determining if an output from one shader stage matches 9281an input of the next stage, the <strong>precise</strong> qualifier need not match between 9282the input and the output.</p> 9283</div> 9284<div class="paragraph"> 9285<p>All constant expressions are evaluated as if <strong>precise</strong> was present, whether 9286or not it is present. 9287However, as described in “<a href="#constant-expressions">Constant Expressions</a>”, 9288there is no requirement that a compile-time constant expression evaluates to 9289the same value as a corresponding non-constant expression.</p> 9290</div> 9291</div> 9292<div class="sect2"> 9293<h3 id="memory-qualifiers">4.10. Memory Qualifiers</h3> 9294<div class="paragraph"> 9295<p>Shader storage blocks, variables declared within shader storage blocks and 9296variables declared as image types (the basic opaque types with “<strong>image</strong>” 9297in their keyword), can be further qualified with one or more of the 9298following memory qualifiers:</p> 9299</div> 9300<table class="tableblock frame-all grid-all stretch"> 9301<colgroup> 9302<col style="width: 50%;"> 9303<col style="width: 50%;"> 9304</colgroup> 9305<thead> 9306<tr> 9307<th class="tableblock halign-left valign-top">Qualifier</th> 9308<th class="tableblock halign-left valign-top">Meaning</th> 9309</tr> 9310</thead> 9311<tbody> 9312<tr> 9313<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>coherent</strong></p></td> 9314<td class="tableblock halign-left valign-top"><p class="tableblock">memory variable where reads and writes are coherent with 9315 reads and writes from other shader invocations</p></td> 9316</tr> 9317<tr> 9318<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>volatile</strong></p></td> 9319<td class="tableblock halign-left valign-top"><p class="tableblock">memory variable whose underlying value may be changed at any 9320 point during shader execution by some source other than the 9321 current shader invocation</p></td> 9322</tr> 9323<tr> 9324<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>restrict</strong></p></td> 9325<td class="tableblock halign-left valign-top"><p class="tableblock">memory variable where use of that variable is the only way 9326 to read and write the underlying memory in the relevant 9327 shader stage</p></td> 9328</tr> 9329<tr> 9330<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>readonly</strong></p></td> 9331<td class="tableblock halign-left valign-top"><p class="tableblock">memory variable that can be used to read the underlying 9332 memory, but cannot be used to write the underlying memory</p></td> 9333</tr> 9334<tr> 9335<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>writeonly</strong></p></td> 9336<td class="tableblock halign-left valign-top"><p class="tableblock">memory variable that can be used to write the underlying 9337 memory, but cannot be used to read the underlying memory</p></td> 9338</tr> 9339</tbody> 9340</table> 9341<div class="paragraph"> 9342<p>Memory accesses to image variables declared using the <strong>coherent</strong> qualifier 9343are performed coherently with accesses to the same location from other 9344shader invocations. 9345In particular, when reading a variable declared as <strong>coherent</strong>, the values 9346returned will reflect the results of previously completed writes performed 9347by other shader invocations. 9348When writing a variable declared as <strong>coherent</strong>, the values written will be 9349reflected in subsequent coherent reads performed by other shader 9350invocations.</p> 9351</div> 9352<div class="paragraph"> 9353<p>As described in section 93547.12 9355“Shader Memory Access” of the 9356<a href="#references">OpenGL Specification</a>, shader memory reads and writes complete in a 9357largely undefined order. 9358The built-in function <strong>memoryBarrier</strong>() can be used if needed to guarantee 9359the completion and relative ordering of memory accesses performed by a 9360single shader invocation.</p> 9361</div> 9362<div class="paragraph"> 9363<p>When accessing memory using variables not declared as <strong>coherent</strong>, the memory 9364accessed by a shader may be cached by the implementation to service future 9365accesses to the same address. 9366Memory stores may be cached in such a way that the values written may not be 9367visible to other shader invocations accessing the same memory. 9368The implementation may cache the values fetched by memory reads and return 9369the same values to any shader invocation accessing the same memory, even if 9370the underlying memory has been modified since the first memory read. 9371While variables not declared as <strong>coherent</strong> may not be useful for 9372communicating between shader invocations, using non-coherent accesses may 9373result in higher performance.</p> 9374</div> 9375<div class="paragraph"> 9376<p>Memory accesses to image variables declared using the <strong>volatile</strong> qualifier 9377must treat the underlying memory as though it could be read or written at 9378any point during shader execution by some source other than the executing 9379shader invocation. 9380When a volatile variable is read, its value must be re-fetched from the 9381underlying memory, even if the shader invocation performing the read had 9382previously fetched its value from the same memory. 9383When a volatile variable is written, its value must be written to the 9384underlying memory, even if the compiler can conclusively determine that its 9385value will be overwritten by a subsequent write. 9386Since the external source reading or writing a <strong>volatile</strong> variable may be 9387another shader invocation, variables declared as <strong>volatile</strong> are 9388automatically treated as coherent.</p> 9389</div> 9390<div class="paragraph"> 9391<p>Memory accesses to image variables declared using the <strong>restrict</strong> qualifier 9392may be compiled assuming that the variable used to perform the memory access 9393is the only way to access the underlying memory using the shader stage in 9394question. 9395This allows the compiler to coalesce or reorder loads and stores using 9396<strong>restrict</strong>-qualified image variables in ways that wouldn’t be permitted 9397for image variables not so qualified, because the compiler can assume that 9398the underlying image won’t be read or written by other code. 9399Applications are responsible for ensuring that image memory referenced by 9400variables qualified with <strong>restrict</strong> will not be referenced using other 9401variables in the same scope; otherwise, accesses to <strong>restrict</strong>-qualified 9402variables will have undefined results.</p> 9403</div> 9404<div class="paragraph"> 9405<p>Memory accesses to image variables declared using the <strong>readonly</strong> qualifier 9406may only read the underlying memory, which is treated as read-only memory 9407and cannot be written to. 9408It is a compile-time error to pass an image variable qualified with 9409<strong>readonly</strong> to <strong>imageStore</strong>() or other built-in functions that modify image 9410memory.</p> 9411</div> 9412<div class="paragraph"> 9413<p>Memory accesses to image variables declared using the <strong>writeonly</strong> qualifier 9414may only write the underlying memory; the underlying memory cannot be read. 9415It is a compile-time error to pass an image variable qualified with 9416<strong>writeonly</strong> to <strong>imageLoad</strong>() or other built-in functions that read image 9417memory.</p> 9418</div> 9419<div class="paragraph"> 9420<p>A variable could be qualified as both <strong>readonly</strong> and <strong>writeonly</strong>, disallowing 9421both read and write. Such variables can still be used with some queries, for 9422example <strong>imageSize</strong>() and <strong>.length</strong>().</p> 9423</div> 9424<div class="paragraph"> 9425<p>The memory qualifiers <strong>coherent</strong>, <strong>volatile</strong>, <strong>restrict</strong>, <strong>readonly</strong>, and 9426<strong>writeonly</strong> may be used in the declaration of buffer variables (i.e., 9427members of shader storage blocks). 9428When a buffer variable is declared with a memory qualifier, the behavior 9429specified for memory accesses involving image variables described above 9430applies identically to memory accesses involving that buffer variable. 9431It is a compile-time error to assign to a buffer variable qualified with 9432<strong>readonly</strong> or to read from a buffer variable qualified with <strong>writeonly</strong>. 9433The combination <strong>readonly</strong> <strong>writeonly</strong> is allowed.</p> 9434</div> 9435<div class="paragraph"> 9436<p>Additionally, memory qualifiers may be used at the block-level declaration 9437of a shader storage block, including the combination <strong>readonly</strong> <strong>writeonly</strong>. 9438When a block declaration is qualified with a memory qualifier, it is as if 9439all of its members were declared with the same memory qualifier. 9440For example, the block declaration</p> 9441</div> 9442<div class="listingblock"> 9443<div class="content"> 9444<pre class="CodeRay highlight"><code data-lang="c++">coherent buffer Block { 9445 readonly vec4 member1; 9446 vec4 member2; 9447};</code></pre> 9448</div> 9449</div> 9450<div class="paragraph"> 9451<p>is equivalent to</p> 9452</div> 9453<div class="listingblock"> 9454<div class="content"> 9455<pre class="CodeRay highlight"><code data-lang="c++">buffer Block { 9456 coherent readonly vec4 member1; 9457 coherent vec4 member2; 9458};</code></pre> 9459</div> 9460</div> 9461<div class="paragraph"> 9462<p>Memory qualifiers are only supported in the declarations of image variables, 9463buffer variables, and shader storage blocks; it is an error to use such 9464qualifiers in any other declarations.</p> 9465</div> 9466<div class="paragraph"> 9467<p>When calling user-defined functions, variables qualified with <strong>coherent</strong>, 9468<strong>volatile</strong>, <strong>readonly</strong>, or <strong>writeonly</strong> may not be passed to functions whose 9469formal parameters lack such qualifiers. 9470(See “<a href="#function-definitions">Function Definitions</a>” for more detail on 9471function calling.) It is legal to have any additional memory qualifiers on a 9472formal parameter, but only <strong>restrict</strong> can be taken away from a calling 9473argument, by a formal parameter that lacks the <strong>restrict</strong> qualifier.</p> 9474</div> 9475<div class="paragraph"> 9476<p>When a built-in function is called, the code generated is to be based on the 9477actual qualification of the calling argument, not on the list of memory 9478qualifiers specified on the formal parameter in the prototype.</p> 9479</div> 9480<div class="listingblock"> 9481<div class="content"> 9482<pre class="CodeRay highlight"><code data-lang="c++">vec4 funcA(restrict image2D a) { ... } 9483vec4 funcB(image2D a) { ... } 9484layout(rgba32f) uniform image2D img1; 9485layout(rgba32f) coherent uniform image2D img2; 9486 9487funcA(img1); <span class="comment">// OK, adding "restrict" is allowed</span> 9488funcB(img2); <span class="comment">// illegal, stripping "coherent" is not</span></code></pre> 9489</div> 9490</div> 9491<div class="paragraph"> 9492<p>Layout qualifiers cannot be used on formal function parameters, and layout 9493qualification is not included in parameter matching.</p> 9494</div> 9495<div class="paragraph"> 9496<p>Note that the use of <strong>const</strong> in an image variable declaration is qualifying 9497the const-ness of the variable being declared, not the image it refers to. 9498The qualifier <strong>readonly</strong> qualifies the image memory (as accessed through 9499that variable) while <strong>const</strong> qualifies the variable itself.</p> 9500</div> 9501</div> 9502<div class="sect2"> 9503<h3 id="specialization-constant-qualifier">4.11. Specialization-Constant Qualifier</h3> 9504<div class="paragraph"> 9505<p>Specialization constants are used only for SPIR-V and declared using the 9506<strong>constant_id</strong> layout qualifier. 9507For example:</p> 9508</div> 9509<div class="listingblock"> 9510<div class="content"> 9511<pre class="CodeRay highlight"><code data-lang="c++">layout(constant_id = <span class="integer">17</span>) <span class="directive">const</span> <span class="predefined-type">int</span> arraySize = <span class="integer">12</span>;</code></pre> 9512</div> 9513</div> 9514<div class="paragraph"> 9515<p>The above makes a specialization constant with a default value of 12. 9516The number 17 is an example author-chosen id by which the API or other tools 9517can later refer to this specific specialization constant. 9518If it is never changed before final lowering, it will retain the value of 951912. 9520It is a compile-time error to use the <strong>constant_id</strong> qualifier on anything 9521but SPIR-V generation of a scalar <strong>bool</strong>, <strong>int</strong>, <strong>uint</strong>, <strong>float</strong>, or 9522<strong>double</strong>.</p> 9523</div> 9524<div class="paragraph"> 9525<p>Built-in constants can be declared to be specialization constants. 9526For example:</p> 9527</div> 9528<div class="listingblock"> 9529<div class="content"> 9530<pre class="CodeRay highlight"><code data-lang="c++">layout(constant_id = <span class="integer">31</span>) gl_MaxClipDistances; <span class="comment">// add specialization_id</span></code></pre> 9531</div> 9532</div> 9533<div class="paragraph"> 9534<p>The declaration uses just the name of the previously declared built-in 9535variable, with a <strong>constant_id</strong> layout-qualifier declaration. 9536It is a compile-time error to do this after the constant has been used: 9537Constants are strictly either non-specialization constants or specialization 9538constants, not both.</p> 9539</div> 9540<div class="paragraph"> 9541<p>The built-in constant vector <em>gl_WorkGroupSize</em> can be specialized using the 9542<strong>local_size_{xyz}_id</strong> qualifiers, to individually give the components an id. 9543For example:</p> 9544</div> 9545<div class="listingblock"> 9546<div class="content"> 9547<pre class="CodeRay highlight"><code data-lang="c++">layout(local_size_x_id = <span class="integer">18</span>, local_size_z_id = <span class="integer">19</span>) in;</code></pre> 9548</div> 9549</div> 9550<div class="paragraph"> 9551<p>This leaves <em>gl_WorkGroupSize.y</em> as a non-specialization constant, with 9552<em>gl_WorkGroupSize</em> being a partially specialized vector. 9553Its <em>x</em> and <em>z</em> components can be later specialized, after generating 9554SPIR-V, using the ids 18 and 19. 9555These ids are declared independently from declaring the workgroup size:</p> 9556</div> 9557<div class="listingblock"> 9558<div class="content"> 9559<pre class="CodeRay highlight"><code data-lang="c++">layout(local_size_x = <span class="integer">32</span>, local_size_y = <span class="integer">32</span>) in; <span class="comment">// size is (32,32,1)</span> 9560layout(local_size_x_id = <span class="integer">18</span>) in; <span class="comment">// constant_id for x</span> 9561layout(local_size_z_id = <span class="integer">19</span>) in; <span class="comment">// constant_id for z</span></code></pre> 9562</div> 9563</div> 9564<div class="paragraph"> 9565<p>Existing rules for declaring <strong>local_size_x</strong>, <strong>local_size_y</strong>, and 9566<strong>local_size_z</strong> are not changed. 9567For the local-size ids, it is a compile-time error to provide different id 9568values for the same local-size id, or to provide them after any use. 9569Otherwise, order, placement, number of statements, and replication do not 9570cause errors.</p> 9571</div> 9572<div class="paragraph"> 9573<p>Two arrays sized with specialization constants are the same type only if 9574sized with the same symbol, and involving no operations. 9575For example:</p> 9576</div> 9577<div class="listingblock"> 9578<div class="content"> 9579<pre class="CodeRay highlight"><code data-lang="c++">layout(constant_id = <span class="integer">51</span>) <span class="directive">const</span> <span class="predefined-type">int</span> aSize = <span class="integer">20</span>; 9580<span class="directive">const</span> <span class="predefined-type">int</span> pad = <span class="integer">2</span>; 9581<span class="directive">const</span> <span class="predefined-type">int</span> total = aSize + pad; <span class="comment">// specialization constant</span> 9582<span class="predefined-type">int</span> a[total], b[total]; <span class="comment">// a and b have the same type</span> 9583<span class="predefined-type">int</span> c[<span class="integer">22</span>]; <span class="comment">// different type than a or b</span> 9584<span class="predefined-type">int</span> d[aSize + pad]; <span class="comment">// different type than a, b, or c</span> 9585<span class="predefined-type">int</span> e[aSize + <span class="integer">2</span>]; <span class="comment">// different type than a, b, c, or d</span></code></pre> 9586</div> 9587</div> 9588<div class="paragraph"> 9589<p>Types containing arrays sized with a specialization constant cannot be 9590compared, assigned as aggregates, declared with an initializer, or used as 9591an initializer. 9592They can, however, be passed as arguments to functions having formal 9593parameters of the same type. 9594Only the outer-most dimension of a variable declared as an array of arrays 9595can be a specialization constant, otherwise a compile-time error results.</p> 9596</div> 9597<div class="paragraph"> 9598<p>Arrays inside a block may be sized with a specialization constant, but the 9599block will have a static layout. 9600Changing the specialized size will not re-layout the block. 9601In the absence of explicit offsets, the layout will be based on the default 9602size of the array.</p> 9603</div> 9604</div> 9605<div class="sect2"> 9606<h3 id="order-of-qualification">4.12. Order and Repetition of Qualification</h3> 9607<div class="paragraph"> 9608<p>When multiple qualifiers are present in a declaration, they may appear in 9609any order, but they must all appear before the type. 9610The <strong>layout</strong> qualifier is the only qualifier that can appear more than once. 9611Further, a declaration can have at most one storage qualifier, at most one 9612auxiliary storage qualifier, and at most one interpolation qualifier. 9613If <strong>inout</strong> is used, neither <strong>in</strong> nor <strong>out</strong> may be used. 9614Multiple memory qualifiers can be used. 9615Any violation of these rules will cause a compile-time error.</p> 9616</div> 9617</div> 9618<div class="sect2"> 9619<h3 id="empty-declarations">4.13. Empty Declarations</h3> 9620<div class="paragraph"> 9621<p><em>Empty declarations</em> are declarations without a variable name, meaning no 9622object is instantiated by the declaration. 9623Generally, empty declarations are allowed. 9624Some are useful when declaring structures, while many others have no effect. 9625For example:</p> 9626</div> 9627<div class="listingblock"> 9628<div class="content"> 9629<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">int</span>; <span class="comment">// No effect</span> 9630<span class="keyword">struct</span> S {<span class="predefined-type">int</span> x;}; <span class="comment">// Defines a struct S</span></code></pre> 9631</div> 9632</div> 9633<div class="paragraph"> 9634<p>The combinations of qualifiers that cause compile-time or link-time errors 9635are the same whether or not the declaration is empty, for example:</p> 9636</div> 9637<div class="listingblock"> 9638<div class="content"> 9639<pre class="CodeRay highlight"><code data-lang="c++">invariant in <span class="predefined-type">float</span> x; <span class="comment">// Error. An input cannot be invariant.</span> 9640invariant in <span class="predefined-type">float</span>; <span class="comment">// Error even though no variable is declared.</span></code></pre> 9641</div> 9642</div> 9643</div> 9644</div> 9645</div> 9646<div class="sect1"> 9647<h2 id="operators-and-expressions">5. Operators and Expressions</h2> 9648<div class="sectionbody"> 9649<div class="sect2"> 9650<h3 id="operators">5.1. Operators</h3> 9651<div class="paragraph"> 9652<p>The OpenGL Shading Language has the following operators.</p> 9653</div> 9654<table class="tableblock frame-all grid-all stretch"> 9655<colgroup> 9656<col style="width: 25%;"> 9657<col style="width: 25%;"> 9658<col style="width: 25%;"> 9659<col style="width: 25%;"> 9660</colgroup> 9661<thead> 9662<tr> 9663<th class="tableblock halign-left valign-top">Precedence</th> 9664<th class="tableblock halign-left valign-top">Operator Class</th> 9665<th class="tableblock halign-left valign-top">Operators</th> 9666<th class="tableblock halign-left valign-top">Associativity</th> 9667</tr> 9668</thead> 9669<tbody> 9670<tr> 9671<td class="tableblock halign-left valign-top"><p class="tableblock">1 (highest)</p></td> 9672<td class="tableblock halign-left valign-top"><p class="tableblock">parenthetical grouping</p></td> 9673<td class="tableblock halign-left valign-top"><p class="tableblock">( )</p></td> 9674<td class="tableblock halign-left valign-top"><p class="tableblock">NA</p></td> 9675</tr> 9676<tr> 9677<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td> 9678<td class="tableblock halign-left valign-top"><p class="tableblock">array subscript<br> 9679 function call and constructor structure<br> 9680 field or method selector, swizzle<br> 9681 post fix increment and decrement</p></td> 9682<td class="tableblock halign-left valign-top"><p class="tableblock">[ ]<br> 9683 ( )<br> 9684 .<br> 9685 ++ --</p></td> 9686<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9687</tr> 9688<tr> 9689<td class="tableblock halign-left valign-top"><p class="tableblock">3</p></td> 9690<td class="tableblock halign-left valign-top"><p class="tableblock">prefix increment and decrement<br> 9691 unary</p></td> 9692<td class="tableblock halign-left valign-top"><p class="tableblock">++ --<br> 9693 + - ~ !</p></td> 9694<td class="tableblock halign-left valign-top"><p class="tableblock">Right to Left</p></td> 9695</tr> 9696<tr> 9697<td class="tableblock halign-left valign-top"><p class="tableblock">4</p></td> 9698<td class="tableblock halign-left valign-top"><p class="tableblock">multiplicative</p></td> 9699<td class="tableblock halign-left valign-top"><p class="tableblock">* / %</p></td> 9700<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9701</tr> 9702<tr> 9703<td class="tableblock halign-left valign-top"><p class="tableblock">5</p></td> 9704<td class="tableblock halign-left valign-top"><p class="tableblock">additive</p></td> 9705<td class="tableblock halign-left valign-top"><p class="tableblock">+ -</p></td> 9706<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9707</tr> 9708<tr> 9709<td class="tableblock halign-left valign-top"><p class="tableblock">6</p></td> 9710<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise shift</p></td> 9711<td class="tableblock halign-left valign-top"><p class="tableblock"><< >></p></td> 9712<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9713</tr> 9714<tr> 9715<td class="tableblock halign-left valign-top"><p class="tableblock">7</p></td> 9716<td class="tableblock halign-left valign-top"><p class="tableblock">relational</p></td> 9717<td class="tableblock halign-left valign-top"><p class="tableblock">< > <= >=</p></td> 9718<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9719</tr> 9720<tr> 9721<td class="tableblock halign-left valign-top"><p class="tableblock">8</p></td> 9722<td class="tableblock halign-left valign-top"><p class="tableblock">equality</p></td> 9723<td class="tableblock halign-left valign-top"><p class="tableblock">== !=</p></td> 9724<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9725</tr> 9726<tr> 9727<td class="tableblock halign-left valign-top"><p class="tableblock">9</p></td> 9728<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise and</p></td> 9729<td class="tableblock halign-left valign-top"><p class="tableblock">&</p></td> 9730<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9731</tr> 9732<tr> 9733<td class="tableblock halign-left valign-top"><p class="tableblock">10</p></td> 9734<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise exclusive or</p></td> 9735<td class="tableblock halign-left valign-top"><p class="tableblock">^</p></td> 9736<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9737</tr> 9738<tr> 9739<td class="tableblock halign-left valign-top"><p class="tableblock">11</p></td> 9740<td class="tableblock halign-left valign-top"><p class="tableblock">bit-wise inclusive or</p></td> 9741<td class="tableblock halign-left valign-top"><p class="tableblock">|</p></td> 9742<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9743</tr> 9744<tr> 9745<td class="tableblock halign-left valign-top"><p class="tableblock">12</p></td> 9746<td class="tableblock halign-left valign-top"><p class="tableblock">logical and</p></td> 9747<td class="tableblock halign-left valign-top"><p class="tableblock">&&</p></td> 9748<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9749</tr> 9750<tr> 9751<td class="tableblock halign-left valign-top"><p class="tableblock">13</p></td> 9752<td class="tableblock halign-left valign-top"><p class="tableblock">logical exclusive or</p></td> 9753<td class="tableblock halign-left valign-top"><p class="tableblock">^^</p></td> 9754<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9755</tr> 9756<tr> 9757<td class="tableblock halign-left valign-top"><p class="tableblock">14</p></td> 9758<td class="tableblock halign-left valign-top"><p class="tableblock">logical inclusive or</p></td> 9759<td class="tableblock halign-left valign-top"><p class="tableblock">||</p></td> 9760<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9761</tr> 9762<tr> 9763<td class="tableblock halign-left valign-top"><p class="tableblock">15</p></td> 9764<td class="tableblock halign-left valign-top"><p class="tableblock">selection</p></td> 9765<td class="tableblock halign-left valign-top"><p class="tableblock">? :</p></td> 9766<td class="tableblock halign-left valign-top"><p class="tableblock">Right to Left</p></td> 9767</tr> 9768<tr> 9769<td class="tableblock halign-left valign-top"><p class="tableblock">16</p></td> 9770<td class="tableblock halign-left valign-top"><p class="tableblock">Assignment<br> 9771 arithmetic assignments</p></td> 9772<td class="tableblock halign-left valign-top"><p class="tableblock">=<br> 9773 += -=<br> 9774 *= /=<br> 9775 %= <<= >>=<br> 9776 &= ^= |=</p></td> 9777<td class="tableblock halign-left valign-top"><p class="tableblock">Right to Left</p></td> 9778</tr> 9779<tr> 9780<td class="tableblock halign-left valign-top"><p class="tableblock">17 (lowest)</p></td> 9781<td class="tableblock halign-left valign-top"><p class="tableblock">sequence</p></td> 9782<td class="tableblock halign-left valign-top"><p class="tableblock">,</p></td> 9783<td class="tableblock halign-left valign-top"><p class="tableblock">Left to Right</p></td> 9784</tr> 9785</tbody> 9786</table> 9787<div class="paragraph"> 9788<p>There is no address-of operator nor a dereference operator. 9789There is no typecast operator; constructors are used instead.</p> 9790</div> 9791</div> 9792<div class="sect2"> 9793<h3 id="array-operations">5.2. Array Operations</h3> 9794<div class="paragraph"> 9795<p>These are now described in “<a href="#structure-and-array-operations">Structure and 9796Array Operations</a>”.</p> 9797</div> 9798</div> 9799<div class="sect2"> 9800<h3 id="function-calls">5.3. Function Calls</h3> 9801<div class="paragraph"> 9802<p>If a function returns a value, then a call to that function may be used as 9803an expression, whose type will be the type that was used to declare or 9804define the function.</p> 9805</div> 9806<div class="paragraph"> 9807<p>Function definitions and calling conventions are discussed in 9808“<a href="#function-definitions">Function Definitions</a>”.</p> 9809</div> 9810</div> 9811<div class="sect2"> 9812<h3 id="constructors">5.4. Constructors</h3> 9813<div class="paragraph"> 9814<p>Constructors use the function call syntax, where the function name is a 9815type, and the call makes an object of that type. 9816Constructors are used the same way in both initializers and expressions. 9817(See “<a href="#shading-language-grammar">Shading Language Grammar</a>” for details.) 9818The parameters are used to initialize the constructed value. 9819Constructors can be used to request a data type conversion to change from 9820one scalar type to another scalar type, or to build larger types out of 9821smaller types, or to reduce a larger type to a smaller type.</p> 9822</div> 9823<div class="paragraph"> 9824<p>In general, constructors are not built-in functions with predetermined 9825prototypes. 9826For arrays and structures, there must be exactly one argument in the 9827constructor for each element or member. 9828For the other types, the arguments must provide a sufficient number of 9829components to perform the initialization, and it is a compile-time error to 9830include so many arguments that they cannot all be used. 9831Detailed rules follow. 9832The prototypes actually listed below are merely a subset of examples.</p> 9833</div> 9834<div class="sect3"> 9835<h4 id="conversion-and-scalar-constructors">5.4.1. Conversion and Scalar Constructors</h4> 9836<div class="paragraph"> 9837<p>Converting between scalar types is done as the following prototypes 9838indicate:</p> 9839</div> 9840<div class="listingblock"> 9841<div class="content"> 9842<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">int</span>(uint) <span class="comment">// converts an unsigned integer to a signed integer</span> 9843<span class="predefined-type">int</span>(<span class="predefined-type">bool</span>) <span class="comment">// converts a Boolean value to an int</span> 9844<span class="predefined-type">int</span>(<span class="predefined-type">float</span>) <span class="comment">// converts a float value to an int</span> 9845<span class="predefined-type">int</span>(<span class="predefined-type">double</span>) <span class="comment">// converts a double value to a signed integer</span> 9846uint(<span class="predefined-type">int</span>) <span class="comment">// converts a signed integer value to an unsigned integer</span> 9847uint(<span class="predefined-type">bool</span>) <span class="comment">// converts a Boolean value to an unsigned integer</span> 9848uint(<span class="predefined-type">float</span>) <span class="comment">// converts a float value to an unsigned integer</span> 9849uint(<span class="predefined-type">double</span>) <span class="comment">// converts a double value to an unsigned integer</span> 9850<span class="predefined-type">bool</span>(<span class="predefined-type">int</span>) <span class="comment">// converts a signed integer value to a Boolean</span> 9851<span class="predefined-type">bool</span>(uint) <span class="comment">// converts an unsigned integer value to a Boolean value</span> 9852<span class="predefined-type">bool</span>(<span class="predefined-type">float</span>) <span class="comment">// converts a float value to a Boolean</span> 9853<span class="predefined-type">bool</span>(<span class="predefined-type">double</span>) <span class="comment">// converts a double value to a Boolean</span> 9854<span class="predefined-type">float</span>(<span class="predefined-type">int</span>) <span class="comment">// converts a signed integer value to a float</span> 9855<span class="predefined-type">float</span>(uint) <span class="comment">// converts an unsigned integer value to a float value</span> 9856<span class="predefined-type">float</span>(<span class="predefined-type">bool</span>) <span class="comment">// converts a Boolean value to a float</span> 9857<span class="predefined-type">float</span>(<span class="predefined-type">double</span>) <span class="comment">// converts a double value to a float</span> 9858<span class="predefined-type">double</span>(<span class="predefined-type">int</span>) <span class="comment">// converts a signed integer value to a double</span> 9859<span class="predefined-type">double</span>(uint) <span class="comment">// converts an unsigned integer value to a double</span> 9860<span class="predefined-type">double</span>(<span class="predefined-type">bool</span>) <span class="comment">// converts a Boolean value to a double</span> 9861<span class="predefined-type">double</span>(<span class="predefined-type">float</span>) <span class="comment">// converts a float value to a double</span></code></pre> 9862</div> 9863</div> 9864<div class="paragraph"> 9865<p>When constructors are used to convert a floating-point type to an integer 9866type, the fractional part of the floating-point value is dropped. 9867It is undefined to convert a negative floating-point value to an <strong>uint</strong>.</p> 9868</div> 9869<div class="paragraph"> 9870<p>Integer values having more bits of precision than a single-precision 9871floating-point mantissa will lose precision when converted to <strong>float</strong>.</p> 9872</div> 9873<div class="paragraph"> 9874<p>When a constructor is used to convert any integer or floating-point type to 9875a <strong>bool</strong>, 0 and 0.0 are converted to <strong>false</strong>, and non-zero values are 9876converted to <strong>true</strong>. 9877When a constructor is used to convert a <strong>bool</strong> to any integer or 9878floating-point type, <strong>false</strong> is converted to 0 or 0.0, and <strong>true</strong> is 9879converted to 1 or 1.0.</p> 9880</div> 9881<div class="paragraph"> 9882<p>The constructor <strong>int</strong>(<strong>uint</strong>) preserves the bit pattern in the argument, 9883which will change the argument’s value if its sign bit is set. 9884The constructor <strong>uint</strong>(<strong>int</strong>) preserves the bit pattern in the argument, 9885which will change its value if it is negative.</p> 9886</div> 9887<div class="paragraph"> 9888<p>Identity constructors, like <strong>float</strong>(<strong>float</strong>) are also legal, but of little 9889use.</p> 9890</div> 9891<div class="paragraph"> 9892<p>Scalar constructors with non-scalar parameters can be used to take the first 9893element from a non-scalar. 9894For example, the constructor <strong>float</strong>(<strong>vec3</strong>) will select the first component 9895of the <strong>vec3</strong> parameter.</p> 9896</div> 9897</div> 9898<div class="sect3"> 9899<h4 id="vector-and-matrix-constructors">5.4.2. Vector and Matrix Constructors</h4> 9900<div class="paragraph"> 9901<p>Constructors can be used to create vectors or matrices from a set of 9902scalars, vectors, or matrices. 9903This includes the ability to shorten vectors.</p> 9904</div> 9905<div class="paragraph"> 9906<p>If there is a single scalar parameter to a vector constructor, it is used to 9907initialize all components of the constructed vector to that scalar’s value. 9908If there is a single scalar parameter to a matrix constructor, it is used to 9909initialize all the components on the matrix’s diagonal, with the remaining 9910components initialized to 0.0.</p> 9911</div> 9912<div class="paragraph"> 9913<p>If a vector is constructed from multiple scalars, one or more vectors, or 9914one or more matrices, or a mixture of these, the vector’s components will be 9915constructed in order from the components of the arguments. 9916The arguments will be consumed left to right, and each argument will have 9917all its components consumed, in order, before any components from the next 9918argument are consumed. 9919Similarly for constructing a matrix from multiple scalars or vectors, or a 9920mixture of these. 9921Matrix components will be constructed and consumed in column major order. 9922In these cases, there must be enough components provided in the arguments to 9923provide an initializer for every component in the constructed value. 9924It is a compile-time error to provide extra arguments beyond this last used 9925argument.</p> 9926</div> 9927<div class="paragraph"> 9928<p>If a matrix is constructed from a matrix, then each component (column <em>i</em>, 9929row <em>j</em>) in the result that has a corresponding component (column <em>i</em>, row 9930<em>j</em>) in the argument will be initialized from there. 9931All other components will be initialized to the identity matrix. 9932If a matrix argument is given to a matrix constructor, it is 9933a compile-time error to have any other arguments.</p> 9934</div> 9935<div class="paragraph"> 9936<p>If the basic type (<strong>bool</strong>, <strong>int</strong>, 9937<strong>float</strong>, or <strong>double</strong>) 9938of a parameter to a 9939constructor does not match the basic type of the object being constructed, 9940the scalar construction rules (above) are used to convert the parameters.</p> 9941</div> 9942<div class="paragraph"> 9943<p>Some useful vector constructors are as follows:</p> 9944</div> 9945<div class="listingblock"> 9946<div class="content"> 9947<pre class="CodeRay highlight"><code data-lang="c++">vec3(<span class="predefined-type">float</span>) <span class="comment">// initializes each component of the vec3 with the float</span> 9948vec4(ivec4) <span class="comment">// makes a vec4 with component-wise conversion</span> 9949vec4(mat2) <span class="comment">// the vec4 is column 0 followed by column 1</span> 9950vec2(<span class="predefined-type">float</span>, <span class="predefined-type">float</span>) <span class="comment">// initializes a vec2 with 2 floats</span> 9951ivec3(<span class="predefined-type">int</span>, <span class="predefined-type">int</span>, <span class="predefined-type">int</span>) <span class="comment">// initializes an ivec3 with 3 ints</span> 9952bvec4(<span class="predefined-type">int</span>, <span class="predefined-type">int</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>) <span class="comment">// uses 4 Boolean conversions</span> 9953vec2(vec3) <span class="comment">// drops the third component of a vec3</span> 9954vec3(vec4) <span class="comment">// drops the fourth component of a vec4</span> 9955vec3(vec2, <span class="predefined-type">float</span>) <span class="comment">// vec3.x = vec2.x, vec3.y = vec2.y, vec3.z = float</span> 9956vec3(<span class="predefined-type">float</span>, vec2) <span class="comment">// vec3.x = float, vec3.y = vec2.x, vec3.z = vec2.y</span> 9957vec4(vec3, <span class="predefined-type">float</span>) 9958vec4(<span class="predefined-type">float</span>, vec3) 9959vec4(vec2, vec2)</code></pre> 9960</div> 9961</div> 9962<div class="paragraph"> 9963<p>Some examples of these are:</p> 9964</div> 9965<div class="listingblock"> 9966<div class="content"> 9967<pre class="CodeRay highlight"><code data-lang="c++">vec4 color = vec4(<span class="float">0</span><span class="float">.0</span>, <span class="float">1</span><span class="float">.0</span>, <span class="float">0</span><span class="float">.0</span>, <span class="float">1</span><span class="float">.0</span>); 9968vec4 rgba = vec4(<span class="float">1</span><span class="float">.0</span>); <span class="comment">// sets each component to 1.0</span> 9969vec3 rgb = vec3(color); <span class="comment">// drop the 4th component</span></code></pre> 9970</div> 9971</div> 9972<div class="paragraph"> 9973<p>To initialize the diagonal of a matrix with all other elements set to zero:</p> 9974</div> 9975<div class="listingblock"> 9976<div class="content"> 9977<pre class="CodeRay highlight"><code data-lang="c++">mat2(<span class="predefined-type">float</span>) 9978mat3(<span class="predefined-type">float</span>) 9979mat4(<span class="predefined-type">float</span>)</code></pre> 9980</div> 9981</div> 9982<div class="paragraph"> 9983<p>That is, <em>result[i][j]</em> is set to the <em>float</em> argument for all \(i 9984= j\) and set to 0 for all \(i \neq j\).</p> 9985</div> 9986<div class="paragraph"> 9987<p>To initialize a matrix by specifying vectors or scalars, the components are 9988assigned to the matrix elements in column-major order.</p> 9989</div> 9990<div class="listingblock"> 9991<div class="content"> 9992<pre class="CodeRay highlight"><code data-lang="c++">mat2(vec2, vec2); <span class="comment">// one column per argument</span> 9993mat3(vec3, vec3, vec3); <span class="comment">// one column per argument</span> 9994mat4(vec4, vec4, vec4, vec4); <span class="comment">// one column per argument</span> 9995mat3x2(vec2, vec2, vec2); <span class="comment">// one column per argument</span> 9996dmat2(dvec2, dvec2); 9997dmat3(dvec3, dvec3, dvec3); 9998dmat4(dvec4, dvec4, dvec4, dvec4); 9999mat2(<span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="comment">// first column</span> 10000 <span class="predefined-type">float</span>, <span class="predefined-type">float</span>); <span class="comment">// second column</span> 10001mat3(<span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="comment">// first column</span> 10002 <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="comment">// second column</span> 10003 <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>); <span class="comment">// third column</span> 10004mat4(<span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="comment">// first column</span> 10005 <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="comment">// second column</span> 10006 <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="comment">// third column</span> 10007 <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>, <span class="predefined-type">float</span>); <span class="comment">// fourth column</span> 10008mat2x3(vec2, <span class="predefined-type">float</span>, <span class="comment">// first column</span> 10009 vec2, <span class="predefined-type">float</span>); <span class="comment">// second column</span> 10010dmat2x4(dvec3, <span class="predefined-type">double</span>, <span class="comment">// first column</span> 10011 <span class="predefined-type">double</span>, dvec3); <span class="comment">// second column</span></code></pre> 10012</div> 10013</div> 10014<div class="paragraph"> 10015<p>A wide range of other possibilities exist, to construct a matrix from 10016vectors and scalars, as long as enough components are present to initialize 10017the matrix. 10018To construct a matrix from a matrix:</p> 10019</div> 10020<div class="listingblock"> 10021<div class="content"> 10022<pre class="CodeRay highlight"><code data-lang="c++">mat3x3(mat4x4); <span class="comment">// takes the upper-left 3x3 of the mat4x4</span> 10023mat2x3(mat4x2); <span class="comment">// takes the upper-left 2x2 of the mat4x4, last row is 0,0</span> 10024mat4x4(mat3x3); <span class="comment">// puts the mat3x3 in the upper-left, sets the lower right</span> 10025 <span class="comment">// component to 1, and the rest to 0</span></code></pre> 10026</div> 10027</div> 10028</div> 10029<div class="sect3"> 10030<h4 id="structure-constructors">5.4.3. Structure Constructors</h4> 10031<div class="paragraph"> 10032<p>Once a structure is defined, and its type is given a name, a constructor is 10033available with the same name to construct instances of that structure. 10034For example:</p> 10035</div> 10036<div class="listingblock"> 10037<div class="content"> 10038<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">struct</span> light { 10039 <span class="predefined-type">float</span> intensity; 10040 vec3 position; 10041}; 10042 10043light lightVar = light(<span class="float">3</span><span class="float">.0</span>, vec3(<span class="float">1</span><span class="float">.0</span>, <span class="float">2</span><span class="float">.0</span>, <span class="float">3</span><span class="float">.0</span>));</code></pre> 10044</div> 10045</div> 10046<div class="paragraph"> 10047<p>The arguments to the constructor will be used to set the structure’s 10048members, in order, using one argument per member. 10049Each argument must be the same type as the member it 10050sets, or be a type that can be converted to the member’s type according to 10051section “<a href="#implicit-conversions">Implicit Conversions</a>”.</p> 10052</div> 10053<div class="paragraph"> 10054<p>Structure constructors can be used as initializers or in expressions.</p> 10055</div> 10056</div> 10057<div class="sect3"> 10058<h4 id="array-constructors">5.4.4. Array Constructors</h4> 10059<div class="paragraph"> 10060<p>Array types can also be used as constructor names, which can then be used in 10061expressions or initializers. 10062For example,</p> 10063</div> 10064<div class="listingblock"> 10065<div class="content"> 10066<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">const</span> <span class="predefined-type">float</span> c[<span class="integer">3</span>] = <span class="predefined-type">float</span>[<span class="integer">3</span>](<span class="float">5</span><span class="float">.0</span>, <span class="float">7</span><span class="float">.2</span>, <span class="float">1</span><span class="float">.1</span>); 10067<span class="directive">const</span> <span class="predefined-type">float</span> d[<span class="integer">3</span>] = <span class="predefined-type">float</span>[](<span class="float">5</span><span class="float">.0</span>, <span class="float">7</span><span class="float">.2</span>, <span class="float">1</span><span class="float">.1</span>); 10068 10069<span class="predefined-type">float</span> g; 10070... 10071<span class="predefined-type">float</span> a[<span class="integer">5</span>] = <span class="predefined-type">float</span>[<span class="integer">5</span>](g, <span class="integer">1</span>, g, <span class="float">2</span><span class="float">.3</span>, g); 10072<span class="predefined-type">float</span> b[<span class="integer">3</span>]; 10073 10074b = <span class="predefined-type">float</span>[<span class="integer">3</span>](g, g + <span class="float">1</span><span class="float">.0</span>, g + <span class="float">2</span><span class="float">.0</span>);</code></pre> 10075</div> 10076</div> 10077<div class="paragraph"> 10078<p>There must be exactly the same number of arguments as the size of the array 10079being constructed. 10080If no size is present in the constructor, then the array is explicitly sized 10081to the number of arguments provided. 10082The arguments are assigned in order, starting at element 0, to the elements 10083of the constructed array. 10084Each argument must be the same type as the element type of the 10085array, or be 10086a type that can be converted to the element type of the array according to 10087“<a href="#implicit-conversions">Implicit Conversions</a>”.</p> 10088</div> 10089<div class="paragraph"> 10090<p>Arrays of arrays are similarly constructed, and the size for any dimension 10091is <strong class="purple">optional</strong></p> 10092</div> 10093<div class="listingblock"> 10094<div class="content"> 10095<pre class="CodeRay highlight"><code data-lang="c++">vec4 b[<span class="integer">2</span>] = ...; 10096vec4[<span class="integer">3</span>][<span class="integer">2</span>](b, b, b); <span class="comment">// constructor</span> 10097vec4[][<span class="integer">2</span>](b, b, b); <span class="comment">// constructor, valid, size deduced</span> 10098vec4[<span class="integer">3</span>][](b, b, b); <span class="comment">// constructor, valid, size deduced</span> 10099vec4[][](b, b, b); <span class="comment">// constructor, valid, both sizes deduced</span></code></pre> 10100</div> 10101</div> 10102</div> 10103<div class="sect3"> 10104<h4 id="_texture_combined_sampler_constructors">5.4.5. Texture-Combined Sampler Constructors</h4> 10105<div class="paragraph"> 10106<p>Texture-combined sampler constructors are only available when targeting Vulkan.</p> 10107</div> 10108<div class="paragraph"> 10109<p>Texture-combined sampler types, like <strong>sampler2D</strong>, can be declared with an 10110initializer 10111that is a constructor of the same type, and consuming a texture and a 10112<strong>sampler</strong> or <strong>samplerShadow</strong>. 10113For example:</p> 10114</div> 10115<div class="listingblock"> 10116<div class="content"> 10117<pre class="CodeRay highlight"><code data-lang="c++"> layout(...) uniform sampler s; <span class="comment">// handle to filtering information</span> 10118 layout(...) uniform texture2D t; <span class="comment">// handle to a texture</span> 10119 layout(...) in vec2 tCoord; 10120 ... 10121 texture(sampler2D(t, s), tCoord);</code></pre> 10122</div> 10123</div> 10124<div class="paragraph"> 10125<p>The result of a texture-combined sampler constructor cannot be assigned to a 10126variable:</p> 10127</div> 10128<div class="listingblock"> 10129<div class="content"> 10130<pre class="CodeRay highlight"><code data-lang="c++"> ... sampler2D sConstruct = sampler2D(t, s); <span class="comment">// ERROR</span></code></pre> 10131</div> 10132</div> 10133<div class="paragraph"> 10134<p>Texture-combined sampler constructors can only be consumed by a function parameter.</p> 10135</div> 10136<div class="paragraph"> 10137<p>Texture-combined sampler constructors of arrays are illegal:</p> 10138</div> 10139<div class="listingblock"> 10140<div class="content"> 10141<pre class="CodeRay highlight"><code data-lang="c++"> layout(...) uniform texture2D tArray[<span class="integer">6</span>]; 10142 ... 10143 ... sampler2D[](tArray, s) ... <span class="comment">// ERROR</span></code></pre> 10144</div> 10145</div> 10146<div class="paragraph"> 10147<p>Formally:</p> 10148</div> 10149<div class="ulist"> 10150<ul> 10151<li> 10152<p>every texture-combined sampler type can be used as a constructor</p> 10153</li> 10154<li> 10155<p>the type of the constructor must match the type of the variable being declared</p> 10156</li> 10157<li> 10158<p>the constructor’s first argument must be a texture type</p> 10159</li> 10160<li> 10161<p>the constructor’s second argument must be a scalar of type <strong>sampler</strong> 10162or <strong>samplerShadow</strong></p> 10163</li> 10164<li> 10165<p>the dimensionality (1D, 2D, 3D, Cube, Rect, Buffer, MS, and Array) 10166of the texture type must match that of the constructed type 10167(that is, the suffixes of the type of the first argument and the 10168type of the constructor will be spelled the same way)</p> 10169</li> 10170<li> 10171<p>there is no control flow construct (e.g., <code>?:</code>) that consumes any sampler type</p> 10172</li> 10173</ul> 10174</div> 10175<div class="paragraph"> 10176<p>Note: Shadow mismatches are allowed between constructors and the second argument. 10177Texture-combined non-shadow samplers can be constructed from <strong>samplerShadow</strong> and 10178texture-combined shadow samplers can be constructed from <strong>sampler</strong>.</p> 10179</div> 10180</div> 10181</div> 10182<div class="sect2"> 10183<h3 id="vector-components">5.5. Vector and Scalar Components and Length</h3> 10184<div class="paragraph"> 10185<p>The names of the components of a vector 10186or scalar 10187are denoted by a single letter. 10188As a notational convenience, several letters are associated with each 10189component based on common usage of position, color or texture coordinate 10190vectors. 10191The individual components can be selected by following the variable name 10192with period (<strong>.</strong>) and then the component name.</p> 10193</div> 10194<div class="paragraph"> 10195<p>The component names supported are:</p> 10196</div> 10197<table class="tableblock frame-all grid-all fit-content"> 10198<colgroup> 10199<col> 10200<col> 10201</colgroup> 10202<tbody> 10203<tr> 10204<td class="tableblock halign-left valign-top"><p class="tableblock"><em>{ x, y, z, w }</em></p></td> 10205<td class="tableblock halign-left valign-top"><p class="tableblock">Useful when accessing vectors that represent points or normals</p></td> 10206</tr> 10207<tr> 10208<td class="tableblock halign-left valign-top"><p class="tableblock"><em>{ r, g, b, a }</em></p></td> 10209<td class="tableblock halign-left valign-top"><p class="tableblock">Useful when accessing vectors that represent colors</p></td> 10210</tr> 10211<tr> 10212<td class="tableblock halign-left valign-top"><p class="tableblock"><em>{ s, t, p, q }</em></p></td> 10213<td class="tableblock halign-left valign-top"><p class="tableblock">Useful when accessing vectors that represent texture coordinates</p></td> 10214</tr> 10215</tbody> 10216</table> 10217<div class="paragraph"> 10218<p>The component names <em>x</em>, <em>r</em>, and <em>s</em> are, for example, synonyms for the 10219same (first) component in a vector. 10220They are also the names of the only component in a scalar.</p> 10221</div> 10222<div class="paragraph"> 10223<p>Note that the third component of the texture coordinate set 10224has been renamed <em>p</em> so as to avoid the confusion with <em>r</em> (for 10225red) in a color.</p> 10226</div> 10227<div class="paragraph"> 10228<p>Accessing components beyond those declared for the type is 10229a compile-time error so, for example:</p> 10230</div> 10231<div class="listingblock"> 10232<div class="content"> 10233<pre class="CodeRay highlight"><code data-lang="c++">vec2 pos; 10234<span class="predefined-type">float</span> height; 10235pos.x <span class="comment">// is legal</span> 10236pos.z <span class="comment">// is illegal</span> 10237height.x <span class="comment">// is legal</span> 10238height.y <span class="comment">// is illegal</span></code></pre> 10239</div> 10240</div> 10241<div class="paragraph"> 10242<p>The component selection syntax allows multiple components to be selected by 10243appending their names (from the same name set) after the period (<strong>.</strong>).</p> 10244</div> 10245<div class="listingblock"> 10246<div class="content"> 10247<pre class="CodeRay highlight"><code data-lang="c++">vec4 v4; 10248v4.rgba; <span class="comment">// is a vec4 and the same as just using v4,</span> 10249v4.rgb; <span class="comment">// is a vec3,</span> 10250v4.b; <span class="comment">// is a float,</span> 10251v4.xy; <span class="comment">// is a vec2,</span> 10252v4.xgba; <span class="comment">// is illegal - the component names do not come from the same set</span></code></pre> 10253</div> 10254</div> 10255<div class="paragraph"> 10256<p>No more than 4 components can be selected.</p> 10257</div> 10258<div class="listingblock"> 10259<div class="content"> 10260<pre class="CodeRay highlight"><code data-lang="c++">vec4 v4; 10261v4.xyzwxy; <span class="comment">// is illegal since it has 6 components</span> 10262(v4.xyzwxy).xy; <span class="comment">// is illegal since the intermediate value has 6</span> 10263components</code></pre> 10264</div> 10265</div> 10266<div class="paragraph"> 10267<p>The order of the components can be different to swizzle them, or replicated:</p> 10268</div> 10269<div class="listingblock"> 10270<div class="content"> 10271<pre class="CodeRay highlight"><code data-lang="c++">vec4 pos = vec4(<span class="float">1</span><span class="float">.0</span>, <span class="float">2</span><span class="float">.0</span>, <span class="float">3</span><span class="float">.0</span>, <span class="float">4</span><span class="float">.0</span>); 10272vec4 swiz = pos.wzyx; <span class="comment">// swiz = (4.0, 3.0, 2.0, 1.0)</span> 10273vec4 dup = pos.xxyy; <span class="comment">// dup = (1.0, 1.0, 2.0, 2.0)</span></code></pre> 10274</div> 10275</div> 10276<div class="paragraph"> 10277<p>This notation is more concise than the constructor syntax. 10278To form an r-value, it can be applied to any expression that results in a 10279vector or scalar r-value.</p> 10280</div> 10281<div class="paragraph"> 10282<p>The component group notation can occur on the left hand side of an 10283expression.</p> 10284</div> 10285<div class="listingblock"> 10286<div class="content"> 10287<pre class="CodeRay highlight"><code data-lang="c++">vec4 pos = vec4(<span class="float">1</span><span class="float">.0</span>, <span class="float">2</span><span class="float">.0</span>, <span class="float">3</span><span class="float">.0</span>, <span class="float">4</span><span class="float">.0</span>); 10288pos.xw = vec2(<span class="float">5</span><span class="float">.0</span>, <span class="float">6</span><span class="float">.0</span>); <span class="comment">// pos = (5.0, 2.0, 3.0, 6.0)</span> 10289pos.wx = vec2(<span class="float">7</span><span class="float">.0</span>, <span class="float">8</span><span class="float">.0</span>); <span class="comment">// pos = (8.0, 2.0, 3.0, 7.0)</span> 10290pos.xx = vec2(<span class="float">3</span><span class="float">.0</span>, <span class="float">4</span><span class="float">.0</span>); <span class="comment">// illegal - 'x' used twice</span> 10291pos.xy = vec3(<span class="float">1</span><span class="float">.0</span>, <span class="float">2</span><span class="float">.0</span>, <span class="float">3</span><span class="float">.0</span>); <span class="comment">// illegal - mismatch between vec2 and vec3</span></code></pre> 10292</div> 10293</div> 10294<div class="paragraph"> 10295<p>To form an l-value, swizzling must further be applied to an l-value and 10296contain no duplicate components. It results in an l-value of scalar or 10297vector type, depending on number of components specified.</p> 10298</div> 10299<div class="paragraph"> 10300<p>Array subscripting syntax can also be applied to vectors (but not to 10301scalars) to provide numeric indexing. 10302So in</p> 10303</div> 10304<div class="listingblock"> 10305<div class="content"> 10306<pre class="CodeRay highlight"><code data-lang="c++">vec4 pos;</code></pre> 10307</div> 10308</div> 10309<div class="paragraph"> 10310<p><em>pos[2]</em> refers to the third element of <em>pos</em> and is equivalent to <em>pos.z</em>. 10311This allows variable indexing into a vector, as well as a generic way of 10312accessing components. 10313Any integer expression can be used as the subscript. 10314The first component is at index zero. 10315Reading from or writing to a vector using a constant integral expression 10316with a value that is negative or greater than or equal to the size of the 10317vector results in a compile-time error. 10318When indexing with non-constant expressions, behavior is undefined if the 10319index is negative, or greater than or equal to the size of the vector.</p> 10320</div> 10321<div class="paragraph"> 10322<p>The <strong>length</strong>() method may be applied to vectors (but not scalars). 10323The result is the number of components in the vector. 10324For example,</p> 10325</div> 10326<div class="listingblock"> 10327<div class="content"> 10328<pre class="CodeRay highlight"><code data-lang="c++">vec3 v; 10329<span class="directive">const</span> <span class="predefined-type">int</span> L = v.length();</code></pre> 10330</div> 10331</div> 10332<div class="paragraph"> 10333<p>sets the constant <em>L</em> to 3. 10334The type returned by <strong>.length</strong>() on a vector is <strong>int</strong>, and the value 10335returned is a constant expression.</p> 10336</div> 10337</div> 10338<div class="sect2"> 10339<h3 id="matrix-components">5.6. Matrix Components</h3> 10340<div class="paragraph"> 10341<p>The components of a matrix can be accessed using array subscripting syntax. 10342Applying a single subscript to a matrix treats the matrix as an array of 10343column vectors, and selects a single column, whose type is a vector of the 10344same size as the (column size of the) matrix. 10345The leftmost column is column 0. 10346A second subscript would then operate on the resulting vector, as defined 10347earlier for vectors. 10348Hence, two subscripts select a column and then a row.</p> 10349</div> 10350<div class="listingblock"> 10351<div class="content"> 10352<pre class="CodeRay highlight"><code data-lang="c++">mat4 m; 10353m[<span class="integer">1</span>] = vec4(<span class="float">2</span><span class="float">.0</span>); <span class="comment">// sets the second column to all 2.0</span> 10354m[<span class="integer">0</span>][<span class="integer">0</span>] = <span class="float">1</span><span class="float">.0</span>; <span class="comment">// sets the upper left element to 1.0</span> 10355m[<span class="integer">2</span>][<span class="integer">3</span>] = <span class="float">2</span><span class="float">.0</span>; <span class="comment">// sets the 4th element of the third column to 2.0</span></code></pre> 10356</div> 10357</div> 10358<div class="paragraph"> 10359<p>Behavior is undefined when accessing a component outside the bounds of a 10360matrix with a non-constant expression. 10361It is a compile-time error to access a matrix with a constant expression 10362that is outside the bounds of the matrix.</p> 10363</div> 10364<div class="paragraph"> 10365<p>The <strong>length</strong>() method may be applied to matrices. 10366The result is the number of columns of the matrix. 10367For example,</p> 10368</div> 10369<div class="listingblock"> 10370<div class="content"> 10371<pre class="CodeRay highlight"><code data-lang="c++">mat3x4 v; 10372<span class="directive">const</span> <span class="predefined-type">int</span> L = v.length();</code></pre> 10373</div> 10374</div> 10375<div class="paragraph"> 10376<p>sets the constant <em>L</em> to 3. 10377The type returned by <strong>.length</strong>() on a matrix is <strong>int</strong>, and the value 10378returned is a constant expression.</p> 10379</div> 10380</div> 10381<div class="sect2"> 10382<h3 id="structure-and-array-operations">5.7. Structure and Array Operations</h3> 10383<div class="paragraph"> 10384<p>The members of a structure and the <strong>length</strong>() method of an array are 10385selected using the period (<strong>.</strong>).</p> 10386</div> 10387<div class="paragraph"> 10388<p>In total, only the following operators are allowed to operate on arrays and 10389structures as whole entities:</p> 10390</div> 10391<table class="tableblock frame-all grid-all fit-content"> 10392<colgroup> 10393<col> 10394<col> 10395</colgroup> 10396<tbody> 10397<tr> 10398<td class="tableblock halign-left valign-top"><p class="tableblock">field selector</p></td> 10399<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>.</strong></p></td> 10400</tr> 10401<tr> 10402<td class="tableblock halign-left valign-top"><p class="tableblock">equality</p></td> 10403<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>==</strong> <strong>!=</strong></p></td> 10404</tr> 10405<tr> 10406<td class="tableblock halign-left valign-top"><p class="tableblock">assignment</p></td> 10407<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>=</strong></p></td> 10408</tr> 10409<tr> 10410<td class="tableblock halign-left valign-top"><p class="tableblock">Ternary operator</p></td> 10411<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>?:</strong></p></td> 10412</tr> 10413<tr> 10414<td class="tableblock halign-left valign-top"><p class="tableblock">Sequence operator</p></td> 10415<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>,</strong></p></td> 10416</tr> 10417<tr> 10418<td class="tableblock halign-left valign-top"><p class="tableblock">indexing (arrays only)</p></td> 10419<td class="tableblock halign-left valign-top"><p class="tableblock"><strong>[</strong> <strong>]</strong></p></td> 10420</tr> 10421</tbody> 10422</table> 10423<div class="paragraph"> 10424<p>The equality operators and assignment operator are only allowed if the two 10425operands are same size and type. 10426The operands cannot contain any opaque types. 10427Structure types must be of the same declared structure. 10428Both array operands must be 10429explicitly 10430sized. 10431When using the equality operators, two structures are equal if and only if 10432all the members are component-wise equal, and two arrays are equal if and 10433only if all the elements are element-wise equal.</p> 10434</div> 10435<div class="paragraph"> 10436<p>Array elements are accessed using the array subscript operator (<strong>[ ]</strong>). 10437An example of accessing an array element is</p> 10438</div> 10439<div class="listingblock"> 10440<div class="content"> 10441<pre class="CodeRay highlight"><code data-lang="c++">diffuseColor += lightIntensity[<span class="integer">3</span>] * NdotL;</code></pre> 10442</div> 10443</div> 10444<div class="paragraph"> 10445<p>Array indices start at zero. 10446Array elements are accessed using an expression whose type is <strong>int</strong> or 10447<strong>uint</strong>.</p> 10448</div> 10449<div class="paragraph"> 10450<p>Behavior is undefined if a shader subscripts an array with an index less 10451than 0 or greater than or equal to the size the array was declared with.</p> 10452</div> 10453<div class="paragraph"> 10454<p>Arrays can also be accessed with the method operator (<strong>.</strong>) and the <strong>length</strong> 10455method to query the size of the array:</p> 10456</div> 10457<div class="listingblock"> 10458<div class="content"> 10459<pre class="CodeRay highlight"><code data-lang="c++">lightIntensity.length() <span class="comment">// return the size of the array</span></code></pre> 10460</div> 10461</div> 10462</div> 10463<div class="sect2"> 10464<h3 id="assignments">5.8. Assignments</h3> 10465<div class="paragraph"> 10466<p>Assignments of values to variable names are done with the assignment 10467operator (<strong>=</strong>):</p> 10468</div> 10469<div class="dlist"> 10470<dl> 10471<dt class="hdlist1"></dt> 10472<dd> 10473<p><em>lvalue-expression</em> = <em>rvalue-expression</em></p> 10474</dd> 10475</dl> 10476</div> 10477<div class="paragraph"> 10478<p>The <em>lvalue-expression</em> evaluates to an l-value. 10479The assignment operator stores the value of <em>rvalue-expression</em> into the 10480l-value and returns an r-value with the type and precision of 10481<em>lvalue-expression</em>. 10482The <em>lvalue-expression</em> and <em>rvalue-expression</em> must have the same 10483type, or the expression must have a type in the table in section 10484“<a href="#implicit-conversions">Implicit Conversions</a>” that converts to the type 10485of <em>lvalue-expression</em>, in which case an implicit conversion will be done on 10486the <em>rvalue-expression</em> before the assignment is done. 10487Any other desired type-conversions must be specified explicitly via a 10488constructor. 10489It is a compile-time error if the l-value is not writable. 10490Variables that are built-in types, entire structures or arrays, structure 10491members, l-values with the field selector (<strong>.</strong>) applied to select components 10492or swizzles without repeated fields, l-values within parentheses, and 10493l-values dereferenced with the array subscript operator (<strong>[ ]</strong>) are all 10494l-values. 10495Other binary or unary expressions, function names, swizzles with repeated 10496fields, and constants cannot be l-values. 10497The ternary operator (<strong>?:</strong>) is also not allowed as an l-value. 10498Using an incorrect expression as an l-value results in a compile-time error.</p> 10499</div> 10500<div class="paragraph"> 10501<p>Expressions on the left of an assignment are evaluated before expressions on 10502the right of the assignment.</p> 10503</div> 10504<div class="paragraph"> 10505<p>The other assignment operators are</p> 10506</div> 10507<div class="ulist"> 10508<ul> 10509<li> 10510<p>add into (<strong>+=</strong>)</p> 10511</li> 10512<li> 10513<p>subtract from (<strong>-=</strong>)</p> 10514</li> 10515<li> 10516<p>multiply into (<strong>*=</strong>)</p> 10517</li> 10518<li> 10519<p>divide into (<strong>/=</strong>)</p> 10520</li> 10521<li> 10522<p>modulus into (<strong>%=</strong>)</p> 10523</li> 10524<li> 10525<p>left shift by (<strong><<=</strong>)</p> 10526</li> 10527<li> 10528<p>right shift by (<strong>>>=</strong>)</p> 10529</li> 10530<li> 10531<p>and into (<strong>&=</strong>)</p> 10532</li> 10533<li> 10534<p>inclusive-or into (<strong>|=</strong>)</p> 10535</li> 10536<li> 10537<p>exclusive-or into (<strong>^=</strong>)</p> 10538</li> 10539</ul> 10540</div> 10541<div class="paragraph"> 10542<p>where the general expression</p> 10543</div> 10544<div class="dlist"> 10545<dl> 10546<dt class="hdlist1"></dt> 10547<dd> 10548<p><em>lvalue</em> <em>op</em>= <em>expression</em></p> 10549</dd> 10550</dl> 10551</div> 10552<div class="paragraph"> 10553<p>is equivalent to</p> 10554</div> 10555<div class="dlist"> 10556<dl> 10557<dt class="hdlist1"></dt> 10558<dd> 10559<p><em>lvalue</em> = <em>lvalue</em> <em>op</em> <em>expression</em></p> 10560</dd> 10561</dl> 10562</div> 10563<div class="paragraph"> 10564<p>where <em>lvalue</em> is the value returned by <em>lvalue-expression</em>, <em>op</em> is as 10565described below, and the <em>lvalue-expression</em> and <em>expression</em> must satisfy 10566the semantic requirements of both <em>op</em> and equals (<strong>=</strong>).</p> 10567</div> 10568<div class="paragraph"> 10569<p>Reading a variable before writing (or initializing) it is legal, however the 10570value is undefined.</p> 10571</div> 10572</div> 10573<div class="sect2"> 10574<h3 id="expressions">5.9. Expressions</h3> 10575<div class="paragraph"> 10576<p>Expressions in the shading language are built from the following:</p> 10577</div> 10578<div class="ulist"> 10579<ul> 10580<li> 10581<p>Constants of type <strong>bool</strong>, all integral types, all floating-point types, 10582all vector types, and all matrix types.</p> 10583</li> 10584<li> 10585<p>Constructors of all types.</p> 10586</li> 10587<li> 10588<p>Variable names of all types.</p> 10589</li> 10590<li> 10591<p>An array, vector, or matrix expression with the <strong>length</strong>() method 10592applied.</p> 10593</li> 10594<li> 10595<p>Subscripted arrays.</p> 10596</li> 10597<li> 10598<p>Function calls that return values. 10599In some cases, function calls returning <strong>void</strong> are also allowed in 10600expressions as specified below.</p> 10601</li> 10602<li> 10603<p>Component field selectors and array subscript results.</p> 10604</li> 10605<li> 10606<p>Parenthesized expressions. 10607Any expression, including expressions with void type can be 10608parenthesized. 10609Parentheses can be used to group operations. 10610Operations within parentheses are done before operations across 10611parentheses.</p> 10612</li> 10613<li> 10614<p>The arithmetic binary operators add (<strong>+</strong>), subtract (<strong>-</strong>), multiply 10615(<strong>*</strong>), and divide (<strong>/</strong>) operate on integer and floating-point scalars, 10616vectors, and matrices. 10617If the fundamental types in the operands do not match, then the 10618conversions from “<a href="#implicit-conversions">Implicit Conversions</a>” are 10619applied to create matching types. 10620All arithmetic binary operators result in the same fundamental type 10621(signed integer, unsigned integer, single-precision floating-point, or 10622double-precision floating-point) as the operands they operate on, after 10623operand type conversion. 10624After conversion, the following cases are valid</p> 10625<div class="ulist"> 10626<ul> 10627<li> 10628<p>The two operands are scalars. 10629In this case the operation is applied, resulting in a scalar.</p> 10630</li> 10631<li> 10632<p>One operand is a scalar, and the other is a vector or matrix. 10633In this case, the scalar operation is applied independently to each 10634component of the vector or matrix, resulting in the same size vector or 10635matrix.</p> 10636</li> 10637<li> 10638<p>The two operands are vectors of the same size. 10639In this case, the operation is done component-wise resulting in the 10640same size vector.</p> 10641</li> 10642<li> 10643<p>The operator is add (<strong>+</strong>), subtract (<strong>-</strong>), or divide (<strong>/</strong>), and the 10644operands are matrices with the same number of rows and the same number 10645of columns. 10646In this case, the operation is done component-wise resulting in the 10647same size matrix.</p> 10648</li> 10649<li> 10650<p>The operator is multiply (<strong>*</strong>), where both operands are matrices or one 10651operand is a vector and the other a matrix. 10652A right vector operand is treated as a column vector and a left vector 10653operand as a row vector. 10654In all these cases, it is required that the number of columns of the 10655left operand is equal to the number of rows of the right operand. 10656Then, the multiply (<strong>*</strong>) operation does a linear algebraic multiply, 10657yielding an object that has the same number of rows as the left operand 10658and the same number of columns as the right operand. 10659“<a href="#vector-and-matrix-operations">Vector and Matrix Operations</a>” 10660explains in more detail how vectors and matrices are operated on.</p> 10661<div class="openblock"> 10662<div class="content"> 10663<div class="paragraph"> 10664<p>All other cases result in a compile-time error.</p> 10665</div> 10666<div class="paragraph"> 10667<p>Use the built-in functions <strong>dot</strong>, <strong>cross</strong>, <strong>matrixCompMult</strong>, and 10668<strong>outerProduct</strong>, to get, respectively, vector dot product, vector cross 10669product, matrix component-wise multiplication, and the matrix product of a 10670column vector times a row vector.</p> 10671</div> 10672</div> 10673</div> 10674</li> 10675</ul> 10676</div> 10677</li> 10678<li> 10679<p>The operator modulus (<strong>%</strong>) operates on signed or unsigned integers or 10680integer vectors. 10681If the fundamental types in the operands do not match, then the 10682conversions from “<a href="#implicit-conversions">Implicit Conversions</a>” are 10683applied to create matching types. 10684The operands cannot be vectors of differing size; this is 10685a compile-time error. 10686If one operand is a scalar and the other vector, then the scalar is 10687applied component-wise to the vector, resulting in the same type as the 10688vector. 10689If both are vectors of the same size, the result is computed 10690component-wise. 10691The resulting value is undefined for any component computed with a 10692second operand that is zero, while results for other components with 10693non-zero second operands remain defined. 10694If both operands are non-negative, then the remainder is non-negative. 10695Results are undefined if one or both operands are negative. 10696The operator modulus (<strong>%</strong>) is not defined for any other data types 10697(non-integer types).</p> 10698</li> 10699<li> 10700<p>The arithmetic unary operators negate (<strong>-</strong>), post- and pre-increment and 10701decrement (<strong>--</strong> and <strong>++</strong>) operate on integer or floating-point values 10702(including vectors and matrices). 10703All unary operators work component-wise on their operands. 10704These result with the same type they operated on. 10705For post- and pre-increment and decrement, the expression must be a writable 10706l-value. 10707Pre-increment and pre-decrement add or subtract 1 or 1.0 to the contents 10708of the expression they operate on, and the value of the pre-increment or 10709pre-decrement expression is the resulting value of that modification. 10710Post-increment and post-decrement expressions add or subtract 1 or 1.0 10711to the contents of the expression they operate on, but the resulting 10712expression has the expression’s value before the post-increment or 10713post-decrement was executed.</p> 10714</li> 10715<li> 10716<p>The relational operators greater than (<strong>></strong>), less than (<strong><</strong>), greater 10717than or equal (<strong>>=</strong>), and less than or equal (<strong><=</strong>) operate only on 10718scalar integer and scalar floating-point expressions. 10719The result is scalar Boolean. 10720Either the operands' types must match, or the conversions from section 10721“<a href="#implicit-conversions">Implicit Conversions</a>” will be applied to 10722obtain matching types. 10723To do component-wise relational comparisons on vectors, use the built-in 10724functions <strong>lessThan</strong>, <strong>lessThanEqual</strong>, <strong>greaterThan</strong>, and 10725<strong>greaterThanEqual.</strong></p> 10726</li> 10727<li> 10728<p>The equality operators <strong>equal</strong> (<strong>==</strong>), and not equal (<strong>!=</strong>) operate on 10729all types except opaque types, aggregates that contain opaque types, 10730subroutine uniforms, and aggregates that contain subroutine uniforms. 10731They result in a scalar Boolean. 10732If the operand types do not match, then there must be a conversion from 10733“<a href="#implicit-conversions">Implicit Conversions</a>” applied to one operand 10734that can make them match, in which case this conversion is done. 10735For vectors, matrices, structures, and arrays, all components, members, 10736or elements of one operand must equal the corresponding components, 10737members, or elements in the other operand for the operands to be 10738considered equal. 10739To get a vector of component-wise equality results for vectors, use the 10740built-in functions <strong>equal</strong> and <strong>notEqual</strong>.</p> 10741</li> 10742<li> 10743<p>The logical binary operators and (<strong>&&</strong>), or (<strong>||</strong>), and exclusive or 10744(<strong>^^</strong>) operate only on two Boolean expressions and result in a Boolean 10745expression. 10746And (<strong>&&</strong>) will only evaluate the right hand operand if the left hand 10747operand evaluated to <strong>true</strong>. 10748Or (<strong>||</strong>) will only evaluate the right hand operand if the left hand 10749operand evaluated to <strong>false</strong>. 10750Exclusive or (<strong>^^</strong>) will always evaluate both operands.</p> 10751</li> 10752<li> 10753<p>The logical unary operator not (<strong>!</strong>). 10754It operates only on a Boolean expression and results in a Boolean 10755expression. 10756To operate on a vector, use the built-in function <strong>not</strong>.</p> 10757</li> 10758<li> 10759<p>The sequence (<strong>,</strong>) operator that operates on expressions by returning 10760the type and value of the right-most expression in a comma separated 10761list of expressions. 10762All expressions are evaluated, in order, from left to right. 10763The operands to the sequence operator may have <strong>void</strong> type. 10764Opaque types cannot be used with the sequence (,) operator.</p> 10765</li> 10766<li> 10767<p>The ternary selection operator (<strong>?:</strong>). 10768It operates on three expressions (<em>exp1</em> <strong>?</strong> <em>exp2</em> <strong>:</strong> <em>exp3</em>). 10769This operator evaluates the first expression, which must result in a 10770scalar Boolean. 10771If the result is true, it selects to evaluate the second expression, 10772otherwise it selects to evaluate the third expression. 10773Only one of the second and third expressions is evaluated. 10774The second and third expressions cannot be opaque types, 10775or there will be a compile-time error. 10776Otherwise, 10777the second and third expressions can be any type, including <strong>void</strong>, as 10778long their types match, or there is a conversion in section 10779“<a href="#implicit-conversions">Implicit Conversions</a>” that can be applied to 10780one of the expressions to make their types match. 10781This resulting matching type is the type of the entire expression.</p> 10782</li> 10783<li> 10784<p>The one’s complement operator (<strong>~</strong>). 10785The operand must be of type signed or unsigned integer or integer 10786vector, and the result is the one’s complement of its operand; each bit 10787of each component is complemented, including any sign bits.</p> 10788</li> 10789<li> 10790<p>The shift operators (<strong><<</strong>) and (<strong>>></strong>). 10791For both operators, the operands must be signed or unsigned integers or 10792integer vectors. 10793One operand can be signed while the other is unsigned. 10794In all cases, the resulting type will be the same type as the left 10795operand. 10796If the first operand is a scalar, the second operand has to be a scalar 10797as well. 10798If the first operand is a vector, the second operand must be a scalar or 10799a vector with the same size as the first operand, and the result is 10800computed component-wise. 10801The result is undefined if the right operand is negative, or greater 10802than or equal to the number of bits in the left expression’s base type. 10803The value of E1 << E2 is E1 (interpreted as a bit pattern) left-shifted 10804by E2 bits. 10805The value of E1 >> E2 is E1 right-shifted by E2 bit positions. 10806If E1 is a signed integer, the right-shift will extend the sign bit. 10807If E1 is an unsigned integer, the right-shift will zero-extend.</p> 10808</li> 10809<li> 10810<p>The bitwise operators and (<strong>&</strong>), exclusive-or (<strong>^</strong>), and inclusive-or 10811(<strong>|</strong>). 10812The operands must be of type signed or unsigned integers or integer 10813vectors. 10814The operands cannot be vectors of differing size; this is a compile-time error. 10815If one operand is a scalar and the other a vector, the scalar is applied 10816component-wise to the vector, resulting in the same type as the vector. 10817If the fundamental types in the operands do not match, then the 10818conversions from “<a href="#implicit-conversions">Implicit Conversions</a>” are 10819applied to create matching types, and this will be the resulting 10820fundamental type. 10821For and (<strong>&</strong>), the result is the bitwise-and function of the operands. 10822For exclusive-or (<strong>^</strong>), the result is the bitwise exclusive-or function 10823of the operands. 10824For inclusive-or (<strong>|</strong>), the result is the bitwise inclusive-or function 10825of the operands.</p> 10826</li> 10827</ul> 10828</div> 10829<div class="paragraph"> 10830<p>For a complete specification of the syntax of expressions, see 10831“<a href="#shading-language-grammar">Shading Language Grammar</a>”.</p> 10832</div> 10833</div> 10834<div class="sect2"> 10835<h3 id="vector-and-matrix-operations">5.10. Vector and Matrix Operations</h3> 10836<div class="paragraph"> 10837<p>With a few exceptions, operations are component-wise. 10838Usually, when an operator operates on a vector or matrix, it is operating 10839independently on each component of the vector or matrix, in a component-wise 10840fashion. 10841For example,</p> 10842</div> 10843<div class="listingblock"> 10844<div class="content"> 10845<pre class="CodeRay highlight"><code data-lang="c++">vec3 v, u; 10846<span class="predefined-type">float</span> f; 10847v = u + f;</code></pre> 10848</div> 10849</div> 10850<div class="paragraph"> 10851<p>will be equivalent to</p> 10852</div> 10853<div class="listingblock"> 10854<div class="content"> 10855<pre class="CodeRay highlight"><code data-lang="c++">v.x = u.x + f; 10856v.y = u.y + f; 10857v.z = u.z + f;</code></pre> 10858</div> 10859</div> 10860<div class="paragraph"> 10861<p>And</p> 10862</div> 10863<div class="listingblock"> 10864<div class="content"> 10865<pre class="CodeRay highlight"><code data-lang="c++">vec3 v, u, w; 10866w = v + u;</code></pre> 10867</div> 10868</div> 10869<div class="paragraph"> 10870<p>will be equivalent to</p> 10871</div> 10872<div class="listingblock"> 10873<div class="content"> 10874<pre class="CodeRay highlight"><code data-lang="c++">w.x = v.x + u.x; 10875w.y = v.y + u.y; 10876w.z = v.z + u.z;</code></pre> 10877</div> 10878</div> 10879<div class="paragraph"> 10880<p>and likewise for most operators and all integer and floating-point vector 10881and matrix types. 10882The exceptions are matrix multiplied by vector, vector multiplied by matrix, 10883and matrix multiplied by matrix. 10884These do not operate component-wise, but rather perform the correct linear 10885algebraic multiply.</p> 10886</div> 10887<div class="listingblock"> 10888<div class="content"> 10889<pre class="CodeRay highlight"><code data-lang="c++">vec3 v, u; 10890mat3 m; 10891u = v * m;</code></pre> 10892</div> 10893</div> 10894<div class="paragraph"> 10895<p>is equivalent to</p> 10896</div> 10897<div class="listingblock"> 10898<div class="content"> 10899<pre class="CodeRay highlight"><code data-lang="c++">u.x = dot(v, m[<span class="integer">0</span>]); <span class="comment">// m[0] is the left column of m</span> 10900u.y = dot(v, m[<span class="integer">1</span>]); <span class="comment">// dot(a,b) is the inner (dot) product of a and b</span> 10901u.z = dot(v, m[<span class="integer">2</span>]);</code></pre> 10902</div> 10903</div> 10904<div class="paragraph"> 10905<p>And</p> 10906</div> 10907<div class="listingblock"> 10908<div class="content"> 10909<pre class="CodeRay highlight"><code data-lang="c++">u = m * v;</code></pre> 10910</div> 10911</div> 10912<div class="paragraph"> 10913<p>is equivalent to</p> 10914</div> 10915<div class="listingblock"> 10916<div class="content"> 10917<pre class="CodeRay highlight"><code data-lang="c++">u.x = m[<span class="integer">0</span>].x * v.x + m[<span class="integer">1</span>].x * v.y + m[<span class="integer">2</span>].x * v.z; 10918u.y = m[<span class="integer">0</span>].y * v.x + m[<span class="integer">1</span>].y * v.y + m[<span class="integer">2</span>].y * v.z; 10919u.z = m[<span class="integer">0</span>].z * v.x + m[<span class="integer">1</span>].z * v.y + m[<span class="integer">2</span>].z * v.z;</code></pre> 10920</div> 10921</div> 10922<div class="paragraph"> 10923<p>And</p> 10924</div> 10925<div class="listingblock"> 10926<div class="content"> 10927<pre class="CodeRay highlight"><code data-lang="c++">mat3 m, n, r; 10928r = m * n;</code></pre> 10929</div> 10930</div> 10931<div class="paragraph"> 10932<p>is equivalent to</p> 10933</div> 10934<div class="listingblock"> 10935<div class="content"> 10936<pre class="CodeRay highlight"><code data-lang="c++">r[<span class="integer">0</span>].x = m[<span class="integer">0</span>].x * n[<span class="integer">0</span>].x + m[<span class="integer">1</span>].x * n[<span class="integer">0</span>].y + m[<span class="integer">2</span>].x * n[<span class="integer">0</span>].z; 10937r[<span class="integer">1</span>].x = m[<span class="integer">0</span>].x * n[<span class="integer">1</span>].x + m[<span class="integer">1</span>].x * n[<span class="integer">1</span>].y + m[<span class="integer">2</span>].x * n[<span class="integer">1</span>].z; 10938r[<span class="integer">2</span>].x = m[<span class="integer">0</span>].x * n[<span class="integer">2</span>].x + m[<span class="integer">1</span>].x * n[<span class="integer">2</span>].y + m[<span class="integer">2</span>].x * n[<span class="integer">2</span>].z; 10939r[<span class="integer">0</span>].y = m[<span class="integer">0</span>].y * n[<span class="integer">0</span>].x + m[<span class="integer">1</span>].y * n[<span class="integer">0</span>].y + m[<span class="integer">2</span>].y * n[<span class="integer">0</span>].z; 10940r[<span class="integer">1</span>].y = m[<span class="integer">0</span>].y * n[<span class="integer">1</span>].x + m[<span class="integer">1</span>].y * n[<span class="integer">1</span>].y + m[<span class="integer">2</span>].y * n[<span class="integer">1</span>].z; 10941r[<span class="integer">2</span>].y = m[<span class="integer">0</span>].y * n[<span class="integer">2</span>].x + m[<span class="integer">1</span>].y * n[<span class="integer">2</span>].y + m[<span class="integer">2</span>].y * n[<span class="integer">2</span>].z; 10942r[<span class="integer">0</span>].z = m[<span class="integer">0</span>].z * n[<span class="integer">0</span>].x + m[<span class="integer">1</span>].z * n[<span class="integer">0</span>].y + m[<span class="integer">2</span>].z * n[<span class="integer">0</span>].z; 10943r[<span class="integer">1</span>].z = m[<span class="integer">0</span>].z * n[<span class="integer">1</span>].x + m[<span class="integer">1</span>].z * n[<span class="integer">1</span>].y + m[<span class="integer">2</span>].z * n[<span class="integer">1</span>].z; 10944r[<span class="integer">2</span>].z = m[<span class="integer">0</span>].z * n[<span class="integer">2</span>].x + m[<span class="integer">1</span>].z * n[<span class="integer">2</span>].y + m[<span class="integer">2</span>].z * n[<span class="integer">2</span>].z;</code></pre> 10945</div> 10946</div> 10947<div class="paragraph"> 10948<p>and similarly for other sizes of vectors and matrices.</p> 10949</div> 10950</div> 10951<div class="sect2"> 10952<h3 id="out-of-bounds-accesses">5.11. Out-of-Bounds Accesses</h3> 10953<div class="paragraph"> 10954<p>In the subsections described above for array, vector, matrix and structure 10955accesses, any out-of-bounds access produced undefined behavior. 10956However, if robust buffer access is enabled via the API, such 10957accesses will be bound within the memory extent of the active program. 10958It will not be possible to access memory from other programs, and accesses 10959will not result in abnormal program termination. 10960Out-of-bounds reads return undefined values, which include values from other 10961variables of the active program or zero. 10962Out-of-bounds writes may be discarded or overwrite other variables of the 10963active program, depending on the value of the computed index and how this 10964relates to the extent of the active program’s memory. 10965Applications that require defined behavior for out-of-bounds accesses should 10966range check all computed indices before dereferencing an array.</p> 10967</div> 10968</div> 10969<div class="sect2"> 10970<h3 id="specialization-constant-operations">5.12. Specialization-Constant Operations</h3> 10971<div class="paragraph"> 10972<p>Specialization-constant operations are only available when targeting SPIR-V.</p> 10973</div> 10974<div class="paragraph"> 10975<p>Only some operations discussed in this section may be applied to a 10976specialization constant and still yield a result that is a specialization 10977constant. 10978The operations that do so are listed below. 10979When a specialization constant is operated on with one of these operators 10980and with another constant or specialization constant, the result is 10981implicitly a specialization constant.</p> 10982</div> 10983<div class="ulist"> 10984<ul> 10985<li> 10986<p><strong>int</strong>(), <strong>uint</strong>(), and <strong>bool</strong>() constructors for type conversions from 10987any of the following types to any of the following types:</p> 10988<div class="ulist"> 10989<ul> 10990<li> 10991<p><strong>int</strong></p> 10992</li> 10993<li> 10994<p><strong>uint</strong></p> 10995</li> 10996<li> 10997<p><strong>bool</strong></p> 10998</li> 10999</ul> 11000</div> 11001</li> 11002<li> 11003<p>vector versions of the above conversion constructors</p> 11004</li> 11005<li> 11006<p>allowed implicit conversions of the above</p> 11007</li> 11008<li> 11009<p>swizzles (e.g. <code>foo.yx</code>)</p> 11010</li> 11011<li> 11012<p>the following when applied to integer or unsigned integer types:</p> 11013<div class="ulist"> 11014<ul> 11015<li> 11016<p>unary negative (<strong>-</strong>)</p> 11017</li> 11018<li> 11019<p>binary operations (<strong>+</strong>, <strong>-</strong>, <strong>*</strong>, <strong>/</strong>, <strong>%</strong>)</p> 11020</li> 11021<li> 11022<p>shift (<strong><<</strong>, <strong>>></strong>)</p> 11023</li> 11024<li> 11025<p>bitwise operations (<strong>&</strong>, <strong>|</strong>, <strong>^</strong>)</p> 11026</li> 11027</ul> 11028</div> 11029</li> 11030<li> 11031<p>the following when applied to integer or unsigned integer scalar types:</p> 11032<div class="ulist"> 11033<ul> 11034<li> 11035<p>comparison (<strong>==</strong>, <strong>!=</strong>, <strong>></strong>, <strong>>=</strong>, <strong><</strong>, <strong>⇐</strong>)</p> 11036</li> 11037</ul> 11038</div> 11039</li> 11040<li> 11041<p>The following when applied to the Boolean scalar type:</p> 11042<div class="ulist"> 11043<ul> 11044<li> 11045<p>not (<strong>!</strong>)</p> 11046</li> 11047<li> 11048<p>logical operations (<strong>&&</strong>, <strong>||</strong>, <strong>^^</strong>)</p> 11049</li> 11050<li> 11051<p>comparison (<strong>==</strong>, <strong>!=</strong>)</p> 11052</li> 11053</ul> 11054</div> 11055</li> 11056<li> 11057<p>the ternary operator (<strong>?:</strong>)</p> 11058</li> 11059</ul> 11060</div> 11061</div> 11062</div> 11063</div> 11064<div class="sect1"> 11065<h2 id="statements-and-structure">6. Statements and Structure</h2> 11066<div class="sectionbody"> 11067<div class="paragraph"> 11068<p>The fundamental building blocks of the OpenGL Shading Language are:</p> 11069</div> 11070<div class="ulist"> 11071<ul> 11072<li> 11073<p>statements and declarations</p> 11074</li> 11075<li> 11076<p>function definitions</p> 11077</li> 11078<li> 11079<p>selection (<strong>if</strong>-<strong>else</strong> and <strong>switch</strong>-<strong>case</strong>-<strong>default</strong>)</p> 11080</li> 11081<li> 11082<p>iteration (<strong>for</strong>, <strong>while</strong>, and <strong>do</strong>-<strong>while</strong>)</p> 11083</li> 11084<li> 11085<p>jumps (<strong>discard</strong>, <strong>return</strong>, <strong>break</strong>, and <strong>continue</strong>)</p> 11086</li> 11087</ul> 11088</div> 11089<div class="paragraph"> 11090<p>The overall structure of a shader is as follows</p> 11091</div> 11092<div class="openblock bnf"> 11093<div class="content"> 11094<div class="dlist"> 11095<dl> 11096<dt class="hdlist1"><em>translation-unit</em> : </dt> 11097<dd> 11098<p><em>global-declaration</em><br> 11099<em>translation-unit</em> <em>global-declaration</em></p> 11100</dd> 11101<dt class="hdlist1"><em>global-declaration</em> : </dt> 11102<dd> 11103<p><em>function-definition</em><br> 11104<em>declaration</em></p> 11105</dd> 11106</dl> 11107</div> 11108</div> 11109</div> 11110<div class="paragraph"> 11111<p>That is, a shader is a sequence of declarations and function bodies. 11112Function bodies are defined as</p> 11113</div> 11114<div class="openblock bnf"> 11115<div class="content"> 11116<div class="dlist"> 11117<dl> 11118<dt class="hdlist1"><em>function-definition</em> : </dt> 11119<dd> 11120<p><em>function-prototype</em> <strong>{</strong> <em>statement-list</em> <strong>}</strong></p> 11121</dd> 11122<dt class="hdlist1"><em>statement-list</em> : </dt> 11123<dd> 11124<p><em>statement</em><br> 11125<em>statement-list</em> <em>statement</em></p> 11126</dd> 11127<dt class="hdlist1"><em>statement</em> : </dt> 11128<dd> 11129<p><em>compound-statement</em><br> 11130<em>simple-statement</em></p> 11131</dd> 11132</dl> 11133</div> 11134</div> 11135</div> 11136<div class="paragraph"> 11137<p>Curly braces are used to group sequences of statements into compound 11138statements.</p> 11139</div> 11140<div class="openblock bnf"> 11141<div class="content"> 11142<div class="dlist"> 11143<dl> 11144<dt class="hdlist1"><em>compound-statement</em> : </dt> 11145<dd> 11146<p><strong>{</strong> <em>statement-list</em> <strong>}</strong></p> 11147</dd> 11148<dt class="hdlist1"><em>simple-statement</em> : </dt> 11149<dd> 11150<p><em>declaration-statement</em><br> 11151<em>expression-statement</em><br> 11152<em>selection-statement</em><br> 11153<em>iteration-statement</em><br> 11154<em>jump-statement</em></p> 11155</dd> 11156</dl> 11157</div> 11158</div> 11159</div> 11160<div class="paragraph"> 11161<p>Simple declaration, expression, and jump statements end in a semi-colon.</p> 11162</div> 11163<div class="paragraph"> 11164<p>This above is slightly simplified, and the complete grammar specified in 11165“<a href="#shading-language-grammar">Shading Language Grammar</a>” should be used as 11166the definitive specification.</p> 11167</div> 11168<div class="paragraph"> 11169<p>Declarations and expressions have already been discussed.</p> 11170</div> 11171<div class="sect2"> 11172<h3 id="function-definitions">6.1. Function Definitions</h3> 11173<div class="paragraph"> 11174<p>As indicated by the grammar above, a valid shader is a sequence of global 11175declarations and function definitions. 11176A function is declared as the following example shows:</p> 11177</div> 11178<div class="listingblock"> 11179<div class="content"> 11180<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// prototype</span> 11181returnType functionName (type0 arg0, type1 arg1, ..., typen argn);</code></pre> 11182</div> 11183</div> 11184<div class="paragraph"> 11185<p>and a function is defined like</p> 11186</div> 11187<div class="listingblock"> 11188<div class="content"> 11189<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// definition</span> 11190returnType functionName (type0 arg0, type1 arg1, ..., typen argn) 11191{ 11192 <span class="comment">// do some computation</span> 11193 <span class="keyword">return</span> returnValue; 11194}</code></pre> 11195</div> 11196</div> 11197<div class="paragraph"> 11198<p>where <em>returnType</em> must be present and cannot be void, or:</p> 11199</div> 11200<div class="listingblock"> 11201<div class="content"> 11202<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">void</span> functionName (type0 arg0, type1 arg1, ..., typen argn) 11203{ 11204 <span class="comment">// do some computation</span> 11205 <span class="keyword">return</span>; <span class="comment">// optional</span> 11206}</code></pre> 11207</div> 11208</div> 11209<div class="paragraph"> 11210<p>If the type of <em>returnValue</em> does not match <em>returnType</em>, there must be an 11211implicit conversion in “<a href="#implicit-conversions">Implicit Conversions</a>” 11212that converts the type of <em>returnValue</em> to <em>returnType</em>, or a compile-time 11213error will result.</p> 11214</div> 11215<div class="paragraph"> 11216<p>Each of the <em>typeN</em> must include a type and can optionally include parameter 11217qualifiers. 11218The formal argument names (<em>args</em> above) in the declarations are optional 11219for both the declaration and definition forms.</p> 11220</div> 11221<div class="paragraph"> 11222<p>A function is called by using its name followed by a list of arguments in 11223parentheses.</p> 11224</div> 11225<div class="paragraph"> 11226<p>Arrays are allowed as arguments and as the return type. 11227In both cases, the array must be 11228explicitly 11229sized. 11230An array is passed or returned by using just its name, without brackets, and 11231the size of the array must match the size specified in the function’s 11232declaration.</p> 11233</div> 11234<div class="paragraph"> 11235<p>Structures are also allowed as argument types. 11236The return type can also be a structure.</p> 11237</div> 11238<div class="paragraph"> 11239<p>See “<a href="#shading-language-grammar">Shading Language Grammar</a>” for the 11240definitive reference on the syntax to declare and define functions.</p> 11241</div> 11242<div class="paragraph"> 11243<p>All functions must be either declared with a prototype or defined with a 11244body before they are called. 11245For example:</p> 11246</div> 11247<div class="listingblock"> 11248<div class="content"> 11249<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> myfunc (<span class="predefined-type">float</span> f, <span class="comment">// f is an input parameter</span> 11250 out <span class="predefined-type">float</span> g); <span class="comment">// g is an output parameter</span></code></pre> 11251</div> 11252</div> 11253<div class="paragraph"> 11254<p>Functions that return no value must be declared as <strong>void</strong>. 11255A <strong>void</strong> function can only use <strong>return</strong> without a return argument, even if 11256the return argument has <strong>void</strong> type. 11257Return statements only accept values:</p> 11258</div> 11259<div class="listingblock"> 11260<div class="content"> 11261<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">void</span> func1() { } 11262<span class="directive">void</span> func2() { <span class="keyword">return</span> func1(); } <span class="comment">// illegal return statement</span></code></pre> 11263</div> 11264</div> 11265<div class="paragraph"> 11266<p>Only a precision qualifier is allowed on the return type of a function. 11267Formal parameters can have parameter, precision, and memory qualifiers, but 11268no other qualifiers.</p> 11269</div> 11270<div class="paragraph"> 11271<p>Functions that accept no input arguments need not use <strong>void</strong> in the argument 11272list because prototypes (or definitions) are required and therefore there is 11273no ambiguity when an empty argument list “( )” is declared. 11274The idiom “(<strong>void</strong>)” as a parameter list is provided for convenience.</p> 11275</div> 11276<div class="paragraph"> 11277<p>Function names can be overloaded. 11278The same function name can be used for multiple functions, as long as the 11279parameter types differ. 11280If a function name is declared twice with the same parameter types, then the 11281return types and all qualifiers must also match, and it is the same function 11282being declared.</p> 11283</div> 11284<div class="paragraph"> 11285<p>For example,</p> 11286</div> 11287<div class="listingblock"> 11288<div class="content"> 11289<pre class="CodeRay highlight"><code data-lang="c++">vec4 f(in vec4 x, out vec4 y); <span class="comment">// (A)</span> 11290vec4 f(in vec4 x, out uvec4 y); <span class="comment">// (B) okay, different argument type</span> 11291vec4 f(in ivec4 x, out dvec4 y); <span class="comment">// (C) okay, different argument type</span> 11292<span class="predefined-type">int</span> f(in vec4 x, out vec4 y); <span class="comment">// error, only return type differs</span> 11293vec4 f(in vec4 x, in vec4 y); <span class="comment">// error, only qualifier differs</span> 11294vec4 f(<span class="directive">const</span> in vec4 x, out vec4 y); <span class="comment">// error, only qualifier differs</span></code></pre> 11295</div> 11296</div> 11297<div class="paragraph"> 11298<p>When function calls are resolved, an exact type match for all the arguments 11299is sought. 11300If an exact match is found, all other functions are ignored, and the exact 11301match is used. 11302If no exact match is found, then the implicit conversions in section 11303“<a href="#implicit-conversions">Implicit Conversions</a>” will be applied to find a 11304match. 11305Mismatched types on input parameters (<strong>in</strong> or <strong>inout</strong> or default) <strong>must</strong> 11306have a conversion from the calling argument type to the formal parameter 11307type. 11308Mismatched types on output parameters (<strong>out</strong> or <strong>inout</strong>) must have a 11309conversion from the formal parameter type to the calling argument type.</p> 11310</div> 11311<div class="paragraph"> 11312<p>If implicit conversions can be used to find more than one matching function, 11313a single best-matching function is sought. 11314To determine a best match, the conversions between calling argument and 11315formal parameter types are compared for each function argument and pair of 11316matching functions. 11317After these comparisons are performed, each pair of matching functions are 11318compared. 11319A function declaration <em>A</em> is considered a better match than function 11320declaration <em>B</em> if</p> 11321</div> 11322<div class="ulist"> 11323<ul> 11324<li> 11325<p>for at least one function argument, the conversion for that argument in 11326<em>A</em> is better than the corresponding conversion in <em>B</em>; and</p> 11327</li> 11328<li> 11329<p>there is no function argument for which the conversion in <em>B</em> is better 11330than the corresponding conversion in <em>A</em>.</p> 11331</li> 11332</ul> 11333</div> 11334<div class="paragraph"> 11335<p>If a single function declaration is considered a better match than every 11336other matching function declaration, it will be used. 11337Otherwise, a compile-time semantic error for an ambiguous overloaded 11338function call occurs.</p> 11339</div> 11340<div class="paragraph"> 11341<p>To determine whether the conversion for a single argument in one match is 11342better than that for another match, the following rules are applied, in 11343order:</p> 11344</div> 11345<div class="olist arabic"> 11346<ol class="arabic"> 11347<li> 11348<p>An exact match is better than a match involving any implicit conversion.</p> 11349</li> 11350<li> 11351<p>A match involving an implicit conversion from <strong>float</strong> to <strong>double</strong> is 11352better than a match involving any other implicit conversion.</p> 11353</li> 11354<li> 11355<p>A match involving an implicit conversion from either <strong>int</strong> or <strong>uint</strong> to 11356<strong>float</strong> is better than a match involving an implicit conversion from 11357either <strong>int</strong> or <strong>uint</strong> to <strong>double</strong>.</p> 11358</li> 11359</ol> 11360</div> 11361<div class="paragraph"> 11362<p>If none of the rules above apply to a particular pair of conversions, 11363neither conversion is considered better than the other.</p> 11364</div> 11365<div class="paragraph"> 11366<p>For the example function prototypes (A), (B), and © above, the following 11367examples show how the rules apply to different sets of calling argument 11368types:</p> 11369</div> 11370<div class="listingblock"> 11371<div class="content"> 11372<pre class="CodeRay highlight"><code data-lang="c++">f(vec4, vec4) <span class="comment">// exact match of vec4 f(in vec4 x, out vec4 y)</span> 11373f(vec4, uvec4) <span class="comment">// exact match of vec4 f(in vec4 x, out uvec4 y)</span> 11374f(vec4, ivec4) <span class="comment">// matched to vec4 f(in vec4 x, out vec4 y)</span> 11375 <span class="comment">// (C) not relevant, can't convert vec4 to</span> 11376 <span class="comment">// ivec4. (A) better than (B) for 2nd</span> 11377 <span class="comment">// argument (rule 3), same on first argument.</span> 11378f(ivec4, vec4); <span class="comment">// NOT matched. All three match by implicit</span> 11379 <span class="comment">// conversion. (C) is better than (A) and (B)</span> 11380 <span class="comment">// on the first argument. (A) is better than</span> 11381 <span class="comment">// (B) and (C).</span></code></pre> 11382</div> 11383</div> 11384<div class="paragraph"> 11385<p>User-defined functions can have multiple declarations, but only one 11386definition.</p> 11387</div> 11388<div class="paragraph"> 11389<p>A shader can redefine built-in functions. 11390If a built-in function is redeclared in a shader (i.e., a prototype is 11391visible) before a call to it, then the linker will only attempt to resolve 11392that call within the set of shaders that are linked with it.</p> 11393</div> 11394<div class="paragraph"> 11395<p>The function <em>main</em> is used as the entry point to a shader executable. 11396A shader need not contain a function named <em>main</em>, but one shader in a set 11397of shaders linked together to form a single shader executable must, or a 11398link-time error results. 11399This function takes no arguments, returns no value, and must be declared as 11400type <strong>void</strong>:</p> 11401</div> 11402<div class="listingblock"> 11403<div class="content"> 11404<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">void</span> main() 11405{ 11406 ... 11407}</code></pre> 11408</div> 11409</div> 11410<div class="paragraph"> 11411<p>The function <em>main</em> can contain uses of <strong>return</strong>. 11412See “<a href="#jumps">Jumps</a>” for more details.</p> 11413</div> 11414<div class="paragraph"> 11415<p>It is a compile-time or link-time error to declare or define a function 11416<strong>main</strong> with any other parameters or return type.</p> 11417</div> 11418<div class="sect3"> 11419<h4 id="function-calling-conventions">6.1.1. Function Calling Conventions</h4> 11420<div class="paragraph"> 11421<p>Functions are called by value-return. 11422This means input arguments are copied into the function at call time, and 11423output arguments are copied back to the caller before function exit. 11424Because the function works with local copies of parameters, there are no 11425issues regarding aliasing of variables within a function. 11426To control what parameters are copied in and/or out through a function 11427definition or declaration:</p> 11428</div> 11429<div class="ulist"> 11430<ul> 11431<li> 11432<p>The keyword <strong>in</strong> is used as a qualifier to denote a parameter is to be 11433copied in, but not copied out.</p> 11434</li> 11435<li> 11436<p>The keyword <strong>out</strong> is used as a qualifier to denote a parameter is to be 11437copied out, but not copied in. 11438This should be used whenever possible to avoid unnecessarily copying 11439parameters in.</p> 11440</li> 11441<li> 11442<p>The keyword <strong>inout</strong> is used as a qualifier to denote the parameter is to 11443be both copied in and copied out. 11444It means the same thing as specifying both <strong>in</strong> and <strong>out</strong>.</p> 11445</li> 11446<li> 11447<p>A function parameter declared with no such qualifier means the same 11448thing as specifying <strong>in</strong>.</p> 11449</li> 11450</ul> 11451</div> 11452<div class="paragraph"> 11453<p>All arguments are evaluated at call time, exactly once, in order, from left 11454to right. 11455Evaluation of an <strong>in</strong> parameter results in a value that is copied to the 11456formal parameter. 11457Evaluation of an <strong>out</strong> parameter results in an l-value that is used to copy 11458out a value when the function returns. 11459Evaluation of an <strong>inout</strong> parameter results in both a value and an l-value; 11460the value is copied to the formal parameter at call time and the l-value is 11461used to copy out a value when the function returns.</p> 11462</div> 11463<div class="paragraph"> 11464<p>The order in which output parameters are copied back to the caller is 11465undefined.</p> 11466</div> 11467<div class="paragraph"> 11468<p>If the function matching described in the previous section required argument 11469type conversions, these conversions are applied at copy-in and copy-out 11470times.</p> 11471</div> 11472<div class="paragraph"> 11473<p>In a function, writing to an input-only parameter is allowed. 11474Only the function’s copy is modified. 11475This can be prevented by declaring a parameter with the <strong>const</strong> qualifier.</p> 11476</div> 11477<div class="paragraph"> 11478<p>When calling a function, expressions that do not evaluate to l-values cannot 11479be passed to parameters declared as <strong>out</strong> or <strong>inout</strong>, or a compile-time error 11480results.</p> 11481</div> 11482<div class="openblock bnf"> 11483<div class="content"> 11484<div class="dlist"> 11485<dl> 11486<dt class="hdlist1"><em>function-prototype</em> : </dt> 11487<dd> 11488<p><em>precision-qualifier</em> <em>type</em> <em>function-name</em> <strong>(</strong> <em>parameter-qualifiers</em> 11489<em>precision-qualifier</em> <em>type</em> <em>name</em> <em>array-specifier</em> <strong>,</strong> …​ 11490<strong>)</strong></p> 11491</dd> 11492<dt class="hdlist1"><em>type</em> : </dt> 11493<dd> 11494<p>any basic type, array type, structure name, or structure definition</p> 11495</dd> 11496<dt class="hdlist1"><em>parameter-qualifiers</em> : </dt> 11497<dd> 11498<p><em>empty</em><br> 11499list of <em>parameter-qualifier</em></p> 11500</dd> 11501<dt class="hdlist1"><em>parameter-qualifier</em> : </dt> 11502<dd> 11503<p><strong>const</strong><br> 11504<strong>in</strong><br> 11505<strong>out</strong><br> 11506<strong>inout</strong><br> 11507<strong>precise</strong><br> 11508<em>memory-qualifier</em><br> 11509<em>precision-qualifier</em></p> 11510</dd> 11511<dt class="hdlist1"><em>name</em> : </dt> 11512<dd> 11513<p>empty<br> 11514identifier</p> 11515</dd> 11516<dt class="hdlist1"><em>array-specifier</em> : </dt> 11517<dd> 11518<p>empty<br> 11519<strong>[</strong> <em>integral-constant-expression</em> <strong>]</strong></p> 11520</dd> 11521</dl> 11522</div> 11523</div> 11524</div> 11525<div class="paragraph"> 11526<p>The <strong>const</strong> qualifier cannot be used with <strong>out</strong> or <strong>inout</strong>, or 11527a compile-time error results. 11528The above is used both for function declarations (i.e., prototypes) and for 11529function definitions. 11530Hence, function definitions can have unnamed arguments.</p> 11531</div> 11532<div class="paragraph"> 11533<p>Recursion is not allowed, not even statically. 11534Static recursion is present if the static function-call graph of a program 11535contains cycles. 11536This includes all potential function calls through variables declared as 11537<strong>subroutine</strong> <strong>uniform</strong> (described below). 11538It is a compile-time or link-time error if a single compilation unit 11539(shader) contains either static recursion or the potential for recursion 11540through subroutine variables.</p> 11541</div> 11542</div> 11543<div class="sect3"> 11544<h4 id="subroutines">6.1.2. Subroutines</h4> 11545<div class="paragraph"> 11546<p>Subroutines provide a mechanism allowing shaders to be compiled in a manner 11547where the target of one or more function calls can be changed at run-time 11548without requiring any shader recompilation. 11549For example, a single shader may be compiled with support for multiple 11550illumination algorithms to handle different kinds of lights or surface 11551materials. 11552An application using such a shader may switch illumination algorithms by 11553changing the value of its subroutine uniforms. 11554To use subroutines, a subroutine type is declared, one or more functions are 11555associated with that subroutine type, and a subroutine variable of that type 11556is declared. 11557The function currently assigned to the variable function is then called by 11558using function calling syntax replacing a function name with the name of the 11559subroutine variable. 11560Subroutine variables are uniforms, and are assigned to specific functions 11561only through commands (<strong>UniformSubroutinesuiv</strong>) in the OpenGL API.</p> 11562</div> 11563<div class="paragraph"> 11564<p>Subroutine functionality is not available when generating SPIR-V.</p> 11565</div> 11566<div class="paragraph"> 11567<p>Subroutine types are declared using a statement similar to a function 11568declaration, with the <strong>subroutine</strong> keyword, as follows:</p> 11569</div> 11570<div class="listingblock"> 11571<div class="content"> 11572<pre class="CodeRay highlight"><code data-lang="c++">subroutine returnType subroutineTypeName(type0 arg0, type1 arg1, 11573 ..., typen argn);</code></pre> 11574</div> 11575</div> 11576<div class="paragraph"> 11577<p>As with function declarations, the formal argument names (<em>args</em> above) are 11578optional. 11579Functions are associated with subroutine types of matching declarations by 11580defining the function with the <strong>subroutine</strong> keyword and a list of subroutine 11581types the function matches:</p> 11582</div> 11583<div class="listingblock"> 11584<div class="content"> 11585<pre class="CodeRay highlight"><code data-lang="c++">subroutine(subroutineTypeName0, ..., subroutineTypeNameN) 11586returnType functionName(type0 arg0, type1 arg1, ..., typen argn) 11587{ ... } <span class="comment">// function body</span></code></pre> 11588</div> 11589</div> 11590<div class="paragraph"> 11591<p>It is a compile-time error if arguments and return type don’t match between 11592the function and each associated subroutine type.</p> 11593</div> 11594<div class="paragraph"> 11595<p>Functions declared with <strong>subroutine</strong> must include a body. 11596An overloaded function cannot be declared with <strong>subroutine</strong>; a program will 11597fail to compile or link if any shader or stage contains two or more 11598functions with the same name if the name is associated with a subroutine 11599type.</p> 11600</div> 11601<div class="paragraph"> 11602<p>A function declared with <strong>subroutine</strong> can also be called directly with a 11603static use of <em>functionName</em>, as is done with non-subroutine function 11604declarations and calls.</p> 11605</div> 11606<div class="paragraph"> 11607<p>Subroutine type variables are required to be <em>subroutine uniforms</em>, and are 11608declared with a specific subroutine type in a subroutine uniform variable 11609declaration:</p> 11610</div> 11611<div class="listingblock"> 11612<div class="content"> 11613<pre class="CodeRay highlight"><code data-lang="c++">subroutine uniform subroutineTypeName subroutineVarName;</code></pre> 11614</div> 11615</div> 11616<div class="paragraph"> 11617<p>Subroutine uniform variables are called the same way functions are called. 11618When a subroutine variable (or an element of a subroutine variable array) is 11619associated with a particular function, all function calls through that 11620variable will call that particular function.</p> 11621</div> 11622<div class="paragraph"> 11623<p>Unlike other uniform variables, subroutine uniform variables are scoped to 11624the shader execution stage the variable is declared in.</p> 11625</div> 11626<div class="paragraph"> 11627<p>Subroutine variables may be declared as explicitly-sized arrays, which can 11628be indexed only with dynamically uniform expressions.</p> 11629</div> 11630<div class="paragraph"> 11631<p>It is a compile-time error to use the <strong>subroutine</strong> keyword in any places 11632other than (as shown above) to</p> 11633</div> 11634<div class="ulist"> 11635<ul> 11636<li> 11637<p>declare a subroutine type at global scope,</p> 11638</li> 11639<li> 11640<p>declare a function as a subroutine, or</p> 11641</li> 11642<li> 11643<p>declare a subroutine variable at global scope.</p> 11644</li> 11645</ul> 11646</div> 11647</div> 11648</div> 11649<div class="sect2"> 11650<h3 id="selection">6.2. Selection</h3> 11651<div class="paragraph"> 11652<p>Conditional control flow in the shading language is done by either <strong>if</strong>, 11653<strong>if</strong>-<strong>else</strong>, or <strong>switch</strong> statements:</p> 11654</div> 11655<div class="openblock bnf"> 11656<div class="content"> 11657<div class="dlist"> 11658<dl> 11659<dt class="hdlist1"><em>selection-statement</em> : </dt> 11660<dd> 11661<p><strong>if</strong> <strong>(</strong> <em>bool-expression</em> <strong>)</strong> <em>statement</em><br> 11662<strong>if</strong> <strong>(</strong> <em>bool-expression</em> <strong>)</strong> <em>statement</em> <strong>else</strong> <em>statement</em><br> 11663<strong>switch</strong> <strong>(</strong> <em>init-expression</em> <strong>)</strong> <strong>{</strong> <em>switch-statement-list<sub>opt</sub></em> <strong>}</strong></p> 11664</dd> 11665</dl> 11666</div> 11667</div> 11668</div> 11669<div class="paragraph"> 11670<p>Where <em>switch-statement-list</em> is a nested scope containing a list of zero or 11671more <em>switch-statement</em> and other statements defined by the language, where 11672<em>switch-statement</em> adds some forms of labels. 11673That is</p> 11674</div> 11675<div class="openblock bnf"> 11676<div class="content"> 11677<div class="dlist"> 11678<dl> 11679<dt class="hdlist1"><em>switch-statement-list</em> : </dt> 11680<dd> 11681<p><em>switch-statement</em><br> 11682<em>switch-statement-list</em> <em>switch-statement</em></p> 11683</dd> 11684<dt class="hdlist1"><em>switch-statement</em> : </dt> 11685<dd> 11686<p><strong>case</strong> <em>constant-expression</em> <strong>:</strong><br> 11687<strong>default</strong> <strong>:</strong> <em>statement</em></p> 11688</dd> 11689</dl> 11690</div> 11691</div> 11692</div> 11693<div class="paragraph"> 11694<p>Note the above grammar’s purpose is to aid discussion in this section; the 11695normative grammar is in “<a href="#shading-language-grammar">Shading Language 11696Grammar</a>”.</p> 11697</div> 11698<div class="paragraph"> 11699<p>If an <strong>if</strong>-expression evaluates to <strong>true</strong>, then the first <em>statement</em> is 11700executed. 11701If it evaluates to <strong>false</strong> and there is an <strong>else</strong> part then the second 11702<em>statement</em> is executed.</p> 11703</div> 11704<div class="paragraph"> 11705<p>Any expression whose type evaluates to a Boolean can be used as the 11706conditional expression <em>bool-expression</em>. 11707Vector types are not accepted as the expression to <strong>if</strong>.</p> 11708</div> 11709<div class="paragraph"> 11710<p>Conditionals can be nested.</p> 11711</div> 11712<div class="paragraph"> 11713<p>The type of <em>init-expression</em> in a <strong>switch</strong> statement must be a scalar 11714integer. 11715The type of the <em>constant-expression</em> value in a case label also must be a 11716scalar integer. 11717When any pair of these values is tested for “equal value” and the types do 11718not match, an implicit conversion will be done to convert the <strong>int</strong> to a 11719<strong>uint</strong> (see “<a href="#implicit-conversions">Implicit Conversions</a>”) before the 11720compare is done. 11721If a <strong>case</strong> label has a <em>constant-expression</em> of equal value to 11722<em>init-expression</em>, execution will continue after that label. 11723Otherwise, if there is a <strong>default</strong> label, execution will continue after that 11724label. 11725Otherwise, execution skips the rest of the switch statement. 11726It is a compile-time error to have more than one <strong>default</strong> or a replicated 11727<em>constant-expression</em>. 11728A <strong>break</strong> statement not nested in a loop or other switch statement (either 11729not nested or nested only in <strong>if</strong> or <strong>if</strong>-<strong>else</strong> statements) will also skip 11730the rest of the switch statement. 11731Fall through labels are allowed, but it is a compile-time error to have no 11732statement between a label and the end of the switch statement. 11733No statements are allowed in a switch statement before the first <strong>case</strong> 11734statement.</p> 11735</div> 11736<div class="paragraph"> 11737<p>The <strong>case</strong> and <strong>default</strong> labels can only appear within a <strong>switch</strong> statement. 11738No <strong>case</strong> or <strong>default</strong> labels can be nested inside other statements or 11739compound statements within their corresponding <strong>switch</strong>.</p> 11740</div> 11741</div> 11742<div class="sect2"> 11743<h3 id="iteration">6.3. Iteration</h3> 11744<div class="paragraph"> 11745<p>For, while, and do loops are allowed as follows:</p> 11746</div> 11747<div class="listingblock"> 11748<div class="content"> 11749<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">for</span> (init-expression; condition-expression; loop-expression) 11750 sub-statement 11751<span class="keyword">while</span> (condition-expression) 11752 sub-statement 11753<span class="keyword">do</span> 11754 statement 11755<span class="keyword">while</span> (condition-expression)</code></pre> 11756</div> 11757</div> 11758<div class="paragraph"> 11759<p>See “<a href="#shading-language-grammar">Shading Language Grammar</a>” for the 11760definitive specification of loops.</p> 11761</div> 11762<div class="paragraph"> 11763<p>The <strong>for</strong> loop first evaluates the <em>init-expression</em>, then the 11764<em>condition-expression</em>. 11765If the <em>condition-expression</em> evaluates to <strong>true</strong>, then the body of the loop 11766is executed. 11767After the body is executed, a <strong>for</strong> loop will then evaluate the 11768<em>loop-expression</em>, and then loop back to evaluate the 11769<em>condition-expression</em>, repeating until the <em>condition-expression</em> evaluates 11770to <strong>false</strong>. 11771The loop is then exited, skipping its body and skipping its 11772<em>loop-expression</em>. 11773Variables modified by the <em>loop-expression</em> maintain their value after the 11774loop is exited, provided they are still in scope. 11775Variables declared in <em>init-expression</em> or <em>condition-expression</em> are only 11776in scope until the end of the sub-statement of the <strong>for</strong> loop.</p> 11777</div> 11778<div class="paragraph"> 11779<p>The <strong>while</strong> loop first evaluates the <em>condition-expression</em>. 11780If <strong>true</strong>, then the body is executed. 11781This is then repeated, until the <em>condition-expression</em> evaluates to 11782<strong>false</strong>, exiting the loop and skipping its body. 11783Variables declared in the <em>condition-expression</em> are only in scope until the 11784end of the sub-statement of the <strong>while</strong> loop.</p> 11785</div> 11786<div class="paragraph"> 11787<p>The <strong>do</strong>-<strong>while</strong> loop first executes the body, then executes the 11788<em>condition-expression</em>. 11789This is repeated until <em>condition-expression</em> evaluates to <strong>false</strong>, and then 11790the loop is exited.</p> 11791</div> 11792<div class="paragraph"> 11793<p>Expressions for <em>condition-expression</em> must evaluate to a Boolean.</p> 11794</div> 11795<div class="paragraph"> 11796<p>Both the <em>condition-expression</em> and the <em>init-expression</em> can declare and 11797initialize a variable, except in the <strong>do</strong>-<strong>while</strong> loop, which cannot declare 11798a variable in its <em>condition-expression</em>. 11799The variable’s scope lasts only until the end of the sub-statement that 11800forms the body of the loop.</p> 11801</div> 11802<div class="paragraph"> 11803<p>Loops can be nested.</p> 11804</div> 11805<div class="paragraph"> 11806<p>Non-terminating loops are allowed. 11807The consequences of very long or non-terminating loops are platform 11808dependent.</p> 11809</div> 11810</div> 11811<div class="sect2"> 11812<h3 id="jumps">6.4. Jumps</h3> 11813<div class="paragraph"> 11814<p>These are the jumps:</p> 11815</div> 11816<div class="openblock bnf"> 11817<div class="content"> 11818<div class="dlist"> 11819<dl> 11820<dt class="hdlist1"><em>jump_statement</em> : </dt> 11821<dd> 11822<p><strong>continue</strong> <strong>;</strong><br> 11823<strong>break</strong> <strong>;</strong><br> 11824<strong>return</strong> <strong>;</strong><br> 11825<strong>return</strong> <em>expression</em> <strong>;</strong><br> 11826<strong>discard</strong> <strong>;</strong> // in the fragment shader language only</p> 11827</dd> 11828</dl> 11829</div> 11830</div> 11831</div> 11832<div class="paragraph"> 11833<p>There is no “goto” or other non-structured flow of control.</p> 11834</div> 11835<div class="paragraph"> 11836<p>The <strong>continue</strong> jump is used only in loops. 11837It skips the remainder of the body of the inner-most loop of which it is 11838inside. 11839For <strong>while</strong> and <strong>do</strong>-<strong>while</strong> loops, this jump is to the next evaluation of 11840the loop <em>condition-expression</em> from which the loop continues as previously 11841defined. 11842For <strong>for</strong> loops, the jump is to the <em>loop-expression</em>, followed by the 11843<em>condition-expression</em>.</p> 11844</div> 11845<div class="paragraph"> 11846<p>The <strong>break</strong> jump can also be used only in loops and <strong>switch</strong> statements. 11847It is simply an immediate exit of the inner-most loop or <strong>switch</strong> statements 11848containing the <strong>break</strong>. 11849No further execution of <em>condition-expression</em>, <em>loop-expression</em>, or 11850<em>switch-statement</em> is done.</p> 11851</div> 11852<div class="paragraph"> 11853<p>The <strong>discard</strong> keyword is only allowed within fragment shaders. 11854It can be used within a fragment shader to abandon the operation on the 11855current fragment. 11856This keyword causes the fragment to be discarded and no updates to any 11857buffers will occur. 11858Any prior writes to other buffers such as shader storage buffers are 11859unaffected. 11860Control flow exits the shader, and subsequent implicit or explicit 11861derivatives are undefined when this control flow is non-uniform (meaning 11862different fragments within the primitive take different control paths). 11863It would typically be used within a conditional statement, for example:</p> 11864</div> 11865<div class="listingblock"> 11866<div class="content"> 11867<pre class="CodeRay highlight"><code data-lang="c++"><span class="keyword">if</span> (intensity < <span class="float">0</span><span class="float">.0</span>) 11868 discard;</code></pre> 11869</div> 11870</div> 11871<div class="paragraph"> 11872<p>A fragment shader may test a fragment’s alpha value and discard the fragment 11873based on that test. 11874However, it should be noted that coverage testing occurs after the fragment 11875shader runs, and the coverage test can change the alpha value.</p> 11876</div> 11877<div class="paragraph"> 11878<p>The <strong>return</strong> jump causes immediate exit of the current function. 11879If it has <em>expression</em> then that is the return value for the function.</p> 11880</div> 11881<div class="paragraph"> 11882<p>The function <em>main</em> can use <strong>return</strong>. 11883This simply causes <em>main</em> to exit in the same way as when the end of the 11884function had been reached. 11885It does not imply a use of <strong>discard</strong> in a fragment shader. 11886Using <strong>return</strong> in <em>main</em> before defining outputs will have the same behavior 11887as reaching the end of <em>main</em> before defining outputs.</p> 11888</div> 11889</div> 11890</div> 11891</div> 11892<div class="sect1"> 11893<h2 id="built-in-variables">7. Built-In Variables</h2> 11894<div class="sectionbody"> 11895<div class="sect2"> 11896<h3 id="built-in-language-variables">7.1. Built-In Language Variables</h3> 11897<div class="paragraph"> 11898<p>Some operations occur outside shader functionality and need to provide 11899values to or receive values from shader executables. 11900Shaders communicate with fixed-function pipeline stages, and 11901optionally with other shader executables, through the use of built-in input 11902and output variables.</p> 11903</div> 11904<div class="sect3"> 11905<h4 id="vertex-shader-special-variables">7.1.1. Vertex Shader Special Variables</h4> 11906<div class="paragraph"> 11907<p>The built-in vertex shader variables are intrinsically declared as follows:</p> 11908</div> 11909<div class="listingblock"> 11910<div class="content"> 11911<pre class="CodeRay highlight"><code data-lang="c++">in <span class="predefined-type">int</span> gl_VertexID; <span class="comment">// only present when not targeting Vulkan</span> 11912in <span class="predefined-type">int</span> gl_InstanceID; <span class="comment">// only present when not targeting Vulkan</span> 11913in <span class="predefined-type">int</span> gl_VertexIndex; <span class="comment">// only present when targeting Vulkan</span> 11914in <span class="predefined-type">int</span> gl_InstanceIndex; <span class="comment">// only present when targeting Vulkan</span> 11915in <span class="predefined-type">int</span> gl_DrawID; 11916in <span class="predefined-type">int</span> gl_BaseVertex; 11917in <span class="predefined-type">int</span> gl_BaseInstance; 11918 11919out gl_PerVertex { 11920 vec4 gl_Position; 11921 <span class="predefined-type">float</span> gl_PointSize; 11922 <span class="predefined-type">float</span> gl_ClipDistance[]; 11923 <span class="predefined-type">float</span> gl_CullDistance[]; 11924};</code></pre> 11925</div> 11926</div> 11927<div class="paragraph"> 11928<p>The variable <em>gl_Position</em> is intended for writing the homogeneous vertex 11929position. 11930It can be written at any time during shader execution. 11931This value will be used by primitive assembly, clipping, culling, and other 11932fixed functionality operations, if present, that operate on primitives after 11933vertex processing has occurred. 11934Its value is undefined after the vertex processing stage if the vertex 11935shader executable does not write <em>gl_Position</em>.</p> 11936</div> 11937<div class="paragraph"> 11938<p>The variable <em>gl_PointSize</em> is intended for a shader to write the size of 11939the point to be rasterized. 11940It is measured in pixels. 11941If <em>gl_PointSize</em> is not written to, its value is undefined in subsequent 11942pipe stages.</p> 11943</div> 11944<div class="paragraph"> 11945<p>The variable <em>gl_ClipDistance</em> is intended for writing clip distances, and 11946provides the forward compatible mechanism for controlling user clipping. 11947The element <em>gl_ClipDistance[i]</em> specifies a clip distance for each plane 11948<em>i</em>. 11949A distance of 0 means the vertex is on the plane, a positive distance means 11950the vertex is inside the clip plane, and a negative distance means the point 11951is outside the clip plane. 11952The clip distances will be linearly interpolated across the primitive and 11953the portion of the primitive with interpolated distances less than 0 will be 11954clipped.</p> 11955</div> 11956<div class="paragraph"> 11957<p>The <em>gl_ClipDistance</em> array is predeclared as unsized and must be explicitly 11958sized by the shader either redeclaring it with a size or implicitly sized by 11959indexing it only with constant integral expressions. 11960This needs to size the array to include all the clip planes that are enabled 11961via the API; if the size does not include all enabled planes, 11962results are undefined. 11963The size can be at most <em>gl_MaxClipDistances</em>. 11964The number of varying components (see <em>gl_MaxVaryingComponents)</em> consumed by 11965<em>gl_ClipDistance</em> will match the size of the array, no matter how many 11966planes are enabled. 11967The shader must also set all values in <em>gl_ClipDistance</em> that have been 11968enabled via the API, or results are undefined. 11969Values written into <em>gl_ClipDistance</em> for planes that are not enabled have 11970no effect.</p> 11971</div> 11972<div class="paragraph"> 11973<p>The variable <em>gl_CullDistance</em> provides a mechanism for controlling user 11974culling. 11975The element <em>gl_CullDistance[i]</em> specifies a cull distance for plane <em>i</em>. 11976A distance of 0 means the vertex is on the plane, a positive distance means 11977the vertex is inside the cull volume, and a negative distance means the 11978point is outside the cull volume. 11979Primitives whose vertices all have a negative cull distance for plane <em>i</em> 11980will be discarded.</p> 11981</div> 11982<div class="paragraph"> 11983<p>The <em>gl_CullDistance</em> array is predeclared as unsized and must be sized by 11984the shader either redeclaring it with a size or indexing it only with 11985constant integral expressions. 11986The size determines the number and set of enabled cull distances and can be 11987at most <em>gl_MaxCullDistances</em>. 11988The number of varying components (see <em>gl_MaxVaryingComponents</em>) consumed by 11989<em>gl_CullDistance</em> will match the size of the array. 11990Shaders writing <em>gl_CullDistance</em> must write all enabled distances, or 11991culling results are undefined.</p> 11992</div> 11993<div class="paragraph"> 11994<p>As an output variable, <em>gl_CullDistance</em> provides the place for the shader 11995to write these distances. 11996As an input in all but the fragment language, it reads the values written in 11997the previous shader stage. 11998In the fragment language, <em>gl_CullDistance</em> array contains linearly 11999interpolated values for the vertex values written by a shader to the 12000<em>gl_CullDistance</em> vertex output variable.</p> 12001</div> 12002<div class="paragraph"> 12003<p>It is a compile-time or link-time error for the set of shaders forming a 12004program to have the sum of the sizes of the <em>gl_ClipDistance</em> and 12005<em>gl_CullDistance</em> arrays to be larger than 12006<em>gl_MaxCombinedClipAndCullDistances</em>.</p> 12007</div> 12008<div class="paragraph"> 12009<p>The variable <em>gl_VertexID</em> is a vertex shader input variable that holds an 12010integer index for the vertex, as defined under “Shader Inputs” in section 1201111.1.3.9 “Shader Inputs” of the <a href="#references">OpenGL Specification</a>. 12012It is only present when not targeting Vulkan. 12013Even when present, the value of <em>gl_VertexID</em> is not always defined.</p> 12014</div> 12015<div class="paragraph"> 12016<p>The variable <em>gl_InstanceID</em> is a vertex shader input variable that holds 12017the instance number of the current primitive in an instanced draw call (see 12018“Shader Inputs” in section 11.1.3.9 “Shader Inputs” of the 12019<a href="#references">OpenGL Specification</a>). 12020It is only present when not targeting Vulkan. 12021If the current primitive does not come from an instanced draw call, the 12022value of <em>gl_InstanceID</em> is zero.</p> 12023</div> 12024<div class="paragraph"> 12025<p>The variable <em>gl_VertexIndex</em> is a vertex language input variable that 12026holds an integer index for the vertex, relative to a base. 12027It is only present when targeting Vulkan. 12028Even when present, the value of <em>gl_VertexIndex</em> is not always defined.</p> 12029</div> 12030<div class="paragraph"> 12031<p>The variable <em>gl_InstanceIndex</em> is a vertex language input variable that 12032holds the instance number of the current primitive in an instanced draw 12033call, relative to a base. 12034It is only present when targeting Vulkan. 12035If the current primitive does not come from an instanced draw call, 12036the value of gl_InstanceIndex is zero.</p> 12037</div> 12038<div class="paragraph"> 12039<p>The variable <em>gl_DrawID</em> is a vertex shader input variable that holds the 12040integer index of the drawing command to which the current vertex belongs 12041(see “Shader Inputs” in section 11.1.3.9 of the <a href="#references">OpenGL Specification</a>). 12042If the vertex is not invoked by a <strong>Multi</strong>* form of a draw command, then the 12043value of <em>gl_DrawID</em> is zero.</p> 12044</div> 12045<div class="paragraph"> 12046<p>The variable <em>gl_BaseVertex</em> is a vertex shader input variable that holds 12047the integer value passed to the baseVertex parameter of the command that 12048resulted in the current shader invocation (see “Shader Inputs” in section 1204911.1.3.9 of the <a href="#references">OpenGL Specification</a>).</p> 12050</div> 12051<div class="paragraph"> 12052<p>The variable <em>gl_BaseInstance</em> is a vertex shader input variable that holds 12053the integer value passed to the baseInstance parameter of the command that 12054resulted in the current shader invocation (see “Shader Inputs” in section 1205511.1.3.9 of the <a href="#references">OpenGL Specification</a>).</p> 12056</div> 12057</div> 12058<div class="sect3"> 12059<h4 id="tessellation-control-shader-special-variables">7.1.2. Tessellation Control Shader Special Variables</h4> 12060<div class="paragraph"> 12061<p>In the tessellation control shader, built-in variables are intrinsically 12062declared as:</p> 12063</div> 12064<div class="listingblock"> 12065<div class="content"> 12066<pre class="CodeRay highlight"><code data-lang="c++">in gl_PerVertex { 12067 vec4 gl_Position; 12068 <span class="predefined-type">float</span> gl_PointSize; 12069 <span class="predefined-type">float</span> gl_ClipDistance[]; 12070 <span class="predefined-type">float</span> gl_CullDistance[]; 12071} gl_in[gl_MaxPatchVertices]; 12072 12073in <span class="predefined-type">int</span> gl_PatchVerticesIn; 12074in <span class="predefined-type">int</span> gl_PrimitiveID; 12075in <span class="predefined-type">int</span> gl_InvocationID; 12076 12077out gl_PerVertex { 12078 vec4 gl_Position; 12079 <span class="predefined-type">float</span> gl_PointSize; 12080 <span class="predefined-type">float</span> gl_ClipDistance[]; 12081 <span class="predefined-type">float</span> gl_CullDistance[]; 12082} gl_out[]; 12083 12084patch out <span class="predefined-type">float</span> gl_TessLevelOuter[<span class="integer">4</span>]; 12085patch out <span class="predefined-type">float</span> gl_TessLevelInner[<span class="integer">2</span>];</code></pre> 12086</div> 12087</div> 12088<div class="sect4"> 12089<h5 id="tessellation-control-input-variables">Tessellation Control Input Variables</h5> 12090<div class="paragraph"> 12091<p><em>gl_Position</em>, <em>gl_PointSize</em>, <em>gl_ClipDistance</em>, and <em>gl_CullDistance</em> 12092contain the values written in the previous shader stage to the corresponding 12093outputs.</p> 12094</div> 12095<div class="paragraph"> 12096<p><em>gl_PatchVerticesIn</em> contains the number of vertices in the input patch 12097being processed by the shader. 12098A single shader can read patches of differing sizes, so the value of 12099<em>gl_PatchVerticesIn</em> may differ between patches.</p> 12100</div> 12101<div class="paragraph"> 12102<p><em>gl_PrimitiveID</em> contains the number of primitives processed by the shader 12103since the current set of rendering primitives was started.</p> 12104</div> 12105<div class="paragraph"> 12106<p><em>gl_InvocationID</em> contains the number of the output patch vertex assigned to 12107the tessellation control shader invocation. 12108It is assigned integer values in the range [0, N-1], where N is the number 12109of output patch vertices per primitive.</p> 12110</div> 12111</div> 12112<div class="sect4"> 12113<h5 id="tessellation-control-output-variables">Tessellation Control Output Variables</h5> 12114<div class="paragraph"> 12115<p><em>gl_Position</em>, <em>gl_PointSize</em>, <em>gl_ClipDistance</em>, and <em>gl_CullDistance</em> are 12116used in the same fashion as the corresponding output variables in the vertex 12117shader.</p> 12118</div> 12119<div class="paragraph"> 12120<p>The values written to <em>gl_TessLevelOuter</em> and <em>gl_TessLevelInner</em> are 12121assigned to the corresponding outer and inner tessellation levels of the 12122output patch. 12123They are used by the tessellation primitive generator to control primitive 12124tessellation and may be read by tessellation evaluation shaders.</p> 12125</div> 12126</div> 12127</div> 12128<div class="sect3"> 12129<h4 id="tessellation-evaluation-shader-special-variables">7.1.3. Tessellation Evaluation Shader Special Variables</h4> 12130<div class="paragraph"> 12131<p>In the tessellation evaluation shader, built-in variables are intrinsically 12132declared as:</p> 12133</div> 12134<div class="listingblock"> 12135<div class="content"> 12136<pre class="CodeRay highlight"><code data-lang="c++">in gl_PerVertex { 12137 vec4 gl_Position; 12138 <span class="predefined-type">float</span> gl_PointSize; 12139 <span class="predefined-type">float</span> gl_ClipDistance[]; 12140 <span class="predefined-type">float</span> gl_CullDistance[]; 12141} gl_in[gl_MaxPatchVertices]; 12142 12143in <span class="predefined-type">int</span> gl_PatchVerticesIn; 12144in <span class="predefined-type">int</span> gl_PrimitiveID; 12145in vec3 gl_TessCoord; 12146patch in <span class="predefined-type">float</span> gl_TessLevelOuter[<span class="integer">4</span>]; 12147patch in <span class="predefined-type">float</span> gl_TessLevelInner[<span class="integer">2</span>]; 12148 12149out gl_PerVertex { 12150 vec4 gl_Position; 12151 <span class="predefined-type">float</span> gl_PointSize; 12152 <span class="predefined-type">float</span> gl_ClipDistance[]; 12153 <span class="predefined-type">float</span> gl_CullDistance[]; 12154};</code></pre> 12155</div> 12156</div> 12157<div class="sect4"> 12158<h5 id="tessellation-evaluation-input-variables">Tessellation Evaluation Input Variables</h5> 12159<div class="paragraph"> 12160<p><em>gl_Position</em>, <em>gl_PointSize</em>, <em>gl_ClipDistance</em>, and <em>gl_CullDistance</em> 12161contain the values written in the previous shader stage to the corresponding 12162outputs.</p> 12163</div> 12164<div class="paragraph"> 12165<p><em>gl_PatchVerticesIn</em> and <em>gl_PrimitiveID</em> are defined in the same fashion as 12166the corresponding input variables in the tessellation control shader.</p> 12167</div> 12168<div class="paragraph"> 12169<p><em>gl_TessCoord</em> specifies a three-component <em>(u,v,w)</em> vector identifying the 12170position of the vertex being processed by the shader relative to the 12171primitive being tessellated. 12172Its values will obey the properties</p> 12173</div> 12174<div class="listingblock"> 12175<div class="content"> 12176<pre class="CodeRay highlight"><code data-lang="c++">gl_TessCoord.x == <span class="float">1</span><span class="float">.0</span> - (<span class="float">1</span><span class="float">.0</span> - gl_TessCoord.x) <span class="comment">// two operations performed</span> 12177gl_TessCoord.y == <span class="float">1</span><span class="float">.0</span> - (<span class="float">1</span><span class="float">.0</span> - gl_TessCoord.y) <span class="comment">// two operations performed</span> 12178gl_TessCoord.z == <span class="float">1</span><span class="float">.0</span> - (<span class="float">1</span><span class="float">.0</span> - gl_TessCoord.z) <span class="comment">// two operations performed</span></code></pre> 12179</div> 12180</div> 12181<div class="paragraph"> 12182<p>to aid in replicating subdivision computations.</p> 12183</div> 12184<div class="paragraph"> 12185<p>If a tessellation control shader is active, the input variables 12186<em>gl_TessLevelOuter</em> and <em>gl_TessLevelInner</em> are filled with the 12187corresponding outputs written by the tessellation control shader. 12188Otherwise, they are assigned with default tessellation levels specified in 12189section 11.2.3.3 “Tessellation Evaluation Shader Inputs” of the 12190<a href="#references">OpenGL Specification</a>.</p> 12191</div> 12192</div> 12193<div class="sect4"> 12194<h5 id="tessellation-evaluation-output-variables">Tessellation Evaluation Output Variables</h5> 12195<div class="paragraph"> 12196<p><em>gl_Position</em>, <em>gl_PointSize</em>, <em>gl_ClipDistance</em>, and <em>gl_CullDistance</em> are 12197used in the same fashion as the corresponding output variables in the vertex 12198shader.</p> 12199</div> 12200</div> 12201</div> 12202<div class="sect3"> 12203<h4 id="geometry-shader-special-variables">7.1.4. Geometry Shader Special Variables</h4> 12204<div class="paragraph"> 12205<p>In the geometry shader, built-in variables are intrinsically declared as:</p> 12206</div> 12207<div class="listingblock"> 12208<div class="content"> 12209<pre class="CodeRay highlight"><code data-lang="c++">in gl_PerVertex { 12210 vec4 gl_Position; 12211 <span class="predefined-type">float</span> gl_PointSize; 12212 <span class="predefined-type">float</span> gl_ClipDistance[]; 12213 <span class="predefined-type">float</span> gl_CullDistance[]; 12214} gl_in[]; 12215 12216in <span class="predefined-type">int</span> gl_PrimitiveIDIn; 12217in <span class="predefined-type">int</span> gl_InvocationID; 12218 12219out gl_PerVertex { 12220 vec4 gl_Position; 12221 <span class="predefined-type">float</span> gl_PointSize; 12222 <span class="predefined-type">float</span> gl_ClipDistance[]; 12223 <span class="predefined-type">float</span> gl_CullDistance[]; 12224}; 12225 12226out <span class="predefined-type">int</span> gl_PrimitiveID; 12227out <span class="predefined-type">int</span> gl_Layer; 12228out <span class="predefined-type">int</span> gl_ViewportIndex;</code></pre> 12229</div> 12230</div> 12231<div class="sect4"> 12232<h5 id="geometry-shader-input-variables">Geometry Shader Input Variables</h5> 12233<div class="paragraph"> 12234<p><em>gl_Position</em>, <em>gl_PointSize</em>, <em>gl_ClipDistance</em>, and <em>gl_CullDistance</em> 12235contain the values written in the previous shader stage to the corresponding 12236outputs.</p> 12237</div> 12238<div class="paragraph"> 12239<p><em>gl_PrimitiveIDIn</em> contains the number of primitives processed by the shader 12240since the current set of rendering primitives was started.</p> 12241</div> 12242<div class="paragraph"> 12243<p><em>gl_InvocationID</em> contains the invocation number assigned to the geometry 12244shader invocation. 12245It is assigned integer values in the range [0, N-1], where N is the number 12246of geometry shader invocations per primitive.</p> 12247</div> 12248</div> 12249<div class="sect4"> 12250<h5 id="geometry-shader-output-variables">Geometry Shader Output Variables</h5> 12251<div class="paragraph"> 12252<p><em>gl_Position</em>, <em>gl_PointSize</em>, <em>gl_ClipDistance</em>, and <em>gl_CullDistance</em> are 12253used in the same fashion as the corresponding output variables in the vertex 12254shader.</p> 12255</div> 12256<div class="paragraph"> 12257<p><em>gl_PrimitiveID</em> is filled with a single integer that serves as a primitive 12258identifier to the fragment shader. 12259This is then available to fragment shaders, which will select the written 12260primitive ID from the provoking vertex of the primitive being shaded. 12261If a fragment shader using <em>gl_PrimitiveID</em> is active and a geometry shader 12262is also active, the geometry shader must write to <em>gl_PrimitiveID</em> or the 12263fragment shader input <em>gl_PrimitiveID</em> is undefined. 12264See section 11.3.4.5 “Geometry Shader Outputs” of the 12265<a href="#references">OpenGL Specification</a> for more information.</p> 12266</div> 12267<div class="paragraph"> 12268<p><em>gl_Layer</em> is used to select a specific layer (or face and layer of a cube 12269map) of a multi-layer framebuffer attachment. 12270The actual layer used will come from one of the vertices in the primitive 12271being shaded. 12272Which vertex the layer comes from is determined as discussed in section 1227311.3.4.6 “Layer and Viewport Selection” of the <a href="#references">OpenGL Specification</a> 12274but may be undefined, so it is best to write the same layer value for all 12275vertices of a primitive. 12276If a shader statically assigns a value to <em>gl_Layer</em>, layered rendering mode 12277is enabled. 12278See section 11.3.4.5 “Geometry Shader Outputs” and section 9.4.9 “Layered 12279Framebuffers” of the <a href="#references">OpenGL Specification</a> for more information. 12280If a shader statically assigns a value to <em>gl_Layer</em>, and there is an 12281execution path through the shader that does not set <em>gl_Layer</em>, then the 12282value of <em>gl_Layer</em> is undefined for executions of the shader that take that 12283path.</p> 12284</div> 12285<div class="paragraph"> 12286<p>The output variable <em>gl_Layer</em> takes on a special value when used with an 12287array of cube map textures. 12288Instead of only referring to the layer, it is used to select a cube map face 12289and a layer. 12290Setting <em>gl_Layer</em> to the value <em>layer*6+face</em> will render to face <em>face</em> of 12291the cube defined in layer <em>layer</em>. 12292The face values are defined in table 9.3 of section 9.4.9 “Layered 12293Framebuffers” of the <a href="#references">OpenGL Specification</a>, 12294but repeated below for clarity.</p> 12295</div> 12296<table class="tableblock frame-all grid-all stretch"> 12297<colgroup> 12298<col style="width: 50%;"> 12299<col style="width: 50%;"> 12300</colgroup> 12301<thead> 12302<tr> 12303<th class="tableblock halign-left valign-top">Face Value</th> 12304<th class="tableblock halign-left valign-top">Resulting Target</th> 12305</tr> 12306</thead> 12307<tbody> 12308<tr> 12309<td class="tableblock halign-left valign-top"><p class="tableblock">0</p></td> 12310<td class="tableblock halign-left valign-top"><p class="tableblock">TEXTURE_CUBE_MAP_POSITIVE_X</p></td> 12311</tr> 12312<tr> 12313<td class="tableblock halign-left valign-top"><p class="tableblock">1</p></td> 12314<td class="tableblock halign-left valign-top"><p class="tableblock">TEXTURE_CUBE_MAP_NEGATIVE_X</p></td> 12315</tr> 12316<tr> 12317<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td> 12318<td class="tableblock halign-left valign-top"><p class="tableblock">TEXTURE_CUBE_MAP_POSITIVE_Y</p></td> 12319</tr> 12320<tr> 12321<td class="tableblock halign-left valign-top"><p class="tableblock">3</p></td> 12322<td class="tableblock halign-left valign-top"><p class="tableblock">TEXTURE_CUBE_MAP_NEGATIVE_Y</p></td> 12323</tr> 12324<tr> 12325<td class="tableblock halign-left valign-top"><p class="tableblock">4</p></td> 12326<td class="tableblock halign-left valign-top"><p class="tableblock">TEXTURE_CUBE_MAP_POSITIVE_Z</p></td> 12327</tr> 12328<tr> 12329<td class="tableblock halign-left valign-top"><p class="tableblock">5</p></td> 12330<td class="tableblock halign-left valign-top"><p class="tableblock">TEXTURE_CUBE_MAP_NEGATIVE_Z</p></td> 12331</tr> 12332</tbody> 12333</table> 12334<div class="paragraph"> 12335<p>For example, to render to the positive <em>y</em> cube map face located in the 5th 12336layer of the cube map array, <em>gl_Layer</em> should be set to <em>5 * 6 + 2</em>.</p> 12337</div> 12338<div class="paragraph"> 12339<p>The output variable <em>gl_ViewportIndex</em> provides the index of the viewport to 12340which the next primitive emitted from the geometry shader should be drawn. 12341Primitives generated by the geometry shader will undergo viewport 12342transformation and scissor testing using the viewport transformation and 12343scissor rectangle selected by the value of <em>gl_ViewportIndex</em>. 12344The viewport index used will come from one of the vertices in the primitive 12345being shaded. 12346However, which vertex the viewport index comes from is 12347implementation-dependent, so it is best to use the same viewport index for 12348all vertices of the primitive. 12349If a geometry shader does not assign a value to <em>gl_ViewportIndex</em>, viewport 12350transform and scissor rectangle zero will be used. 12351If a geometry shader statically assigns a value to <em>gl_ViewportIndex</em> and 12352there is a path through the shader that does not assign a value to 12353<em>gl_ViewportIndex</em>, the value of <em>gl_ViewportIndex</em> is undefined for 12354executions of the shader that take that path. 12355See section 11.3.4.6 “Layer and Viewport Selection” of the 12356<a href="#references">OpenGL Specification</a> for more information.</p> 12357</div> 12358</div> 12359</div> 12360<div class="sect3"> 12361<h4 id="fragment-shader-special-variables">7.1.5. Fragment Shader Special Variables</h4> 12362<div class="paragraph"> 12363<p>The built-in special variables that are accessible from a fragment shader 12364are intrinsically declared as follows:</p> 12365</div> 12366<div class="listingblock"> 12367<div class="content"> 12368<pre class="CodeRay highlight"><code data-lang="c++">in vec4 gl_FragCoord; 12369in <span class="predefined-type">bool</span> gl_FrontFacing; 12370in <span class="predefined-type">float</span> gl_ClipDistance[]; 12371in <span class="predefined-type">float</span> gl_CullDistance[]; 12372in vec2 gl_PointCoord; 12373in <span class="predefined-type">int</span> gl_PrimitiveID; 12374in <span class="predefined-type">int</span> gl_SampleID; 12375in vec2 gl_SamplePosition; 12376in <span class="predefined-type">int</span> gl_SampleMaskIn[]; 12377in <span class="predefined-type">int</span> gl_Layer; 12378in <span class="predefined-type">int</span> gl_ViewportIndex; 12379in <span class="predefined-type">bool</span> gl_HelperInvocation; 12380 12381out <span class="predefined-type">float</span> gl_FragDepth; 12382out <span class="predefined-type">int</span> gl_SampleMask[];</code></pre> 12383</div> 12384</div> 12385<div class="paragraph"> 12386<p>The output of the fragment shader executable is processed by the fixed 12387function operations at the back end of the API pipeline.</p> 12388</div> 12389<div class="paragraph"> 12390<p>The fixed functionality computed depth for a fragment may be obtained by 12391reading <em>gl_FragCoord.z</em>, described below.</p> 12392</div> 12393<div class="paragraph"> 12394<p>Writing to <em>gl_FragDepth</em> will establish the depth value for the fragment 12395being processed. 12396If depth buffering is enabled, and no shader writes <em>gl_FragDepth</em>, then the 12397fixed function value for depth will be used as the fragment’s depth value. 12398If a shader statically assigns a value to <em>gl_FragDepth</em>, and there is an 12399execution path through the shader that does not set <em>gl_FragDepth</em>, then the 12400value of the fragment’s depth may be undefined for executions of the shader 12401that take that path. 12402That is, if the set of linked fragment shaders statically contain a write to 12403<em>gl_FragDepth</em>, then it is responsible for always writing it.</p> 12404</div> 12405<div class="paragraph"> 12406<p>If a shader executes the <strong>discard</strong> keyword, the fragment is discarded, and 12407the values of any user-defined fragment outputs, <em>gl_FragDepth</em>, and 12408<em>gl_SampleMask</em> become irrelevant.</p> 12409</div> 12410<div class="paragraph"> 12411<p>The variable <em>gl_FragCoord</em> is available as an input variable from within 12412fragment shaders and it holds the window relative coordinates (<em>x</em>, <em>y</em>, 12413<em>z</em>, <em>1/w</em>) values for the fragment. 12414If multi-sampling, this value can be for any location within the pixel, or 12415one of the fragment samples. 12416The use of <strong>centroid</strong> does not further restrict this value to be inside the 12417current primitive. 12418This value is the result of the fixed functionality that interpolates 12419primitives after vertex processing to generate fragments. 12420The <em>z</em> component is the depth value that would be used for the fragment’s 12421depth if no shader contained any writes to <em>gl_FragDepth</em>. 12422This is useful for invariance if a shader conditionally computes 12423<em>gl_FragDepth</em> but otherwise wants the fixed functionality fragment depth.</p> 12424</div> 12425<div class="paragraph"> 12426<p>Fragment shaders have access to the input built-in variable 12427<em>gl_FrontFacing</em>, whose value is <strong>true</strong> if the fragment belongs to a 12428front-facing primitive. 12429One use of this is to emulate two-sided lighting by selecting one of two 12430colors calculated by a vertex or geometry shader.</p> 12431</div> 12432<div class="paragraph"> 12433<p>The values in <em>gl_PointCoord</em> are two-dimensional coordinates indicating 12434where within a point primitive the current fragment is located, when point 12435sprites are enabled. 12436They range from 0.0 to 1.0 across the point. 12437If the current primitive is not a point, or if point sprites are not 12438enabled, then the values read from <em>gl_PointCoord</em> are undefined.</p> 12439</div> 12440<div class="paragraph"> 12441<p>For both the input array <em>gl_SampleMaskIn[]</em> and the output array 12442<em>gl_SampleMask[]</em>, bit <em>B</em> of mask <em>M</em> (<em>gl_SampleMaskIn[M]</em> or 12443<em>gl_SampleMask[M]</em>) corresponds to sample <em>32*M+B</em>. 12444These arrays have <strong>ceil</strong>(<em>s</em>/32) elements, where <em>s</em> is the maximum number 12445of color samples supported by the implementation.</p> 12446</div> 12447<div class="paragraph"> 12448<p>The input variable <em>gl_SampleMaskIn</em> indicates the set of samples covered by 12449the primitive generating the fragment during multisample rasterization. 12450It has a sample bit set if and only if the sample is considered covered for 12451this fragment shader invocation.</p> 12452</div> 12453<div class="paragraph"> 12454<p>The output array <em>gl_SampleMask[]</em> sets the sample mask for the fragment 12455being processed. 12456Coverage for the current fragment will become the logical AND of the 12457coverage mask and the output <em>gl_SampleMask</em>. 12458This array must be sized in the fragment shader either implicitly or 12459explicitly, to be no larger than the implementation-dependent maximum 12460sample-mask (as an array of 32bit elements), determined by the maximum 12461number of samples.. 12462If the fragment shader statically assigns a value to <em>gl_SampleMask</em>, the 12463sample mask will be undefined for any array elements of any fragment shader 12464invocations that fail to assign a value. 12465If a shader does not statically assign a value to <em>gl_SampleMask</em>, the 12466sample mask has no effect on the processing of a fragment.</p> 12467</div> 12468<div class="paragraph"> 12469<p>The input variable <em>gl_SampleID</em> is filled with the sample number of the 12470sample currently being processed. 12471This variable is in the range <em>0</em> to <em>gl_NumSamples-1</em>, where 12472<em>gl_NumSamples</em> is the total number of samples in the framebuffer, or 1 if 12473rendering to a non-multisample framebuffer. 12474Any static use of this variable in a fragment shader causes the entire 12475shader to be evaluated per-sample.</p> 12476</div> 12477<div class="paragraph"> 12478<p>The input variable <em>gl_SamplePosition</em> contains the position of the current 12479sample within the multisample draw buffer. 12480The <em>x</em> and <em>y</em> components of <em>gl_SamplePosition</em> contain the sub-pixel 12481coordinate of the current sample and will have values in the range 0.0 to 124821.0. 12483Any static use of this variable in a fragment shader causes the entire 12484shader to be evaluated per sample.</p> 12485</div> 12486<div class="paragraph"> 12487<p>The value <em>gl_HelperInvocation</em> is <strong>true</strong> if the fragment shader invocation 12488is considered a <em>helper invocation</em> and is <strong>false</strong> otherwise. 12489A helper invocation is a fragment shader invocation that is created solely 12490for the purposes of evaluating derivatives for use in non-helper fragment 12491shader invocations. 12492Such derivatives are computed implicitly in the built-in function 12493<strong>texture</strong>() (see “<a href="#texture-functions">Texture Functions</a>”), and 12494explicitly in the derivative functions in 12495“<a href="#derivative-functions">Derivative Functions</a>”, for example <strong>dFdx</strong>() and 12496<strong>dFdy</strong>().</p> 12497</div> 12498<div class="paragraph"> 12499<p>Fragment shader helper invocations execute the same shader code as 12500non-helper invocations, but will not have side effects that modify the 12501framebuffer or other shader-accessible memory. 12502In particular:</p> 12503</div> 12504<div class="ulist"> 12505<ul> 12506<li> 12507<p>Fragments corresponding to helper invocations are discarded when shader 12508execution is complete, without updating the framebuffer.</p> 12509</li> 12510<li> 12511<p>Stores to image and buffer variables performed by helper invocations 12512have no effect on the underlying image or buffer memory.</p> 12513</li> 12514<li> 12515<p>Atomic operations to image, buffer, or atomic counter variables 12516performed by helper invocations have no effect on the underlying image 12517or buffer memory. 12518The values returned by such atomic operations are undefined.</p> 12519</li> 12520</ul> 12521</div> 12522<div class="paragraph"> 12523<p>Helper invocations may be generated for pixels not covered by a primitive 12524being rendered. 12525While fragment shader inputs qualified with <strong>centroid</strong> are normally required 12526to be sampled in the intersection of the pixel and the primitive, the 12527requirement is ignored for such pixels since there is no intersection 12528between the pixel and primitive.</p> 12529</div> 12530<div class="paragraph"> 12531<p>Helper invocations may also be generated for fragments that are covered by a 12532primitive being rendered when the fragment is killed by early fragment tests 12533(using the <strong>early_fragment_tests</strong> qualifier) or where the implementation is 12534able to determine that executing the fragment shader would have no effect 12535other than assisting in computing derivatives for other fragment shader 12536invocations.</p> 12537</div> 12538<div class="paragraph"> 12539<p>The set of helper invocations generated when processing any set of 12540primitives is implementation-dependent.</p> 12541</div> 12542<div class="paragraph"> 12543<p><em>gl_ClipDistance</em> contains linearly interpolated values for the vertex- 12544pipeline values written by a shader to the <em>gl_ClipDistance</em> output 12545variable. Only elements in this array that have clipping enabled will 12546have defined values.</p> 12547</div> 12548<div class="paragraph"> 12549<p>The input variable <em>gl_PrimitiveID</em> is filled with the value written to the 12550<em>gl_PrimitiveID</em> geometry shader output, if a geometry shader is present. 12551Otherwise, it is filled with the number of primitives processed by the 12552shader since the current set of rendering primitives was started.</p> 12553</div> 12554<div class="paragraph"> 12555<p>The input variable <em>gl_Layer</em> is filled with the value written to the 12556<em>gl_Layer</em> geometry shader output, if a geometry shader is present. 12557If the geometry stage does not dynamically assign a value to <em>gl_Layer</em>, the 12558value of <em>gl_Layer</em> in the fragment stage will be undefined. 12559If the geometry stage makes no static assignment to <em>gl_Layer</em>, the input 12560value in the fragment stage will be zero. 12561Otherwise, the fragment stage will read the same value written by the 12562geometry stage, even if that value is out of range. 12563If a fragment shader contains a static access to <em>gl_Layer</em>, it will count 12564against the implementation defined limit for the maximum number of inputs to 12565the fragment stage.</p> 12566</div> 12567<div class="paragraph"> 12568<p>The input variable <em>gl_ViewportIndex</em> is filled with the value written to 12569the output variable <em>gl_ViewportIndex</em> in the geometry stage, if a geometry 12570shader is present. 12571If the geometry stage does not dynamically assign a value to 12572<em>gl_ViewportIndex</em>, the value of <em>gl_ViewportIndex</em> in the fragment shader 12573will be undefined. 12574If the geometry stage makes no static assignment to <em>gl_ViewportIndex</em>, the 12575fragment stage will read zero. 12576Otherwise, the fragment stage will read the same value written by the 12577geometry stage, even if that value is out of range. 12578If a fragment shader contains a static access to <em>gl_ViewportIndex</em>, it will 12579count against the implementation defined limit for the maximum number of 12580inputs to the fragment stage.</p> 12581</div> 12582</div> 12583<div class="sect3"> 12584<h4 id="compute-shader-special-variables">7.1.6. Compute Shader Special Variables</h4> 12585<div class="paragraph"> 12586<p>In the compute shader, built-in variables are declared as follows:</p> 12587</div> 12588<div class="listingblock"> 12589<div class="content"> 12590<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">// workgroup dimensions</span> 12591in uvec3 gl_NumWorkGroups; 12592<span class="directive">const</span> uvec3 gl_WorkGroupSize; 12593 12594<span class="comment">// workgroup and invocation IDs</span> 12595in uvec3 gl_WorkGroupID; 12596in uvec3 gl_LocalInvocationID; 12597 12598<span class="comment">// derived variables</span> 12599in uvec3 gl_GlobalInvocationID; 12600in uint gl_LocalInvocationIndex;</code></pre> 12601</div> 12602</div> 12603<div class="paragraph"> 12604<p>The built-in variable <em>gl_NumWorkGroups</em> is a compute-shader input variable 12605containing the number of workgroups in each dimension of the dispatch that 12606will execute the compute shader. 12607Its content is equal to the values specified in the <em>num_groups_x</em>, 12608<em>num_groups_y</em>, and <em>num_groups_z</em> parameters passed to the 12609<em>DispatchCompute</em> API entry point.</p> 12610</div> 12611<div class="paragraph"> 12612<p>The built-in constant <em>gl_WorkGroupSize</em> is a compute-shader constant 12613containing the workgroup size of the shader. 12614The size of the workgroup in the <em>X</em>, <em>Y</em>, and <em>Z</em> dimensions is stored in 12615the <em>x</em>, <em>y</em>, and <em>z</em> components. 12616The constants values in <em>gl_WorkGroupSize</em> will match those specified in the 12617required <strong>local_size_x</strong>, <strong>local_size_y</strong>, and <strong>local_size_z</strong> layout 12618qualifiers for the current shader. 12619This is a constant so that it can be used to size arrays of memory that can 12620be shared within the workgroup. 12621It is a compile-time error to use <em>gl_WorkGroupSize</em> in a shader that does 12622not declare a fixed workgroup size, or before that shader has declared a 12623fixed workgroup size, using <strong>local_size_x</strong>, <strong>local_size_y</strong>, and 12624<strong>local_size_z</strong>.</p> 12625</div> 12626<div class="paragraph"> 12627<p>The built-in variable <em>gl_WorkGroupID</em> is a compute-shader input variable 12628containing the three-dimensional index of the workgroup that the 12629current invocation is executing in. 12630The possible values range across the parameters passed into 12631<em>DispatchCompute</em>, i.e., from (0, 0, 0) to (<em>gl_NumWorkGroups.x</em> - 1, 12632<em>gl_NumWorkGroups.y</em> - 1, <em>gl_NumWorkGroups.z</em> -1).</p> 12633</div> 12634<div class="paragraph"> 12635<p>The built-in variable <em>gl_LocalInvocationID</em> is a compute-shader input 12636variable containing the three-dimensional index of the current work item 12637within the workgroup. 12638The possible values for this variable range across the workgroup 12639size, i.e., (0,0,0) to (<em>gl_WorkGroupSize.x</em> - 1, <em>gl_WorkGroupSize.y</em> - 1, 12640<em>gl_WorkGroupSize.z</em> - 1). Use of <em>gl_LocalInvocationID</em> is allowed 12641before declarations of <strong>local_size_x</strong>, <strong>local_size_y</strong>, and <strong>local_size_z</strong>.</p> 12642</div> 12643<div class="paragraph"> 12644<p>The built-in variable <em>gl_GlobalInvocationID</em> is a compute shader input 12645variable containing the global index of the current work item. 12646This value uniquely identifies this invocation from all other invocations 12647across all workgroups initiated by the current <em>DispatchCompute</em> call. 12648This is computed as:</p> 12649</div> 12650<div class="listingblock"> 12651<div class="content"> 12652<pre class="CodeRay highlight"><code data-lang="c++">gl_GlobalInvocationID = 12653 gl_WorkGroupID * gl_WorkGroupSize + gl_LocalInvocationID;</code></pre> 12654</div> 12655</div> 12656<div class="paragraph"> 12657<p>The built-in variable <em>gl_LocalInvocationIndex</em> is a compute shader input 12658variable that contains the one-dimensional representation of the 12659<em>gl_LocalInvocationID</em>. 12660This is computed as:</p> 12661</div> 12662<div class="listingblock"> 12663<div class="content"> 12664<pre class="CodeRay highlight"><code data-lang="c++">gl_LocalInvocationIndex = 12665 gl_LocalInvocationID.z * gl_WorkGroupSize.x * gl_WorkGroupSize.y + 12666 gl_LocalInvocationID.y * gl_WorkGroupSize.x + 12667 gl_LocalInvocationID.x;</code></pre> 12668</div> 12669</div> 12670<div class="paragraph"> 12671<p>Use of <em>gl_LocalInvocationIndex</em> is allowed before declarations of 12672<strong>local_size_x</strong>, <strong>local_size_y</strong>, and <strong>local_size_z</strong>.</p> 12673</div> 12674</div> 12675<div class="sect3"> 12676<h4 id="compatibility-profile-built-in-language-variables">7.1.7. Compatibility Profile Built-In Language Variables</h4> 12677<div class="paragraph"> 12678<p>When using the compatibility profile, the GL can provide fixed functionality 12679behavior for the vertex and fragment programmable pipeline stages. 12680For example, mixing a fixed functionality vertex stage with a programmable 12681fragment stage.</p> 12682</div> 12683<div class="paragraph"> 12684<p>The following built-in vertex, tessellation control, tessellation 12685evaluation, and geometry output variables are available to specify inputs 12686for the subsequent programmable shader stage or the fixed functionality 12687fragment stage. 12688A particular one should be written to if any functionality in a 12689corresponding fragment shader or fixed pipeline uses it or state derived 12690from it. 12691Otherwise, behavior is undefined. 12692The following members are added to the output <em>gl_PerVertex</em> block in these 12693languages:</p> 12694</div> 12695<div class="listingblock"> 12696<div class="content"> 12697<pre class="CodeRay highlight"><code data-lang="c++">out gl_PerVertex { <span class="comment">// part of the gl_PerVertex block described in 7.1</span> 12698 <span class="comment">// in addition to other gl_PerVertex members...</span> 12699 vec4 gl_ClipVertex; 12700 vec4 gl_FrontColor; 12701 vec4 gl_BackColor; 12702 vec4 gl_FrontSecondaryColor; 12703 vec4 gl_BackSecondaryColor; 12704 vec4 gl_TexCoord[]; 12705 <span class="predefined-type">float</span> gl_FogFragCoord; 12706};</code></pre> 12707</div> 12708</div> 12709<div class="paragraph"> 12710<p>The output variable <em>gl_ClipVertex</em> provides a place for vertex and geometry 12711shaders to write the coordinate to be used with the user clipping planes. 12712Writing to <em>gl_ClipDistance</em> is the preferred method for user clipping. 12713It is a compile-time or link-time error for the set of shaders forming a 12714program to statically read or write both <em>gl_ClipVertex</em> and either 12715<em>gl_ClipDistance</em> or <em>gl_CullDistance</em>. 12716If neither <em>gl_ClipVertex</em> nor <em>gl_ClipDistance</em> is written, their values 12717are undefined and any clipping against user clip planes is also undefined.</p> 12718</div> 12719<div class="paragraph"> 12720<p>Similarly to what was previously described for the core profile, the 12721<em>gl_PerVertex</em> block can be redeclared in a shader to explicitly include 12722these additional members. 12723For example:</p> 12724</div> 12725<div class="listingblock"> 12726<div class="content"> 12727<pre class="CodeRay highlight"><code data-lang="c++">out gl_PerVertex { 12728 vec4 gl_Position; <span class="comment">// will use gl_Position</span> 12729 vec4 gl_FrontColor; <span class="comment">// will consume gl_color in the fragment shader</span> 12730 vec4 gl_BackColor; 12731 vec4 gl_TexCoord[<span class="integer">3</span>]; <span class="comment">// 3 elements of gl_TexCoord will be used</span> 12732}; <span class="comment">// no other aspects of the fixed interface will be used</span></code></pre> 12733</div> 12734</div> 12735<div class="paragraph"> 12736<p>The user must ensure the clip vertex and user clipping planes are defined in 12737the same coordinate space. 12738User clip planes work properly only under linear transform. 12739It is undefined what happens under non-linear transform.</p> 12740</div> 12741<div class="paragraph"> 12742<p>The output variables <em>gl_FrontColor</em>, <em>glFrontSecondaryColor</em>, 12743<em>gl_BackColor</em>, and <em>glBackSecondaryColor</em> assign primary and secondary 12744colors for front and back faces of primitives containing the vertex being 12745processed. 12746The output variable <em>gl_TexCoord</em> assigns texture coordinates for the vertex 12747being processed.</p> 12748</div> 12749<div class="paragraph"> 12750<p>For <em>gl_FogFragCoord</em>, the value written will be used as the “c” value in 12751section 16.4 “Fog” of the Compatibility profile of the 12752<a href="#references">OpenGL Specification</a>, by the fixed functionality pipeline. 12753For example, if the z-coordinate of the fragment in eye space is desired as 12754“c”, then that’s what the vertex shader executable should write into 12755<em>gl_FogFragCoord</em>.</p> 12756</div> 12757<div class="paragraph"> 12758<p>As with all arrays, indices used to subscript <em>gl_TexCoord</em> must either be a 12759constant integral expressions, or this array must be redeclared by the 12760shader with a size. 12761The size can be at most <em>gl_MaxTextureCoords</em>. 12762Using indices close to 0 may aid the implementation in preserving varying 12763resources. 12764The redeclaration of <em>gl_TexCoord</em> can also be done at global scope as, for 12765example:</p> 12766</div> 12767<div class="listingblock"> 12768<div class="content"> 12769<pre class="CodeRay highlight"><code data-lang="c++">in vec4 gl_TexCoord[<span class="integer">3</span>]; 12770out vec4 gl_TexCoord[<span class="integer">4</span>];</code></pre> 12771</div> 12772</div> 12773<div class="paragraph"> 12774<p>(This treatment is a special case for <em>gl_TexCoord[]</em>, not a general method 12775for redeclaring members of blocks.) It is a compile-time error to redeclare 12776<em>gl_TexCoord[]</em> at global scope if there is a redeclaration of the 12777corresponding built-in block; only one form of redeclaration is allowed 12778within a shader (and hence within a stage, as block redeclarations must 12779match across all shaders using it).</p> 12780</div> 12781<div class="paragraph"> 12782<p>In the tessellation control, evaluation, and geometry shaders, the outputs 12783of the previous stage described above are also available in the input 12784<em>gl_PerVertex</em> block in these languages.</p> 12785</div> 12786<div class="listingblock"> 12787<div class="content"> 12788<pre class="CodeRay highlight"><code data-lang="c++">in gl_PerVertex { <span class="comment">// part of the gl_PerVertex block described in 7.1</span> 12789 <span class="comment">// in addition to other gl_PerVertex members...</span> 12790 vec4 gl_ClipVertex; 12791 vec4 gl_FrontColor; 12792 vec4 gl_BackColor; 12793 vec4 gl_FrontSecondaryColor; 12794 vec4 gl_BackSecondaryColor; 12795 vec4 gl_TexCoord[]; 12796 <span class="predefined-type">float</span> gl_FogFragCoord; 12797} gl_in[];</code></pre> 12798</div> 12799</div> 12800<div class="paragraph"> 12801<p>These can be redeclared to establish an explicit pipeline interface, the 12802same way as described above for the output block <em>gl_PerVertex</em>, and the 12803input redeclaration must match the output redeclaration of the previous 12804stage. 12805However, when a built-in interface block with an instance name is redeclared 12806(e.g. <em>gl_in</em>), the instance name must be included in the redeclaration. 12807It is a compile-time error to not include the built-in instance name or to 12808change its name. 12809For example,</p> 12810</div> 12811<div class="listingblock"> 12812<div class="content"> 12813<pre class="CodeRay highlight"><code data-lang="c++">in gl_PerVertex { 12814 vec4 gl_ClipVertex; 12815 vec4 gl_FrontColor; 12816} gl_in[]; <span class="comment">// must be present and must be "gl_in[]"</span></code></pre> 12817</div> 12818</div> 12819<div class="paragraph"> 12820<p>Built-in block arrays predeclared with a size can be redeclared with unsized syntax. 12821This keeps their size equal to the original predeclared size.</p> 12822</div> 12823<div class="paragraph"> 12824<p>Treatment of <em>gl_TexCoord[]</em> redeclaration is also identical to that 12825described for the output block <em>gl_TexCoord[]</em> redeclaration.</p> 12826</div> 12827<div class="paragraph"> 12828<p>The following fragment input block is also available in a fragment shader 12829when using the compatibility profile:</p> 12830</div> 12831<div class="listingblock"> 12832<div class="content"> 12833<pre class="CodeRay highlight"><code data-lang="c++">in gl_PerFragment { 12834 in <span class="predefined-type">float</span> gl_FogFragCoord; 12835 in vec4 gl_TexCoord[]; 12836 in vec4 gl_Color; 12837 in vec4 gl_SecondaryColor; 12838};</code></pre> 12839</div> 12840</div> 12841<div class="paragraph"> 12842<p>The values in <em>gl_Color</em> and <em>gl_SecondaryColor</em> will be derived 12843automatically by the system from <em>gl_FrontColor</em>, <em>gl_BackColor</em>, 12844<em>gl_FrontSecondaryColor</em>, and <em>gl_BackSecondaryColor</em> based on which face is 12845visible in the primitive producing the fragment. 12846If fixed functionality is used for vertex processing, then <em>gl_FogFragCoord</em> 12847will either be the z-coordinate of the fragment in eye space, or the 12848interpolation of the fog coordinate, as described in section 16.4 “Fog” of 12849the Compatibility profile of the <a href="#references">OpenGL Specification</a>. 12850The <em>gl_TexCoord[]</em> values are the interpolated <em>gl_TexCoord[]</em> values from 12851a vertex shader or the texture coordinates of any fixed pipeline based 12852vertex functionality.</p> 12853</div> 12854<div class="paragraph"> 12855<p>Indices to the fragment shader <em>gl_TexCoord</em> array are as described above in 12856the vertex shader text.</p> 12857</div> 12858<div class="paragraph"> 12859<p>As described above for the input and output <em>gl_PerVertex</em> blocks, the 12860<em>gl_PerFragment</em> block can be redeclared to create an explicit interface to 12861another program. 12862When matching these interfaces between separate programs, members in the 12863<em>gl_PerVertex</em> output block must be declared if and only if the 12864corresponding fragment shader members generated from them are present in the 12865<em>gl_PerFragment</em> input block. 12866These matches are described in detail in section 7.4.1 “Shader Interface 12867Matching” of the <a href="#references">OpenGL Specification</a>. 12868If they don’t match within a program, a link-time error will result. 12869If the mismatch is between two programs, values passed between programs are 12870undefined. 12871Unlike with all other block matching, the order of declaration within 12872<em>gl_PerFragment</em> does not have to match across shaders and does not have to 12873correspond with order of declaration in a matching <em>gl_PerVertex</em> 12874redeclaration.</p> 12875</div> 12876<div class="paragraph"> 12877<p>The following fragment output variables are available in a fragment shader 12878when using the compatibility profile:</p> 12879</div> 12880<div class="listingblock"> 12881<div class="content"> 12882<pre class="CodeRay highlight"><code data-lang="c++">out vec4 gl_FragColor; 12883out vec4 gl_FragData[gl_MaxDrawBuffers];</code></pre> 12884</div> 12885</div> 12886<div class="paragraph"> 12887<p>Writing to <em>gl_FragColor</em> specifies the fragment color that will be used by 12888the subsequent fixed functionality pipeline. 12889If subsequent fixed functionality consumes fragment color and an execution 12890of the fragment shader executable does not write a value to <em>gl_FragColor</em> 12891then the fragment color consumed is undefined.</p> 12892</div> 12893<div class="paragraph"> 12894<p>The variable <em>gl_FragData</em> is an array. 12895Writing to <em>gl_FragData[n]</em> specifies the fragment data that will be used by 12896the subsequent fixed functionality pipeline for data <em>n</em>. 12897If subsequent fixed functionality consumes fragment data and an execution of 12898a fragment shader executable does not write a value to it, then the fragment 12899data consumed is undefined.</p> 12900</div> 12901<div class="paragraph"> 12902<p>If a shader statically assigns a value to <em>gl_FragColor</em>, it may not assign 12903a value to any element of <em>gl_FragData</em>. 12904If a shader statically writes a value to any element of <em>gl_FragData</em>, it 12905may not assign a value to <em>gl_FragColor</em>. 12906That is, a shader may assign values to either <em>gl_FragColor</em> or 12907<em>gl_FragData</em>, but not both. 12908Multiple shaders linked together must also consistently write just one of 12909these variables. 12910Similarly, if user-declared output variables are in use (statically assigned 12911to), then the built-in variables <em>gl_FragColor</em> and <em>gl_FragData</em> may not be 12912assigned to. 12913These incorrect usages all generate compile-time or link-time errors.</p> 12914</div> 12915<div class="paragraph"> 12916<p>If a shader executes the <strong>discard</strong> keyword, the fragment is discarded, and 12917the values of <em>gl_FragDepth</em> and <em>gl_FragColor</em> become irrelevant.</p> 12918</div> 12919</div> 12920</div> 12921<div class="sect2"> 12922<h3 id="compatibility-profile-vertex-shader-built-in-inputs">7.2. Compatibility Profile Vertex Shader Built-In Inputs</h3> 12923<div class="paragraph"> 12924<p>The following predeclared input names can be used from within a vertex 12925shader to access the current values of OpenGL state when using the 12926compatibility profile.</p> 12927</div> 12928<div class="listingblock"> 12929<div class="content"> 12930<pre class="CodeRay highlight"><code data-lang="c++">in vec4 gl_Color; 12931in vec4 gl_SecondaryColor; 12932in vec3 gl_Normal; 12933in vec4 gl_Vertex; 12934in vec4 gl_MultiTexCoord0; 12935in vec4 gl_MultiTexCoord1; 12936in vec4 gl_MultiTexCoord2; 12937in vec4 gl_MultiTexCoord3; 12938in vec4 gl_MultiTexCoord4; 12939in vec4 gl_MultiTexCoord5; 12940in vec4 gl_MultiTexCoord6; 12941in vec4 gl_MultiTexCoord7; 12942in <span class="predefined-type">float</span> gl_FogCoord;</code></pre> 12943</div> 12944</div> 12945</div> 12946<div class="sect2"> 12947<h3 id="built-in-constants">7.3. Built-In Constants</h3> 12948<div class="paragraph"> 12949<p>The following built-in constants are declared in all shaders. 12950The actual values used are implementation-dependent, but must be at least 12951the value shown.</p> 12952</div> 12953<div class="listingblock"> 12954<div class="content"> 12955<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">//</span> 12956<span class="comment">// Implementation-dependent constants. The example values below</span> 12957<span class="comment">// are the minimum values allowed for these maximums.</span> 12958<span class="comment">//</span></code></pre> 12959</div> 12960</div> 12961<div class="listingblock"> 12962<div class="content"> 12963<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexAttribs = <span class="integer">16</span>; 12964<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexUniformVectors = <span class="integer">256</span>; 12965<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexUniformComponents = <span class="integer">1024</span>; 12966<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexOutputComponents = <span class="integer">64</span>; 12967<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVaryingComponents = <span class="integer">60</span>; 12968<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVaryingVectors = <span class="integer">15</span>; 12969<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexTextureImageUnits = <span class="integer">16</span>; 12970<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexImageUniforms = <span class="integer">0</span>; 12971<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexAtomicCounters = <span class="integer">0</span>; 12972<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVertexAtomicCounterBuffers = <span class="integer">0</span>; 12973 12974<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessPatchComponents = <span class="integer">120</span>; 12975<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxPatchVertices = <span class="integer">32</span>; 12976<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessGenLevel = <span class="integer">64</span>; 12977 12978<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlInputComponents = <span class="integer">128</span>; 12979<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlOutputComponents = <span class="integer">128</span>; 12980<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlTextureImageUnits = <span class="integer">16</span>; 12981<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlUniformComponents = <span class="integer">1024</span>; 12982<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlTotalOutputComponents = <span class="integer">4096</span>; 12983<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlImageUniforms = <span class="integer">0</span>; 12984<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlAtomicCounters = <span class="integer">0</span>; 12985<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessControlAtomicCounterBuffers = <span class="integer">0</span>; 12986 12987<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessEvaluationInputComponents = <span class="integer">128</span>; 12988<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessEvaluationOutputComponents = <span class="integer">128</span>; 12989<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessEvaluationTextureImageUnits = <span class="integer">16</span>; 12990<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessEvaluationUniformComponents = <span class="integer">1024</span>; 12991<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessEvaluationImageUniforms = <span class="integer">0</span>; 12992<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessEvaluationAtomicCounters = <span class="integer">0</span>; 12993<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTessEvaluationAtomicCounterBuffers = <span class="integer">0</span>; 12994 12995<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryInputComponents = <span class="integer">64</span>; 12996<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryOutputComponents = <span class="integer">128</span>; 12997<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryImageUniforms = <span class="integer">0</span>; 12998<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryTextureImageUnits = <span class="integer">16</span>; 12999<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryOutputVertices = <span class="integer">256</span>; 13000<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryTotalOutputComponents = <span class="integer">1024</span>; 13001<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryUniformComponents = <span class="integer">1024</span>; 13002<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryVaryingComponents = <span class="integer">64</span>; <span class="comment">// deprecated</span> 13003<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryAtomicCounters = <span class="integer">0</span>; 13004<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxGeometryAtomicCounterBuffers = <span class="integer">0</span>; 13005 13006<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxFragmentImageUniforms = <span class="integer">8</span>; 13007<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxFragmentInputComponents = <span class="integer">128</span>; 13008<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxFragmentUniformVectors = <span class="integer">256</span>; 13009<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxFragmentUniformComponents = <span class="integer">1024</span>; 13010<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxFragmentAtomicCounters = <span class="integer">8</span>; 13011<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxFragmentAtomicCounterBuffers = <span class="integer">1</span>; 13012 13013<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxDrawBuffers = <span class="integer">8</span>; 13014<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTextureImageUnits = <span class="integer">16</span>; 13015<span class="directive">const</span> <span class="predefined-type">int</span> gl_MinProgramTexelOffset = -<span class="integer">8</span>; 13016<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxProgramTexelOffset = <span class="integer">7</span>; 13017<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxImageUnits = <span class="integer">8</span>; 13018<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxSamples = <span class="integer">4</span>; 13019<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxImageSamples = <span class="integer">0</span>; 13020<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxClipDistances = <span class="integer">8</span>; 13021<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCullDistances = <span class="integer">8</span>; 13022<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxViewports = <span class="integer">16</span>; 13023 13024<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxComputeImageUniforms = <span class="integer">8</span>; 13025<span class="directive">const</span> ivec3 gl_MaxComputeWorkGroupCount = { <span class="integer">65535</span>, <span class="integer">65535</span>, <span class="integer">65535</span> }; 13026<span class="directive">const</span> ivec3 gl_MaxComputeWorkGroupSize = { <span class="integer">1024</span>, <span class="integer">1024</span>, <span class="integer">64</span> }; 13027<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxComputeUniformComponents = <span class="integer">1024</span>; 13028<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxComputeTextureImageUnits = <span class="integer">16</span>; 13029<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxComputeAtomicCounters = <span class="integer">8</span>; 13030<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxComputeAtomicCounterBuffers = <span class="integer">8</span>; 13031 13032<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCombinedTextureImageUnits = <span class="integer">96</span>; 13033<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCombinedImageUniforms = <span class="integer">48</span>; 13034<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCombinedImageUnitsAndFragmentOutputs = <span class="integer">8</span>; <span class="comment">// deprecated</span> 13035<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCombinedShaderOutputResources = <span class="integer">16</span>; 13036<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCombinedAtomicCounters = <span class="integer">8</span>; 13037<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCombinedAtomicCounterBuffers = <span class="integer">1</span>; 13038<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxCombinedClipAndCullDistances = <span class="integer">8</span>; 13039<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxAtomicCounterBindings = <span class="integer">1</span>; 13040<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxAtomicCounterBufferSize = <span class="integer">32</span>; 13041 13042<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTransformFeedbackBuffers = <span class="integer">4</span>; 13043<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTransformFeedbackInterleavedComponents = <span class="integer">64</span>; 13044 13045<span class="directive">const</span> highp <span class="predefined-type">int</span> gl_MaxInputAttachments = <span class="integer">1</span>; <span class="comment">// only present when targeting Vulkan</span></code></pre> 13046</div> 13047</div> 13048<div class="paragraph"> 13049<p>The constant <em>gl_MaxVaryingFloats</em> is removed in the core profile, use 13050<em>gl_MaxVaryingComponents</em> instead.</p> 13051</div> 13052<div class="sect3"> 13053<h4 id="compatibility-profile-built-in-constants">7.3.1. Compatibility Profile Built-In Constants</h4> 13054<div class="listingblock"> 13055<div class="content"> 13056<pre class="CodeRay highlight"><code data-lang="c++"><span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTextureUnits = <span class="integer">2</span>; 13057<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxTextureCoords = <span class="integer">8</span>; 13058<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxClipPlanes = <span class="integer">8</span>; 13059<span class="directive">const</span> <span class="predefined-type">int</span> gl_MaxVaryingFloats = <span class="integer">60</span>;</code></pre> 13060</div> 13061</div> 13062</div> 13063</div> 13064<div class="sect2"> 13065<h3 id="built-in-uniform-state">7.4. Built-In Uniform State</h3> 13066<div class="paragraph"> 13067<p>Built-in uniform state is not available when generating SPIR-V. 13068Otherwise, as an aid to accessing OpenGL processing state, the following 13069uniform variables are built into the OpenGL Shading Language.</p> 13070</div> 13071<div class="listingblock"> 13072<div class="content"> 13073<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">//</span> 13074<span class="comment">// Depth range in window coordinates,</span> 13075<span class="comment">// section 13.6.1 "Controlling the Viewport" in the</span> 13076<span class="comment">// OpenGL Specification.</span> 13077<span class="comment">//</span> 13078<span class="comment">// Note: Depth-range state is only for viewport 0.</span> 13079<span class="comment">//</span> 13080<span class="keyword">struct</span> gl_DepthRangeParameters { 13081 <span class="predefined-type">float</span> near; <span class="comment">// n</span> 13082 <span class="predefined-type">float</span> far; <span class="comment">// f</span> 13083 <span class="predefined-type">float</span> diff; <span class="comment">// f - n</span> 13084}; 13085uniform gl_DepthRangeParameters gl_DepthRange; 13086uniform <span class="predefined-type">int</span> gl_NumSamples;</code></pre> 13087</div> 13088</div> 13089<div class="paragraph"> 13090<p>These variables are only guaranteed to be available in the fragment stage. 13091In other stages, their presence and function is implementation-defined.</p> 13092</div> 13093<div class="sect3"> 13094<h4 id="compatibility-profile-state">7.4.1. Compatibility Profile State</h4> 13095<div class="paragraph"> 13096<p>These variables are present only in the compatibility profile. 13097They are not available to compute shaders, but are available to all other 13098shaders.</p> 13099</div> 13100<div class="listingblock"> 13101<div class="content"> 13102<pre class="CodeRay highlight"><code data-lang="c++"><span class="comment">//</span> 13103<span class="comment">// compatibility profile only</span> 13104<span class="comment">//</span> 13105uniform mat4 gl_ModelViewMatrix; 13106uniform mat4 gl_ProjectionMatrix; 13107uniform mat4 gl_ModelViewProjectionMatrix; 13108uniform mat4 gl_TextureMatrix[gl_MaxTextureCoords]; 13109 13110<span class="comment">//</span> 13111<span class="comment">// compatibility profile only</span> 13112<span class="comment">//</span> 13113uniform mat3 gl_NormalMatrix; <span class="comment">// transpose of the inverse of the</span> 13114 <span class="comment">// upper leftmost 3x3 of gl_ModelViewMatrix</span> 13115 13116uniform mat4 gl_ModelViewMatrixInverse; 13117uniform mat4 gl_ProjectionMatrixInverse; 13118uniform mat4 gl_ModelViewProjectionMatrixInverse; 13119uniform mat4 gl_TextureMatrixInverse[gl_MaxTextureCoords]; 13120 13121uniform mat4 gl_ModelViewMatrixTranspose; 13122uniform mat4 gl_ProjectionMatrixTranspose; 13123uniform mat4 gl_ModelViewProjectionMatrixTranspose; 13124uniform mat4 gl_TextureMatrixTranspose[gl_MaxTextureCoords]; 13125 13126uniform mat4 gl_ModelViewMatrixInverseTranspose; 13127uniform mat4 gl_ProjectionMatrixInverseTranspose; 13128uniform mat4 gl_ModelViewProjectionMatrixInverseTranspose; 13129uniform mat4 gl_TextureMatrixInverseTranspose[gl_MaxTextureCoords]; 13130 13131<span class="comment">//</span> 13132<span class="comment">// compatibility profile only</span> 13133<span class="comment">//</span> 13134uniform <span class="predefined-type">float</span> gl_NormalScale; 13135 13136<span class="comment">//</span> 13137<span class="comment">// compatibility profile only</span> 13138<span class="comment">//</span> 13139uniform vec4 gl_ClipPlane[gl_MaxClipPlanes]; 13140 13141<span class="comment">//</span> 13142<span class="comment">// compatibility profile only</span> 13143<span class="comment">//</span> 13144<span class="keyword">struct</span> gl_PointParameters { 13145 <span class="predefined-type">float</span> size; 13146 <span class="predefined-type">float</span> sizeMin; 13147 <span class="predefined-type">float</span> sizeMax; 13148 <span class="predefined-type">float</span> fadeThresholdSize; 13149 <span class="predefined-type">float</span> distanceConstantAttenuation; 13150 <span class="predefined-type">float</span> distanceLinearAttenuation; 13151 <span class="predefined-type">float</span> distanceQuadraticAttenuation; 13152}; 13153 13154uniform gl_PointParameters gl_Point; 13155 13156<span class="comment">//</span> 13157<span class="comment">// compatibility profile only</span> 13158<span class="comment">//</span> 13159<span class="keyword">struct</span> gl_MaterialParameters { 13160 vec4 emission; <span class="comment">// Ecm</span> 13161 vec4 ambient; <span class="comment">// Acm</span> 13162 vec4 diffuse; <span class="comment">// Dcm</span> 13163 vec4 specular; <span class="comment">// Scm</span> 13164 <span class="predefined-type">float</span> shininess; <span class="comment">// Srm</span> 13165}; 13166uniform gl_MaterialParameters gl_FrontMaterial; 13167uniform gl_MaterialParameters gl_BackMaterial; 13168 13169<span class="comment">//</span> 13170<span class="comment">// compatibility profile only</span> 13171<span class="comment">//</span> 13172<span class="keyword">struct</span> gl_LightSourceParameters { 13173 vec4 ambient; <span class="comment">// Acli</span> 13174 vec4 diffuse; <span class="comment">// Dcli</span> 13175 vec4 specular; <span class="comment">// Scli</span> 13176 vec4 position; <span class="comment">// Ppli</span> 13177 vec4 halfVector; <span class="comment">// Derived: Hi</span> 13178 vec3 spotDirection; <span class="comment">// Sdli</span> 13179 <span class="predefined-type">float</span> spotExponent; <span class="comment">// Srli</span> 13180 <span class="predefined-type">float</span> spotCutoff; <span class="comment">// Crli</span> 13181 <span class="comment">// (range: [0.0,90.0], 180.0)</span> 13182 <span class="predefined-type">float</span> spotCosCutoff; <span class="comment">// Derived: cos(Crli)</span> 13183 <span class="comment">// (range: [1.0,0.0],-1.0)</span> 13184 <span class="predefined-type">float</span> constantAttenuation; <span class="comment">// K0</span> 13185 <span class="predefined-type">float</span> linearAttenuation; <span class="comment">// K1</span> 13186 <span class="predefined-type">float</span> quadraticAttenuation; <span class="comment">// K2</span> 13187}; 13188 13189uniform gl_LightSourceParameters gl_LightSource[gl_MaxLights]; 13190 13191<span class="keyword">struct</span> gl_LightModelParameters { 13192 vec4 ambient; <span class="comment">// Acs</span> 13193}; 13194 13195uniform gl_LightModelParameters gl_LightModel; 13196 13197<span class="comment">//</span> 13198<span class="comment">// compatibility profile only</span> 13199<span class="comment">//</span> 13200<span class="comment">// Derived state from products of light and material.</span> 13201<span class="comment">//</span> 13202 13203<span class="keyword">struct</span> gl_LightModelProducts { 13204 vec4 sceneColor; <span class="comment">// Derived. Ecm + Acm * Acs</span> 13205}; 13206 13207uniform gl_LightModelProducts gl_FrontLightModelProduct; 13208uniform gl_LightModelProducts gl_BackLightModelProduct; 13209 13210<span class="keyword">struct</span> gl_LightProducts { 13211 vec4 ambient; <span class="comment">// Acm * Acli</span> 13212 vec4 diffuse; <span class="comment">// Dcm * Dcli</span> 13213 vec4 specular; <span class="comment">// Scm * Scli</span> 13214}; 13215 13216uniform gl_LightProducts gl_FrontLightProduct[gl_MaxLights]; 13217uniform gl_LightProducts gl_BackLightProduct[gl_MaxLights]; 13218 13219<span class="comment">//</span> 13220<span class="comment">// compatibility profile only</span> 13221<span class="comment">//</span> 13222uniform vec4 gl_TextureEnvColor[gl_MaxTextureUnits]; 13223uniform vec4 gl_EyePlaneS[gl_MaxTextureCoords]; 13224uniform vec4 gl_EyePlaneT[gl_MaxTextureCoords]; 13225uniform vec4 gl_EyePlaneR[gl_MaxTextureCoords]; 13226uniform vec4 gl_EyePlaneQ[gl_MaxTextureCoords]; 13227uniform vec4 gl_ObjectPlaneS[gl_MaxTextureCoords]; 13228uniform vec4 gl_ObjectPlaneT[gl_MaxTextureCoords]; 13229uniform vec4 gl_ObjectPlaneR[gl_MaxTextureCoords]; 13230uniform vec4 gl_ObjectPlaneQ[gl_MaxTextureCoords]; 13231 13232<span class="comment">//</span> 13233<span class="comment">// compatibility profile only</span> 13234<span class="comment">//</span> 13235<span class="keyword">struct</span> gl_FogParameters { 13236 vec4 color; 13237 <span class="predefined-type">float</span> density; 13238 <span class="predefined-type">float</span> start; 13239 <span class="predefined-type">float</span> end; 13240 <span class="predefined-type">float</span> scale; <span class="comment">// Derived: 1.0 / (end - start)</span> 13241}; 13242 13243uniform gl_FogParameters gl_Fog;</code></pre> 13244</div> 13245</div> 13246</div> 13247</div> 13248<div class="sect2"> 13249<h3 id="redeclaring-built-in-blocks">7.5. Redeclaring Built-In Blocks</h3> 13250<div class="paragraph"> 13251<p>The <em>gl_PerVertex</em> block can be redeclared in a shader to explicitly 13252indicate what subset of the fixed pipeline interface will be used. 13253This is necessary to establish the interface between multiple programs. 13254For example:</p> 13255</div> 13256<div class="listingblock"> 13257<div class="content"> 13258<pre class="CodeRay highlight"><code data-lang="c++">out gl_PerVertex { 13259 vec4 gl_Position; <span class="comment">// will use gl_Position</span> 13260 <span class="predefined-type">float</span> gl_PointSize; <span class="comment">// will use gl_PointSize</span> 13261 vec4 t; <span class="comment">// error, only gl_PerVertex members allowed</span> 13262}; <span class="comment">// no other members of gl_PerVertex will be used</span></code></pre> 13263</div> 13264</div> 13265<div class="paragraph"> 13266<p>This establishes the output interface the shader will use with the 13267subsequent pipeline stage. 13268It must be a subset of the built-in members of <em>gl_PerVertex</em>. 13269Such a redeclaration can also add the <strong>invariant</strong> qualifier, interpolation 13270qualifiers, and the layout qualifiers <strong>xfb_offset</strong>, <strong>xfb_buffer</strong>, and 13271<strong>xfb_stride</strong>. 13272It can also add an array size for unsized arrays. 13273For example:</p> 13274</div> 13275<div class="listingblock"> 13276<div class="content"> 13277<pre class="CodeRay highlight"><code data-lang="c++">out layout(xfb_buffer = <span class="integer">1</span>, xfb_stride = <span class="integer">16</span>) gl_PerVertex { 13278 vec4 gl_Position; 13279 layout(xfb_offset = <span class="integer">0</span>) <span class="predefined-type">float</span> gl_ClipDistance[<span class="integer">4</span>]; 13280};</code></pre> 13281</div> 13282</div> 13283<div class="paragraph"> 13284<p>Other layout qualifiers, like <strong>location</strong>, cannot be added to such a 13285redeclaration, unless specifically stated.</p> 13286</div> 13287<div class="paragraph"> 13288<p>If a built-in interface block is redeclared, it must appear in the shader 13289before any use of any member included in the built-in declaration, or a 13290compile-time error will result. 13291It is also a compile-time error to redeclare the block more than once or to 13292redeclare a built-in block and then use a member from that built-in block 13293that was not included in the redeclaration. 13294Also, if a built-in interface block is redeclared, no member of the built-in 13295declaration can be redeclared outside the block redeclaration. 13296If multiple shaders using members of a built-in block belonging to the same 13297interface are linked together in the same program, they must all redeclare 13298the built-in block in the same way, as described in 13299“<a href="#interface-blocks">Interface Blocks</a>” for interface block matching, or a 13300link-time error will result. 13301It will also be a link-time error if some shaders in a program redeclare a 13302specific built-in interface block while another shader in that program does 13303not redeclare that interface block yet still uses a member of that interface 13304block. 13305If a built-in block interface is formed across shaders in different 13306programs, the shaders must all redeclare the built-in block in the same way 13307(as described for a single program), or the values passed along the 13308interface are undefined.</p> 13309</div> 13310</div> 13311</div> 13312</div> 13313<div class="sect1"> 13314<h2 id="built-in-functions">8. Built-In Functions</h2> 13315<div class="sectionbody"> 13316<div class="paragraph"> 13317<p>The OpenGL Shading Language defines an assortment of built-in convenience functions for 13318scalar and vector operations. 13319Many of these built-in functions can be used in more than one type of 13320shader, but some are intended to provide a direct mapping to hardware and so 13321are available only for a specific type of shader.</p> 13322</div> 13323<div class="paragraph"> 13324<p>The built-in functions basically fall into three categories:</p> 13325</div> 13326<div class="ulist"> 13327<ul> 13328<li> 13329<p>They expose some necessary hardware functionality in a convenient way 13330such as accessing a texture map. 13331There is no way in the language for these functions to be emulated by a 13332shader.</p> 13333</li> 13334<li> 13335<p>They represent a trivial operation (clamp, mix, etc.) that is very 13336simple for the user to write, but they are very common and may have 13337direct hardware support. 13338It is a very hard problem for the compiler to map expressions to complex 13339assembler instructions.</p> 13340</li> 13341<li> 13342<p>They represent an operation graphics hardware is likely to accelerate at 13343some point. 13344The trigonometry functions fall into this category.</p> 13345</li> 13346</ul> 13347</div> 13348<div class="paragraph"> 13349<p>Many of the functions are similar to the same named ones in common C 13350libraries, but they support vector input as well as the more traditional 13351scalar input.</p> 13352</div> 13353<div class="paragraph"> 13354<p>Applications should be encouraged to use the built-in functions rather than 13355do the equivalent computations in their own shader code since the built-in 13356functions are assumed to be optimal (e.g. perhaps supported directly in 13357hardware).</p> 13358</div> 13359<div class="paragraph"> 13360<p>User code can replace built-in functions with their own if they choose, by 13361simply redeclaring and defining the same name and argument list. 13362Because built-in functions are in a more outer scope than user built-in 13363functions, doing this will hide all built-in functions with the same name as 13364the redeclared function.</p> 13365</div> 13366<div class="paragraph"> 13367<p>When the built-in functions are specified below, where the input arguments 13368(and corresponding output) can be <strong>float</strong>, <strong>vec2</strong>, <strong>vec3</strong>, or <strong>vec4</strong>, 13369<em>genFType</em> is used as the argument. 13370Where the input arguments (and corresponding output) can be <strong>int</strong>, <strong>ivec2</strong>, 13371<strong>ivec3</strong>, or <strong>ivec4</strong>, <em>genIType</em> is used as the argument. 13372Where the input arguments (and corresponding output) can be <strong>uint</strong>, <strong>uvec2</strong>, 13373<strong>uvec3</strong>, or <strong>uvec4</strong>, <em>genUType</em> is used as the argument. 13374Where the input arguments (or corresponding output) can be <strong>bool</strong>, <strong>bvec2</strong>, 13375<strong>bvec3</strong>, or <strong>bvec4</strong>, <em>genBType</em> is used as the argument. 13376Where the input arguments (and corresponding output) can be <strong>double</strong>, 13377<strong>dvec2</strong>, <strong>dvec3</strong>, <strong>dvec4</strong>, <em>genDType</em> is used as the argument. 13378For any specific use of a function, the actual types substituted for 13379<em>genFType</em>, <em>genIType</em>, <em>genUType</em>, or <em>genBType</em> have to have the same 13380number of components for all arguments and for the return type. 13381Similarly, <em>mat</em> is used for any matrix basic 13382type with single-precision 13383components and <em>dmat</em> is used for any matrix basic type with 13384double-precision components.</p> 13385</div> 13386<div class="paragraph"> 13387<p>Built-in functions have an effective precision qualification. 13388This qualification cannot be set explicitly and may be different from the 13389precision qualification of the result.</p> 13390</div> 13391<div class="paragraph"> 13392<p>Note: In general, as has been noted, precision qualification is ignored 13393unless targeting Vulkan.</p> 13394</div> 13395<div class="paragraph"> 13396<p>The precision qualification of the operation of a built-in function is based 13397on the precision qualification of its formal parameters and actual 13398parameters (input arguments): When a formal parameter specifies a precision 13399qualifier, that is used, otherwise, the precision qualification of the 13400actual (calling) argument is used. 13401The highest precision of these will be the precision of the operation of the 13402built-in function. 13403Generally, this is applied across all arguments to a built-in function, with 13404the exceptions being:</p> 13405</div> 13406<div class="ulist"> 13407<ul> 13408<li> 13409<p><strong>bitfieldExtract</strong> and <strong>bitfieldInsert</strong> ignore the <em>offset</em> and <em>bits</em> 13410arguments.</p> 13411</li> 13412<li> 13413<p><strong>interpolateAt</strong> functions only look at the <em>interpolant</em> argument.</p> 13414</li> 13415</ul> 13416</div> 13417<div class="paragraph"> 13418<p>The precision qualification of the result of a built-in function is 13419determined in one of the following ways:</p> 13420</div> 13421<div class="paragraph"> 13422<p>For the texture sampling, image load and image store functions, the 13423precision of the return type matches the precision of the 13424texture-combined sampler type:</p> 13425</div> 13426<div class="listingblock"> 13427<div class="content"> 13428<pre class="CodeRay highlight"><code data-lang="c++">uniform lowp sampler2D texSampler; 13429highp vec2 coord; 13430... 13431lowp vec4 col = texture (texSampler, coord); <span class="comment">// texture() returns lowp</span></code></pre> 13432</div> 13433</div> 13434<div class="paragraph"> 13435<p>Otherwise:</p> 13436</div> 13437<div class="ulist"> 13438<ul> 13439<li> 13440<p>For prototypes that do not specify a resulting precision qualifier, the 13441precision will be the same as the precision of the operation (as defined 13442earlier).</p> 13443</li> 13444<li> 13445<p>For prototypes that do specify a resulting precision qualifier, the 13446specified precision qualifier is the precision qualification of the 13447result.</p> 13448</li> 13449</ul> 13450</div> 13451<div class="paragraph"> 13452<p>Where the built-in functions in the following sections specify an equation, 13453the entire equation will be evaluated at the operation’s precision. 13454This may lead to underflow or overflow in the result, even when the correct 13455result could be represented in the operation precision.</p> 13456</div> 13457<div class="sect2"> 13458<h3 id="angle-and-trigonometry-functions">8.1. Angle and Trigonometry Functions</h3> 13459<div class="paragraph"> 13460<p>Function parameters specified as <em>angle</em> are assumed to be in units of 13461radians. 13462In no case will any of these functions result in a divide by zero error. 13463If the divisor of a ratio is 0, then results will be undefined.</p> 13464</div> 13465<div class="paragraph"> 13466<p>These all operate component-wise. 13467The description is per component.</p> 13468</div> 13469<table class="tableblock frame-all grid-all stretch"> 13470<colgroup> 13471<col style="width: 50%;"> 13472<col style="width: 50%;"> 13473</colgroup> 13474<thead> 13475<tr> 13476<th class="tableblock halign-left valign-top">Syntax</th> 13477<th class="tableblock halign-left valign-top">Description</th> 13478</tr> 13479</thead> 13480<tbody> 13481<tr> 13482<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>radians</strong>(genFType <em>degrees</em>)</p></td> 13483<td class="tableblock halign-left valign-top"><p class="tableblock">Converts <em>degrees</em> to radians, i.e., 13484 <span class="eq">(π / 180) · degrees</span>.</p></td> 13485</tr> 13486<tr> 13487<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>degrees</strong>(genFType <em>radians</em>)</p></td> 13488<td class="tableblock halign-left valign-top"><p class="tableblock">Converts <em>radians</em> to degrees, i.e., 13489 <span class="eq">(180 / π) · radians</span>.</p></td> 13490</tr> 13491<tr> 13492<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>sin</strong>(genFType <em>angle</em>)</p></td> 13493<td class="tableblock halign-left valign-top"><p class="tableblock">The standard trigonometric sine function.</p></td> 13494</tr> 13495<tr> 13496<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>cos</strong>(genFType <em>angle</em>)</p></td> 13497<td class="tableblock halign-left valign-top"><p class="tableblock">The standard trigonometric cosine function.</p></td> 13498</tr> 13499<tr> 13500<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>tan</strong>(genFType <em>angle</em>)</p></td> 13501<td class="tableblock halign-left valign-top"><p class="tableblock">The standard trigonometric tangent.</p></td> 13502</tr> 13503<tr> 13504<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>asin</strong>(genFType <em>x</em>)</p></td> 13505<td class="tableblock halign-left valign-top"><p class="tableblock">Arc sine. 13506 Returns an angle whose sine is <em>x</em>. 13507 The range of values returned by this function is 13508 <span class="eq">[-π / 2, π / 2]</span>. 13509 Results are undefined if <span class="eq">|x| > 1</span>.</p></td> 13510</tr> 13511<tr> 13512<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>acos</strong>(genFType <em>x</em>)</p></td> 13513<td class="tableblock halign-left valign-top"><p class="tableblock">Arc cosine. 13514 Returns an angle whose cosine is <em>x</em>. 13515 The range of values returned by this function is <span class="eq">[0,π]</span>. 13516 Results are undefined if <span class="eq">|x| > 1</span>.</p></td> 13517</tr> 13518<tr> 13519<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>atan</strong>(genFType <em>y</em>, genFType <em>x</em>)</p></td> 13520<td class="tableblock halign-left valign-top"><p class="tableblock">Arc tangent. 13521 Returns an angle whose tangent is <span class="eq">y / x</span>. 13522 The signs of <em>x</em> and <em>y</em> are used to determine what quadrant the angle 13523 is in. 13524 The range of values returned by this function is <span class="eq">[-π, π</span>. 13525 Results are undefined if <em>x</em> and <em>y</em> are both 0.</p></td> 13526</tr> 13527<tr> 13528<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>atan</strong>(genFType <em>y_over_x</em>)</p></td> 13529<td class="tableblock halign-left valign-top"><p class="tableblock">Arc tangent. 13530 Returns an angle whose tangent is <em>y_over_x</em>. 13531 The range of values returned by this function is 13532 <span class="eq">[-π / 2, π / 2]</span>.</p></td> 13533</tr> 13534<tr> 13535<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>sinh</strong>(genFType <em>x</em>)</p></td> 13536<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the hyperbolic sine function <span class="eq">(e<sup>x</sup> - e<sup>-x</sup>) / 2</span>.</p></td> 13537</tr> 13538<tr> 13539<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>cosh</strong>(genFType <em>x</em>)</p></td> 13540<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the hyperbolic cosine function <span class="eq">(e<sup>x</sup> + e<sup>-x</sup>) / 2</span>.</p></td> 13541</tr> 13542<tr> 13543<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>tanh</strong>(genFType <em>x</em>)</p></td> 13544<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the hyperbolic tangent function <span class="eq">sinh(x) / cosh(x)</span>.</p></td> 13545</tr> 13546<tr> 13547<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>asinh</strong>(genFType <em>x</em>)</p></td> 13548<td class="tableblock halign-left valign-top"><p class="tableblock">Arc hyperbolic sine; returns the inverse of <strong>sinh</strong>.</p></td> 13549</tr> 13550<tr> 13551<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>acosh</strong>(genFType <em>x</em>)</p></td> 13552<td class="tableblock halign-left valign-top"><p class="tableblock">Arc hyperbolic cosine; returns the non-negative inverse of <strong>cosh</strong>. 13553 Results are undefined if <span class="eq">x < 1</span>.</p></td> 13554</tr> 13555<tr> 13556<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>atanh</strong>(genFType <em>x</em>)</p></td> 13557<td class="tableblock halign-left valign-top"><p class="tableblock">Arc hyperbolic tangent; returns the inverse of <strong>tanh</strong>. 13558 Results are undefined if <span class="eq">x ≥ 1</span>.</p></td> 13559</tr> 13560</tbody> 13561</table> 13562</div> 13563<div class="sect2"> 13564<h3 id="exponential-functions">8.2. Exponential Functions</h3> 13565<div class="paragraph"> 13566<p>These all operate component-wise. 13567The description is per component.</p> 13568</div> 13569<table class="tableblock frame-all grid-all stretch"> 13570<colgroup> 13571<col style="width: 50%;"> 13572<col style="width: 50%;"> 13573</colgroup> 13574<thead> 13575<tr> 13576<th class="tableblock halign-left valign-top">Syntax</th> 13577<th class="tableblock halign-left valign-top">Description</th> 13578</tr> 13579</thead> 13580<tbody> 13581<tr> 13582<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>pow</strong>(genFType <em>x</em>, genFType <em>y</em>)</p></td> 13583<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <em>x</em> raised to the <em>y</em> power, i.e., <span class="eq">x<sup>y</sup></span>. 13584 Results are undefined if <span class="eq">x < 0</span>. 13585 Results are undefined if <span class="eq">x = 0</span> and <span class="eq">y ≤ 0</span>.</p></td> 13586</tr> 13587<tr> 13588<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>exp</strong>(genFType <em>x</em>)</p></td> 13589<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the natural exponentiation of <em>x</em>, i.e., <span class="eq">e<sup>x</sup></span>.</p></td> 13590</tr> 13591<tr> 13592<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>log</strong>(genFType <em>x</em>)</p></td> 13593<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the natural logarithm of <em>x</em>, i.e., returns the value <em>y</em> 13594 which satisfies the equation <span class="eq">x = e<sup>y</sup></span>. 13595 Results are undefined if <span class="eq">x ≤ 0</span>.</p></td> 13596</tr> 13597<tr> 13598<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>exp2</strong>(genFType <em>x</em>)</p></td> 13599<td class="tableblock halign-left valign-top"><p class="tableblock">Returns 2 raised to the <em>x</em> power, i.e., <span class="eq">2<sup>x</sup></span>.</p></td> 13600</tr> 13601<tr> 13602<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>log2</strong>(genFType <em>x</em>)</p></td> 13603<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the base 2 logarithm of <em>x</em>, i.e., returns the value <em>y</em> which 13604 satisfies the equation <span class="eq">x = 2<sup>y</sup></span>. 13605 Results are undefined if <span class="eq">x ≤ 0</span>.</p></td> 13606</tr> 13607<tr> 13608<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>sqrt</strong>(genFType <em>x</em>)<br> 13609 genDType <strong>sqrt</strong>(genDType <em>x</em>)</p></td> 13610<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <span class="eq">sqrt(x)</span>. 13611 Results are undefined if <span class="eq">x < 0</span>.</p></td> 13612</tr> 13613<tr> 13614<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>inversesqrt</strong>(genFType <em>x</em>)<br> 13615 genDType <strong>inversesqrt</strong>(genDType <em>x</em>)</p></td> 13616<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <span class="eq">1 / sqrt(x)</span>. 13617 Results are undefined if <span class="eq">x ≤ 0</span>.</p></td> 13618</tr> 13619</tbody> 13620</table> 13621</div> 13622<div class="sect2"> 13623<h3 id="common-functions">8.3. Common Functions</h3> 13624<div class="paragraph"> 13625<p>These all operate component-wise. 13626The description is per component.</p> 13627</div> 13628<table class="tableblock frame-all grid-all stretch"> 13629<colgroup> 13630<col style="width: 50%;"> 13631<col style="width: 50%;"> 13632</colgroup> 13633<thead> 13634<tr> 13635<th class="tableblock halign-left valign-top">Syntax</th> 13636<th class="tableblock halign-left valign-top">Description</th> 13637</tr> 13638</thead> 13639<tbody> 13640<tr> 13641<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>abs</strong>(genFType <em>x</em>)<br> 13642 genIType <strong>abs</strong>(genIType <em>x</em>)<br> 13643 genDType <strong>abs</strong>(genDType <em>x</em>)</p></td> 13644<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <em>x</em> if <span class="eq">x ≥ 0</span>; otherwise it returns -<em>x</em>.</p></td> 13645</tr> 13646<tr> 13647<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>sign</strong>(genFType <em>x</em>)<br> 13648 genIType <strong>sign</strong>(genIType <em>x</em>)<br> 13649 genDType <strong>sign</strong>(genDType <em>x</em>)</p></td> 13650<td class="tableblock halign-left valign-top"><p class="tableblock">Returns 1.0 if <em>x</em> > 0, 0.0 if <em>x</em> = 0, or -1.0 if <em>x</em> < 0.</p></td> 13651</tr> 13652<tr> 13653<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>floor</strong>(genFType <em>x</em>)<br> 13654 genDType <strong>floor</strong>(genDType <em>x</em>)</p></td> 13655<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a value equal to the nearest integer that is less than or 13656 equal to <em>x</em>.</p></td> 13657</tr> 13658<tr> 13659<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>trunc</strong>(genFType <em>x</em>)<br> 13660 genDType <strong>trunc</strong>(genDType <em>x</em>)</p></td> 13661<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a value equal to the nearest integer to <em>x</em> whose absolute 13662 value is not larger than the absolute value of <em>x</em>.</p></td> 13663</tr> 13664<tr> 13665<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>round</strong>(genFType <em>x</em>)<br> 13666 genDType <strong>round</strong>(genDType <em>x</em>)</p></td> 13667<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a value equal to the nearest integer to <em>x</em>. 13668 The fraction 0.5 will round in a direction chosen by the 13669 implementation, presumably the direction that is fastest. 13670 This includes the possibility that <strong>round</strong>(<em>x</em>) returns the same value 13671 as <strong>roundEven</strong>(<em>x</em>) for all values of <em>x</em>.</p></td> 13672</tr> 13673<tr> 13674<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>roundEven</strong>(genFType <em>x</em>)<br> 13675 genDType <strong>roundEven</strong>(genDType <em>x</em>)</p></td> 13676<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a value equal to the nearest integer to <em>x</em>. 13677 A fractional part of 0.5 will round toward the nearest even integer. 13678 (Both 3.5 and 4.5 for x will return 4.0.)</p></td> 13679</tr> 13680<tr> 13681<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>ceil</strong>(genFType <em>x</em>)<br> 13682 genDType <strong>ceil</strong>(genDType <em>x</em>)</p></td> 13683<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a value equal to the nearest integer that is greater than or 13684 equal to <em>x</em>.</p></td> 13685</tr> 13686<tr> 13687<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>fract</strong>(genFType <em>x</em>)<br> 13688 genDType <strong>fract</strong>(genDType <em>x</em>)<br></p></td> 13689<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <em>x</em> - <strong>floor</strong>(<em>x</em>).</p></td> 13690</tr> 13691<tr> 13692<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>mod</strong>(genFType <em>x</em>, float <em>y</em>)<br> 13693 genFType <strong>mod</strong>(genFType <em>x</em>, genFType <em>y</em>)<br> 13694 genDType <strong>mod</strong>(genDType <em>x</em>, double <em>y</em>)<br> 13695 genDType <strong>mod</strong>(genDType <em>x</em>, genDType <em>y</em>)<br></p></td> 13696<td class="tableblock halign-left valign-top"><p class="tableblock">Modulus. 13697 Returns <span class="eq">x - y · <strong>floor</strong>(x / y)</span>.</p></td> 13698</tr> 13699<tr> 13700<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>modf</strong>(genFType <em>x</em>, out genFType <em>i</em>)<br> 13701 genDType <strong>modf</strong>(genDType <em>x</em>, out genDType <em>i</em>)</p></td> 13702<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the fractional part of <em>x</em> and sets <em>i</em> to the integer part (as 13703 a whole number floating-point value). 13704 Both the return value and the output parameter will have the same sign 13705 as <em>x</em>.</p></td> 13706</tr> 13707<tr> 13708<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>min</strong>(genFType <em>x</em>, genFType <em>y</em>)<br> 13709 genFType <strong>min</strong>(genFType <em>x</em>, float <em>y</em>)<br> 13710 genDType <strong>min</strong>(genDType <em>x</em>, genDType <em>y</em>)<br> 13711 genDType <strong>min</strong>(genDType <em>x</em>, double <em>y</em>)<br> 13712 genIType <strong>min</strong>(genIType <em>x</em>, genIType <em>y</em>)<br> 13713 genIType <strong>min</strong>(genIType <em>x</em>, int <em>y</em>)<br> 13714 genUType <strong>min</strong>(genUType <em>x</em>, genUType <em>y</em>)<br> 13715 genUType <strong>min</strong>(genUType <em>x</em>, uint <em>y</em>)</p></td> 13716<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <em>y</em> if <em>y</em> < <em>x;</em> otherwise it returns <em>x</em>.</p></td> 13717</tr> 13718<tr> 13719<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>max</strong>(genFType <em>x</em>, genFType <em>y</em>)<br> 13720 genFType <strong>max</strong>(genFType <em>x</em>, float <em>y</em>)<br> 13721 genDType <strong>max</strong>(genDType <em>x</em>, genDType <em>y</em>)<br> 13722 genDType <strong>max</strong>(genDType <em>x</em>, double <em>y</em>)<br> 13723 genIType <strong>max</strong>(genIType <em>x</em>, genIType <em>y</em>)<br> 13724 genIType <strong>max</strong>(genIType <em>x</em>, int <em>y</em>)<br> 13725 genUType <strong>max</strong>(genUType <em>x</em>, genUType <em>y</em>)<br> 13726 genUType <strong>max</strong>(genUType <em>x</em>, uint <em>y</em>)</p></td> 13727<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <em>y</em> if <em>x</em> < <em>y;</em> otherwise it returns <em>x</em>.</p></td> 13728</tr> 13729<tr> 13730<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>clamp</strong>(genFType <em>x</em>, genFType <em>minVal</em>, genFType <em>maxVal</em>)<br> 13731 genFType <strong>clamp</strong>(genFType <em>x</em>, float <em>minVal</em>, float <em>maxVal</em>)<br> 13732 genDType <strong>clamp</strong>(genDType <em>x</em>, genDType <em>minVal</em>, genDType <em>maxVal</em>)<br> 13733 genDType <strong>clamp</strong>(genDType <em>x</em>, double <em>minVal</em>, double <em>maxVal</em>)<br> 13734 genIType <strong>clamp</strong>(genIType <em>x</em>, genIType <em>minVal</em>, genIType <em>maxVal</em>)<br> 13735 genIType <strong>clamp</strong>(genIType <em>x</em>, int <em>minVal</em>, int <em>maxVal</em>)<br> 13736 genUType <strong>clamp</strong>(genUType <em>x</em>, genUType <em>minVal</em>, genUType <em>maxVal</em>)<br> 13737 genUType <strong>clamp</strong>(genUType <em>x</em>, uint <em>minVal</em>, uint <em>maxVal</em>)</p></td> 13738<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>min</strong>(<strong>max</strong>(<em>x</em>, <em>minVal</em>), <em>maxVal</em>). 13739 Results are undefined if <em>minVal</em> > <em>maxVal</em>.</p></td> 13740</tr> 13741<tr> 13742<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>mix</strong>(genFType <em>x</em>, genFType <em>y</em>, genFType <em>a</em>)<br> 13743 genFType <strong>mix</strong>(genFType <em>x</em>, genFType <em>y</em>, float <em>a</em>)<br> 13744 genDType <strong>mix</strong>(genDType <em>x</em>, genDType <em>y</em>, genDType <em>a</em>)<br> 13745 genDType <strong>mix</strong>(genDType <em>x</em>, genDType <em>y</em>, double <em>a</em>)<br></p></td> 13746<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the linear blend of <em>x</em> and <em>y</em>, i.e., 13747 <span class="eq">x · (1 - a) + y · a</span>.</p></td> 13748</tr> 13749<tr> 13750<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>mix</strong>(genFType <em>x</em>, genFType <em>y</em>, genBType <em>a</em>)<br> 13751 genDType <strong>mix</strong>(genDType <em>x</em>, genDType <em>y</em>, genBType <em>a</em>)<br> 13752 genIType <strong>mix</strong>(genIType <em>x</em>, genIType <em>y</em>, genBType <em>a</em>)<br> 13753 genUType <strong>mix</strong>(genUType <em>x</em>, genUType <em>y</em>, genBType <em>a</em>)<br> 13754 genBType <strong>mix</strong>(genBType <em>x</em>, genBType <em>y</em>, genBType <em>a</em>)</p></td> 13755<td class="tableblock halign-left valign-top"><p class="tableblock">Selects which vector each returned component comes from. 13756 For a component of <em>a</em> that is <strong>false</strong>, the corresponding component of 13757 <em>x</em> is returned. 13758 For a component of <em>a</em> that is <strong>true</strong>, the corresponding component of 13759 <em>y</em> is returned. 13760 Components of <em>x</em> and <em>y</em> that are not selected are allowed to be 13761 invalid floating-point values and will have no effect on the results. 13762 Thus, this provides different functionality than, for example,<br> 13763 genFType <strong>mix</strong>(genFType <em>x</em>, genFType <em>y</em>, genFType(<em>a</em>))<br> 13764 where <em>a</em> is a Boolean vector.</p></td> 13765</tr> 13766<tr> 13767<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>step</strong>(genFType <em>edge</em>, genFType <em>x</em>)<br> 13768 genFType <strong>step</strong>(float <em>edge</em>, genFType <em>x</em>)<br> 13769 genDType <strong>step</strong>(genDType <em>edge</em>, genDType <em>x</em>)<br> 13770 genDType <strong>step</strong>(double <em>edge</em>, genDType <em>x</em>)</p></td> 13771<td class="tableblock halign-left valign-top"><p class="tableblock">Returns 0.0 if <em>x</em> < <em>edge;</em> otherwise it returns 1.0.</p></td> 13772</tr> 13773<tr> 13774<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>smoothstep</strong>(genFType <em>edge0</em>, genFType <em>edge1</em>, genFType <em>x</em>)<br> 13775 genFType <strong>smoothstep</strong>(float <em>edge0</em>, float <em>edge1</em>, genFType <em>x</em>)<br> 13776 genDType <strong>smoothstep</strong>(genDType <em>edge0</em>, genDType <em>edge1</em>, genDType <em>x</em>)<br> 13777 genDType <strong>smoothstep</strong>(double <em>edge0</em>, double <em>edge1</em>, genDType <em>x</em>)<br></p></td> 13778<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 13779<p>Returns 0.0 if <span class="eq">x ≤ edge0</span> and 1.0 if <span class="eq">x ≥ edge1</span>, and 13780 performs smooth Hermite interpolation between 0 and 1 when <span class="eq">edge0 13781 < x < edge1</span>. 13782 This is useful in cases where you would want a threshold function with 13783 a smooth transition. 13784 This is equivalent to:</p> 13785</div> 13786<div class="openblock"> 13787<div class="content"> 13788<div class="listingblock"> 13789<div class="content"> 13790<pre class="CodeRay highlight"><code data-lang="c++">genFType t; 13791t = clamp ((x - edge0) / (edge1 - edge0), <span class="integer">0</span>, <span class="integer">1</span>); 13792<span class="keyword">return</span> t * t * (<span class="integer">3</span> - <span class="integer">2</span> * t);</code></pre> 13793</div> 13794</div> 13795<div class="paragraph"> 13796<p>(And similarly for doubles.) Results are undefined if <span class="eq">edge0 ≥ 13797edge1</span>.</p> 13798</div> 13799</div> 13800</div></div></td> 13801</tr> 13802<tr> 13803<td class="tableblock halign-left valign-top"><p class="tableblock">genBType <strong>isnan</strong>(genFType <em>x</em>)<br> 13804 genBType <strong>isnan</strong>(genDType <em>x</em>)</p></td> 13805<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>true</strong> if <em>x</em> holds a NaN. 13806 Returns <strong>false</strong> otherwise. 13807 Always returns <strong>false</strong> if NaNs are not implemented.</p></td> 13808</tr> 13809<tr> 13810<td class="tableblock halign-left valign-top"><p class="tableblock">genBType <strong>isinf</strong>(genFType <em>x</em>)<br> 13811 genBType <strong>isinf</strong>(genDType <em>x</em>)</p></td> 13812<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>true</strong> if <em>x</em> holds a positive infinity or negative infinity. 13813 Returns <strong>false</strong> otherwise.</p></td> 13814</tr> 13815<tr> 13816<td class="tableblock halign-left valign-top"><p class="tableblock">genIType <strong>floatBitsToInt</strong>(highp genFType <em>value</em>)<br> 13817 genUType <strong>floatBitsToUint</strong>(highp genFType <em>value</em>)</p></td> 13818<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a signed or unsigned integer value representing the encoding 13819 of a floating-point value. 13820 The <strong>float</strong> value’s bit-level representation is preserved.</p></td> 13821</tr> 13822<tr> 13823<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>intBitsToFloat</strong>(highp genIType <em>value</em>)<br> 13824 genFType <strong>uintBitsToFloat</strong>(highp genUType <em>value</em>)</p></td> 13825<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a floating-point value corresponding to a signed or unsigned 13826 integer encoding of a floating-point value. 13827 If a NaN is passed in, it will not signal, and the resulting value is 13828 unspecified. 13829 If an Inf is passed in, the resulting value is the corresponding Inf. 13830 Otherwise, the bit-level representation is preserved.</p></td> 13831</tr> 13832<tr> 13833<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>fma</strong>(genFType <em>a</em>, genFType <em>b</em>, genFType <em>c</em>)<br> 13834 genDType <strong>fma</strong>(genDType <em>a</em>, genDType <em>b</em>, genDType <em>c</em>)</p></td> 13835<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 13836<p>Computes and returns <code>a * b + c</code>. 13837 In uses where the return value is eventually consumed by a variable 13838 declared as <strong>precise</strong>:</p> 13839</div> 13840<div class="openblock"> 13841<div class="content"> 13842<div class="ulist"> 13843<ul> 13844<li> 13845<p><strong>fma</strong>() is considered a single operation, whereas the expression <code>a * b 13846+ c</code> consumed by a variable declared <strong>precise</strong> is considered two 13847operations.</p> 13848</li> 13849<li> 13850<p>The precision of <strong>fma</strong>() can differ from the precision of the expression 13851<code>a * b + c</code>.</p> 13852</li> 13853<li> 13854<p><strong>fma</strong>() will be computed with the same precision as any other <strong>fma</strong>() 13855consumed by a precise variable, giving invariant results for the same 13856input values of <em>a</em>, <em>b</em>, and <em>c</em>.</p> 13857</li> 13858</ul> 13859</div> 13860<div class="paragraph"> 13861<p>Otherwise, in the absence of <strong>precise</strong> consumption, there are no special 13862constraints on the number of operations or difference in precision between 13863<strong>fma</strong>() and the expression <code>a * b + c</code>.</p> 13864</div> 13865</div> 13866</div></div></td> 13867</tr> 13868<tr> 13869<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>frexp</strong>(highp genFType <em>x</em>, out highp genIType <em>exp</em>) 13870 genDType <strong>frexp</strong>(genDType <em>x</em>, out genIType <em>exp</em>)<br></p></td> 13871<td class="tableblock halign-left valign-top"><p class="tableblock">Splits <em>x</em> into a floating-point significand in the range 13872 <span class="eq">[0.5,1.0]</span>, and an integral exponent of two, such that</p> 13873<p class="tableblock"> <span class="eq">x = significant · 2<sup>exponent</sup></span></p> 13874<p class="tableblock"> The significand is returned by the function and the exponent is 13875 returned in the parameter <em>exp</em>. 13876 For a floating-point value of zero, the significand and exponent are 13877 both zero.</p> 13878<p class="tableblock"> If an implementation supports signed zero, an input value of minus 13879 zero should return a significand of minus zero. 13880 For a floating-point value that is an infinity or is not a number, the 13881 results are undefined.</p> 13882<p class="tableblock"> If the input <em>x</em> is a vector, this operation is performed in a 13883 component-wise manner; the value returned by the function and the 13884 value written to <em>exp</em> are vectors with the same number of components 13885 as <em>x</em>.</p></td> 13886</tr> 13887<tr> 13888<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>ldexp</strong>(highp genFType <em>x</em>, highp genIType <em>exp</em>)<br> 13889 genDType <strong>ldexp</strong>(genDType <em>x</em>, genIType <em>exp</em>)</p></td> 13890<td class="tableblock halign-left valign-top"><p class="tableblock">Builds a floating-point number from <em>x</em> and the corresponding integral 13891 exponent of two in <em>exp</em>, returning:</p> 13892<p class="tableblock"> <span class="eq">significand · 2<sup>exponent</sup></span></p> 13893<p class="tableblock"> If this product is too large to be represented in the floating-point 13894 type, the result is undefined.</p> 13895<p class="tableblock"> If <em>exp</em> is greater than +128 (single-precision) or +1024 13896 (double-precision), the value returned is undefined. 13897 If <em>exp</em> is less than -126 (single-precision) or -1022 13898 (double-precision), the value returned may be flushed to zero. 13899 Additionally, splitting the value into a significand and exponent 13900 using <strong>frexp</strong>() and then reconstructing a floating-point value using 13901 <strong>ldexp</strong>() should yield the original input for zero and all finite 13902 non-denormalized values.<br> 13903 If the input <em>x</em> is a vector, this operation is performed in a 13904 component-wise manner; the value passed in <em>exp</em> and returned by the 13905 function are vectors with the same number of components as <em>x</em>.</p></td> 13906</tr> 13907</tbody> 13908</table> 13909</div> 13910<div class="sect2"> 13911<h3 id="floating-point-pack-and-unpack-functions">8.4. Floating-Point Pack and Unpack Functions</h3> 13912<div class="paragraph"> 13913<p>These functions do not operate component-wise, rather, as described in each 13914case.</p> 13915</div> 13916<table class="tableblock frame-all grid-all stretch"> 13917<colgroup> 13918<col style="width: 50%;"> 13919<col style="width: 50%;"> 13920</colgroup> 13921<thead> 13922<tr> 13923<th class="tableblock halign-left valign-top">Syntax</th> 13924<th class="tableblock halign-left valign-top">Description</th> 13925</tr> 13926</thead> 13927<tbody> 13928<tr> 13929<td class="tableblock halign-left valign-top"><p class="tableblock">highp uint <strong>packUnorm2x16</strong>(vec2 <em>v</em>)<br> 13930 highp uint <strong>packSnorm2x16</strong>(vec2 <em>v</em>)<br> 13931 uint <strong>packUnorm4x8</strong>(vec4 <em>v</em>)<br> 13932 uint <strong>packSnorm4x8</strong>(vec4 <em>v</em>)</p></td> 13933<td class="tableblock halign-left valign-top"><p class="tableblock">First, converts each component of the normalized floating-point value 13934 <em>v</em> into 16-bit (<strong>2x16</strong>) or 8-bit (<strong>4x8</strong>) integer values. 13935 Then, the results are packed into the returned 32-bit unsigned 13936 integer.</p> 13937<p class="tableblock"> The conversion for component <em>c</em> of <em>v</em> to fixed point is done as 13938 follows:</p> 13939<p class="tableblock"> <strong>packUnorm2x16</strong>: <strong>round</strong>(<strong>clamp</strong>(<em>c</em>, 0, +1) * 65535.0)<br> 13940 <strong>packSnorm2x16:</strong> <strong>round</strong>(<strong>clamp</strong>(<em>c</em>, -1, +1) * 32767.0)<br> 13941 <strong>packUnorm4x8</strong>: <strong>round</strong>(<strong>clamp</strong>(<em>c</em>, 0, +1) * 255.0)<br> 13942 <strong>packSnorm4x8</strong>: <strong>round</strong>(<strong>clamp</strong>(<em>c</em>, -1, +1) * 127.0)</p> 13943<p class="tableblock"> The first component of the vector will be written to the least 13944 significant bits of the output; the last component will be written to 13945 the most significant bits.</p></td> 13946</tr> 13947<tr> 13948<td class="tableblock halign-left valign-top"><p class="tableblock"> vec2 <strong>unpackUnorm2x16</strong>(highp uint <em>p</em>)<br> 13949 vec2 <strong>unpackSnorm2x16</strong>(highp uint <em>p</em>)<br> 13950 vec4 <strong>unpackUnorm4x8</strong>(highp uint <em>p</em>)<br> 13951 vec4 <strong>unpackSnorm4x8</strong>(highp uint <em>p</em>)</p></td> 13952<td class="tableblock halign-left valign-top"><p class="tableblock">First, unpacks a single 32-bit unsigned integer <em>p</em> into a pair of 13953 16-bit unsigned integers, a pair of 16-bit signed integers, four 8-bit 13954 unsigned integers, or four 8-bit signed integers, respectively. 13955 Then, each component is converted to a normalized floating-point value 13956 to generate the returned two- or four-component vector.</p> 13957<p class="tableblock"> The conversion for unpacked fixed-point value <em>f</em> to floating-point is 13958 done as follows:</p> 13959<p class="tableblock"> <strong>unpackUnorm2x16</strong>: <em>f</em> / 65535.0<br> 13960 <strong>unpackSnorm2x16</strong>: <strong>clamp</strong>(<em>f</em> / 32767.0, -1, +1)<br> 13961 <strong>unpackUnorm4x8</strong>: <em>f</em> / 255.0<br> 13962 <strong>unpackSnorm4x8</strong>: <strong>clamp</strong>(<em>f</em> / 127.0, -1, +1)</p> 13963<p class="tableblock"> The first component of the returned vector will be extracted from the 13964 least significant bits of the input; the last component will be 13965 extracted from the most significant bits.</p></td> 13966</tr> 13967<tr> 13968<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>packHalf2x16</strong>(vec2 <em>v</em>)</p></td> 13969<td class="tableblock halign-left valign-top"><p class="tableblock">Returns an unsigned integer obtained by converting the components of a 13970 two-component floating-point vector to the 16-bit floating-point 13971 representation of the <a href="#references">API</a>, and 13972 then packing these two 16-bit integers into a 32-bit unsigned integer.</p> 13973<p class="tableblock"> The first vector component specifies the 16 least-significant bits of 13974 the result; the second component specifies the 16 most-significant 13975 bits.</p></td> 13976</tr> 13977<tr> 13978<td class="tableblock halign-left valign-top"><p class="tableblock"> vec2 <strong>unpackHalf2x16</strong>( uint <em>v</em>)</p></td> 13979<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a two-component floating-point vector with components obtained 13980 by unpacking a 32-bit unsigned integer into a pair of 16-bit values, 13981 interpreting those values as 16-bit floating-point numbers according 13982 to the <a href="#references">API</a>, and converting them to 13983 32-bit floating-point values.</p> 13984<p class="tableblock"> The first component of the vector is obtained from the 16 13985 least-significant bits of <em>v</em>; the second component is obtained from 13986 the 16 most-significant bits of <em>v</em>.</p></td> 13987</tr> 13988<tr> 13989<td class="tableblock halign-left valign-top"><p class="tableblock">double <strong>packDouble2x32</strong>(uvec2 <em>v</em>)<br></p></td> 13990<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a double-precision value obtained by packing the components of 13991 <em>v</em> into a 64-bit value. 13992 If an IEEE 754 Inf or NaN is created, it will not signal, and the 13993 resulting floating-point value is unspecified. 13994 Otherwise, the bit-level representation of <em>v</em> is preserved. 13995 The first vector component specifies the 32 least significant bits; 13996 the second component specifies the 32 most significant bits.</p></td> 13997</tr> 13998<tr> 13999<td class="tableblock halign-left valign-top"><p class="tableblock">uvec2 <strong>unpackDouble2x32</strong>(double <em>v</em>)</p></td> 14000<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a two-component unsigned integer vector representation of <em>v</em>. 14001 The bit-level representation of <em>v</em> is preserved. 14002 The first component of the vector contains the 32 least significant 14003 bits of the double; the second component consists of the 32 most 14004 significant bits.</p></td> 14005</tr> 14006</tbody> 14007</table> 14008</div> 14009<div class="sect2"> 14010<h3 id="geometric-functions">8.5. Geometric Functions</h3> 14011<div class="paragraph"> 14012<p>These operate on vectors as vectors, not component-wise.</p> 14013</div> 14014<table class="tableblock frame-all grid-all stretch"> 14015<colgroup> 14016<col style="width: 50%;"> 14017<col style="width: 50%;"> 14018</colgroup> 14019<thead> 14020<tr> 14021<th class="tableblock halign-left valign-top">Syntax</th> 14022<th class="tableblock halign-left valign-top">Description</th> 14023</tr> 14024</thead> 14025<tbody> 14026<tr> 14027<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>length</strong>(genFType <em>x</em>)<br> 14028 double <strong>length</strong>(genDType <em>x</em>)</p></td> 14029<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 14030<p>Returns the length of vector <em>x</em>, i.e., 14031 <span class="eq">sqrt( x<sub>0</sub><sup>2</sup> + x<sub>1</sub><sup>2</sup> + …​ )</span>.</p> 14032</div></div></td> 14033</tr> 14034<tr> 14035<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>distance</strong>(genFType <em>p0</em>, genFType <em>p1</em>)<br> 14036 double <strong>distance</strong>(genDType <em>p0</em>, genDType <em>p1</em>)</p></td> 14037<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the distance between <em>p0</em> and <em>p1</em>, i.e., 14038 <strong>length</strong>(<em>p0</em> - <em>p1</em>)</p></td> 14039</tr> 14040<tr> 14041<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>dot</strong>(genFType <em>x</em>, genFType <em>y</em>)<br> 14042 double <strong>dot</strong>(genDType <em>x</em>, genDType <em>y</em>)</p></td> 14043<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the dot product of <em>x</em> and <em>y</em>, i.e., 14044 <span class="eq">x<sub>0</sub> · y<sub>0</sub> + x<sub>1</sub> · y<sub>1</sub> + …​</span></p></td> 14045</tr> 14046<tr> 14047<td class="tableblock halign-left valign-top"><p class="tableblock">vec3 <strong>cross</strong>(vec3 <em>x</em>, vec3 <em>y</em>)<br> 14048 dvec3 <strong>cross</strong>(dvec3 <em>x</em>, dvec3 <em>y</em>)</p></td> 14049<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 14050<p>Returns the cross product of <em>x</em> and <em>y</em>, i.e., 14051 <span class="eq">(x<sub>1</sub> · y<sub>2</sub> - y<sub>1</sub> · x<sub>2</sub>, 14052 x<sub>2</sub> · y<sub>0</sub> - y<sub>2</sub> · x<sub>0</sub>, 14053 x<sub>0</sub> · y<sub>1</sub> - y<sub>0</sub> · x<sub>1</sub>)</span>.</p> 14054</div></div></td> 14055</tr> 14056<tr> 14057<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>normalize</strong>(genFType <em>x</em>)<br> 14058 genDType <strong>normalize</strong>(genDType <em>x</em>)</p></td> 14059<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a vector in the same direction as <em>x</em> but with a length of 1, 14060 i.e. <em>x</em> / <strong>length</strong>(x).</p></td> 14061</tr> 14062<tr> 14063<td class="tableblock halign-left valign-top"><p class="tableblock">compatibility profile only<br> 14064 vec4 <strong>ftransform</strong>()</p></td> 14065<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 14066<p>Available only when using the compatibility profile. 14067 For core OpenGL, use <strong>invariant</strong>.<br> 14068 For vertex shaders only. 14069 This function will ensure that the incoming vertex value will be 14070 transformed in a way that produces exactly the same result as would be 14071 produced by OpenGL’s fixed functionality transform. 14072 It is intended to be used to compute <em>gl_Position</em>, e.g.</p> 14073</div> 14074<div class="openblock"> 14075<div class="content"> 14076<div class="dlist"> 14077<dl> 14078<dt class="hdlist1"></dt> 14079<dd> 14080<p><em>gl_Position</em> = <strong>ftransform</strong>()</p> 14081</dd> 14082</dl> 14083</div> 14084<div class="paragraph"> 14085<p>This function should be used, for example, when an application is rendering 14086the same geometry in separate passes, and one pass uses the fixed 14087functionality path to render and another pass uses programmable shaders.</p> 14088</div> 14089</div> 14090</div></div></td> 14091</tr> 14092<tr> 14093<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>faceforward</strong>(genFType <em>N</em>, genFType <em>I</em>, genFType <em>Nref</em>)<br> 14094 genDType <strong>faceforward</strong>(genDType <em>N</em>, genDType <em>I</em>, genDType <em>Nref</em>)</p></td> 14095<td class="tableblock halign-left valign-top"><p class="tableblock">If <strong>dot</strong>(<em>Nref</em>, <em>I</em>) < 0 return <em>N</em>, otherwise return -<em>N</em>.</p></td> 14096</tr> 14097<tr> 14098<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>reflect</strong>(genFType <em>I</em>, genFType <em>N</em>)<br> 14099 genDType <strong>reflect</strong>(genDType <em>I</em>, genDType <em>N</em>)</p></td> 14100<td class="tableblock halign-left valign-top"><p class="tableblock">For the incident vector <em>I</em> and surface orientation <em>N</em>, returns the 14101 reflection direction: <span class="eq">I - 2 · <strong>dot</strong>(N, I) · N</span>. 14102 <em>N</em> must already be normalized in order to achieve the desired result.</p></td> 14103</tr> 14104<tr> 14105<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>refract</strong>(genFType <em>I</em>, genFType <em>N</em>, float <em>eta</em>)<br> 14106 genDType <strong>refract</strong>(genDType <em>I</em>, genDType <em>N</em>, double <em>eta</em>)</p></td> 14107<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 14108<p>For the incident vector <em>I</em> and surface normal <em>N</em>, and the ratio of 14109 indices of refraction <em>eta</em>, return the refraction vector. 14110 The result is computed by the <a href="#refraction-equation">refraction 14111 equation</a> shown below.</p> 14112</div> 14113<div class="literalblock"> 14114<div class="content"> 14115<pre>The input parameters for the incident vector _I_ and the surface 14116normal _N_ must already be normalized to get the desired results.</pre> 14117</div> 14118</div></div></td> 14119</tr> 14120</tbody> 14121</table> 14122<div class="sect3"> 14123<h4 id="refraction-equation">8.5.1. Refraction Equation</h4> 14124<div class="stemblock"> 14125<div class="content"> 14126\[k = 1.0 - eta * eta * (1.0 - \textbf{dot}(N,I) \cdot \textbf{dot}(N,I))\] 14127</div> 14128</div> 14129<div class="stemblock"> 14130<div class="content"> 14131\[\begin{aligned} 14132result &= 14133 \begin{cases} 14134 genFType(0.0), & k < 0.0 \\ 14135 eta * I - (eta * \textbf{dot}(N,I) + \sqrt { k }) * N, & \textbf{otherwise} 14136 \end{cases} 14137\end{aligned}\] 14138</div> 14139</div> 14140</div> 14141</div> 14142<div class="sect2"> 14143<h3 id="matrix-functions">8.6. Matrix Functions</h3> 14144<div class="paragraph"> 14145<p>For each of the following built-in matrix functions, there is both a 14146single-precision floating-point version, where all arguments and return 14147values are single precision, and a double-precision floating-point version, 14148where all arguments and return values are double precision. 14149Only the single-precision floating-point version is shown.</p> 14150</div> 14151<table class="tableblock frame-all grid-all stretch"> 14152<colgroup> 14153<col style="width: 50%;"> 14154<col style="width: 50%;"> 14155</colgroup> 14156<thead> 14157<tr> 14158<th class="tableblock halign-left valign-top">Syntax</th> 14159<th class="tableblock halign-left valign-top">Description</th> 14160</tr> 14161</thead> 14162<tbody> 14163<tr> 14164<td class="tableblock halign-left valign-top"><p class="tableblock">mat <strong>matrixCompMult</strong>(mat <em>x</em>, mat <em>y</em>)</p></td> 14165<td class="tableblock halign-left valign-top"><p class="tableblock">Multiply matrix <em>x</em> by matrix <em>y</em> component-wise, i.e., result[i][j] 14166 is the scalar product of <em>x</em>[i][j] and <em>y</em>[i][j].<br></p> 14167<p class="tableblock"> Note: to get linear algebraic matrix multiplication, use the multiply 14168 operator (<strong>*</strong>).</p></td> 14169</tr> 14170<tr> 14171<td class="tableblock halign-left valign-top"><p class="tableblock">mat2 <strong>outerProduct</strong>(vec2 <em>c</em>, vec2 <em>r</em>)<br> 14172 mat3 <strong>outerProduct</strong>(vec3 <em>c</em>, vec3 <em>r</em>)<br> 14173 mat4 <strong>outerProduct</strong>(vec4 <em>c</em>, vec4 <em>r</em>)<br> 14174 mat2x3 <strong>outerProduct</strong>(vec3 <em>c</em>, vec2 <em>r</em>)<br> 14175 mat3x2 <strong>outerProduct</strong>(vec2 <em>c</em>, vec3 <em>r</em>)<br> 14176 mat2x4 <strong>outerProduct</strong>(vec4 <em>c</em>, vec2 <em>r</em>)<br> 14177 mat4x2 <strong>outerProduct</strong>(vec2 <em>c</em>, vec4 <em>r</em>)<br> 14178 mat3x4 <strong>outerProduct</strong>(vec4 <em>c</em>, vec3 <em>r</em>)<br> 14179 mat4x3 <strong>outerProduct</strong>(vec3 <em>c</em>, vec4 <em>r</em>)</p></td> 14180<td class="tableblock halign-left valign-top"><p class="tableblock">Treats the first parameter <em>c</em> as a column vector (matrix with one 14181 column) and the second parameter <em>r</em> as a row vector (matrix with one 14182 row) and does a linear algebraic matrix multiply <em>c</em> * <em>r</em>, yielding a 14183 matrix whose number of rows is the number of components in <em>c</em> and 14184 whose number of columns is the number of components in <em>r</em>.</p></td> 14185</tr> 14186<tr> 14187<td class="tableblock halign-left valign-top"><p class="tableblock">mat2 <strong>transpose</strong>(mat2 <em>m</em>)<br> 14188 mat3 <strong>transpose</strong>(mat3 <em>m</em>)<br> 14189 mat4 <strong>transpose</strong>(mat4 <em>m</em>)<br> 14190 mat2x3 <strong>transpose</strong>(mat3x2 <em>m</em>)<br> 14191 mat3x2 <strong>transpose</strong>(mat2x3 <em>m</em>)<br> 14192 mat2x4 <strong>transpose</strong>(mat4x2 <em>m</em>)<br> 14193 mat4x2 <strong>transpose</strong>(mat2x4 <em>m</em>)<br> 14194 mat3x4 <strong>transpose</strong>(mat4x3 <em>m</em>)<br> 14195 mat4x3 <strong>transpose</strong>(mat3x4 <em>m</em>)</p></td> 14196<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a matrix that is the transpose of <em>m</em>. 14197 The input matrix <em>m</em> is not modified.</p></td> 14198</tr> 14199<tr> 14200<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>determinant</strong>(mat2 <em>m</em>)<br> 14201 float <strong>determinant</strong>(mat3 <em>m</em>)<br> 14202 float <strong>determinant</strong>(mat4 <em>m</em>)</p></td> 14203<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the determinant of <em>m</em>.</p></td> 14204</tr> 14205<tr> 14206<td class="tableblock halign-left valign-top"><p class="tableblock">mat2 <strong>inverse</strong>(mat2 <em>m</em>)<br> 14207 mat3 <strong>inverse</strong>(mat3 <em>m</em>)<br> 14208 mat4 <strong>inverse</strong>(mat4 <em>m</em>)</p></td> 14209<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a matrix that is the inverse of <em>m</em>. 14210 The input matrix <em>m</em> is not modified. 14211 The values in the returned matrix are undefined if <em>m</em> is singular or 14212 poorly-conditioned (nearly singular).</p></td> 14213</tr> 14214</tbody> 14215</table> 14216</div> 14217<div class="sect2"> 14218<h3 id="vector-relational-functions">8.7. Vector Relational Functions</h3> 14219<div class="paragraph"> 14220<p>Relational and equality operators (<strong><</strong>, <strong><=</strong>, <strong>></strong>, <strong>>=</strong>, <strong>==</strong>, <strong>!=</strong>) are 14221defined to operate on scalars and produce scalar Boolean results. 14222For vector results, use the following built-in functions. 14223Below, the following placeholders are used for the listed specific types:</p> 14224</div> 14225<table class="tableblock frame-all grid-all stretch"> 14226<colgroup> 14227<col style="width: 50%;"> 14228<col style="width: 50%;"> 14229</colgroup> 14230<thead> 14231<tr> 14232<th class="tableblock halign-left valign-top">Placeholder</th> 14233<th class="tableblock halign-left valign-top">Specific Types Allowed</th> 14234</tr> 14235</thead> 14236<tbody> 14237<tr> 14238<td class="tableblock halign-left valign-top"><p class="tableblock">bvec</p></td> 14239<td class="tableblock halign-left valign-top"><p class="tableblock">bvec2, bvec3, bvec4</p></td> 14240</tr> 14241<tr> 14242<td class="tableblock halign-left valign-top"><p class="tableblock">ivec</p></td> 14243<td class="tableblock halign-left valign-top"><p class="tableblock">ivec2, ivec3, ivec4</p></td> 14244</tr> 14245<tr> 14246<td class="tableblock halign-left valign-top"><p class="tableblock">uvec</p></td> 14247<td class="tableblock halign-left valign-top"><p class="tableblock">uvec2, uvec3, uvec4</p></td> 14248</tr> 14249<tr> 14250<td class="tableblock halign-left valign-top"><p class="tableblock">vec</p></td> 14251<td class="tableblock halign-left valign-top"><p class="tableblock">vec2, vec3, vec4, dvec2, dvec3, dvec4</p></td> 14252</tr> 14253</tbody> 14254</table> 14255<div class="paragraph"> 14256<p>In all cases, the sizes of all the input and return vectors for any 14257particular call must match.</p> 14258</div> 14259<table class="tableblock frame-all grid-all stretch"> 14260<colgroup> 14261<col style="width: 50%;"> 14262<col style="width: 50%;"> 14263</colgroup> 14264<thead> 14265<tr> 14266<th class="tableblock halign-left valign-top">Syntax</th> 14267<th class="tableblock halign-left valign-top">Description</th> 14268</tr> 14269</thead> 14270<tbody> 14271<tr> 14272<td class="tableblock halign-left valign-top"><p class="tableblock">bvec <strong>lessThan</strong>(vec x, vec y)<br> 14273 bvec <strong>lessThan</strong>(ivec x, ivec y)<br> 14274 bvec <strong>lessThan</strong>(uvec x, uvec y)</p></td> 14275<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the component-wise compare of <span class="eq">x < y</span>.</p></td> 14276</tr> 14277<tr> 14278<td class="tableblock halign-left valign-top"><p class="tableblock">bvec <strong>lessThanEqual</strong>(vec x, vec y)<br> 14279 bvec <strong>lessThanEqual</strong>(ivec x, ivec y)<br> 14280 bvec <strong>lessThanEqual</strong>(uvec x, uvec y)</p></td> 14281<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the component-wise compare of <span class="eq">x ≤ y</span>.</p></td> 14282</tr> 14283<tr> 14284<td class="tableblock halign-left valign-top"><p class="tableblock">bvec <strong>greaterThan</strong>(vec x, vec y)<br> 14285 bvec <strong>greaterThan</strong>(ivec x, ivec y)<br> 14286 bvec <strong>greaterThan</strong>(uvec x, uvec y)</p></td> 14287<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the component-wise compare of <span class="eq">x > y</span>.</p></td> 14288</tr> 14289<tr> 14290<td class="tableblock halign-left valign-top"><p class="tableblock">bvec <strong>greaterThanEqual</strong>(vec x, vec y)<br> 14291 bvec <strong>greaterThanEqual</strong>(ivec x, ivec y)<br> 14292 bvec <strong>greaterThanEqual</strong>(uvec x, uvec y)</p></td> 14293<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the component-wise compare of <span class="eq">x ≥ y</span>.</p></td> 14294</tr> 14295<tr> 14296<td class="tableblock halign-left valign-top"><p class="tableblock">bvec <strong>equal</strong>(vec x, vec y)<br> 14297 bvec <strong>equal</strong>(ivec x, ivec y)<br> 14298 bvec <strong>equal</strong>(uvec x, uvec y)<br> 14299 bvec <strong>equal</strong>(bvec x, bvec y)</p></td> 14300<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the component-wise compare of <span class="eq">x == y</span>.</p></td> 14301</tr> 14302<tr> 14303<td class="tableblock halign-left valign-top"><p class="tableblock">bvec <strong>notEqual</strong>(vec x, vec y)<br> 14304 bvec <strong>notEqual</strong>(ivec x, ivec y)<br> 14305 bvec <strong>notEqual</strong>(uvec x, uvec y)<br> 14306 bvec <strong>notEqual</strong>(bvec x, bvec y)</p></td> 14307<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the component-wise compare of <span class="eq">x ≠ y</span>.</p></td> 14308</tr> 14309<tr> 14310<td class="tableblock halign-left valign-top"><p class="tableblock">bool <strong>any</strong>(bvec x)</p></td> 14311<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>true</strong> if any component of <em>x</em> is <strong>true</strong>.</p></td> 14312</tr> 14313<tr> 14314<td class="tableblock halign-left valign-top"><p class="tableblock">bool <strong>all</strong>(bvec x)</p></td> 14315<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>true</strong> only if all components of <em>x</em> are <strong>true</strong>.</p></td> 14316</tr> 14317<tr> 14318<td class="tableblock halign-left valign-top"><p class="tableblock">bvec <strong>not</strong>(bvec x)</p></td> 14319<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the component-wise logical complement of <em>x</em>.</p></td> 14320</tr> 14321</tbody> 14322</table> 14323</div> 14324<div class="sect2"> 14325<h3 id="integer-functions">8.8. Integer Functions</h3> 14326<div class="paragraph"> 14327<p>These all operate component-wise. 14328The description is per component. 14329The notation [<em>a</em>, <em>b</em>] means the set of bits from bit-number <em>a</em> through 14330bit-number <em>b</em>, inclusive. 14331The lowest-order bit is bit 0. 14332“Bit number” will always refer to counting up from the lowest-order bit as 14333bit 0.</p> 14334</div> 14335<table class="tableblock frame-all grid-all stretch"> 14336<colgroup> 14337<col style="width: 50%;"> 14338<col style="width: 50%;"> 14339</colgroup> 14340<thead> 14341<tr> 14342<th class="tableblock halign-left valign-top">Syntax</th> 14343<th class="tableblock halign-left valign-top">Description</th> 14344</tr> 14345</thead> 14346<tbody> 14347<tr> 14348<td class="tableblock halign-left valign-top"><p class="tableblock">genUType <strong>uaddCarry</strong>(highp genUType <em>x</em>, highp genUType <em>y</em>, out lowp genUType <em>carry</em>)</p></td> 14349<td class="tableblock halign-left valign-top"><p class="tableblock">Adds 32-bit unsigned integers <em>x</em> and <em>y</em>, returning the sum modulo 14350 2<sup>32</sup>. 14351 The value <em>carry</em> is set to zero if the sum was less than 2<sup>32</sup>, or 14352 one otherwise.</p></td> 14353</tr> 14354<tr> 14355<td class="tableblock halign-left valign-top"><p class="tableblock">genUType <strong>usubBorrow</strong>(highp genUType <em>x</em>, highp genUType <em>y</em>, out lowp genUType <em>borrow</em>)</p></td> 14356<td class="tableblock halign-left valign-top"><p class="tableblock">Subtracts the 32-bit unsigned integer <em>y</em> from <em>x</em>, returning the 14357 difference if non-negative, or 2<sup>32</sup> plus the difference otherwise. 14358 The value <em>borrow</em> is set to zero if <span class="eq">x ≥ y</span>, or one 14359 otherwise.</p></td> 14360</tr> 14361<tr> 14362<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>umulExtended</strong>(highp genUType <em>x</em>, highp genUType <em>y</em>, out highp genUType <em>msb</em>, out highp genUType <em>lsb</em>)<br> 14363 void <strong>imulExtended</strong>(highp genIType <em>x</em>, highp genIType <em>y</em>, out highp genIType <em>msb</em>, out highp genIType <em>lsb</em>)</p></td> 14364<td class="tableblock halign-left valign-top"><p class="tableblock">Multiplies 32-bit unsigned or signed integers <em>x</em> and <em>y</em>, producing a 14365 64-bit result. 14366 The 32 least-significant bits are returned in <em>lsb</em>. 14367 The 32 most-significant bits are returned in <em>msb</em>.</p></td> 14368</tr> 14369<tr> 14370<td class="tableblock halign-left valign-top"><p class="tableblock">genIType <strong>bitfieldExtract</strong>(genIType <em>value</em>, int <em>offset</em>, int <em>bits</em>)<br> 14371 genUType <strong>bitfieldExtract</strong>(genUType <em>value</em>, int <em>offset</em>, int <em>bits</em>)</p></td> 14372<td class="tableblock halign-left valign-top"><p class="tableblock">Extracts bits <span class="eq">[offset, offset + bits - 1]</span> from <em>value</em>, 14373 returning them in the least significant bits of the result.<br></p> 14374<p class="tableblock"> For unsigned data types, the most significant bits of the result will 14375 be set to zero. 14376 For signed data types, the most significant bits will be set to the 14377 value of bit <span class="eq">offset + bits - 1</span>.<br></p> 14378<p class="tableblock"> If <em>bits</em> is zero, the result will be zero. 14379 The result will be undefined if <em>offset</em> or <em>bits</em> is negative, or if 14380 the sum of <em>offset</em> and <em>bits</em> is greater than the number of bits used 14381 to store the operand. 14382 Note that for vector versions of <strong>bitfieldExtract</strong>(), a single pair of 14383 <em>offset</em> and <em>bits</em> values is shared for all components.</p></td> 14384</tr> 14385<tr> 14386<td class="tableblock halign-left valign-top"><p class="tableblock">genIType <strong>bitfieldInsert</strong>(genIType <em>base</em>, genIType <em>insert</em>, int <em>offset</em>, int <em>bits</em>)<br> 14387 genUType <strong>bitfieldInsert</strong>(genUType <em>base</em>, genUType <em>insert</em>, int <em>offset</em>, int <em>bits</em>)</p></td> 14388<td class="tableblock halign-left valign-top"><p class="tableblock">Inserts the <em>bits</em> least significant bits of <em>insert</em> into <em>base</em>.</p> 14389<p class="tableblock"> The result will have bits <span class="eq">[offset, offset + bits - 1]</span> taken from 14390 bits <span class="eq">[0, bits - 1]</span> of <em>insert</em>, and all other bits taken 14391 directly from the corresponding bits of <em>base</em>. 14392 If <em>bits</em> is zero, the result will simply be <em>base</em>. 14393 The result will be undefined if <em>offset</em> or <em>bits</em> is negative, or if 14394 the sum of <em>offset</em> and <em>bits</em> is greater than the number of bits used 14395 to store the operand.<br> 14396 Note that for vector versions of <strong>bitfieldInsert</strong>(), a single pair of 14397 <em>offset</em> and <em>bits</em> values is shared for all components.</p></td> 14398</tr> 14399<tr> 14400<td class="tableblock halign-left valign-top"><p class="tableblock">genIType <strong>bitfieldReverse</strong>(highp genIType <em>value</em>)<br> 14401 genUType <strong>bitfieldReverse</strong>(highp genUType <em>value</em>)</p></td> 14402<td class="tableblock halign-left valign-top"><p class="tableblock">Reverses the bits of <em>value</em>. 14403 The bit numbered <em>n</em> of the result will be taken from bit <span class="eq">(bits - 14404 1) - n</span> of <em>value</em>, where <em>bits</em> is the total number of bits used to 14405 represent <em>value</em>.</p></td> 14406</tr> 14407<tr> 14408<td class="tableblock halign-left valign-top"><p class="tableblock"> genIType <strong>bitCount</strong>(genIType <em>value</em>)<br> 14409 genIType <strong>bitCount</strong>(genUType <em>value</em>)</p></td> 14410<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the number of one bits in the binary representation of 14411 <em>value</em>.</p></td> 14412</tr> 14413<tr> 14414<td class="tableblock halign-left valign-top"><p class="tableblock"> genIType <strong>findLSB</strong>(genIType <em>value</em>)<br> 14415 genIType <strong>findLSB</strong>(genUType <em>value</em>)</p></td> 14416<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the bit number of the least significant one bit in the binary 14417 representation of <em>value</em>. 14418 If <em>value</em> is zero, -1 will be returned.</p></td> 14419</tr> 14420<tr> 14421<td class="tableblock halign-left valign-top"><p class="tableblock"> genIType <strong>findMSB</strong>(highp genIType <em>value</em>)<br> 14422 genIType <strong>findMSB</strong>(highp genUType <em>value</em>)</p></td> 14423<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the bit number of the most significant bit in the binary 14424 representation of <em>value</em>.</p> 14425<p class="tableblock"> For positive integers, the result will be the bit number of the most 14426 significant one bit. 14427 For negative integers, the result will be the bit number of the most 14428 significant zero bit. 14429 For a <em>value</em> of zero or negative one, -1 will be returned.</p></td> 14430</tr> 14431</tbody> 14432</table> 14433</div> 14434<div class="sect2"> 14435<h3 id="texture-functions">8.9. Texture Functions</h3> 14436<div class="paragraph"> 14437<p>Texture lookup functions are available in all shading stages. 14438However, level-of-detail is implicitly computed only for fragment shaders. 14439Other shaders operate as though the base level-of-detail were computed as 14440zero. 14441The functions in the table below provide access to textures through 14442texture-combined samplers, as set up through the API. 14443Texture properties such as size, pixel format, number of dimensions, 14444filtering method, number of mipmap levels, depth comparison, and so on are 14445also defined by API calls. 14446Such properties are taken into account as the texture is accessed via the 14447built-in functions defined below.</p> 14448</div> 14449<div class="paragraph"> 14450<p>Texture data can be stored by the GL as single-precision floating-point, 14451unsigned normalized integer, unsigned integer or signed integer data. 14452This is determined by the type of the internal format of the texture.</p> 14453</div> 14454<div class="paragraph"> 14455<p>Texture lookup functions are provided that can return their result as 14456floating-point, unsigned integer or signed integer, depending on the sampler 14457type passed to the lookup function. 14458Care must be taken to use the right sampler type for texture access. 14459The following table lists the supported combinations of sampler types and 14460texture internal formats. 14461Blank entries are unsupported. 14462Doing a texture lookup will return undefined values for unsupported 14463combinations.</p> 14464</div> 14465<div class="paragraph"> 14466<p>For depth/stencil textures, the internal texture format is determined by the 14467component being accessed as set through the API. 14468When the depth/stencil texture mode is set to DEPTH_COMPONENT, the internal 14469format of the depth component should be used. 14470When the depth/stencil texture mode is set to STENCIL_INDEX, the internal format 14471of the stencil component should be used.</p> 14472</div> 14473<table class="tableblock frame-all grid-all stretch"> 14474<colgroup> 14475<col style="width: 25%;"> 14476<col style="width: 25%;"> 14477<col style="width: 25%;"> 14478<col style="width: 25%;"> 14479</colgroup> 14480<thead> 14481<tr> 14482<th class="tableblock halign-left valign-top">Internal Texture Format</th> 14483<th class="tableblock halign-left valign-top">Floating-Point Sampler Types</th> 14484<th class="tableblock halign-left valign-top">Signed Integer Sampler Types</th> 14485<th class="tableblock halign-left valign-top">Unsigned Integer Sampler Types</th> 14486</tr> 14487</thead> 14488<tbody> 14489<tr> 14490<td class="tableblock halign-left valign-top"><p class="tableblock">Floating-point</p></td> 14491<td class="tableblock halign-left valign-top"><p class="tableblock">Supported</p></td> 14492<td class="tableblock halign-left valign-top"></td> 14493<td class="tableblock halign-left valign-top"></td> 14494</tr> 14495<tr> 14496<td class="tableblock halign-left valign-top"><p class="tableblock">Normalized Integer</p></td> 14497<td class="tableblock halign-left valign-top"><p class="tableblock">Supported</p></td> 14498<td class="tableblock halign-left valign-top"></td> 14499<td class="tableblock halign-left valign-top"></td> 14500</tr> 14501<tr> 14502<td class="tableblock halign-left valign-top"><p class="tableblock">Signed Integer</p></td> 14503<td class="tableblock halign-left valign-top"></td> 14504<td class="tableblock halign-left valign-top"><p class="tableblock">Supported</p></td> 14505<td class="tableblock halign-left valign-top"></td> 14506</tr> 14507<tr> 14508<td class="tableblock halign-left valign-top"><p class="tableblock">Unsigned Integer</p></td> 14509<td class="tableblock halign-left valign-top"></td> 14510<td class="tableblock halign-left valign-top"></td> 14511<td class="tableblock halign-left valign-top"><p class="tableblock">Supported</p></td> 14512</tr> 14513</tbody> 14514</table> 14515<div class="paragraph"> 14516<p>If an integer sampler type is used, the result of a texture lookup is an 14517<strong>ivec4</strong>. 14518If an unsigned integer sampler type is used, the result of a texture lookup 14519is a <strong>uvec4</strong>. 14520If a floating-point sampler type is used, the result of a texture lookup is 14521a <strong>vec4</strong>.</p> 14522</div> 14523<div class="paragraph"> 14524<p>In the prototypes below, the <code>g</code> in the return type <code>gvec4</code> is used 14525as a placeholder for either nothing, <code>i</code>, or <code>u</code> making a return type of 14526<strong>vec4</strong>, <strong>ivec4</strong>, or <strong>uvec4</strong>. 14527In these cases, the sampler argument type also starts with <code>g</code>, 14528indicating the same substitution done on the return type; it is either a 14529single-precision 14530floating-point, signed integer, or unsigned integer sampler, matching the 14531basic type of the return type, as described above.</p> 14532</div> 14533<div class="paragraph"> 14534<p>For shadow forms (the sampler parameter is a shadow-type), a depth 14535comparison lookup on the depth texture bound to <em>sampler</em> is done as 14536described in section 145378.23 14538“Texture Comparison Modes” of the 14539<a href="#references">OpenGL Specification</a>. 14540See the table below for which component specifies <em>D<sub>ref</sub></em>. 14541The texture bound to <em>sampler</em> must be a depth texture, or results are 14542undefined. 14543If a non-shadow texture call is made to a sampler that represents a depth 14544texture with depth comparisons turned on, then results are undefined. 14545If a shadow texture call is made to a sampler that represents a depth 14546texture with depth comparisons turned off, then results are undefined. 14547If a shadow texture call is made to a sampler that does not represent a 14548depth texture, then results are undefined.</p> 14549</div> 14550<div class="paragraph"> 14551<p>In all functions below, the <em>bias</em> parameter is optional for fragment 14552shaders. 14553The <em>bias</em> parameter is not accepted in any other shader stage. 14554For a fragment shader, if <em>bias</em> is present, it is added to the implicit 14555level-of-detail prior to performing the texture access operation. 14556No <em>bias</em> or <em>lod</em> parameters for 14557rectangle textures, 14558multisample textures, or texture buffers 14559are supported because mipmaps are not allowed for these types of textures.</p> 14560</div> 14561<div class="paragraph"> 14562<p>The implicit level-of-detail is selected as follows: For a texture that is 14563not mipmapped, the texture is used directly. 14564If it is mipmapped and running in a fragment shader, the level-of-detail 14565computed by the implementation is used to do the texture lookup. 14566If it is mipmapped and running in a non-fragment shader, then the base 14567texture is used.</p> 14568</div> 14569<div class="paragraph"> 14570<p>Some texture functions (non-“<strong>Lod</strong>” and non-“<strong>Grad</strong>” versions) may 14571require implicit derivatives. 14572Implicit derivatives are undefined within non-uniform control flow and for 14573non-fragment shader texture fetches.</p> 14574</div> 14575<div class="paragraph"> 14576<p>For <strong>Cube</strong> forms, the direction of <em>P</em> is used to select which face to do a 145772-dimensional texture lookup in, as described in section 8.13 “Cube Map 14578Texture Selection” of the <a href="#references">OpenGL Specification</a>.</p> 14579</div> 14580<div class="paragraph"> 14581<p>For <strong>Array</strong> forms, the array layer used will be</p> 14582</div> 14583<div class="paragraph"> 14584<p>\(\max(0,\min(d-1,\left\lfloor layer + 0.5\right\rfloor))\)</p> 14585</div> 14586<div class="paragraph"> 14587<p>where <em>d</em> is the depth of the texture array and <em>layer</em> comes from the 14588component indicated in the tables below.</p> 14589</div> 14590<div class="sect3"> 14591<h4 id="texture-query-functions">8.9.1. Texture Query Functions</h4> 14592<div class="paragraph"> 14593<p>The <strong>textureSize</strong> functions query the dimensions of a specific texture level 14594for a texture-combined sampler.</p> 14595</div> 14596<div class="paragraph"> 14597<p>The <strong>textureQueryLod</strong> functions are available only in a fragment shader. 14598They take the components of <em>P</em> and compute the level-of-detail information 14599that the texture pipe would use to access that texture through a normal 14600texture lookup. 14601The level-of-detail \(\lambda^{'}\) (equation 3.18 of the 14602<a href="#references">OpenGL Specification</a>) is obtained after any level-of-detail bias, but 14603prior to clamping to [TEXTURE_MIN_LOD, TEXTURE_MAX_LOD]. 14604The mipmap array(s) that would be accessed are also computed. 14605If a single level-of-detail would be accessed, the level-of-detail number 14606relative to the base level is returned. 14607If multiple levels-of-detail would be accessed, a floating-point number 14608between the two levels is returned, with the fractional part equal to the 14609fractional part of the computed and clamped level-of-detail.</p> 14610</div> 14611<div class="paragraph"> 14612<p>The algorithm used is given by the following pseudo-code:</p> 14613</div> 14614<div class="listingblock"> 14615<div class="content"> 14616<pre class="CodeRay highlight"><code data-lang="c++"><span class="predefined-type">float</span> ComputeAccessedLod(<span class="predefined-type">float</span> computedLod) 14617{ 14618 <span class="comment">// Clamp the computed LOD according to the texture LOD clamps.</span> 14619 <span class="keyword">if</span> (computedLod < TEXTURE_MIN_LOD) computedLod = TEXTURE_MIN_LOD; 14620 <span class="keyword">if</span> (computedLod > TEXTURE_MAX_LOD) computedLod = TEXTURE_MAX_LOD; 14621 14622 <span class="comment">// Clamp the computed LOD to the range of accessible levels.</span> 14623 <span class="keyword">if</span> (computedLod < <span class="float">0</span><span class="float">.0</span>) 14624 computedLod = <span class="float">0</span><span class="float">.0</span>; 14625 <span class="keyword">if</span> (computedLod > (<span class="predefined-type">float</span>) maxAccessibleLevel) 14626 computedLod = (<span class="predefined-type">float</span>) maxAccessibleLevel; 14627 14628 <span class="comment">// Return a value according to the min filter.</span> 14629 <span class="keyword">if</span> (TEXTURE_MIN_FILTER is LINEAR <span class="keyword">or</span> NEAREST) { 14630 <span class="keyword">return</span> <span class="float">0</span><span class="float">.0</span>; 14631 } <span class="keyword">else</span> <span class="keyword">if</span> (TEXTURE_MIN_FILTER is NEAREST_MIPMAP_NEAREST 14632 <span class="keyword">or</span> LINEAR_MIPMAP_NEAREST) { 14633 <span class="keyword">return</span> ceil(computedLod + <span class="float">0</span><span class="float">.5</span>) - <span class="float">1</span><span class="float">.0</span>; 14634 } <span class="keyword">else</span> { 14635 <span class="keyword">return</span> computedLod; 14636 } 14637}</code></pre> 14638</div> 14639</div> 14640<div class="paragraph"> 14641<p>The value <em>maxAccessibleLevel</em> is the level number of the smallest 14642accessible level of the mipmap array (the value <em>q</em> in section 8.14.3 14643“Mipmapping” of the <a href="#references">OpenGL Specification</a>) minus the base level.</p> 14644</div> 14645<table class="tableblock frame-all grid-all stretch"> 14646<colgroup> 14647<col style="width: 50%;"> 14648<col style="width: 50%;"> 14649</colgroup> 14650<thead> 14651<tr> 14652<th class="tableblock halign-left valign-top">Syntax</th> 14653<th class="tableblock halign-left valign-top">Description</th> 14654</tr> 14655</thead> 14656<tbody> 14657<tr> 14658<td class="tableblock halign-left valign-top"><p class="tableblock"> int <strong>textureSize</strong>(gsampler1D <em>sampler</em>, int <em>lod</em>)<br> 14659 ivec2 <strong>textureSize</strong>(gsampler2D <em>sampler</em>, int <em>lod</em>)<br> 14660 ivec3 <strong>textureSize</strong>(gsampler3D <em>sampler</em>, int <em>lod</em>)<br> 14661 ivec2 <strong>textureSize</strong>(gsamplerCube <em>sampler</em>, int <em>lod</em>)<br> 14662 int <strong>textureSize</strong>(sampler1DShadow <em>sampler</em>, int <em>lod</em>)<br> 14663 ivec2 <strong>textureSize</strong>(sampler2DShadow <em>sampler</em>, int <em>lod</em>)<br> 14664 ivec2 <strong>textureSize</strong>(samplerCubeShadow <em>sampler</em>, int <em>lod</em>) 14665 ivec3 <strong>textureSize</strong>(gsamplerCubeArray <em>sampler</em>, int <em>lod</em>)<br> 14666 ivec3 <strong>textureSize</strong>(samplerCubeArrayShadow <em>sampler</em>, int <em>lod</em>)<br> 14667 ivec2 <strong>textureSize</strong>(gsampler2DRect <em>sampler</em>)<br> 14668 ivec2 <strong>textureSize</strong>(sampler2DRectShadow <em>sampler</em>)<br> 14669 ivec2 <strong>textureSize</strong>(gsampler1DArray <em>sampler</em>, int <em>lod</em>)<br> 14670 ivec2 <strong>textureSize</strong>(sampler1DArrayShadow <em>sampler</em>, int <em>lod</em>)<br> 14671 ivec3 <strong>textureSize</strong>(gsampler2DArray <em>sampler</em>, int <em>lod</em>)<br> 14672 ivec3 <strong>textureSize</strong>(sampler2DArrayShadow <em>sampler</em>, int <em>lod</em>)<br> 14673 int <strong>textureSize</strong>(gsamplerBuffer <em>sampler</em>)<br> 14674 ivec2 <strong>textureSize</strong>(gsampler2DMS <em>sampler</em>)<br> 14675 ivec3 <strong>textureSize</strong>(gsampler2DMSArray <em>sampler</em>)</p></td> 14676<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the dimensions of level <em>lod</em> (if present) for the texture 14677 bound to <em>sampler</em>, as described in section 14678 8.11 “Texture Queries” of the <a href="#references">OpenGL Specification</a>.<br> 14679 The components in the return value are filled in, in order, with the 14680 width, height, and depth of the texture.</p> 14681<p class="tableblock"> For the array forms, the last component of the return value is the 14682 number of layers in the texture array, or the number of cubes in the 14683 texture cube map array.</p></td> 14684</tr> 14685<tr> 14686<td class="tableblock halign-left valign-top"><p class="tableblock">vec2 <strong>textureQueryLod</strong>(gsampler1D <em>sampler</em>, float <em>P</em>)<br> 14687 vec2 <strong>textureQueryLod</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>)<br> 14688 vec2 <strong>textureQueryLod</strong>(gsampler3D <em>sampler</em>, vec3 <em>P</em>)<br> 14689 vec2 <strong>textureQueryLod</strong>(gsamplerCube <em>sampler</em>, vec3 <em>P</em>)<br> 14690 vec2 <strong>textureQueryLod</strong>(gsampler1DArray <em>sampler</em>, float <em>P</em>)<br> 14691 vec2 <strong>textureQueryLod</strong>(gsampler2DArray <em>sampler</em>, vec2 <em>P</em>)<br> 14692 vec2 <strong>textureQueryLod</strong>(gsamplerCubeArray <em>sampler</em>, vec3 <em>P</em>)<br> 14693 vec2 <strong>textureQueryLod</strong>(sampler1DShadow <em>sampler</em>, float <em>P</em>)<br> 14694 vec2 <strong>textureQueryLod</strong>(sampler2DShadow <em>sampler</em>, vec2 <em>P</em>)<br> 14695 vec2 <strong>textureQueryLod</strong>(samplerCubeShadow <em>sampler</em>, vec3 <em>P</em>)<br> 14696 vec2 <strong>textureQueryLod</strong>(sampler1DArrayShadow <em>sampler</em>, float <em>P</em>)<br> 14697 vec2 <strong>textureQueryLod</strong>(sampler2DArrayShadow <em>sampler</em>, vec2 <em>P</em>)<br> 14698 vec2 <strong>textureQueryLod</strong>(samplerCubeArrayShadow <em>sampler</em>, vec3 <em>P</em>)</p></td> 14699<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the mipmap array(s) that would be accessed in the <em>x</em> 14700 component of the return value.</p> 14701<p class="tableblock"> Returns the computed level-of-detail relative to the base level in the 14702 <em>y</em> component of the return value.</p> 14703<p class="tableblock"> If called on an incomplete texture, the results are undefined.</p></td> 14704</tr> 14705<tr> 14706<td class="tableblock halign-left valign-top"><p class="tableblock">int <strong>textureQueryLevels</strong>(gsampler1D <em>sampler</em>)<br> 14707 int <strong>textureQueryLevels</strong>(gsampler2D <em>sampler</em>)<br> 14708 int <strong>textureQueryLevels</strong>(gsampler3D <em>sampler</em>)<br> 14709 int <strong>textureQueryLevels</strong>(gsamplerCube <em>sampler</em>)<br> 14710 int <strong>textureQueryLevels</strong>(gsampler1DArray <em>sampler</em>)<br> 14711 int <strong>textureQueryLevels</strong>(gsampler2DArray <em>sampler</em>)<br> 14712 int <strong>textureQueryLevels</strong>(gsamplerCubeArray <em>sampler</em>)<br> 14713 int <strong>textureQueryLevels</strong>(sampler1DShadow <em>sampler</em>)<br> 14714 int <strong>textureQueryLevels</strong>(sampler2DShadow <em>sampler</em>)<br> 14715 int <strong>textureQueryLevels</strong>(samplerCubeShadow <em>sampler</em>)<br> 14716 int <strong>textureQueryLevels</strong>(sampler1DArrayShadow <em>sampler</em>)<br> 14717 int <strong>textureQueryLevels</strong>(sampler2DArrayShadow <em>sampler</em>)<br> 14718 int <strong>textureQueryLevels</strong>(samplerCubeArrayShadow <em>sampler</em>)</p></td> 14719<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the number of mipmap levels accessible in the texture 14720 associated with <em>sampler</em>, as defined in the <a href="#references">OpenGL Specification.</a></p> 14721<p class="tableblock"> The value zero will be returned if no texture or an incomplete texture 14722 is associated with <em>sampler</em>.</p> 14723<p class="tableblock"> Available in all shader stages.</p></td> 14724</tr> 14725<tr> 14726<td class="tableblock halign-left valign-top"><p class="tableblock">int <strong>textureSamples</strong>(gsampler2DMS <em>sampler</em>)<br> 14727 int <strong>textureSamples</strong>(gsampler2DMSArray <em>sampler</em>)</p></td> 14728<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the number of samples of the texture or textures bound to 14729 <em>sampler</em>.</p></td> 14730</tr> 14731</tbody> 14732</table> 14733</div> 14734<div class="sect3"> 14735<h4 id="texel-lookup-functions">8.9.2. Texel Lookup Functions</h4> 14736<table class="tableblock frame-all grid-all stretch"> 14737<colgroup> 14738<col style="width: 50%;"> 14739<col style="width: 50%;"> 14740</colgroup> 14741<thead> 14742<tr> 14743<th class="tableblock halign-left valign-top">Syntax</th> 14744<th class="tableblock halign-left valign-top">Description</th> 14745</tr> 14746</thead> 14747<tbody> 14748<tr> 14749<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>texture</strong>(gsampler1D <em>sampler</em>, float <em>P</em> [, float <em>bias</em>] )<br> 14750 gvec4 <strong>texture</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em> [, float <em>bias</em>] )<br> 14751 gvec4 <strong>texture</strong>(gsampler3D <em>sampler</em>, vec3 <em>P</em> [, float <em>bias</em>] )<br> 14752 gvec4 <strong>texture</strong>(gsamplerCube <em>sampler</em>, vec3 <em>P</em>[, float <em>bias</em>] )<br> 14753 float <strong>texture</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>P</em> [, float <em>bias</em>])<br> 14754 float <strong>texture</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>P</em> [, float <em>bias</em>])<br> 14755 float <strong>texture</strong>(samplerCubeShadow <em>sampler</em>, vec4 <em>P</em> [, float <em>bias</em>] )<br> 14756 gvec4 <strong>texture</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em> [, float <em>bias</em>] )<br> 14757 gvec4 <strong>texture</strong>(gsamplerCubeArray <em>sampler</em>, vec4 <em>P</em> [, float <em>bias</em>] )<br> 14758 gvec4 <strong>texture</strong>(gsampler1DArray <em>sampler</em>, vec2 <em>P</em> [, float <em>bias</em>] )<br> 14759 float <strong>texture</strong>(sampler1DArrayShadow <em>sampler</em>, vec3 <em>P</em> [, float <em>bias</em>] )<br> 14760 float <strong>texture</strong>(sampler2DArrayShadow <em>sampler</em>, vec4 <em>P</em>)<br> 14761 gvec4 <strong>texture</strong>(gsampler2DRect <em>sampler</em>, vec2 <em>P</em>)<br> 14762 float <strong>texture</strong>(sampler2DRectShadow <em>sampler</em>, vec3 <em>P</em>)<br> 14763 float <strong>texture</strong>(samplerCubeArrayShadow <em>sampler</em>, vec4 <em>P</em>, float <em>compare</em>)</p></td> 14764<td class="tableblock halign-left valign-top"><p class="tableblock">Use the texture coordinate <em>P</em> to do a texture lookup in the texture 14765 currently bound to <em>sampler</em>.</p> 14766<p class="tableblock"> For shadow forms: When <em>compare</em> is present, it is used as <em>D<sub>ref</sub></em> 14767 and the array layer comes from the last component of <em>P</em>. 14768 When <em>compare</em> is not present, the last component of <em>P</em> is used as 14769 <em>D<sub>ref</sub></em> and the array layer comes from the second to last component 14770 of <em>P</em>. 14771 (The second component of <em>P</em> is unused for <strong>1D</strong> shadow lookups.)</p> 14772<p class="tableblock"> For non-shadow forms: the array layer comes from the last component of 14773 <em>P</em>.</p></td> 14774</tr> 14775<tr> 14776<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureProj</strong>(gsampler1D <em>sampler</em>, vec2 <em>P</em> [, float <em>bias</em>] )<br> 14777 gvec4 <strong>textureProj</strong>(gsampler1D <em>sampler</em>, vec4 <em>P</em> [, float <em>bias</em>] )<br> 14778 gvec4 <strong>textureProj</strong>(gsampler2D <em>sampler</em>, vec3 <em>P</em> [, float <em>bias</em>] )<br> 14779 gvec4 <strong>textureProj</strong>(gsampler2D <em>sampler</em>, vec4 <em>P</em> [, float <em>bias</em>] )<br> 14780 gvec4 <strong>textureProj</strong>(gsampler3D <em>sampler</em>, vec4 <em>P</em> [, float <em>bias</em>] )<br> 14781 float <strong>textureProj</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>P</em> [, float <em>bias</em>] )<br> 14782 float <strong>textureProj</strong>(sampler2DShadow <em>sampler</em>, vec4 <em>P</em> [, float <em>bias</em>] )<br> 14783 gvec4 <strong>textureProj</strong>(gsampler2DRect <em>sampler</em>, vec3 <em>P</em>)<br> 14784 gvec4 <strong>textureProj</strong>(gsampler2DRect <em>sampler</em>, vec4 <em>P</em>)<br> 14785 float <strong>textureProj</strong>(sampler2DRectShadow <em>sampler</em>, vec4 <em>P</em>)<br></p></td> 14786<td class="tableblock halign-left valign-top"><p class="tableblock">Do a texture lookup with projection. 14787 The texture coordinates consumed from <em>P</em>, not including the last 14788 component of <em>P</em>, are divided by the last component of <em>P</em> to 14789 form projected coordinates <em>P'</em>. 14790 The resulting third component of <em>P</em> in the shadow forms is used as 14791 <em>D<sub>ref</sub></em>. 14792 The third component of <em>P</em> is ignored when <em>sampler</em> has type 14793 <strong>gsampler2D</strong> and <em>P</em> has type <strong>vec4</strong>. 14794 After these values are computed, texture lookup proceeds as in 14795 <strong>texture</strong>.</p></td> 14796</tr> 14797<tr> 14798<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureLod</strong>(gsampler1D <em>sampler</em>, float <em>P</em>, float <em>lod</em>)<br> 14799 gvec4 <strong>textureLod</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>, float <em>lod</em>)<br> 14800 gvec4 <strong>textureLod</strong>(gsampler3D <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>)<br> 14801 gvec4 <strong>textureLod</strong>(gsamplerCube <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>)<br> 14802 float <strong>textureLod</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>)<br> 14803 float <strong>textureLod</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>)<br> 14804 gvec4 <strong>textureLod</strong>(gsampler1DArray <em>sampler</em>, vec2 <em>P</em>, float <em>lod</em>)<br> 14805 float <strong>textureLod</strong>(sampler1DArrayShadow <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>)<br> 14806 gvec4 <strong>textureLod</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>)<br> 14807 gvec4 <strong>textureLod</strong>(gsamplerCubeArray <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>)</p></td> 14808<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 14809<p>Do a texture lookup as in <strong>texture</strong> but with explicit level-of-detail; 14810 <em>lod</em> specifies <span class="eq">λ<sub>base</sub>]</span> and sets the partial derivatives 14811 as follows:<br> 14812 (See section 8.14 “Texture Minification” and equations 8.4-8.6 of 14813 the <a href="#references">OpenGL Specification</a>.)<br> 14814 <br> 14815 <span class="eq">∂u / ∂x = 14816 ∂v / ∂x = 14817 ∂w / ∂x = 0</span> 14818 <br> 14819 <span class="eq">∂u / ∂y = 14820 ∂v / ∂y = 14821 ∂w / ∂y = 0</span></p> 14822</div></div></td> 14823</tr> 14824<tr> 14825<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureOffset</strong>(gsampler1D <em>sampler</em>, float <em>P</em>, int <em>offset</em> [, float <em>bias</em>] )<br> 14826 gvec4 <strong>textureOffset</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>, ivec2 <em>offset</em> [, float <em>bias</em>] )<br> 14827 gvec4 <strong>textureOffset</strong>(gsampler3D <em>sampler</em>, vec3 <em>P</em>, ivec3 <em>offset</em> [, float <em>bias</em>] )<br> 14828 float <strong>textureOffset</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>P</em>, ivec2 <em>offset</em> [, float <em>bias</em>] )<br> 14829 gvec4 <strong>textureOffset</strong>(gsampler2DRect <em>sampler</em>, vec2 <em>P</em>, ivec2 <em>offset</em>)<br> 14830 float <strong>textureOffset</strong>(sampler2DRectShadow <em>sampler</em>, vec3 <em>P</em>, ivec2 <em>offset</em>)<br> 14831 float <strong>textureOffset</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>P</em>, int <em>offset</em> [, float <em>bias</em>] )<br> 14832 gvec4 <strong>textureOffset</strong>(gsampler1DArray <em>sampler</em>, vec2 <em>P</em>, int <em>offset</em> [, float <em>bias</em>] )<br> 14833 gvec4 <strong>textureOffset</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em>, ivec2 <em>offset</em> [, float <em>bias</em>] )<br> 14834 float <strong>textureOffset</strong>(sampler1DArrayShadow <em>sampler</em>, vec3 <em>P</em>, int <em>offset</em> [, float <em>bias</em>] )<br> 14835 float <strong>textureOffset</strong>(sampler2DArrayShadow <em>sampler</em>, vec4 <em>P</em>, ivec2 <em>offset</em>)</p></td> 14836<td class="tableblock halign-left valign-top"><p class="tableblock">Do a texture lookup as in <strong>texture</strong> but with <em>offset</em> added to the 14837 <span class="eq">(u,v,w)</span> texel coordinates before looking up each texel. 14838 The offset value must be a constant expression. 14839 A limited range of offset values are supported; the minimum and 14840 maximum offset values are implementation-dependent and given by 14841 <em>gl_MinProgramTexelOffset</em> and <em>gl_MaxProgramTexelOffset</em>, 14842 respectively.</p> 14843<p class="tableblock"> Note that <em>offset</em> does not apply to the layer coordinate for texture 14844 arrays. 14845 This is explained in detail in section 8.14.2 “Coordinate Wrapping 14846 and Texel Selection” of the <a href="#references">OpenGL Specification</a>, where <em>offset</em> 14847 is <span class="eq">(δ<sub>u</sub>, δ<sub>v</sub>, δ<sub>w</sub>)</span>.<br> 14848 Note that texel offsets are also not supported for cube maps.</p></td> 14849</tr> 14850<tr> 14851<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>texelFetch</strong>(gsampler1D <em>sampler</em>, int <em>P</em>, int <em>lod</em>)<br> 14852 gvec4 <strong>texelFetch</strong>(gsampler2D <em>sampler</em>, ivec2 <em>P</em>, int <em>lod</em>)<br> 14853 gvec4 <strong>texelFetch</strong>(gsampler3D <em>sampler</em>, ivec3 <em>P</em>, int <em>lod</em>) 14854 gvec4 <strong>texelFetch</strong>(gsampler2DRect <em>sampler</em>, ivec2 <em>P</em>)<br> 14855 gvec4 <strong>texelFetch</strong>(gsampler1DArray <em>sampler</em>, ivec2 <em>P</em>, int <em>lod</em>)<br> 14856 gvec4 <strong>texelFetch</strong>(gsampler2DArray <em>sampler</em>, ivec3 <em>P</em>, int <em>lod</em>)<br> 14857 gvec4 <strong>texelFetch</strong>(gsamplerBuffer <em>sampler</em>, int <em>P</em>)<br> 14858 gvec4 <strong>texelFetch</strong>(gsampler2DMS <em>sampler</em>, ivec2 <em>P</em>, int <em>sample</em>)<br> 14859 gvec4 <strong>texelFetch</strong>(gsampler2DMSArray <em>sampler</em>, ivec3 <em>P</em>, int <em>sample</em>)</p></td> 14860<td class="tableblock halign-left valign-top"><p class="tableblock">Use integer texture coordinate <em>P</em> to lookup a single texel from 14861 <em>sampler</em>. 14862 The array layer comes from the last component of <em>P</em> for the array 14863 forms. 14864 The level-of-detail <em>lod</em> (if present) is as described in sections 14865 11.1.3.2 “Texel Fetches” and 8.14.1 “Scale Factor and Level of 14866 Detail” of the <a href="#references">OpenGL Specification</a>.</p></td> 14867</tr> 14868<tr> 14869<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>texelFetchOffset</strong>(gsampler1D <em>sampler</em>, int <em>P</em>, int <em>lod</em>, int <em>offset</em>)<br> 14870 gvec4 <strong>texelFetchOffset</strong>(gsampler2D <em>sampler</em>, ivec2 <em>P</em>, int <em>lod</em>, ivec2 <em>offset</em>)<br> 14871 gvec4 <strong>texelFetchOffset</strong>(gsampler3D <em>sampler</em>, ivec3 <em>P</em>, int <em>lod</em>, ivec3 <em>offset</em>)<br> 14872 gvec4 <strong>texelFetchOffset</strong>(gsampler2DRect <em>sampler</em>, ivec2 <em>P</em>, ivec2 <em>offset</em>)<br> 14873 gvec4 <strong>texelFetchOffset</strong>(gsampler1DArray <em>sampler</em>, ivec2 <em>P</em>, int <em>lod</em>, int <em>offset</em>)<br> 14874 gvec4 <strong>texelFetchOffset</strong>(gsampler2DArray <em>sampler</em>, ivec3 <em>P</em>, int <em>lod</em>, ivec2 <em>offset</em>)</p></td> 14875<td class="tableblock halign-left valign-top"><p class="tableblock">Fetch a single texel as in <strong>texelFetch</strong>, offset by <em>offset</em> as 14876 described in <strong>textureOffset</strong>.</p></td> 14877</tr> 14878<tr> 14879<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureProjOffset</strong>(gsampler1D <em>sampler</em>, vec2 <em>P</em>, int <em>offset</em> [, float <em>bias</em>] )<br> 14880 gvec4 <strong>textureProjOffset</strong>(gsampler1D <em>sampler</em>, vec4 <em>P</em>, int <em>offset</em> [, float <em>bias</em>] )<br> 14881 gvec4 <strong>textureProjOffset</strong>(gsampler2D <em>sampler</em>, vec3 <em>P</em>, ivec2 <em>offset</em> [, float <em>bias</em>] )<br> 14882 gvec4 <strong>textureProjOffset</strong>(gsampler2D <em>sampler</em>, vec4 <em>P</em>, ivec2 <em>offset</em> [, float <em>bias</em>] )<br> 14883 gvec4 <strong>textureProjOffset</strong>(gsampler3D <em>sampler</em>, vec4 <em>P</em>, ivec3 <em>offset</em> [, float <em>bias</em>] )<br> 14884 gvec4 <strong>textureProjOffset</strong>(gsampler2DRect <em>sampler</em>, vec3 <em>P</em>, ivec2 <em>offset</em>)<br> 14885 gvec4 <strong>textureProjOffset</strong>(gsampler2DRect <em>sampler</em>, vec4 <em>P</em>, ivec2 <em>offset</em>)<br> 14886 float <strong>textureProjOffset</strong>(sampler2DRectShadow <em>sampler</em>, vec4 <em>P</em>, ivec2 <em>offset</em>)<br> 14887 float <strong>textureProjOffset</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>P</em>, int <em>offset</em> [, float <em>bias</em>] )<br> 14888 float <strong>textureProjOffset</strong>(sampler2DShadow <em>sampler</em>, vec4 <em>P</em>, ivec2 <em>offset</em> [, float <em>bias</em>] )</p></td> 14889<td class="tableblock halign-left valign-top"><p class="tableblock">Do a projective texture lookup as described in <strong>textureProj</strong>, offset 14890 by <em>offset</em> as described in <strong>textureOffset</strong>.</p></td> 14891</tr> 14892<tr> 14893<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureLodOffset</strong>(gsampler1D <em>sampler</em>, float <em>P</em>, float <em>lod</em>, int <em>offset</em>)<br> 14894 gvec4 <strong>textureLodOffset</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>, float <em>lod</em>, ivec2 <em>offset</em>)<br> 14895 gvec4 <strong>textureLodOffset</strong>(gsampler3D <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>, ivec3 <em>offset</em>)<br> 14896 float <strong>textureLodOffset</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>, int <em>offset</em>)<br> 14897 float <strong>textureLodOffset</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>, ivec2 <em>offset</em>)<br> 14898 gvec4 <strong>textureLodOffset</strong>(gsampler1DArray <em>sampler</em>, vec2 <em>P</em>, float <em>lod</em>, int <em>offset</em>)<br> 14899 gvec4 <strong>textureLodOffset</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>, ivec2 <em>offset</em>)<br> 14900 float <strong>textureLodOffset</strong>(sampler1DArrayShadow <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>, int <em>offset</em>)</p></td> 14901<td class="tableblock halign-left valign-top"><p class="tableblock">Do an offset texture lookup with explicit level-of-detail. 14902 See <strong>textureLod</strong> and <strong>textureOffset</strong>.</p></td> 14903</tr> 14904<tr> 14905<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureProjLod</strong>(gsampler1D <em>sampler</em>, vec2 <em>P</em>, float <em>lod</em>)<br> 14906 gvec4 <strong>textureProjLod</strong>(gsampler1D <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>)<br> 14907 gvec4 <strong>textureProjLod</strong>(gsampler2D <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>)<br> 14908 gvec4 <strong>textureProjLod</strong>(gsampler2D <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>)<br> 14909 gvec4 <strong>textureProjLod</strong>(gsampler3D <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>)<br> 14910 float <strong>textureProjLod</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>)<br> 14911 float <strong>textureProjLod</strong>(sampler2DShadow <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>)</p></td> 14912<td class="tableblock halign-left valign-top"><p class="tableblock">Do a projective texture lookup with explicit level-of-detail. 14913 See <strong>textureProj</strong> and <strong>textureLod</strong>.</p></td> 14914</tr> 14915<tr> 14916<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureProjLodOffset</strong>(gsampler1D <em>sampler</em>, vec2 <em>P</em>, float <em>lod</em>, int <em>offset</em>)<br> 14917 gvec4 <strong>textureProjLodOffset</strong>(gsampler1D <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>, int <em>offset</em>)<br> 14918 gvec4 <strong>textureProjLodOffset</strong>(gsampler2D <em>sampler</em>, vec3 <em>P</em>, float <em>lod</em>, ivec2 <em>offset</em>)<br> 14919 gvec4 <strong>textureProjLodOffset</strong>(gsampler2D <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>, ivec2 <em>offset</em>)<br> 14920 gvec4 <strong>textureProjLodOffset</strong>(gsampler3D <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>, ivec3 <em>offset</em>)<br> 14921 float <strong>textureProjLodOffset</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>, int <em>offset</em>)<br> 14922 float <strong>textureProjLodOffset</strong>(sampler2DShadow <em>sampler</em>, vec4 <em>P</em>, float <em>lod</em>, ivec2 <em>offset</em>)</p></td> 14923<td class="tableblock halign-left valign-top"><p class="tableblock">Do an offset projective texture lookup with explicit level-of-detail. 14924 See <strong>textureProj</strong>, <strong>textureLod</strong>, and <strong>textureOffset</strong>.</p></td> 14925</tr> 14926<tr> 14927<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureGrad</strong>(gsampler1D <em>sampler</em>, <em>float _P</em>, float <em>dPdx</em>, float <em>dPdy</em>)<br> 14928 gvec4 <strong>textureGrad</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14929 gvec4 <strong>textureGrad</strong>(gsampler3D <em>sampler</em>, <em>P</em>, vec3 <em>dPdx</em>, vec3 <em>dPdy</em>)<br> 14930 gvec4 <strong>textureGrad</strong>(gsamplerCube <em>sampler</em>, vec3 <em>P</em>, vec3 <em>dPdx</em>, vec3 <em>dPdy</em>)<br> 14931 gvec4 <strong>textureGrad</strong>(gsampler2DRect <em>sampler</em>, vec2 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14932 float <strong>textureGrad</strong>(sampler2DRectShadow <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14933 float <strong>textureGrad</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>)<br> 14934 gvec4 <strong>textureGrad</strong>(gsampler1DArray <em>sampler</em>, vec2 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>)<br> 14935 gvec4 <strong>textureGrad</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14936 float <strong>textureGrad</strong>(sampler1DArrayShadow <em>sampler</em>, vec3 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>)<br> 14937 float <strong>textureGrad</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14938 float <strong>textureGrad</strong>(samplerCubeShadow <em>sampler</em>, vec4 <em>P</em>, vec3 <em>dPdx</em>, vec3 <em>dPdy</em>)<br> 14939 float <strong>textureGrad</strong>(sampler2DArrayShadow <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14940 gvec4 <strong>textureGrad</strong>(gsamplerCubeArray <em>sampler</em>, vec4 <em>P</em>, vec3 <em>dPdx</em>, vec3 <em>dPdy</em>)<br></p></td> 14941<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 14942<p>Do a texture lookup as in <strong>texture</strong> but with <a href="#explicit-gradients">explicit gradients</a> as shown below. 14943 The partial derivatives of <em>P</em> are with respect to window <em>x</em> and 14944 window <em>y</em>. 14945 For the cube version, the partial derivatives of <em>P</em> are assumed to be 14946 in the coordinate system used before texture coordinates are projected 14947 onto the appropriate cube face.</p> 14948</div></div></td> 14949</tr> 14950<tr> 14951<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureGradOffset</strong>(gsampler1D <em>sampler</em>, float <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>, int <em>offset</em>)<br> 14952 gvec4 <strong>textureGradOffset</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14953 gvec4 <strong>textureGradOffset</strong>(gsampler3D <em>sampler</em>, vec3 <em>P</em>, vec3 <em>dPdx</em>, vec3 <em>dPdy</em>, ivec3 <em>offset</em>)<br> 14954 gvec4 <strong>textureGradOffset</strong>(gsampler2DRect <em>sampler</em>, vec2 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14955 float <strong>textureGradOffset</strong>(sampler2DRectShadow <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14956 float <strong>textureGradOffset</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>, int <em>offset</em>)<br> 14957 float <strong>textureGradOffset</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14958 gvec4 <strong>textureGradOffset</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14959 gvec4 <strong>textureGradOffset</strong>(gsampler1DArray <em>sampler</em>, vec2 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>, int <em>offset</em>)<br> 14960 float <strong>textureGradOffset</strong>(sampler1DArrayShadow <em>sampler</em>, vec3 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>, int <em>offset</em>)<br> 14961 float <strong>textureGradOffset</strong>(sampler2DArrayShadow <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br></p></td> 14962<td class="tableblock halign-left valign-top"><p class="tableblock">Do a texture lookup with both explicit gradient and offset, as 14963 described in <strong>textureGrad</strong> and <strong>textureOffset</strong>.</p></td> 14964</tr> 14965<tr> 14966<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureProjGrad</strong>(gsampler1D <em>sampler</em>, vec2 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>)<br> 14967 gvec4 <strong>textureProjGrad</strong>(gsampler1D <em>sampler</em>, vec4 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>)<br> 14968 gvec4 <strong>textureProjGrad</strong>(gsampler2D <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14969 gvec4 <strong>textureProjGrad</strong>(gsampler2D <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14970 gvec4 <strong>textureProjGrad</strong>(gsampler3D <em>sampler</em>, vec4 <em>P</em>, vec3 <em>dPdx</em>, vec3 <em>dPdy</em>)<br> 14971 gvec4 <strong>textureProjGrad</strong>(gsampler2DRect <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14972 gvec4 <strong>textureProjGrad</strong>(gsampler2DRect <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14973 float <strong>textureProjGrad</strong>(sampler2DRectShadow <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)<br> 14974 float <strong>textureProjGrad</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>)<br> 14975 float <strong>textureProjGrad</strong>(sampler2DShadow <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>)</p></td> 14976<td class="tableblock halign-left valign-top"><p class="tableblock">Do a texture lookup both projectively, as described in <strong>textureProj</strong>, 14977 and with explicit gradient as described in <strong>textureGrad</strong>. 14978 The partial derivatives <em>dPdx</em> and <em>dPdy</em> are assumed to be already 14979 projected.</p></td> 14980</tr> 14981<tr> 14982<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureProjGradOffset</strong>(gsampler1D <em>sampler</em>, vec2 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>, int <em>offset</em>)<br> 14983 gvec4 <strong>textureProjGradOffset</strong>(gsampler1D <em>sampler</em>, vec4 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>, int <em>offset</em>)<br> 14984 gvec4 <strong>textureProjGradOffset</strong>(gsampler2D <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14985 gvec4 <strong>textureProjGradOffset</strong>(gsampler2D <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14986 gvec4 <strong>textureProjGradOffset</strong>(gsampler3D <em>sampler</em>, vec4 <em>P</em>, vec3 <em>dPdx</em>, vec3 <em>dPdy</em>, ivec3 <em>offset</em>)<br> 14987 gvec4 <strong>textureProjGradOffset</strong>(gsampler2DRect <em>sampler</em>, vec3 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14988 gvec4 <strong>textureProjGradOffset</strong>(gsampler2DRect <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14989 float <strong>textureProjGradOffset</strong>(sampler2DRectShadow <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)<br> 14990 float <strong>textureProjGradOffset</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>P</em>, float <em>dPdx</em>, float <em>dPdy</em>, int <em>offset</em>)<br> 14991 float <strong>textureProjGradOffset</strong>(sampler2DShadow <em>sampler</em>, vec4 <em>P</em>, vec2 <em>dPdx</em>, vec2 <em>dPdy</em>, ivec2 <em>offset</em>)</p></td> 14992<td class="tableblock halign-left valign-top"><p class="tableblock">Do a texture lookup projectively and with explicit gradient as 14993 described in <strong>textureProjGrad</strong>, as well as with offset, as described in 14994 <strong>textureOffset</strong>.</p></td> 14995</tr> 14996</tbody> 14997</table> 14998</div> 14999<div class="sect3"> 15000<h4 id="explicit-gradients">8.9.3. Explicit Gradients</h4> 15001<div class="paragraph"> 15002<p>In the <strong>textureGrad</strong> functions described above, explicit gradients control 15003texture lookups as follows:</p> 15004</div> 15005<div class="stemblock"> 15006<div class="content"> 15007\[\begin{aligned} 15008 \frac{\partial{s}}{\partial{x}} & = 15009 \begin{cases} 15010 \frac{\partial{P}}{\partial{x}}, & \text{for a 1D texture} \\[0.8em] 15011 \frac{\partial{P.s}}{\partial{x}}, & \text{otherwise} 15012 \end{cases} \\[2.5em] 15013 \frac{\partial{s}}{\partial{y}} & = 15014 \begin{cases} 15015 \frac{\partial{P}}{\partial{y}}, & \text{for a 1D texture} \\[0.8em] 15016 \frac{\partial{P.s}}{\partial{y}}, & \text{otherwise} 15017 \end{cases} \\[2.5em] 15018 \frac{\partial{t}}{\partial{x}} & = 15019 \begin{cases} 15020 0.0, & \text{for a 1D texture} \\[0.8em] 15021 \frac{\partial{P.t}}{\partial{x}}, & \text{otherwise} 15022 \end{cases} \\[2.5em] 15023 \frac{\partial{t}}{\partial{y}} & = 15024 \begin{cases} 15025 0.0, & \text{for a 1D texture} \\[0.8em] 15026 \frac{\partial{P.t}}{\partial{y}}, & \text{otherwise} 15027 \end{cases} \\[2.5em] 15028 \frac{\partial{r}}{\partial{x}} & = 15029 \begin{cases} 15030 0.0, & \text{for 1D or 2D} \\[0.8em] 15031 \frac{\partial{P.p}}{\partial{x}}, & \text{cube, other} 15032 \end{cases} \\[2.5em] 15033 \frac{\partial{r}}{\partial{y}} & = 15034 \begin{cases} 15035 0.0, & \text{for 1D or 2D} \\[0.8em] 15036 \frac{\partial{P.p}}{\partial{y}}, & \text{cube, other} 15037 \end{cases} 15038\end{aligned}\] 15039</div> 15040</div> 15041</div> 15042<div class="sect3"> 15043<h4 id="texture-gather-functions">8.9.4. Texture Gather Functions</h4> 15044<div class="paragraph"> 15045<p>The texture gather functions take components of a single floating-point 15046vector operand as a texture coordinate, determine a set of four texels to 15047sample from the base level-of-detail of the specified texture image, and 15048return one component from each texel in a four-component result vector.</p> 15049</div> 15050<div class="paragraph"> 15051<p>When performing a texture gather operation, the minification and 15052magnification filters are ignored, and the rules for LINEAR filtering in the 15053<a href="#references">OpenGL Specification</a> are applied to the base level of the texture image 15054to identify the four texels <em>i<sub>0</sub> j<sub>1</sub></em>, <em>i<sub>1</sub> j<sub>1</sub></em>, <em>i<sub>1</sub> j<sub>0</sub></em>, and <em>i<sub>0</sub> 15055j<sub>0</sub></em>. 15056The texels are then converted to texture base colors (<em>R<sub>s</sub></em>, <em>G<sub>s</sub></em>, 15057<em>B<sub>s</sub></em>, <em>A<sub>s</sub></em>) according to table 15.1, followed by application of the 15058texture swizzle as described in section 15.2.1 “Texture Access” of the 15059<a href="#references">OpenGL Specification</a>. 15060A four-component vector is assembled by taking the selected component from 15061each of the post-swizzled texture source colors in the order (<em>i<sub>0</sub> j<sub>1</sub></em>, 15062<em>i<sub>1</sub> j<sub>1</sub></em>, <em>i<sub>1</sub> j<sub>0</sub></em>, <em>i<sub>0</sub> j<sub>0</sub></em>).</p> 15063</div> 15064<div class="paragraph"> 15065<p>For texture gather functions using a texture-combined shadow sampler type, 15066each of the four 15067texel lookups perform a depth comparison against the depth reference value 15068passed in (<em>refZ</em>), and returns the result of that comparison in the 15069appropriate component of the result vector.</p> 15070</div> 15071<div class="paragraph"> 15072<p>As with other texture lookup functions, the results of a texture gather are 15073undefined for shadow samplers if the texture referenced is not a depth 15074texture or has depth comparisons disabled; or for non-shadow samplers if the 15075texture referenced is a depth texture with depth comparisons enabled.</p> 15076</div> 15077<table class="tableblock frame-all grid-all stretch"> 15078<colgroup> 15079<col style="width: 50%;"> 15080<col style="width: 50%;"> 15081</colgroup> 15082<thead> 15083<tr> 15084<th class="tableblock halign-left valign-top">Syntax</th> 15085<th class="tableblock halign-left valign-top">Description</th> 15086</tr> 15087</thead> 15088<tbody> 15089<tr> 15090<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureGather</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em> [, int <em>comp</em>])<br> 15091 gvec4 <strong>textureGather</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em> [, int <em>comp</em>])<br> 15092 gvec4 <strong>textureGather</strong>(gsamplerCube <em>sampler</em>, vec3 <em>P</em> [, int <em>comp</em>])<br> 15093 gvec4 <strong>textureGather</strong>(gsamplerCubeArray <em>sampler</em>, vec4 <em>P</em>[, int <em>comp</em>])<br> 15094 gvec4 <strong>textureGather</strong>(gsampler2DRect <em>sampler</em>, vec2 <em>P</em>[, int <em>comp</em>])<br> 15095 vec4 <strong>textureGather</strong>(sampler2DShadow <em>sampler</em>, vec2 <em>P</em>, float <em>refZ</em>)<br> 15096 vec4 <strong>textureGather</strong>(sampler2DArrayShadow <em>sampler</em>, vec3 <em>P</em>, float <em>refZ</em>)<br> 15097 vec4 <strong>textureGather</strong>(samplerCubeShadow <em>sampler</em>, vec3 <em>P</em>, float <em>refZ</em>)<br> 15098 vec4 <strong>textureGather</strong>(samplerCubeArrayShadow <em>sampler</em>, vec4 <em>P</em>, float <em>refZ</em>)<br> 15099 vec4 <strong>textureGather</strong>(sampler2DRectShadow <em>sampler</em>, vec2 <em>P</em>, float <em>refZ</em>)</p></td> 15100<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15101<p>Returns the value<br></p> 15102</div> 15103<div class="openblock"> 15104<div class="content"> 15105<div class="listingblock"> 15106<div class="content"> 15107<pre class="CodeRay highlight"><code data-lang="c++">vec4(Sample_i0_j1(P, base).comp, 15108 Sample_i1_j1(P, base).comp, 15109 Sample_i1_j0(P, base).comp, 15110 Sample_i0_j0(P, base).comp)</code></pre> 15111</div> 15112</div> 15113<div class="paragraph"> 15114<p>If specified, the value of <em>comp</em> must be a constant integer expression with 15115a value of 0, 1, 2, or 3, identifying the <em>x</em>, <em>y</em>, <em>z</em>, or <em>w</em> 15116post-swizzled component of the four-component vector lookup result for each 15117texel, respectively. 15118If <em>comp</em> is not specified, it is treated as 0, selecting the <em>x</em> component 15119of each texel to generate the result.</p> 15120</div> 15121</div> 15122</div></div></td> 15123</tr> 15124<tr> 15125<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureGatherOffset</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>, ivec2 <em>offset</em>, [ int <em>comp</em>])<br> 15126 gvec4 <strong>textureGatherOffset</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em>, ivec2 <em>offset</em> [ int <em>comp</em>])<br> 15127 vec4 <strong>textureGatherOffset</strong>(sampler2DShadow <em>sampler</em>, vec2 <em>P</em>, float <em>refZ</em>, ivec2 <em>offset</em>)<br> 15128 vec4 <strong>textureGatherOffset</strong>(sampler2DArrayShadow <em>sampler</em>, vec3 <em>P</em>, float <em>refZ</em>, ivec2 <em>offset</em>)<br> 15129 gvec4 <strong>textureGatherOffset</strong>(gsampler2DRect <em>sampler</em>, vec2 <em>P</em>, ivec2 <em>offset</em> [ int <em>comp</em>])<br> 15130 vec4 <strong>textureGatherOffset</strong>(sampler2DRectShadow <em>sampler</em>, vec2 <em>P</em>, float <em>refZ</em>, ivec2 <em>offset</em>)</p></td> 15131<td class="tableblock halign-left valign-top"><p class="tableblock">Perform a texture gather operation as in <strong>textureGather</strong> by <em>offset</em> 15132 as described in <strong>textureOffset</strong> except that the <em>offset</em> can be 15133 variable (non constant) and the implementation-dependent minimum and 15134 maximum offset values are given by MIN_PROGRAM_TEXTURE_GATHER_OFFSET 15135 and MAX_PROGRAM_TEXTURE_GATHER_OFFSET, respectively.</p></td> 15136</tr> 15137<tr> 15138<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>textureGatherOffsets</strong>(gsampler2D <em>sampler</em>, vec2 <em>P</em>, ivec2 <em>offsets</em>[4] [, int <em>comp</em>])<br> 15139 gvec4 <strong>textureGatherOffsets</strong>(gsampler2DArray <em>sampler</em>, vec3 <em>P</em>, ivec2 <em>offsets</em>[4] [, int <em>comp</em>])<br> 15140 vec4 <strong>textureGatherOffsets</strong>(sampler2DShadow <em>sampler</em>, vec2 <em>P</em>, float <em>refZ</em>, ivec2 <em>offsets</em>[4])<br> 15141 vec4 <strong>textureGatherOffsets</strong>(sampler2DArrayShadow <em>sampler</em>, vec3 <em>P</em>, float <em>refZ</em>, ivec2 <em>offsets</em>[4])<br> 15142 gvec4 <strong>textureGatherOffsets</strong>(gsampler2DRect <em>sampler</em>, vec2 <em>P</em>, ivec2 <em>offsets</em>[4] [, int <em>comp</em>])<br> 15143 vec4 <strong>textureGatherOffsets</strong>(sampler2DRectShadow <em>sampler</em>, vec2 <em>P</em>, float <em>refZ</em>, ivec2 <em>offsets</em>[4])</p></td> 15144<td class="tableblock halign-left valign-top"><p class="tableblock">Operate identically to <strong>textureGatherOffset</strong> except that <em>offsets</em> is 15145 used to determine the location of the four texels to sample. 15146 Each of the four texels is obtained by applying the corresponding 15147 offset in <em>offsets</em> as a (<em>u</em>, <em>v</em>) coordinate offset to <em>P</em>, 15148 identifying the four-texel LINEAR footprint, and then selecting the 15149 texel <em>i<sub>0</sub> j<sub>0</sub></em> of that footprint. 15150 The specified values in <em>offsets</em> must be constant integral 15151 expressions.</p></td> 15152</tr> 15153</tbody> 15154</table> 15155</div> 15156<div class="sect3"> 15157<h4 id="compatibility-profile-texture-functions">8.9.5. Compatibility Profile Texture Functions</h4> 15158<div class="paragraph"> 15159<p>The following texture functions are only in the compatibility profile.</p> 15160</div> 15161<table class="tableblock frame-all grid-all stretch"> 15162<colgroup> 15163<col style="width: 50%;"> 15164<col style="width: 50%;"> 15165</colgroup> 15166<thead> 15167<tr> 15168<th class="tableblock halign-left valign-top">Syntax</th> 15169<th class="tableblock halign-left valign-top">Description</th> 15170</tr> 15171</thead> 15172<tbody> 15173<tr> 15174<td class="tableblock halign-left valign-top"><p class="tableblock">vec4 <strong>texture1D</strong>(sampler1D <em>sampler</em>, float <em>coord</em> [, float <em>bias</em>] )<br> 15175 vec4 <strong>texture1DProj</strong>(sampler1D <em>sampler</em>, vec2 <em>coord</em> [, float <em>bias</em>] )<br> 15176 vec4 <strong>texture1DProj</strong>(sampler1D <em>sampler</em>, vec4 <em>coord</em> [, float <em>bias</em>] )<br> 15177 vec4 <strong>texture1DLod</strong>(sampler1D <em>sampler</em>, float <em>coord</em>, float <em>lod</em>)<br> 15178 vec4 <strong>texture1DProjLod</strong>(sampler1D <em>sampler</em>, vec2 <em>coord</em>, float <em>lod</em>)<br> 15179 vec4 <strong>texture1DProjLod</strong>(sampler1D <em>sampler</em>, vec4 <em>coord</em>, float <em>lod</em>)</p></td> 15180<td class="tableblock halign-left valign-top"><p class="tableblock">See corresponding signature above without “1D” in the name.</p></td> 15181</tr> 15182<tr> 15183<td class="tableblock halign-left valign-top"><p class="tableblock">vec4 <strong>texture2D</strong>(sampler2D <em>sampler</em>, vec2 <em>coord</em> [, float <em>bias</em>] )<br> 15184 vec4 <strong>texture2DProj</strong>(sampler2D <em>sampler</em>, vec3 <em>coord</em> [, float <em>bias</em>] )<br> 15185 vec4 <strong>texture2DProj</strong>(sampler2D <em>sampler</em>, vec4 <em>coord</em> [, float <em>bias</em>] )<br> 15186 vec4 <strong>texture2DLod</strong>(sampler2D <em>sampler</em>, vec2 <em>coord</em>, float <em>lod</em>)<br> 15187 vec4 <strong>texture2DProjLod</strong>(sampler2D <em>sampler</em>, vec3 <em>coord</em>, float <em>lod</em>)<br> 15188 vec4 <strong>texture2DProjLod</strong>(sampler2D <em>sampler</em>, vec4 <em>coord</em>, float <em>lod</em>)</p></td> 15189<td class="tableblock halign-left valign-top"><p class="tableblock">See corresponding signature above without “2D” in the name.</p></td> 15190</tr> 15191<tr> 15192<td class="tableblock halign-left valign-top"><p class="tableblock">vec4 <strong>texture3D</strong>(sampler3D <em>sampler</em>, vec3 <em>coord</em> [, float <em>bias</em>] )<br> 15193 vec4 <strong>texture3DProj</strong>(sampler3D <em>sampler</em>, vec4 <em>coord</em> [, float <em>bias</em>] )<br> 15194 vec4 <strong>texture3DLod</strong>(sampler3D <em>sampler</em>, vec3 <em>coord</em>, float <em>lod</em>)<br> 15195 vec4 <strong>texture3DProjLod</strong>(sampler3D <em>sampler</em>, vec4 <em>coord</em>, float <em>lod</em>)</p></td> 15196<td class="tableblock halign-left valign-top"><p class="tableblock">See corresponding signature above without “3D” in the name.<br> 15197 Use the texture coordinate <em>coord</em> to do a texture lookup in the 3D 15198 texture currently bound to <em>sampler</em>. 15199 For the projective (“<strong>Proj</strong>”) versions, the texture coordinate is 15200 divided by <em>coord.q</em>.</p></td> 15201</tr> 15202<tr> 15203<td class="tableblock halign-left valign-top"><p class="tableblock">vec4 <strong>textureCube</strong>(samplerCube <em>sampler</em>, vec3 <em>coord</em> [, float <em>bias</em>] )<br> 15204 vec4 <strong>textureCubeLod</strong>(samplerCube <em>sampler</em>, vec3 <em>coord</em>, float <em>lod</em>)</p></td> 15205<td class="tableblock halign-left valign-top"><p class="tableblock">See corresponding signature above without “Cube” in the name.</p></td> 15206</tr> 15207<tr> 15208<td class="tableblock halign-left valign-top"><p class="tableblock">vec4 <strong>shadow1D</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>coord</em> [, float <em>bias</em>] )<br> 15209 vec4 <strong>shadow2D</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>coord</em> [, float <em>bias</em>] )<br> 15210 vec4 <strong>shadow1DProj</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>coord</em> [, float <em>bias</em>] )<br> 15211 vec4 <strong>shadow2DProj</strong>(sampler2DShadow <em>sampler</em>, vec4 <em>coord</em> [, float <em>bias</em>] )<br> 15212 vec4 <strong>shadow1DLod</strong>(sampler1DShadow <em>sampler</em>, vec3 <em>coord</em>, float <em>lod</em>)<br> 15213 vec4 <strong>shadow2DLod</strong>(sampler2DShadow <em>sampler</em>, vec3 <em>coord</em>, float <em>lod</em>)<br> 15214 vec4 <strong>shadow1DProjLod</strong>(sampler1DShadow <em>sampler</em>, vec4 <em>coord</em>, float <em>lod</em>)<br> 15215 vec4 <strong>shadow2DProjLod</strong>(sampler2DShadow <em>sampler</em>, vec4 coord, float <em>lod</em>)</p></td> 15216<td class="tableblock halign-left valign-top"><p class="tableblock">Same functionality as the “<strong>texture</strong>” based names above with the 15217 same signature.</p></td> 15218</tr> 15219</tbody> 15220</table> 15221</div> 15222</div> 15223<div class="sect2"> 15224<h3 id="atomic-counter-functions">8.10. Atomic Counter Functions</h3> 15225<div class="paragraph"> 15226<p>The atomic-counter operations in this section operate atomically with 15227respect to each other. 15228They are atomic for any single counter, meaning any of these operations on a 15229specific counter in one shader instantiation will be indivisible by any of 15230these operations on the same counter from another shader instantiation. 15231There is no guarantee that these operations are atomic with respect to other 15232forms of access to the counter or that they are serialized when applied to 15233separate counters. 15234Such cases would require additional use of fences, barriers, or other forms 15235of synchronization, if atomicity or serialization is desired.</p> 15236</div> 15237<div class="paragraph"> 15238<p>The underlying counter is a 32-bit unsigned integer. 15239The result of operations will wrap to [0, 2<sup>32</sup>-1].</p> 15240</div> 15241<table class="tableblock frame-all grid-all stretch"> 15242<colgroup> 15243<col style="width: 50%;"> 15244<col style="width: 50%;"> 15245</colgroup> 15246<thead> 15247<tr> 15248<th class="tableblock halign-left valign-top">Syntax</th> 15249<th class="tableblock halign-left valign-top">Description</th> 15250</tr> 15251</thead> 15252<tbody> 15253<tr> 15254<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterIncrement</strong>(atomic_uint <em>c</em>)</p></td> 15255<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15256<p>Atomically<br></p> 15257</div> 15258<div class="openblock"> 15259<div class="content"> 15260<div class="olist arabic"> 15261<ol class="arabic"> 15262<li> 15263<p>increments the counter for <em>c</em>, and</p> 15264</li> 15265<li> 15266<p>returns its value prior to the increment operation.</p> 15267</li> 15268</ol> 15269</div> 15270<div class="paragraph"> 15271<p>These two steps are done atomically with respect to the atomic counter 15272functions in this table.</p> 15273</div> 15274</div> 15275</div></div></td> 15276</tr> 15277<tr> 15278<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterDecrement</strong>(atomic_uint <em>c</em>)</p></td> 15279<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15280<p>Atomically<br></p> 15281</div> 15282<div class="openblock"> 15283<div class="content"> 15284<div class="olist arabic"> 15285<ol class="arabic"> 15286<li> 15287<p>decrements the counter for <em>c</em>, and</p> 15288</li> 15289<li> 15290<p>returns the value resulting from the decrement operation.</p> 15291</li> 15292</ol> 15293</div> 15294<div class="paragraph"> 15295<p>These two steps are done atomically with respect to the atomic counter 15296functions in this table.</p> 15297</div> 15298</div> 15299</div></div></td> 15300</tr> 15301<tr> 15302<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounter</strong>(atomic_uint <em>c</em>)</p></td> 15303<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the counter value for <em>c</em>.</p></td> 15304</tr> 15305<tr> 15306<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterAdd</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15307<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15308<p>Atomically<br></p> 15309</div> 15310<div class="openblock"> 15311<div class="content"> 15312<div class="olist arabic"> 15313<ol class="arabic"> 15314<li> 15315<p>adds the value of <em>data</em> to the counter for <em>c</em>, and</p> 15316</li> 15317<li> 15318<p>returns its value prior to the operation.</p> 15319</li> 15320</ol> 15321</div> 15322<div class="paragraph"> 15323<p>These two steps are done atomically with respect to the atomic counter 15324functions in this table.</p> 15325</div> 15326</div> 15327</div></div></td> 15328</tr> 15329<tr> 15330<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterSubtract</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15331<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15332<p>Atomically<br></p> 15333</div> 15334<div class="openblock"> 15335<div class="content"> 15336<div class="olist arabic"> 15337<ol class="arabic"> 15338<li> 15339<p>subtracts the value of <em>data</em> from the counter for <em>c</em>, and</p> 15340</li> 15341<li> 15342<p>returns its value prior to the operation.</p> 15343</li> 15344</ol> 15345</div> 15346<div class="paragraph"> 15347<p>These two steps are done atomically with respect to the atomic counter 15348functions in this table.</p> 15349</div> 15350</div> 15351</div></div></td> 15352</tr> 15353<tr> 15354<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterMin</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15355<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15356<p>Atomically<br></p> 15357</div> 15358<div class="openblock"> 15359<div class="content"> 15360<div class="olist arabic"> 15361<ol class="arabic"> 15362<li> 15363<p>sets the counter for <em>c</em> to the minimum of the value of the counter and 15364the value of <em>data</em>, and</p> 15365</li> 15366<li> 15367<p>returns the value prior to the operation.</p> 15368</li> 15369</ol> 15370</div> 15371<div class="paragraph"> 15372<p>These two steps are done atomically with respect to the atomic counter 15373functions in this table.</p> 15374</div> 15375</div> 15376</div></div></td> 15377</tr> 15378<tr> 15379<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterMax</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15380<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15381<p>Atomically<br></p> 15382</div> 15383<div class="openblock"> 15384<div class="content"> 15385<div class="olist arabic"> 15386<ol class="arabic"> 15387<li> 15388<p>sets the counter for <em>c</em> to the maximum of the value of the counter and 15389the value of <em>data</em>, and</p> 15390</li> 15391<li> 15392<p>returns the value prior to the operation.</p> 15393</li> 15394</ol> 15395</div> 15396<div class="paragraph"> 15397<p>These two steps are done atomically with respect to the atomic counter 15398functions in this table.</p> 15399</div> 15400</div> 15401</div></div></td> 15402</tr> 15403<tr> 15404<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterAnd</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15405<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15406<p>Atomically<br></p> 15407</div> 15408<div class="openblock"> 15409<div class="content"> 15410<div class="olist arabic"> 15411<ol class="arabic"> 15412<li> 15413<p>sets the counter for <em>c</em> to the bitwise AND of the value of the counter 15414and the value of <em>data</em>, and</p> 15415</li> 15416<li> 15417<p>returns the value prior to the operation.</p> 15418</li> 15419</ol> 15420</div> 15421<div class="paragraph"> 15422<p>These two steps are done atomically with respect to the atomic counter 15423functions in this table.</p> 15424</div> 15425</div> 15426</div></div></td> 15427</tr> 15428<tr> 15429<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterOr</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15430<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15431<p>Atomically<br></p> 15432</div> 15433<div class="openblock"> 15434<div class="content"> 15435<div class="olist arabic"> 15436<ol class="arabic"> 15437<li> 15438<p>sets the counter for <em>c</em> to the bitwise OR of the value of the counter 15439and the value of <em>data</em>, and</p> 15440</li> 15441<li> 15442<p>returns the value prior to the operation.</p> 15443</li> 15444</ol> 15445</div> 15446<div class="paragraph"> 15447<p>These two steps are done atomically with respect to the atomic counter 15448functions in this table.</p> 15449</div> 15450</div> 15451</div></div></td> 15452</tr> 15453<tr> 15454<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterXor</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15455<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15456<p>Atomically<br></p> 15457</div> 15458<div class="openblock"> 15459<div class="content"> 15460<div class="olist arabic"> 15461<ol class="arabic"> 15462<li> 15463<p>sets the counter for <em>c</em> to the bitwise XOR of the value of the counter 15464and the value of <em>data</em>, and</p> 15465</li> 15466<li> 15467<p>returns the value prior to the operation.</p> 15468</li> 15469</ol> 15470</div> 15471<div class="paragraph"> 15472<p>These two steps are done atomically with respect to the atomic counter 15473functions in this table.</p> 15474</div> 15475</div> 15476</div></div></td> 15477</tr> 15478<tr> 15479<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterExchange</strong>(atomic_uint <em>c</em>, uint <em>data</em>)</p></td> 15480<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15481<p>Atomically<br></p> 15482</div> 15483<div class="openblock"> 15484<div class="content"> 15485<div class="olist arabic"> 15486<ol class="arabic"> 15487<li> 15488<p>sets the counter value for <em>c</em> to the value of <em>data</em>, and</p> 15489</li> 15490<li> 15491<p>returns its value prior to the operation.</p> 15492</li> 15493</ol> 15494</div> 15495<div class="paragraph"> 15496<p>These two steps are done atomically with respect to the atomic counter 15497functions in this table.</p> 15498</div> 15499</div> 15500</div></div></td> 15501</tr> 15502<tr> 15503<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCounterCompSwap</strong>(atomic_uint <em>c</em>, uint <em>compare</em>, uint <em>data</em>)</p></td> 15504<td class="tableblock halign-left valign-top"><div class="content"><div class="paragraph"> 15505<p>Atomically<br></p> 15506</div> 15507<div class="openblock"> 15508<div class="content"> 15509<div class="olist arabic"> 15510<ol class="arabic"> 15511<li> 15512<p>compares the value of <em>compare</em> and the counter value for <em>c</em></p> 15513</li> 15514<li> 15515<p>if the values are equal, sets the counter value for <em>c</em> to the value of 15516<em>data</em>, and</p> 15517</li> 15518<li> 15519<p>returns its value prior to the operation.</p> 15520</li> 15521</ol> 15522</div> 15523<div class="paragraph"> 15524<p>These three steps are done atomically with respect to the atomic counter 15525functions in this table.</p> 15526</div> 15527</div> 15528</div></div></td> 15529</tr> 15530</tbody> 15531</table> 15532</div> 15533<div class="sect2"> 15534<h3 id="atomic-memory-functions">8.11. Atomic Memory Functions</h3> 15535<div class="paragraph"> 15536<p>Atomic memory functions perform atomic operations on an individual signed or 15537unsigned integer stored in buffer object or shared variable storage. 15538All of the atomic memory operations read a value from memory, compute a new 15539value using one of the operations described below, write the new value to 15540memory, and return the original value read. 15541The contents of the memory being updated by the atomic operation are 15542guaranteed not to be modified by any other assignment or atomic memory 15543function in any shader invocation between the time the original value is 15544read and the time the new value is written.</p> 15545</div> 15546<div class="paragraph"> 15547<p>Atomic memory functions are supported only for a limited set of variables. 15548A shader will fail to compile if the value passed to the <em>mem</em> argument of 15549an atomic memory function does not correspond to a buffer or shared 15550variable. 15551It is acceptable to pass an element of an array or a single component of a 15552vector to the <em>mem</em> argument of an atomic memory function, as long as the 15553underlying array or vector is a buffer or shared variable.</p> 15554</div> 15555<div class="paragraph"> 15556<p>All the built-in functions in this section accept arguments with 15557combinations of <strong>restrict</strong>, <strong>coherent</strong>, and <strong>volatile</strong> memory qualification, 15558despite not having them listed in the prototypes. 15559The atomic operation will operate as required by the calling argument’s 15560memory qualification, not by the built-in function’s formal parameter memory 15561qualification.</p> 15562</div> 15563<table class="tableblock frame-all grid-all stretch"> 15564<colgroup> 15565<col style="width: 50%;"> 15566<col style="width: 50%;"> 15567</colgroup> 15568<thead> 15569<tr> 15570<th class="tableblock halign-left valign-top">Syntax</th> 15571<th class="tableblock halign-left valign-top">Description</th> 15572</tr> 15573</thead> 15574<tbody> 15575<tr> 15576<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicAdd</strong>(inout uint <em>mem</em>, uint <em>data</em>)<br> 15577 int <strong>atomicAdd</strong>(inout int <em>mem</em>, int <em>data</em>)</p></td> 15578<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by adding the value of <em>data</em> to the contents 15579 <em>mem</em>.</p></td> 15580</tr> 15581<tr> 15582<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicMin</strong>(inout uint <em>mem</em>, uint <em>data</em>)<br> 15583 int <strong>atomicMin</strong>(inout int <em>mem</em>, int <em>data</em>)</p></td> 15584<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by taking the minimum of the value of <em>data</em> and 15585 the contents of <em>mem</em>.</p></td> 15586</tr> 15587<tr> 15588<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicMax</strong>(inout uint <em>mem</em>, uint <em>data</em>)<br> 15589 int <strong>atomicMax</strong>(inout int <em>mem</em>, int <em>data</em>)</p></td> 15590<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by taking the maximum of the value of <em>data</em> and 15591 the contents of <em>mem</em>.</p></td> 15592</tr> 15593<tr> 15594<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicAnd</strong>(inout uint <em>mem</em>, uint <em>data</em>)<br> 15595 int <strong>atomicAnd</strong>(inout int <em>mem</em>, int <em>data</em>)</p></td> 15596<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by performing a bit-wise AND of the value of 15597 <em>data</em> and the contents of <em>mem</em>.</p></td> 15598</tr> 15599<tr> 15600<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicOr</strong>(inout uint <em>mem</em>, uint <em>data</em>)<br> 15601 int <strong>atomicOr</strong>(inout int <em>mem</em>, int <em>data</em>)</p></td> 15602<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by performing a bit-wise OR of the value of 15603 <em>data</em> and the contents of <em>mem</em>.</p></td> 15604</tr> 15605<tr> 15606<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicXor</strong>(inout uint <em>mem</em>, uint <em>data</em>)<br> 15607 int <strong>atomicXor</strong>(inout int <em>mem</em>, int <em>data</em>)</p></td> 15608<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by performing a bit-wise EXCLUSIVE OR of the 15609 value of <em>data</em> and the contents of <em>mem</em>.</p></td> 15610</tr> 15611<tr> 15612<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicExchange</strong>(inout uint <em>mem</em>, uint <em>data</em>)<br> 15613 int <strong>atomicExchange</strong>(inout int <em>mem</em>, int <em>data</em>)</p></td> 15614<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by simply copying the value of <em>data</em>.</p></td> 15615</tr> 15616<tr> 15617<td class="tableblock halign-left valign-top"><p class="tableblock">uint <strong>atomicCompSwap</strong>(inout uint <em>mem</em>, uint <em>compare</em>, uint <em>data</em>)<br> 15618 int <strong>atomicCompSwap</strong>(inout int <em>mem</em>, int <em>compare</em>, int <em>data</em>)</p></td> 15619<td class="tableblock halign-left valign-top"><p class="tableblock">Compares the value of <em>compare</em> and the contents of <em>mem</em>. 15620 If the values are equal, the new value is given by <em>data</em>; otherwise, 15621 it is taken from the original contents of <em>mem</em>.</p></td> 15622</tr> 15623</tbody> 15624</table> 15625</div> 15626<div class="sect2"> 15627<h3 id="image-functions">8.12. Image Functions</h3> 15628<div class="paragraph"> 15629<p>Variables using one of the image basic types may be used by the built-in 15630shader image memory functions defined in this section to read and write 15631individual texels of a texture. 15632Each image variable references an image unit, which has a texture image 15633attached.</p> 15634</div> 15635<div class="paragraph"> 15636<p>When image memory functions below access memory, an individual texel in the 15637image is identified using an (<em>i</em>), (<em>i, j</em>), or (<em>i, j, k</em>) coordinate 15638corresponding to the values of <em>P</em>. 15639For <strong>image2DMS</strong> and <strong>image2DMSArray</strong> variables (and the corresponding 15640int/unsigned int types) corresponding to multisample textures, each texel 15641may have multiple samples and an individual sample is identified using the 15642integer <em>sample</em> parameter. 15643The coordinates 15644and sample number 15645are used to select an individual texel in the manner described in section 156468.26 15647“Texture Image Loads and Stores” of the <a href="#references">OpenGL Specification</a>.</p> 15648</div> 15649<div class="paragraph"> 15650<p>Loads and stores support float, integer, and unsigned integer types. 15651The data types below starting <code>gimage</code> serve as placeholders meaning 15652types starting either “<strong>image</strong>”, “<strong>iimage</strong>”, or “<strong>uimage</strong>” in the same 15653way as "<strong>gvec</strong>" or "<strong>gsampler</strong>" in earlier sections.</p> 15654</div> 15655<div class="paragraph"> 15656<p>The <em>IMAGE_PARAMS</em> in the prototypes below is a placeholder representing 1565733 15658separate functions, each for a different type of image variable. 15659The <em>IMAGE_PARAMS</em> placeholder is replaced by one of the following parameter 15660lists:</p> 15661</div> 15662<div class="dlist"> 15663<dl> 15664<dt class="hdlist1"></dt> 15665<dd> 15666<p>gimage2D <em>image</em>, ivec2 <em>P</em></p> 15667</dd> 15668<dt class="hdlist1"></dt> 15669<dd> 15670<p>gimage3D <em>image</em>, ivec3 <em>P</em></p> 15671</dd> 15672<dt class="hdlist1"></dt> 15673<dd> 15674<p>gimageCube <em>image</em>, ivec3 <em>P</em></p> 15675</dd> 15676<dt class="hdlist1"></dt> 15677<dd> 15678<p>gimageBuffer <em>image</em>, int <em>P</em></p> 15679</dd> 15680<dt class="hdlist1"></dt> 15681<dd> 15682<p>gimage2DArray <em>image</em>, ivec3 <em>P</em></p> 15683</dd> 15684<dt class="hdlist1"></dt> 15685<dd> 15686<p>gimageCubeArray <em>image</em>, ivec3 <em>P</em></p> 15687</dd> 15688<dt class="hdlist1"></dt> 15689<dd> 15690<p>gimage1D <em>image</em>, int <em>P</em></p> 15691</dd> 15692<dt class="hdlist1"></dt> 15693<dd> 15694<p>gimage1DArray <em>image</em>, ivec2 <em>P</em></p> 15695</dd> 15696<dt class="hdlist1"></dt> 15697<dd> 15698<p>gimage2DRect <em>image</em>, ivec2 <em>P</em></p> 15699</dd> 15700<dt class="hdlist1"></dt> 15701<dd> 15702<p>gimage2DMS <em>image</em>, ivec2 <em>P</em>, int <em>sample</em></p> 15703</dd> 15704<dt class="hdlist1"></dt> 15705<dd> 15706<p>gimage2DMSArray <em>image</em>, ivec3 <em>P</em>, int <em>sample</em></p> 15707</dd> 15708</dl> 15709</div> 15710<div class="paragraph"> 15711<p>where each of the lines represents one of three different image variable 15712types, and <em>image</em>, 15713<em>P</em>, and <em>sample</em> 15714specify the individual texel to operate on. 15715The method for identifying the individual texel operated on from <em>image</em>, 15716<em>P</em>, 15717and <em>sample</em>, 15718and the method for reading and writing the texel are specified in section 157198.26 15720“Texture Image Loads and Stores” of the <a href="#references">OpenGL Specification</a>.</p> 15721</div> 15722<div class="paragraph"> 15723<p>The atomic functions perform operations on individual texels or samples of 15724an image variable. 15725Atomic memory operations read a value from the selected texel, compute a new 15726value using one of the operations described below, write the new value to 15727the selected texel, and return the original value read. 15728The contents of the texel being updated by the atomic operation are 15729guaranteed not to be modified by any other image store or atomic function 15730between the time the original value is read and the time the new value is 15731written.</p> 15732</div> 15733<div class="paragraph"> 15734<p>Atomic memory operations are supported on only a subset of all image 15735variable types; <em>image</em> must be either:</p> 15736</div> 15737<div class="ulist"> 15738<ul> 15739<li> 15740<p>a signed integer image variable (type starts “<strong>iimage</strong>”) and a format 15741qualifier of <strong>r32i</strong>, used with a <em>data</em> argument of type <strong>int</strong>, or</p> 15742</li> 15743<li> 15744<p>an unsigned integer image variable (type starts “<strong>uimage</strong>”) and a 15745format qualifier of <strong>r32ui</strong>, used with a <em>data</em> argument of type <strong>uint</strong>, 15746or</p> 15747</li> 15748<li> 15749<p>a float image variable (type starts “<strong>image</strong>”) and a format qualifier 15750of <strong>r32f</strong>, used with a <em>data</em> argument of type <strong>float</strong> 15751(<strong>imageAtomicExchange</strong> only).</p> 15752</li> 15753</ul> 15754</div> 15755<div class="paragraph"> 15756<p>All the built-in functions in this section accept arguments with 15757combinations of <strong>restrict</strong>, <strong>coherent</strong>, and <strong>volatile</strong> memory qualification, 15758despite not having them listed in the prototypes. 15759The image operation will operate as required by the calling argument’s 15760memory qualification, not by the built-in function’s formal parameter memory 15761qualification.</p> 15762</div> 15763<table class="tableblock frame-all grid-all stretch"> 15764<colgroup> 15765<col style="width: 50%;"> 15766<col style="width: 50%;"> 15767</colgroup> 15768<thead> 15769<tr> 15770<th class="tableblock halign-left valign-top">Syntax</th> 15771<th class="tableblock halign-left valign-top">Description</th> 15772</tr> 15773</thead> 15774<tbody> 15775<tr> 15776<td class="tableblock halign-left valign-top"><p class="tableblock"> int <strong>imageSize</strong>(readonly writeonly gimage1D <em>image</em>)<br> 15777 ivec2 <strong>imageSize</strong>(readonly writeonly gimage2D <em>image</em>)<br> 15778 ivec3 <strong>imageSize</strong>(readonly writeonly gimage3D <em>image</em>)<br> 15779 ivec2 <strong>imageSize</strong>(readonly writeonly gimageCube <em>image</em>)<br> 15780 ivec3 <strong>imageSize</strong>(readonly writeonly gimageCubeArray <em>image</em>)<br> 15781 ivec3 <strong>imageSize</strong>(readonly writeonly gimage2DArray <em>image</em>)<br> 15782 ivec2 <strong>imageSize</strong>(readonly writeonly gimageRect <em>image</em>)<br> 15783 ivec2 <strong>imageSize</strong>(readonly writeonly gimage1DArray <em>image</em>)<br> 15784 ivec2 <strong>imageSize</strong>(readonly writeonly gimage2DMS <em>image</em>)<br> 15785 ivec3 <strong>imageSize</strong>(readonly writeonly gimage2DMSArray <em>image</em>)<br> 15786 int <strong>imageSize</strong>(readonly writeonly gimageBuffer <em>image</em>)</p></td> 15787<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the dimensions of the image or images bound to <em>image</em>. 15788 For arrayed images, the last component of the return value will hold 15789 the size of the array. 15790 Cube images only return the dimensions of one face, and the number of 15791 cubes in the cube map array, if arrayed.<br> 15792 Note: The qualification <strong>readonly writeonly</strong> accepts a variable 15793 qualified with <strong>readonly</strong>, <strong>writeonly</strong>, both, or neither. 15794 It means the formal argument will be used for neither reading nor 15795 writing to the underlying memory.</p></td> 15796</tr> 15797<tr> 15798<td class="tableblock halign-left valign-top"><p class="tableblock">int <strong>imageSamples</strong>(readonly writeonly gimage2DMS <em>image</em>)<br> 15799 int <strong>imageSamples</strong>(readonly writeonly gimage2DMSArray <em>image</em>)</p></td> 15800<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the number of samples of the image or images bound to <em>image</em>.</p></td> 15801</tr> 15802<tr> 15803<td class="tableblock halign-left valign-top"><p class="tableblock"> gvec4 <strong>imageLoad</strong>(readonly <em>IMAGE_PARAMS</em>)</p></td> 15804<td class="tableblock halign-left valign-top"><p class="tableblock">Loads the texel at the coordinate <em>P</em> from the image unit <em>image</em> (in 15805 <em>IMAGE_PARAMS</em>). 15806 For multisample loads, the sample number is given by <em>sample</em>. 15807 When <em>image</em>, <em>P</em>, and <em>sample</em> 15808 identify a valid texel, the bits used to represent the selected texel in 15809 memory are converted to a <strong>vec4</strong>, <strong>ivec4</strong>, or <strong>uvec4</strong> in the manner 15810 described in section 158118.26 15812 “Texture Image Loads and Stores” of the 15813 <a href="#references">OpenGL Specification</a> and returned.</p></td> 15814</tr> 15815<tr> 15816<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>imageStore</strong>(writeonly <em>IMAGE_PARAMS</em>, gvec4 <em>data</em>)</p></td> 15817<td class="tableblock halign-left valign-top"><p class="tableblock">Stores <em>data</em> into the texel at the coordinate <em>P</em> from the image 15818 specified by <em>image</em>. 15819 For multisample stores, the sample number is given by <em>sample</em>. 15820 When <em>image</em>, <em>P</em>, and <em>sample</em> 15821 identify a valid texel, the bits used to represent <em>data</em> are converted 15822 to the format of the image unit in the manner described in section 158238.26 15824 “Texture Image Loads and Stores” of the <a href="#references">OpenGL Specification</a> 15825 and stored to the specified texel.</p></td> 15826</tr> 15827<tr> 15828<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicAdd</strong>(<em>IMAGE_PARAMS</em>, uint <em>data</em>)<br> 15829 int <strong>imageAtomicAdd</strong>(<em>IMAGE_PARAMS</em>, int <em>data</em>)</p></td> 15830<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by adding the value of <em>data</em> to the contents of 15831 the selected texel.</p></td> 15832</tr> 15833<tr> 15834<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicMin</strong>(<em>IMAGE_PARAMS</em>, uint <em>data</em>)<br> 15835 int <strong>imageAtomicMin</strong>(<em>IMAGE_PARAMS</em>, int <em>data</em>)</p></td> 15836<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by taking the minimum of the value of <em>data</em> and 15837 the contents of the selected texel.</p></td> 15838</tr> 15839<tr> 15840<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicMax</strong>(<em>IMAGE_PARAMS</em>, uint <em>data</em>)<br> 15841 int <strong>imageAtomicMax</strong>(<em>IMAGE_PARAMS</em>, int <em>data</em>)</p></td> 15842<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by taking the maximum of the value <em>data</em> and the 15843 contents of the selected texel.</p></td> 15844</tr> 15845<tr> 15846<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicAnd</strong>(<em>IMAGE_PARAMS</em>, uint <em>data</em>)<br> 15847 int <strong>imageAtomicAnd</strong>(<em>IMAGE_PARAMS</em>, int <em>data</em>)</p></td> 15848<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by performing a bit-wise AND of the value of 15849 <em>data</em> and the contents of the selected texel.</p></td> 15850</tr> 15851<tr> 15852<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicOr</strong>(<em>IMAGE_PARAMS</em>, uint <em>data</em>)<br> 15853 int <strong>imageAtomicOr</strong>(<em>IMAGE_PARAMS</em>, int <em>data</em>)</p></td> 15854<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by performing a bit-wise OR of the value of 15855 <em>data</em> and the contents of the selected texel.</p></td> 15856</tr> 15857<tr> 15858<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicXor</strong>(<em>IMAGE_PARAMS</em>, uint <em>data</em>)<br> 15859 int <strong>imageAtomicXor</strong>(<em>IMAGE_PARAMS</em>, int <em>data</em>)</p></td> 15860<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by performing a bit-wise EXCLUSIVE OR of the 15861 value of <em>data</em> and the contents of the selected texel.</p></td> 15862</tr> 15863<tr> 15864<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicExchange</strong>(<em>IMAGE_PARAMS</em>, uint <em>data</em>)<br> 15865 int <strong>imageAtomicExchange</strong>(<em>IMAGE_PARAMS</em>, int <em>data</em>)<br> 15866 float <strong>imageAtomicExchange</strong>(<em>IMAGE_PARAMS</em>, float <em>data</em>)</p></td> 15867<td class="tableblock halign-left valign-top"><p class="tableblock">Computes a new value by simply copying the value of <em>data</em>.</p></td> 15868</tr> 15869<tr> 15870<td class="tableblock halign-left valign-top"><p class="tableblock"> uint <strong>imageAtomicCompSwap</strong>(<em>IMAGE_PARAMS</em>, uint <em>compare</em>, uint <em>data</em>)<br> 15871 int <strong>imageAtomicCompSwap</strong>(<em>IMAGE_PARAMS</em>, int <em>compare</em>, int <em>data</em>)</p></td> 15872<td class="tableblock halign-left valign-top"><p class="tableblock">Compares the value of <em>compare</em> and the contents of the selected 15873 texel. 15874 If the values are equal, the new value is given by <em>data</em>; otherwise, 15875 it is taken from the original value loaded from the texel.</p></td> 15876</tr> 15877</tbody> 15878</table> 15879</div> 15880<div class="sect2"> 15881<h3 id="geometry-shader-functions">8.13. Geometry Shader Functions</h3> 15882<div class="paragraph"> 15883<p>These functions are only available in geometry shaders. 15884They are described in more depth following the table.</p> 15885</div> 15886<table class="tableblock frame-all grid-all stretch"> 15887<colgroup> 15888<col style="width: 50%;"> 15889<col style="width: 50%;"> 15890</colgroup> 15891<thead> 15892<tr> 15893<th class="tableblock halign-left valign-top">Syntax</th> 15894<th class="tableblock halign-left valign-top">Description</th> 15895</tr> 15896</thead> 15897<tbody> 15898<tr> 15899<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>EmitStreamVertex</strong>(int <em>stream</em>)</p></td> 15900<td class="tableblock halign-left valign-top"><p class="tableblock">Emits the current values of output variables to the current output 15901 primitive on stream <em>stream</em>. 15902 The argument to <em>stream</em> must be a constant integral expression. 15903 On return from this call, the values of all output variables are 15904 undefined.<br> 15905 Can only be used if multiple output streams are supported.</p></td> 15906</tr> 15907<tr> 15908<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>EndStreamPrimitive</strong>(int <em>stream</em>)</p></td> 15909<td class="tableblock halign-left valign-top"><p class="tableblock">Completes the current output primitive on stream <em>stream</em> and starts a 15910 new one. 15911 The argument to <em>stream</em> must be a constant integral expression. 15912 No vertex is emitted.<br> 15913 Can only be used if multiple output streams are supported.</p></td> 15914</tr> 15915<tr> 15916<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>EmitVertex</strong>()<br></p></td> 15917<td class="tableblock halign-left valign-top"><p class="tableblock">Emits the current values of output variables to the current output 15918 primitive. 15919 When multiple output streams are supported, this is equivalent to 15920 calling <strong>EmitStreamVertex</strong>(0).<br> 15921 On return from this call, the values of output variables are 15922 undefined.</p></td> 15923</tr> 15924<tr> 15925<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>EndPrimitive</strong>()</p></td> 15926<td class="tableblock halign-left valign-top"><p class="tableblock">Completes the current output primitive and starts a new one. 15927 When multiple output streams are supported, this is equivalent to 15928 calling <strong>EndStreamPrimitive</strong>(0).<br> 15929 No vertex is emitted.</p></td> 15930</tr> 15931</tbody> 15932</table> 15933<div class="paragraph"> 15934<p>The function <strong>EmitStreamVertex</strong>() specifies that a vertex is completed. 15935A vertex is added to the current output primitive in vertex stream <em>stream</em> 15936using the current values of all built-in and user-defined output variables 15937associated with <em>stream</em>. 15938The values of all output variables for all output streams are undefined 15939after a call to <strong>EmitStreamVertex</strong>(). 15940If a geometry shader invocation has emitted more vertices than permitted by 15941the output layout qualifier <strong>max_vertices</strong>, the results of calling 15942<strong>EmitStreamVertex</strong>() are undefined.</p> 15943</div> 15944<div class="paragraph"> 15945<p>The function <strong>EndStreamPrimitive</strong>() specifies that the current output 15946primitive for vertex stream <em>stream</em> is completed and a new output primitive 15947(of the same type) will be started by any subsequent <strong>EmitStreamVertex</strong>(). 15948This function does not emit a vertex. 15949If the output layout is declared to be <strong>points</strong>, calling 15950<strong>EndStreamPrimitive</strong>() is optional.</p> 15951</div> 15952<div class="paragraph"> 15953<p>A geometry shader starts with an output primitive containing no vertices for 15954each stream. 15955When a geometry shader terminates, the current output primitive for each 15956stream is automatically completed. 15957It is not necessary to call <strong>EndStreamPrimitive</strong>() if the geometry shader 15958writes only a single primitive.</p> 15959</div> 15960<div class="paragraph"> 15961<p>Multiple output streams are supported only if the output primitive type is 15962declared to be <strong>points</strong>. 15963It is a compile-time or link-time error if a program contains a geometry 15964shader calling <strong>EmitStreamVertex</strong>() or <strong>EndStreamPrimitive</strong>() if its output 15965primitive type is not <strong>points</strong>.</p> 15966</div> 15967</div> 15968<div class="sect2"> 15969<h3 id="fragment-processing-functions">8.14. Fragment Processing Functions</h3> 15970<div class="paragraph"> 15971<p>Fragment processing functions are only available in fragment shaders.</p> 15972</div> 15973<div class="sect3"> 15974<h4 id="derivative-functions">8.14.1. Derivative Functions</h4> 15975<div class="paragraph"> 15976<p>Derivatives may be computationally expensive and/or numerically unstable. 15977Therefore, an implementation may approximate the true derivatives 15978by using a fast but not entirely accurate derivative computation. 15979Derivatives are undefined within non-uniform control flow.</p> 15980</div> 15981<div class="paragraph"> 15982<p>The expected behavior of a derivative is specified using forward/backward 15983differencing.</p> 15984</div> 15985<div class="paragraph"> 15986<p>Forward differencing:</p> 15987</div> 15988<div class="paragraph"> 15989<p>\(F(x+dx) - F(x) \sim dFdx(x) \cdot dx (1a)\)</p> 15990</div> 15991<div class="paragraph"> 15992<p>\(dFdx(x) \sim \frac{F(x+dx) - F(x)}{dx} (1b)\)</p> 15993</div> 15994<div class="paragraph"> 15995<p>Backward differencing:</p> 15996</div> 15997<div class="paragraph"> 15998<p>\(F(x-dx) - F(x) \sim -dFdx(x) \cdot dx (2a)\)</p> 15999</div> 16000<div class="paragraph"> 16001<p>\(dFdx(x) \sim \frac{F(x) - F(x-dx)}{dx} (2b)\)</p> 16002</div> 16003<div class="paragraph"> 16004<p>With single-sample rasterization, \(dx \leq 1.0\) in equations 1b 16005and 2b. 16006For multisample rasterization, \(dx < 2.0\) in equations 1b and 2b.</p> 16007</div> 16008<div class="paragraph"> 16009<p>\(dFdy\) is approximated similarly, with <em>y</em> replacing <em>x</em>.</p> 16010</div> 16011<div class="paragraph"> 16012<p>With multisample rasterization, for any given fragment or sample, either 16013neighboring fragments or samples may be considered.</p> 16014</div> 16015<div class="paragraph"> 16016<p>It is typical to consider a 2x2 square of fragments or samples, and compute 16017independent <strong>dFdxFine</strong> per row and independent <strong>dFdyFine</strong> per column, while 16018computing only a single <strong>dFdxCoarse</strong> and a single <strong>dFdyCoarse</strong> for the 16019entire 2x2 square. 16020Thus, all second-order coarse derivatives, e.g. 16021<strong>dFdxCoarse</strong>(<strong>dFdxCoarse</strong>(<em>x</em>)), may be 0, even for non-linear arguments. 16022However, second-order fine derivatives, e.g. <strong>dFdxFine</strong>(<strong>dFdyFine</strong>(<em>x</em>)) 16023will properly reflect the difference between the independent fine 16024derivatives computed within the 2x2 square.</p> 16025</div> 16026<div class="paragraph"> 16027<p>The method may differ per fragment, subject to the constraint that the 16028method may vary by window coordinates, not screen coordinates. 16029The invariance requirement described in section 14.2 “Invariance” of the 16030<a href="#references">OpenGL Specification</a>, is relaxed for derivative calculations, because 16031the method may be a function of fragment location.</p> 16032</div> 16033<div class="paragraph"> 16034<p>In some implementations, varying degrees of derivative accuracy for <strong>dFdx</strong> 16035and <strong>dFdy</strong> may be obtained by providing GL hints (see section 21.4 “Hints” 16036of the <a href="#references">OpenGL Specification</a>), allowing a user to make an image quality 16037versus speed trade off. 16038These hints have no effect on <strong>dFdxCoarse</strong>, <strong>dFdyCoarse</strong>, <strong>dFdxFine</strong> and 16039<strong>dFdyFine</strong>.</p> 16040</div> 16041<table class="tableblock frame-all grid-all stretch"> 16042<colgroup> 16043<col style="width: 50%;"> 16044<col style="width: 50%;"> 16045</colgroup> 16046<thead> 16047<tr> 16048<th class="tableblock halign-left valign-top">Syntax</th> 16049<th class="tableblock halign-left valign-top">Description</th> 16050</tr> 16051</thead> 16052<tbody> 16053<tr> 16054<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>dFdx</strong>(genFType <em>p</em>)</p></td> 16055<td class="tableblock halign-left valign-top"><p class="tableblock">Returns either <strong>dFdxFine</strong>(<em>p</em>) or <strong>dFdxCoarse</strong>(<em>p</em>), based on 16056 implementation choice, presumably whichever is the faster, or by whichever 16057 is selected in the API through quality-versus-speed hints.</p></td> 16058</tr> 16059<tr> 16060<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>dFdy</strong>(genFType <em>p</em>)</p></td> 16061<td class="tableblock halign-left valign-top"><p class="tableblock">Returns either <strong>dFdyFine</strong>(<em>p</em>) or <strong>dFdyCoarse</strong>(<em>p</em>), based on 16062 implementation choice, presumably whichever is the faster, or by 16063 whichever is selected in the API through quality-versus-speed hints.</p></td> 16064</tr> 16065<tr> 16066<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>dFdxFine</strong>(genFType <em>p</em>)</p></td> 16067<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the partial derivative of <em>p</em> with respect to the window x 16068 coordinate. 16069 Will use local differencing based on the value of <em>p</em> for the current 16070 fragment and its immediate neighbor(s).</p></td> 16071</tr> 16072<tr> 16073<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>dFdyFine</strong>(genFType <em>p</em>)</p></td> 16074<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the partial derivative of <em>p</em> with respect to the window y 16075 coordinate. 16076 Will use local differencing based on the value of <em>p</em> for the current 16077 fragment and its immediate neighbor(s).</p></td> 16078</tr> 16079<tr> 16080<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>dFdxCoarse</strong>(genFType <em>p</em>)</p></td> 16081<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the partial derivative of <em>p</em> with respect to the window x 16082 coordinate. 16083 Will use local differencing based on the value of <em>p</em> for the current 16084 fragment’s neighbors, and will possibly, but not necessarily, include 16085 the value of <em>p</em> for the current fragment. 16086 That is, over a given area, the implementation can x compute 16087 derivatives in fewer unique locations than would be allowed for 16088 <strong>dFdxFine</strong>(<em>p</em>).</p></td> 16089</tr> 16090<tr> 16091<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>dFdyCoarse</strong>(genFType <em>p</em>)</p></td> 16092<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the partial derivative of <em>p</em> with respect to the window y 16093 coordinate. 16094 Will use local differencing based on the value of <em>p</em> for the current 16095 fragment’s neighbors, and will possibly, but not necessarily, include 16096 the value of <em>p</em> for the current fragment. 16097 That is, over a given area, the implementation can compute y 16098 derivatives in fewer unique locations than would be allowed for 16099 <strong>dFdyFine</strong>(<em>p</em>).</p></td> 16100</tr> 16101<tr> 16102<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>fwidth</strong>(genFType <em>p</em>)</p></td> 16103<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>abs</strong>(<strong>dFdx</strong>(<em>p</em>)) + <strong>abs</strong>(<strong>dFdy</strong>(<em>p</em>)).</p></td> 16104</tr> 16105<tr> 16106<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>fwidthFine</strong>(genFType <em>p</em>)</p></td> 16107<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>abs</strong>(<strong>dFdxFine</strong>(<em>p</em>)) + <strong>abs</strong>(<strong>dFdyFine</strong>(<em>p</em>)).</p></td> 16108</tr> 16109<tr> 16110<td class="tableblock halign-left valign-top"><p class="tableblock">genFType <strong>fwidthCoarse</strong>(genFType <em>p</em>)</p></td> 16111<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>abs</strong>(<strong>dFdxCoarse</strong>(<em>p</em>)) + <strong>abs</strong>(<strong>dFdyCoarse</strong>(<em>p</em>)).</p></td> 16112</tr> 16113</tbody> 16114</table> 16115</div> 16116<div class="sect3"> 16117<h4 id="interpolation-functions">8.14.2. Interpolation Functions</h4> 16118<div class="paragraph"> 16119<p>Built-in interpolation functions are available to compute an interpolated 16120value of a fragment shader input variable at a shader-specified (<em>x</em>, <em>y</em>) 16121location. 16122A separate (<em>x</em>, <em>y</em>) location may be used for each invocation of the 16123built-in function, and those locations may differ from the default (<em>x</em>, 16124<em>y</em>) location used to produce the default value of the input.</p> 16125</div> 16126<div class="paragraph"> 16127<p>For all of the interpolation functions, <em>interpolant</em> must be an l-value 16128from an <strong>in</strong> declaration; 16129this can include a variable, a block or structure member, an array element, or 16130some combination of these. 16131Additionally, component selection operators (e.g. <strong>.xy</strong>, <strong>.xxz</strong>) may be applied 16132to <em>interpolant</em>, in which case the interpolation function will return the 16133result of applying the component selection operator to the interpolated value 16134of <em>interpolant</em> (for example, interpolateAt(v.xxz) is defined to return 16135interpolateAt(v).xxz). 16136Arrayed inputs can be indexed with general (nonuniform) integer expressions.</p> 16137</div> 16138<div class="paragraph"> 16139<p>If <em>interpolant</em> is declared with the <strong>flat</strong> qualifier, the interpolated 16140value will have the same value everywhere for a single primitive, so the 16141location used for interpolation has no effect and the functions just return 16142that same value. 16143If <em>interpolant</em> is declared with the <strong>centroid</strong> qualifier, the value 16144returned by <strong>interpolateAtSample</strong>() and <strong>interpolateAtOffset</strong>() will be 16145evaluated at the specified location, ignoring the location normally used 16146with the <strong>centroid</strong> qualifier. 16147If <em>interpolant</em> is declared with the <strong>noperspective</strong> qualifier, the 16148interpolated value will be computed without perspective correction.</p> 16149</div> 16150<table class="tableblock frame-all grid-all stretch"> 16151<colgroup> 16152<col style="width: 50%;"> 16153<col style="width: 50%;"> 16154</colgroup> 16155<thead> 16156<tr> 16157<th class="tableblock halign-left valign-top">Syntax</th> 16158<th class="tableblock halign-left valign-top">Description</th> 16159</tr> 16160</thead> 16161<tbody> 16162<tr> 16163<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>interpolateAtCentroid</strong>(float <em>interpolant</em>)<br> 16164 vec2 <strong>interpolateAtCentroid</strong>(vec2 <em>interpolant</em>)<br> 16165 vec3 <strong>interpolateAtCentroid</strong>(vec3 <em>interpolant</em>)<br> 16166 vec4 <strong>interpolateAtCentroid</strong>(vec4 <em>interpolant</em>)</p></td> 16167<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the value of the input <em>interpolant</em> sampled at a location 16168 inside both the pixel and the primitive being processed. 16169 The value obtained would be the same value assigned to the input 16170 variable if declared with the <strong>centroid</strong> qualifier.</p></td> 16171</tr> 16172<tr> 16173<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>interpolateAtSample</strong>(float <em>interpolant</em>, int <em>sample</em>)<br> 16174 vec2 <strong>interpolateAtSample</strong>(vec2 <em>interpolant</em>, int <em>sample</em>)<br> 16175 vec3 <strong>interpolateAtSample</strong>(vec3 <em>interpolant</em>, int <em>sample</em>)<br> 16176 vec4 <strong>interpolateAtSample</strong>(vec4 <em>interpolant</em>, int <em>sample</em>)</p></td> 16177<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the value of the input <em>interpolant</em> variable at the location 16178 of sample number <em>sample</em>. 16179 If multisample buffers are not available, the input variable will be 16180 evaluated at the center of the pixel. 16181 If sample <em>sample</em> does not exist, the position used to interpolate 16182 the input variable is undefined.</p></td> 16183</tr> 16184<tr> 16185<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>interpolateAtOffset</strong>(float <em>interpolant</em>, vec2 offset)<br> 16186 vec2 <strong>interpolateAtOffset</strong>(vec2 <em>interpolant</em>, vec2 offset)<br> 16187 vec3 <strong>interpolateAtOffset</strong>(vec3 <em>interpolant</em>, vec2 offset)<br> 16188 vec4 <strong>interpolateAtOffset</strong>(vec4 <em>interpolant</em>, vec2 offset)</p></td> 16189<td class="tableblock halign-left valign-top"><p class="tableblock">Returns the value of the input <em>interpolant</em> variable sampled at an 16190 offset from the center of the pixel specified by <em>offset</em>. 16191 The two floating-point components of <em>offset</em>, give the offset in 16192 pixels in the <em>x</em> and <em>y</em> directions, respectively.<br> 16193 An offset of (0, 0) identifies the center of the pixel. 16194 The range and granularity of offsets supported by this function is 16195 implementation-dependent.</p></td> 16196</tr> 16197</tbody> 16198</table> 16199</div> 16200</div> 16201<div class="sect2"> 16202<h3 id="noise-functions">8.15. Noise Functions</h3> 16203<div class="paragraph"> 16204<p>The noise functions <strong>noise1</strong>, <strong>noise2</strong>, <strong>noise3</strong>, and <strong>noise4</strong> have been 16205deprecated starting with version 4.4 of GLSL. 16206When not generating SPIR-V they are defined to return the value 0.0 or a vector 16207whose components are all 0.0. When generating SPIR-V the noise functions are 16208not declared and may not be used.</p> 16209</div> 16210<div class="paragraph"> 16211<p>As in previous releases, the noise functions are not semantically considered to 16212be compile-time constant expressions.</p> 16213</div> 16214<table class="tableblock frame-all grid-all stretch"> 16215<colgroup> 16216<col style="width: 50%;"> 16217<col style="width: 50%;"> 16218</colgroup> 16219<thead> 16220<tr> 16221<th class="tableblock halign-left valign-top">Syntax (deprecated)</th> 16222<th class="tableblock halign-left valign-top">Description (deprecated)</th> 16223</tr> 16224</thead> 16225<tbody> 16226<tr> 16227<td class="tableblock halign-left valign-top"><p class="tableblock">float <strong>noise1</strong>(genFType <em>x</em>)</p></td> 16228<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a 1D noise value based on the input value <em>x</em>.</p></td> 16229</tr> 16230<tr> 16231<td class="tableblock halign-left valign-top"><p class="tableblock">vec2 <strong>noise2</strong>(genFType <em>x</em>)</p></td> 16232<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a 2D noise value based on the input value <em>x</em>.</p></td> 16233</tr> 16234<tr> 16235<td class="tableblock halign-left valign-top"><p class="tableblock">vec3 <strong>noise3</strong>(genFType <em>x</em>)</p></td> 16236<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a 3D noise value based on the input value <em>x</em>.</p></td> 16237</tr> 16238<tr> 16239<td class="tableblock halign-left valign-top"><p class="tableblock">vec4 <strong>noise4</strong>(genFType <em>x</em>)</p></td> 16240<td class="tableblock halign-left valign-top"><p class="tableblock">Returns a 4D noise value based on the input value <em>x</em>.</p></td> 16241</tr> 16242</tbody> 16243</table> 16244</div> 16245<div class="sect2"> 16246<h3 id="shader-invocation-control-functions">8.16. Shader Invocation Control Functions</h3> 16247<div class="paragraph"> 16248<p>The shader invocation control function is only available in tessellation 16249control and compute shaders. 16250It is used to control the relative execution order of multiple shader 16251invocations used to process a patch (in the case of tessellation control 16252shaders) or a workgroup (in the case of compute shaders), which are 16253otherwise executed with an undefined relative order.</p> 16254</div> 16255<table class="tableblock frame-all grid-all stretch"> 16256<colgroup> 16257<col style="width: 50%;"> 16258<col style="width: 50%;"> 16259</colgroup> 16260<thead> 16261<tr> 16262<th class="tableblock halign-left valign-top">Syntax</th> 16263<th class="tableblock halign-left valign-top">Description</th> 16264</tr> 16265</thead> 16266<tbody> 16267<tr> 16268<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>barrier</strong>()</p></td> 16269<td class="tableblock halign-left valign-top"><p class="tableblock">For any given static instance of <strong>barrier</strong>(), all tessellation control 16270 shader invocations for a single input patch must enter it before any 16271 will be allowed to continue beyond it, or all compute shader 16272 invocations for a single workgroup must enter it before any will 16273 continue beyond it.</p></td> 16274</tr> 16275</tbody> 16276</table> 16277<div class="paragraph"> 16278<p>The function <strong>barrier</strong>() provides a partially defined order of execution 16279between shader invocations. 16280The ensures that, for some types of memory accesses, values written by one 16281invocation prior to a given static instance of <strong>barrier</strong>() can be safely read 16282by other invocations after their call to the same static instance <strong>barrier</strong>(). 16283Because invocations may execute in an undefined order between these barrier 16284calls, the values of a per-vertex or per-patch output variable for tessellation 16285control shaders, or the values of <strong>shared</strong> variables for compute shaders will be 16286undefined in a number of cases enumerated in 16287“<a href="#output-variables">Output Variables</a>” (for tessellation control shaders) 16288and “<a href="#shared-variables">Shared Variables</a>” (for compute shaders).</p> 16289</div> 16290<div class="paragraph"> 16291<p>For tessellation control shaders, the <strong>barrier</strong>() function may only be 16292placed inside the function <strong>main</strong>() of the shader and may not be called 16293within any control flow. 16294Barriers are also disallowed after a return statement in the function 16295<strong>main</strong>(). 16296Any such misplaced barriers result in a compile-time error.</p> 16297</div> 16298<div class="paragraph"> 16299<p>A <strong>barrier</strong>() affects control flow but only synchronizes memory accesses 16300to <strong>shared</strong> variables and tessellation control output variables. 16301For other memory accesses, it does not ensure that values written by one invocation 16302prior to a given static instance of <strong>barrier</strong>() can be safely read by other 16303invocations after their call to the same static instance of <strong>barrier</strong>(). 16304To achieve this requires the use of both <strong>barrier</strong>() and a memory barrier.</p> 16305</div> 16306<div class="paragraph"> 16307<p>For compute shaders, the <strong>barrier</strong>() function may be placed within control 16308flow, but that control flow must be uniform control flow. 16309That is, all the controlling expressions that lead to execution of the 16310barrier must be dynamically uniform expressions. 16311This ensures that if any shader invocation enters a conditional statement, 16312then all invocations will enter it. 16313While compilers are encouraged to give warnings if they can detect this 16314might not happen, compilers cannot completely determine this. 16315Hence, it is the author’s responsibility to ensure <strong>barrier</strong>() only exists 16316inside uniform control flow. 16317Otherwise, some shader invocations will stall indefinitely, waiting for a 16318barrier that is never reached by other invocations.</p> 16319</div> 16320</div> 16321<div class="sect2"> 16322<h3 id="shader-memory-control-functions">8.17. Shader Memory Control Functions</h3> 16323<div class="paragraph"> 16324<p>Within a single shader invocation, the visibility and order of writes made 16325by that invocation are well-defined. 16326However, the relative order of reads and writes to a single shared memory 16327address from multiple separate shader invocations is largely undefined. 16328Additionally, the order of accesses to multiple memory addresses performed 16329by a single shader invocation, as observed by other shader invocations, is 16330also undefined.</p> 16331</div> 16332<div class="paragraph"> 16333<p>The following built-in functions can be used to control the ordering of 16334reads and writes:</p> 16335</div> 16336<table class="tableblock frame-all grid-all stretch"> 16337<colgroup> 16338<col style="width: 50%;"> 16339<col style="width: 50%;"> 16340</colgroup> 16341<thead> 16342<tr> 16343<th class="tableblock halign-left valign-top">Syntax</th> 16344<th class="tableblock halign-left valign-top">Description</th> 16345</tr> 16346</thead> 16347<tbody> 16348<tr> 16349<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>memoryBarrier</strong>()</p></td> 16350<td class="tableblock halign-left valign-top"><p class="tableblock">Control the ordering of memory transactions issued by a single shader 16351 invocation.</p></td> 16352</tr> 16353<tr> 16354<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>memoryBarrierAtomicCounter</strong>()</p></td> 16355<td class="tableblock halign-left valign-top"><p class="tableblock">Control the ordering of accesses to atomic-counter variables issued by 16356 a single shader invocation.</p></td> 16357</tr> 16358<tr> 16359<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>memoryBarrierBuffer</strong>()</p></td> 16360<td class="tableblock halign-left valign-top"><p class="tableblock">Control the ordering of memory transactions to buffer variables issued 16361 within a single shader invocation.</p></td> 16362</tr> 16363<tr> 16364<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>memoryBarrierShared</strong>()</p></td> 16365<td class="tableblock halign-left valign-top"><p class="tableblock">Control the ordering of memory transactions to shared variables issued 16366 within a single shader invocation, as viewed by other invocations in 16367 the same workgroup.<br> 16368 Only available in compute shaders.</p></td> 16369</tr> 16370<tr> 16371<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>memoryBarrierImage</strong>()</p></td> 16372<td class="tableblock halign-left valign-top"><p class="tableblock">Control the ordering of memory transactions to images issued within a 16373 single shader invocation.</p></td> 16374</tr> 16375<tr> 16376<td class="tableblock halign-left valign-top"><p class="tableblock">void <strong>groupMemoryBarrier</strong>()</p></td> 16377<td class="tableblock halign-left valign-top"><p class="tableblock">Control the ordering of all memory transactions issued within a single 16378 shader invocation, as viewed by other invocations in the same workgroup.<br> 16379 Only available in compute shaders.</p></td> 16380</tr> 16381</tbody> 16382</table> 16383<div class="paragraph"> 16384<p>The memory barrier built-in functions can be used to order reads and writes 16385to variables stored in memory accessible to other shader invocations. 16386When called, these functions will wait for the completion of all reads and 16387writes previously performed by the caller that access selected variable 16388types, and then return with no other effect. 16389The built-in functions <strong>memoryBarrierAtomicCounter</strong>(), 16390<strong>memoryBarrierBuffer</strong>(), <strong>memoryBarrierImage</strong>(), and <strong>memoryBarrierShared</strong>() 16391wait for the completion of accesses to atomic counter, buffer, image, and 16392shared variables, respectively. 16393The built-in functions <strong>memoryBarrier</strong>() and <strong>groupMemoryBarrier</strong>() wait for 16394the completion of accesses to all of the above variable types. 16395The functions <strong>memoryBarrierShared</strong>() and <strong>groupMemoryBarrier</strong>() are 16396available only in compute shaders; the other functions are available in all 16397shader types.</p> 16398</div> 16399<div class="paragraph"> 16400<p>When these functions return, the effects of any memory stores performed 16401using coherent variables prior to the call will be visible to any 16402future<sup>1</sup> coherent access to the same memory performed by any other shader 16403invocation. 16404In particular, the values written this way in one shader stage are 16405guaranteed to be visible to coherent memory accesses performed by shader 16406invocations in subsequent stages when those invocations were triggered by 16407the execution of the original shader invocation (e.g. fragment shader 16408invocations for a primitive resulting from a particular geometry 16409shader invocation).</p> 16410</div> 16411<div class="dlist"> 16412<dl> 16413<dt class="hdlist1">1</dt> 16414<dd> 16415<p>An access is only a <em>future</em> access if a <em>happens-before</em> relation can 16416be established between the store and the load.</p> 16417</dd> 16418</dl> 16419</div> 16420<div class="paragraph"> 16421<p>Additionally, memory barrier functions order stores performed by the calling 16422invocation, as observed by other shader invocations. 16423Without memory barriers, if one shader invocation performs two stores to 16424coherent variables, a second shader invocation might see the values written 16425by the second store prior to seeing those written by the first. 16426However, if the first shader invocation calls a memory barrier function 16427between the two stores, selected other shader invocations will never see the 16428results of the second store before seeing those of the first. 16429When using the functions <strong>groupMemoryBarrier</strong>() or <strong>memoryBarrierShared</strong>(), 16430this ordering guarantee applies only to other shader invocations in the same 16431compute shader workgroup; all other memory barrier functions provide the 16432guarantee to all other shader invocations. 16433No memory barrier is required to guarantee the order of memory stores as 16434observed by the invocation performing the stores; an invocation reading from 16435a variable that it previously wrote will always see the most recently 16436written value unless another shader invocation also wrote to the same 16437memory.</p> 16438</div> 16439</div> 16440<div class="sect2"> 16441<h3 id="_subpass_input_functions">8.18. Subpass-Input Functions</h3> 16442<div class="paragraph"> 16443<p>Subpass-input functions are only available when targeting a Vulkan fragment stage.</p> 16444</div> 16445<div class="paragraph"> 16446<p>Subpass inputs are read through the built-in functions below. The <code>g</code> is again 16447a placeholder for either nothing, <code>i</code>, or <code>u</code>, indicating either a floating-point, 16448signed integer, or unsigned integer, and these must match between argument type 16449and return type.</p> 16450</div> 16451<table class="tableblock frame-all grid-all stretch"> 16452<colgroup> 16453<col style="width: 50%;"> 16454<col style="width: 50%;"> 16455</colgroup> 16456<thead> 16457<tr> 16458<th class="tableblock halign-left valign-top">Syntax</th> 16459<th class="tableblock halign-left valign-top">Description</th> 16460</tr> 16461</thead> 16462<tbody> 16463<tr> 16464<td class="tableblock halign-left valign-top"><p class="tableblock">gvec4 <strong>subpassLoad</strong>(gsubpassInput subpass)<br> 16465 gvec4 <strong>subpassLoad</strong>(gsubpassInputMS subpass, int sample)</p></td> 16466<td class="tableblock halign-left valign-top"><p class="tableblock">Read from a subpass input, from the implicit location <em>(x, y, layer)</em> 16467 of the current fragment coordinate.</p></td> 16468</tr> 16469</tbody> 16470</table> 16471</div> 16472<div class="sect2"> 16473<h3 id="shader-invocation-group-functions">8.19. Shader Invocation Group Functions</h3> 16474<div class="paragraph"> 16475<p>Implementations of the OpenGL Shading Language may optionally group multiple shader 16476invocations for a single shader stage into a single SIMD invocation group, 16477where invocations are assigned to groups in an undefined, 16478implementation-dependent manner. 16479Shader algorithms on such implementations may benefit from being able to 16480evaluate a composite of Boolean values over all active invocations in a 16481group.</p> 16482</div> 16483<table class="tableblock frame-all grid-all stretch"> 16484<colgroup> 16485<col style="width: 50%;"> 16486<col style="width: 50%;"> 16487</colgroup> 16488<thead> 16489<tr> 16490<th class="tableblock halign-left valign-top">Syntax</th> 16491<th class="tableblock halign-left valign-top">Description</th> 16492</tr> 16493</thead> 16494<tbody> 16495<tr> 16496<td class="tableblock halign-left valign-top"><p class="tableblock">bool <strong>anyInvocation</strong>(bool <em>value</em>)</p></td> 16497<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>true</strong> if and only if <em>value</em> is <strong>true</strong> for at least one 16498 active invocation in the group.</p></td> 16499</tr> 16500<tr> 16501<td class="tableblock halign-left valign-top"><p class="tableblock">bool <strong>allInvocations</strong>(bool <em>value</em>)</p></td> 16502<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>true</strong> if and only if <em>value</em> is <strong>true</strong> for all active 16503 invocations in the group.</p></td> 16504</tr> 16505<tr> 16506<td class="tableblock halign-left valign-top"><p class="tableblock">bool <strong>allInvocationsEqual</strong>(bool <em>value</em>)</p></td> 16507<td class="tableblock halign-left valign-top"><p class="tableblock">Returns <strong>true</strong> if <em>value</em> is the same for all active invocations in 16508 the group.</p></td> 16509</tr> 16510</tbody> 16511</table> 16512<div class="paragraph"> 16513<p>For all of these functions, the same result is returned to all active 16514invocations in the group.</p> 16515</div> 16516<div class="paragraph"> 16517<p>These functions may be called within conditionally executed code. 16518In groups where some invocations do not execute the function call, the value 16519returned by the function is not affected by any invocation not calling the 16520function, even when value is well-defined for that invocation.</p> 16521</div> 16522<div class="paragraph"> 16523<p>Because these functions depend on the values of <em>value</em> in an undefined 16524group of invocations, the value returned by these functions is largely 16525undefined. 16526However, <strong>anyInvocation</strong>() is guaranteed to return <strong>true</strong> if <em>value</em> is 16527<strong>true</strong>, and <strong>allInvocations</strong>() is guaranteed to return <strong>false</strong> if <em>value</em> is 16528<strong>false</strong>.</p> 16529</div> 16530<div class="paragraph"> 16531<p>Because implementations are not required to combine invocations into groups, 16532simply returning <em>value</em> for <strong>anyInvocation</strong>() and <strong>allInvocations</strong>() and 16533returning true for <strong>allInvocationsEqual</strong>() is a legal implementation of 16534these functions.</p> 16535</div> 16536<div class="paragraph"> 16537<p>For fragment shaders, invocations in a SIMD invocation group may include 16538invocations corresponding to pixels that are covered by a primitive being 16539rasterized, as well as invocations corresponding to neighboring pixels not 16540covered by the primitive. 16541<em>Helper invocations</em> (see “<a href="#built-in-language-variables">Built-In Language 16542Variables</a>”) may be created and the value of <em>value</em> for such 16543helper-invocation pixels may affect the value returned by <strong>anyInvocation</strong>(), 16544<strong>allInvocations</strong>(), and <strong>allInvocationsEqual</strong>().</p> 16545</div> 16546</div> 16547</div> 16548</div> 16549<div class="sect1"> 16550<h2 id="shading-language-grammar">9. Shading Language Grammar</h2> 16551<div class="sectionbody"> 16552<div class="paragraph"> 16553<p>The grammar is fed from the output of lexical analysis. 16554The tokens returned from lexical analysis are</p> 16555</div> 16556<div class="openblock bnf"> 16557<div class="content"> 16558<div class="paragraph"> 16559<p>CONST BOOL FLOAT INT UINT 16560DOUBLE</p> 16561</div> 16562<div class="paragraph"> 16563<p>BVEC2 BVEC3 BVEC4 IVEC2 IVEC3 IVEC4 UVEC2 UVEC3 UVEC4 VEC2 VEC3 VEC4</p> 16564</div> 16565<div class="paragraph"> 16566<p>MAT2 MAT3 MAT4 16567MAT2X2 MAT2X3 MAT2X4 16568MAT3X2 MAT3X3 MAT3X4 16569MAT4X2 MAT4X3 MAT4X4</p> 16570</div> 16571<div class="paragraph"> 16572<p>DVEC2 DVEC3 DVEC4 DMAT2 DMAT3 DMAT4 16573DMAT2X2 DMAT2X3 DMAT2X4 16574DMAT3X2 DMAT3X3 DMAT3X4 16575DMAT4X2 DMAT4X3 DMAT4X4</p> 16576</div> 16577<div class="paragraph"> 16578<p>CENTROID IN OUT INOUT UNIFORM PATCH SAMPLE BUFFER SHARED 16579COHERENT VOLATILE RESTRICT READONLY WRITEONLY 16580NOPERSPECTIVE 16581FLAT SMOOTH LAYOUT</p> 16582</div> 16583<div class="paragraph"> 16584<p>ATOMIC_UINT</p> 16585</div> 16586<div class="paragraph"> 16587<p>SAMPLER2D SAMPLER3D SAMPLERCUBE SAMPLER2DSHADOW 16588SAMPLERCUBESHADOW SAMPLER2DARRAY SAMPLER2DARRAYSHADOW 16589ISAMPLER2D ISAMPLER3D ISAMPLERCUBE ISAMPLER2DARRAY 16590USAMPLER2D USAMPLER3D USAMPLERCUBE USAMPLER2DARRAY</p> 16591</div> 16592<div class="paragraph"> 16593<p>SAMPLER1D SAMPLER1DSHADOW 16594SAMPLER1DARRAY SAMPLER1DARRAYSHADOW 16595ISAMPLER1D ISAMPLER1DARRAY 16596USAMPLER1D USAMPLER1DARRAY 16597SAMPLER2DRECT SAMPLER2DRECTSHADOW ISAMPLER2DRECT USAMPLER2DRECT</p> 16598</div> 16599<div class="paragraph"> 16600<p>SAMPLERBUFFER ISAMPLERBUFFER USAMPLERBUFFER 16601SAMPLERCUBEARRAY SAMPLERCUBEARRAYSHADOW 16602ISAMPLERCUBEARRAY USAMPLERCUBEARRAY 16603SAMPLER2DMS ISAMPLER2DMS USAMPLER2DMS 16604SAMPLER2DMSARRAY ISAMPLER2DMSARRAY USAMPLER2DMSARRAY 16605IMAGE2D IIMAGE2D UIMAGE2D 16606IMAGE3D IIMAGE3D UIMAGE3D 16607IMAGECUBE IIMAGECUBE UIMAGECUBE 16608IMAGEBUFFER IIMAGEBUFFER UIMAGEBUFFER 16609IMAGE2DARRAY IIMAGE2DARRAY UIMAGE2DARRAY 16610IMAGECUBEARRAY IIMAGECUBEARRAY UIMAGECUBEARRAY</p> 16611</div> 16612<div class="paragraph"> 16613<p>IMAGE1D IIMAGE1D UIMAGE1D 16614IMAGE1DARRAY IIMAGE1DARRAY UIMAGE1DARRAY 16615IMAGE2DRECT IIMAGE2DRECT UIMAGE2DRECT 16616IMAGE2DMS IIMAGE2DMS UIMAGE2DMS 16617IMAGE2DMSARRAY IIMAGE2DMSARRAY UIMAGE2DMSARRAY</p> 16618</div> 16619<div class="paragraph"> 16620<p>STRUCT VOID</p> 16621</div> 16622<div class="paragraph"> 16623<p>WHILE BREAK CONTINUE DO ELSE FOR IF DISCARD RETURN SWITCH CASE DEFAULT 16624SUBROUTINE</p> 16625</div> 16626<div class="paragraph"> 16627<p>IDENTIFIER TYPE_NAME 16628FLOATCONSTANT INTCONSTANT UINTCONSTANT BOOLCONSTANT 16629DOUBLECONSTANT 16630FIELD_SELECTION</p> 16631</div> 16632<div class="paragraph"> 16633<p>LEFT_OP RIGHT_OP 16634INC_OP DEC_OP LE_OP GE_OP EQ_OP NE_OP 16635AND_OP OR_OP XOR_OP MUL_ASSIGN DIV_ASSIGN ADD_ASSIGN 16636MOD_ASSIGN LEFT_ASSIGN RIGHT_ASSIGN AND_ASSIGN XOR_ASSIGN OR_ASSIGN 16637SUB_ASSIGN 16638LEFT_PAREN RIGHT_PAREN LEFT_BRACKET RIGHT_BRACKET LEFT_BRACE RIGHT_BRACE DOT 16639COMMA COLON EQUAL SEMICOLON BANG DASH TILDE PLUS STAR SLASH PERCENT 16640LEFT_ANGLE RIGHT_ANGLE VERTICAL_BAR CARET AMPERSAND QUESTION</p> 16641</div> 16642<div class="paragraph"> 16643<p>INVARIANT PRECISE 16644HIGH_PRECISION MEDIUM_PRECISION LOW_PRECISION PRECISION</p> 16645</div> 16646</div> 16647</div> 16648<div class="paragraph"> 16649<p>The following describes the grammar for the OpenGL Shading Language in terms of the above 16650tokens. 16651The starting rule is <em>translation_unit</em>. 16652An empty shader (one having no tokens to parse, after pre-processing) is 16653valid, resulting in no compile-time errors, even though the grammar below 16654does not have a rule to accept an empty token stream.</p> 16655</div> 16656<div class="openblock bnf"> 16657<div class="content"> 16658<div class="dlist"> 16659<dl> 16660<dt class="hdlist1"><em>variable_identifier</em> : </dt> 16661<dd> 16662<p><em>IDENTIFIER</em></p> 16663</dd> 16664<dt class="hdlist1"><em>primary_expression</em> : </dt> 16665<dd> 16666<p><em>variable_identifier</em><br> 16667<em>INTCONSTANT</em><br> 16668<em>UINTCONSTANT</em><br> 16669<em>FLOATCONSTANT</em><br> 16670<em>BOOLCONSTANT</em><br> 16671<em>DOUBLECONSTANT</em><br> 16672<em>LEFT_PAREN</em> <em>expression</em> <em>RIGHT_PAREN</em></p> 16673</dd> 16674<dt class="hdlist1"><em>postfix_expression</em> : </dt> 16675<dd> 16676<p><em>primary_expression</em><br> 16677<em>postfix_expression</em> <em>LEFT_BRACKET</em> <em>integer_expression</em> <em>RIGHT_BRACKET</em><br> 16678<em>function_call</em><br> 16679<em>postfix_expression</em> <em>DOT</em> <em>FIELD_SELECTION</em><br> 16680<em>postfix_expression</em> <em>INC_OP</em><br> 16681<em>postfix_expression</em> <em>DEC_OP</em></p> 16682</dd> 16683</dl> 16684</div> 16685<div class="admonitionblock note"> 16686<table> 16687<tr> 16688<td class="icon"> 16689<i class="fa icon-note" title="Note"></i> 16690</td> 16691<td class="content"> 16692<div class="paragraph"> 16693<p>FIELD_SELECTION includes members in structures, component selection for 16694vectors and the 'length' identifier for the length() method</p> 16695</div> 16696</td> 16697</tr> 16698</table> 16699</div> 16700<div class="dlist"> 16701<dl> 16702<dt class="hdlist1"><em>integer_expression</em> : </dt> 16703<dd> 16704<p><em>expression</em></p> 16705</dd> 16706<dt class="hdlist1"><em>function_call</em> : </dt> 16707<dd> 16708<p><em>function_call_or_method</em></p> 16709</dd> 16710<dt class="hdlist1"><em>function_call_or_method</em> : </dt> 16711<dd> 16712<p><em>function_call_generic</em></p> 16713</dd> 16714<dt class="hdlist1"><em>function_call_generic</em> : </dt> 16715<dd> 16716<p><em>function_call_header_with_parameters</em> <em>RIGHT_PAREN</em><br> 16717<em>function_call_header_no_parameters</em> <em>RIGHT_PAREN</em></p> 16718</dd> 16719<dt class="hdlist1"><em>function_call_header_no_parameters</em> : </dt> 16720<dd> 16721<p><em>function_call_header</em> <em>VOID</em><br> 16722<em>function_call_header</em></p> 16723</dd> 16724<dt class="hdlist1"><em>function_call_header_with_parameters</em> : </dt> 16725<dd> 16726<p><em>function_call_header</em> <em>assignment_expression</em><br> 16727<em>function_call_header_with_parameters</em> <em>COMMA</em> <em>assignment_expression</em></p> 16728</dd> 16729<dt class="hdlist1"><em>function_call_header</em> : </dt> 16730<dd> 16731<p><em>function_identifier</em> <em>LEFT_PAREN</em></p> 16732</dd> 16733</dl> 16734</div> 16735<div class="admonitionblock note"> 16736<table> 16737<tr> 16738<td class="icon"> 16739<i class="fa icon-note" title="Note"></i> 16740</td> 16741<td class="content"> 16742<div class="paragraph"> 16743<p>Grammar Note: Constructors look like functions, but lexical analysis 16744recognized most of them as keywords. 16745They are now recognized through <em>type_specifier</em>.</p> 16746</div> 16747</td> 16748</tr> 16749</table> 16750</div> 16751<div class="admonitionblock note"> 16752<table> 16753<tr> 16754<td class="icon"> 16755<i class="fa icon-note" title="Note"></i> 16756</td> 16757<td class="content"> 16758<div class="paragraph"> 16759<p>Methods (<strong>.length</strong>), subroutine array calls, and identifiers are recognized 16760through <em>postfix_expression</em>.</p> 16761</div> 16762</td> 16763</tr> 16764</table> 16765</div> 16766<div class="dlist"> 16767<dl> 16768<dt class="hdlist1"><em>function_identifier</em> : </dt> 16769<dd> 16770<p><em>type_specifier</em><br> 16771<em>postfix_expression</em></p> 16772</dd> 16773<dt class="hdlist1"><em>unary_expression</em> : </dt> 16774<dd> 16775<p><em>postfix_expression</em><br> 16776<em>INC_OP</em> <em>unary_expression</em><br> 16777<em>DEC_OP</em> <em>unary_expression</em><br> 16778<em>unary_operator</em> <em>unary_expression</em></p> 16779</dd> 16780</dl> 16781</div> 16782<div class="admonitionblock note"> 16783<table> 16784<tr> 16785<td class="icon"> 16786<i class="fa icon-note" title="Note"></i> 16787</td> 16788<td class="content"> 16789<div class="paragraph"> 16790<p>Grammar Note: No traditional style type casts.</p> 16791</div> 16792</td> 16793</tr> 16794</table> 16795</div> 16796<div class="dlist"> 16797<dl> 16798<dt class="hdlist1"><em>unary_operator</em> : </dt> 16799<dd> 16800<p><em>PLUS</em><br> 16801<em>DASH</em><br> 16802<em>BANG</em><br> 16803<em>TILDE</em></p> 16804</dd> 16805</dl> 16806</div> 16807<div class="admonitionblock note"> 16808<table> 16809<tr> 16810<td class="icon"> 16811<i class="fa icon-note" title="Note"></i> 16812</td> 16813<td class="content"> 16814<div class="paragraph"> 16815<p>Grammar Note: No '*' or '&' unary ops. 16816Pointers are not supported.</p> 16817</div> 16818</td> 16819</tr> 16820</table> 16821</div> 16822<div class="dlist"> 16823<dl> 16824<dt class="hdlist1"><em>multiplicative_expression</em> : </dt> 16825<dd> 16826<p><em>unary_expression</em><br> 16827<em>multiplicative_expression</em> <em>STAR</em> <em>unary_expression</em><br> 16828<em>multiplicative_expression</em> <em>SLASH</em> <em>unary_expression</em><br> 16829<em>multiplicative_expression</em> <em>PERCENT</em> <em>unary_expression</em></p> 16830</dd> 16831<dt class="hdlist1"><em>additive_expression</em> : </dt> 16832<dd> 16833<p><em>multiplicative_expression</em><br> 16834<em>additive_expression</em> <em>PLUS</em> <em>multiplicative_expression</em><br> 16835<em>additive_expression</em> <em>DASH</em> <em>multiplicative_expression</em></p> 16836</dd> 16837<dt class="hdlist1"><em>shift_expression</em> : </dt> 16838<dd> 16839<p><em>additive_expression</em><br> 16840<em>shift_expression</em> <em>LEFT_OP</em> <em>additive_expression</em><br> 16841<em>shift_expression</em> <em>RIGHT_OP</em> <em>additive_expression</em></p> 16842</dd> 16843<dt class="hdlist1"><em>relational_expression</em> : </dt> 16844<dd> 16845<p><em>shift_expression</em><br> 16846<em>relational_expression</em> <em>LEFT_ANGLE</em> <em>shift_expression</em><br> 16847<em>relational_expression</em> <em>RIGHT_ANGLE</em> <em>shift_expression</em><br> 16848<em>relational_expression</em> <em>LE_OP</em> <em>shift_expression</em><br> 16849<em>relational_expression</em> <em>GE_OP</em> <em>shift_expression</em></p> 16850</dd> 16851<dt class="hdlist1"><em>equality_expression</em> : </dt> 16852<dd> 16853<p><em>relational_expression</em><br> 16854<em>equality_expression</em> <em>EQ_OP</em> <em>relational_expression</em><br> 16855<em>equality_expression</em> <em>NE_OP</em> <em>relational_expression</em></p> 16856</dd> 16857<dt class="hdlist1"><em>and_expression</em> : </dt> 16858<dd> 16859<p><em>equality_expression</em><br> 16860<em>and_expression</em> <em>AMPERSAND</em> <em>equality_expression</em></p> 16861</dd> 16862<dt class="hdlist1"><em>exclusive_or_expression</em> : </dt> 16863<dd> 16864<p><em>and_expression</em><br> 16865<em>exclusive_or_expression</em> <em>CARET</em> <em>and_expression</em></p> 16866</dd> 16867<dt class="hdlist1"><em>inclusive_or_expression</em> : </dt> 16868<dd> 16869<p><em>exclusive_or_expression</em><br> 16870<em>inclusive_or_expression</em> <em>VERTICAL_BAR</em> <em>exclusive_or_expression</em></p> 16871</dd> 16872<dt class="hdlist1"><em>logical_and_expression</em> : </dt> 16873<dd> 16874<p><em>inclusive_or_expression</em><br> 16875<em>logical_and_expression</em> <em>AND_OP</em> <em>inclusive_or_expression</em></p> 16876</dd> 16877<dt class="hdlist1"><em>logical_xor_expression</em> : </dt> 16878<dd> 16879<p><em>logical_and_expression</em><br> 16880<em>logical_xor_expression</em> <em>XOR_OP</em> <em>logical_and_expression</em></p> 16881</dd> 16882<dt class="hdlist1"><em>logical_or_expression</em> : </dt> 16883<dd> 16884<p><em>logical_xor_expression</em><br> 16885<em>logical_or_expression</em> <em>OR_OP</em> <em>logical_xor_expression</em></p> 16886</dd> 16887<dt class="hdlist1"><em>conditional_expression</em> : </dt> 16888<dd> 16889<p><em>logical_or_expression</em><br> 16890<em>logical_or_expression</em> <em>QUESTION</em> <em>expression</em> <em>COLON</em> 16891<em>assignment_expression</em></p> 16892</dd> 16893<dt class="hdlist1"><em>assignment_expression</em> : </dt> 16894<dd> 16895<p><em>conditional_expression</em><br> 16896<em>unary_expression</em> <em>assignment_operator</em> <em>assignment_expression</em></p> 16897</dd> 16898<dt class="hdlist1"><em>assignment_operator</em> : </dt> 16899<dd> 16900<p><em>EQUAL</em><br> 16901<em>MUL_ASSIGN</em><br> 16902<em>DIV_ASSIGN</em><br> 16903<em>MOD_ASSIGN</em><br> 16904<em>ADD_ASSIGN</em><br> 16905<em>SUB_ASSIGN</em><br> 16906<em>LEFT_ASSIGN</em><br> 16907<em>RIGHT_ASSIGN</em><br> 16908<em>AND_ASSIGN</em><br> 16909<em>XOR_ASSIGN</em><br> 16910<em>OR_ASSIGN</em></p> 16911</dd> 16912<dt class="hdlist1"><em>expression</em> : </dt> 16913<dd> 16914<p><em>assignment_expression</em><br> 16915<em>expression</em> <em>COMMA</em> <em>assignment_expression</em></p> 16916</dd> 16917<dt class="hdlist1"><em>constant_expression</em> : </dt> 16918<dd> 16919<p><em>conditional_expression</em></p> 16920</dd> 16921<dt class="hdlist1"><em>declaration</em> : </dt> 16922<dd> 16923<p><em>function_prototype</em> <em>SEMICOLON</em><br> 16924<em>init_declarator_list</em> <em>SEMICOLON</em><br> 16925<em>PRECISION</em> <em>precision_qualifier</em> <em>type_specifier</em> <em>SEMICOLON</em><br> 16926<em>type_qualifier</em> <em>IDENTIFIER</em> <em>LEFT_BRACE</em> <em>struct_declaration_list</em> 16927<em>RIGHT_BRACE</em> <em>SEMICOLON</em><br> 16928<em>type_qualifier</em> <em>IDENTIFIER</em> <em>LEFT_BRACE</em> <em>struct_declaration_list</em> 16929<em>RIGHT_BRACE</em> <em>IDENTIFIER</em> <em>SEMICOLON</em><br> 16930<em>type_qualifier</em> <em>IDENTIFIER</em> <em>LEFT_BRACE</em> <em>struct_declaration_list</em> 16931<em>RIGHT_BRACE</em> <em>IDENTIFIER</em> <em>array_specifier</em> <em>SEMICOLON</em><br> 16932<em>type_qualifier</em> <em>SEMICOLON</em><br> 16933<em>type_qualifier</em> <em>IDENTIFIER</em> <em>SEMICOLON</em><br> 16934<em>type_qualifier</em> <em>IDENTIFIER</em> <em>identifier_list</em> <em>SEMICOLON</em></p> 16935</dd> 16936<dt class="hdlist1"><em>identifier_list</em> : </dt> 16937<dd> 16938<p><em>COMMA</em> <em>IDENTIFIER</em><br> 16939<em>identifier_list</em> <em>COMMA</em> <em>IDENTIFIER</em></p> 16940</dd> 16941<dt class="hdlist1"><em>function_prototype</em> : </dt> 16942<dd> 16943<p><em>function_declarator</em> <em>RIGHT_PAREN</em></p> 16944</dd> 16945<dt class="hdlist1"><em>function_declarator</em> : </dt> 16946<dd> 16947<p><em>function_header</em><br> 16948<em>function_header_with_parameters</em></p> 16949</dd> 16950<dt class="hdlist1"><em>function_header_with_parameters</em> : </dt> 16951<dd> 16952<p><em>function_header</em> <em>parameter_declaration</em><br> 16953<em>function_header_with_parameters</em> <em>COMMA</em> <em>parameter_declaration</em></p> 16954</dd> 16955<dt class="hdlist1"><em>function_header</em> : </dt> 16956<dd> 16957<p><em>fully_specified_type</em> <em>IDENTIFIER</em> <em>LEFT_PAREN</em></p> 16958</dd> 16959<dt class="hdlist1"><em>parameter_declarator</em> : </dt> 16960<dd> 16961<p><em>type_specifier</em> <em>IDENTIFIER</em><br> 16962<em>type_specifier</em> <em>IDENTIFIER</em> <em>array_specifier</em></p> 16963</dd> 16964<dt class="hdlist1"><em>parameter_declaration</em> : </dt> 16965<dd> 16966<p><em>type_qualifier</em> <em>parameter_declarator</em><br> 16967<em>parameter_declarator</em><br> 16968<em>type_qualifier</em> <em>parameter_type_specifier</em><br> 16969<em>parameter_type_specifier</em></p> 16970</dd> 16971<dt class="hdlist1"><em>parameter_type_specifier</em> : </dt> 16972<dd> 16973<p><em>type_specifier</em></p> 16974</dd> 16975<dt class="hdlist1"><em>init_declarator_list</em> : </dt> 16976<dd> 16977<p><em>single_declaration</em><br> 16978<em>init_declarator_list</em> <em>COMMA</em> <em>IDENTIFIER</em><br> 16979<em>init_declarator_list</em> <em>COMMA</em> <em>IDENTIFIER</em> <em>array_specifier</em><br> 16980<em>init_declarator_list</em> <em>COMMA</em> <em>IDENTIFIER</em> <em>array_specifier</em> <em>EQUAL</em> 16981<em>initializer</em><br> 16982<em>init_declarator_list</em> <em>COMMA</em> <em>IDENTIFIER</em> <em>EQUAL</em> <em>initializer</em></p> 16983</dd> 16984<dt class="hdlist1"><em>single_declaration</em> : </dt> 16985<dd> 16986<p><em>fully_specified_type</em><br> 16987<em>fully_specified_type</em> <em>IDENTIFIER</em><br> 16988<em>fully_specified_type</em> <em>IDENTIFIER</em> <em>array_specifier</em><br> 16989<em>fully_specified_type</em> <em>IDENTIFIER</em> <em>array_specifier</em> <em>EQUAL</em> 16990<em>initializer</em><br> 16991<em>fully_specified_type</em> <em>IDENTIFIER</em> <em>EQUAL</em> <em>initializer</em></p> 16992</dd> 16993</dl> 16994</div> 16995<div class="admonitionblock note"> 16996<table> 16997<tr> 16998<td class="icon"> 16999<i class="fa icon-note" title="Note"></i> 17000</td> 17001<td class="content"> 17002<div class="paragraph"> 17003<p>Grammar Note: No 'enum', or 'typedef'.</p> 17004</div> 17005</td> 17006</tr> 17007</table> 17008</div> 17009<div class="dlist"> 17010<dl> 17011<dt class="hdlist1"><em>fully_specified_type</em> : </dt> 17012<dd> 17013<p><em>type_specifier</em><br> 17014<em>type_qualifier</em> <em>type_specifier</em></p> 17015</dd> 17016<dt class="hdlist1"><em>invariant_qualifier</em> : </dt> 17017<dd> 17018<p><em>INVARIANT</em></p> 17019</dd> 17020<dt class="hdlist1"><em>interpolation_qualifier</em> : </dt> 17021<dd> 17022<p><em>SMOOTH</em><br> 17023<em>FLAT</em><br> 17024<em>NOPERSPECTIVE</em></p> 17025</dd> 17026<dt class="hdlist1"><em>layout_qualifier</em> : </dt> 17027<dd> 17028<p><em>LAYOUT</em> <em>LEFT_PAREN</em> <em>layout_qualifier_id_list</em> <em>RIGHT_PAREN</em></p> 17029</dd> 17030<dt class="hdlist1"><em>layout_qualifier_id_list</em> : </dt> 17031<dd> 17032<p><em>layout_qualifier_id</em><br> 17033<em>layout_qualifier_id_list</em> <em>COMMA</em> <em>layout_qualifier_id</em></p> 17034</dd> 17035<dt class="hdlist1"><em>layout_qualifier_id</em> : </dt> 17036<dd> 17037<p><em>IDENTIFIER</em><br> 17038<em>IDENTIFIER</em> <em>EQUAL</em> <em>constant_expression</em><br> 17039<em>SHARED</em></p> 17040</dd> 17041<dt class="hdlist1"><em>precise_qualifier</em> : </dt> 17042<dd> 17043<p><em>PRECISE</em></p> 17044</dd> 17045<dt class="hdlist1"><em>type_qualifier</em> : </dt> 17046<dd> 17047<p><em>single_type_qualifier</em><br> 17048<em>type_qualifier</em> <em>single_type_qualifier</em></p> 17049</dd> 17050<dt class="hdlist1"><em>single_type_qualifier</em> : </dt> 17051<dd> 17052<p><em>storage_qualifier</em><br> 17053<em>layout_qualifier</em><br> 17054<em>precision_qualifier</em><br> 17055<em>interpolation_qualifier</em><br> 17056<em>invariant_qualifier</em><br> 17057<em>precise_qualifier</em></p> 17058</dd> 17059<dt class="hdlist1"><em>storage_qualifier</em> : </dt> 17060<dd> 17061<p><em>CONST</em><br> 17062<em>IN</em><br> 17063<em>OUT</em><br> 17064<em>INOUT</em><br> 17065<em>CENTROID</em><br> 17066<em>PATCH</em><br> 17067<em>SAMPLE</em><br> 17068<em>UNIFORM</em><br> 17069<em>BUFFER</em><br> 17070<em>SHARED</em><br> 17071<em>COHERENT</em><br> 17072<em>VOLATILE</em><br> 17073<em>RESTRICT</em><br> 17074<em>READONLY</em><br> 17075<em>WRITEONLY</em><br> 17076<em>SUBROUTINE</em><br> 17077<em>SUBROUTINE</em> <em>LEFT_PAREN</em> <em>type_name_list</em> <em>RIGHT_PAREN</em></p> 17078</dd> 17079<dt class="hdlist1"><em>type_name_list</em> : </dt> 17080<dd> 17081<p><em>TYPE_NAME</em><br> 17082<em>type_name_list</em> <em>COMMA</em> <em>TYPE_NAME</em></p> 17083</dd> 17084<dt class="hdlist1"><em>type_specifier</em> : </dt> 17085<dd> 17086<p><em>type_specifier_nonarray</em><br> 17087<em>type_specifier_nonarray</em> <em>array_specifier</em></p> 17088</dd> 17089<dt class="hdlist1"><em>array_specifier</em> : </dt> 17090<dd> 17091<p><em>LEFT_BRACKET</em> <em>RIGHT_BRACKET</em><br> 17092<em>LEFT_BRACKET</em> <em>conditional_expression</em> <em>RIGHT_BRACKET</em><br> 17093<em>array_specifier</em> <em>LEFT_BRACKET</em> <em>RIGHT_BRACKET</em><br> 17094<em>array_specifier</em> <em>LEFT_BRACKET</em> <em>conditional_expression</em> <em>RIGHT_BRACKET</em></p> 17095</dd> 17096<dt class="hdlist1"><em>type_specifier_nonarray</em> : </dt> 17097<dd> 17098<p><em>VOID</em><br> 17099<em>FLOAT</em><br> 17100<em>DOUBLE</em><br> 17101<em>INT</em><br> 17102<em>UINT</em><br> 17103<em>BOOL</em><br> 17104<em>VEC2</em><br> 17105<em>VEC3</em><br> 17106<em>VEC4</em><br> 17107<em>DVEC2</em><br> 17108<em>DVEC3</em><br> 17109<em>DVEC4</em><br> 17110<em>BVEC2</em><br> 17111<em>BVEC3</em><br> 17112<em>BVEC4</em><br> 17113<em>IVEC2</em><br> 17114<em>IVEC3</em><br> 17115<em>IVEC4</em><br> 17116<em>UVEC2</em><br> 17117<em>UVEC3</em><br> 17118<em>UVEC4</em><br> 17119<em>MAT2</em><br> 17120<em>MAT3</em><br> 17121<em>MAT4</em><br> 17122<em>MAT2X2</em><br> 17123<em>MAT2X3</em><br> 17124<em>MAT2X4</em><br> 17125<em>MAT3X2</em><br> 17126<em>MAT3X3</em><br> 17127<em>MAT3X4</em><br> 17128<em>MAT4X2</em><br> 17129<em>MAT4X3</em><br> 17130<em>MAT4X4</em><br> 17131<em>DMAT2</em><br> 17132<em>DMAT3</em><br> 17133<em>DMAT4</em><br> 17134<em>DMAT2X2</em><br> 17135<em>DMAT2X3</em><br> 17136<em>DMAT2X4</em><br> 17137<em>DMAT3X2</em><br> 17138<em>DMAT3X3</em><br> 17139<em>DMAT3X4</em><br> 17140<em>DMAT4X2</em><br> 17141<em>DMAT4X3</em><br> 17142<em>DMAT4X4</em><br> 17143<em>ATOMIC_UINT</em><br> 17144<em>SAMPLER2D</em><br> 17145<em>SAMPLER3D</em><br> 17146<em>SAMPLERCUBE</em><br> 17147<em>SAMPLER2DSHADOW</em><br> 17148<em>SAMPLERCUBESHADOW</em><br> 17149<em>SAMPLER2DARRAY</em><br> 17150<em>SAMPLER2DARRAYSHADOW</em><br> 17151<em>SAMPLERCUBEARRAY</em><br> 17152<em>SAMPLERCUBEARRAYSHADOW</em><br> 17153<em>ISAMPLER2D</em><br> 17154<em>ISAMPLER3D</em><br> 17155<em>ISAMPLERCUBE</em><br> 17156<em>ISAMPLER2DARRAY</em><br> 17157<em>ISAMPLERCUBEARRAY</em><br> 17158<em>USAMPLER2D</em><br> 17159<em>USAMPLER3D</em><br> 17160<em>USAMPLERCUBE</em><br> 17161<em>USAMPLER2DARRAY</em><br> 17162<em>USAMPLERCUBEARRAY</em><br> 17163<em>SAMPLER1D</em><br> 17164<em>SAMPLER1DSHADOW</em><br> 17165<em>SAMPLER1DARRAY</em><br> 17166<em>SAMPLER1DARRAYSHADOW</em><br> 17167<em>ISAMPLER1D</em><br> 17168<em>ISAMPLER1DARRAY</em><br> 17169<em>USAMPLER1D</em><br> 17170<em>USAMPLER1DARRAY</em><br> 17171<em>SAMPLER2DRECT</em><br> 17172<em>SAMPLER2DRECTSHADOW</em><br> 17173<em>ISAMPLER2DRECT</em><br> 17174<em>USAMPLER2DRECT</em><br> 17175<em>SAMPLERBUFFER</em><br> 17176<em>ISAMPLERBUFFER</em><br> 17177<em>USAMPLERBUFFER</em><br> 17178<em>SAMPLER2DMS</em><br> 17179<em>ISAMPLER2DMS</em><br> 17180<em>USAMPLER2DMS</em><br> 17181<em>SAMPLER2DMSARRAY</em><br> 17182<em>ISAMPLER2DMSARRAY</em><br> 17183<em>USAMPLER2DMSARRAY</em><br> 17184<em>IMAGE2D</em><br> 17185<em>IIMAGE2D</em><br> 17186<em>UIMAGE2D</em><br> 17187<em>IMAGE3D</em><br> 17188<em>IIMAGE3D</em><br> 17189<em>UIMAGE3D</em><br> 17190<em>IMAGECUBE</em><br> 17191<em>IIMAGECUBE</em><br> 17192<em>UIMAGECUBE</em><br> 17193<em>IMAGEBUFFER</em><br> 17194<em>IIMAGEBUFFER</em><br> 17195<em>UIMAGEBUFFER</em><br> 17196<em>IMAGE1D</em><br> 17197<em>IIMAGE1D</em><br> 17198<em>UIMAGE1D</em><br> 17199<em>IMAGE1DARRAY</em><br> 17200<em>IIMAGE1DARRAY</em><br> 17201<em>UIMAGE1DARRAY</em><br> 17202<em>IMAGE2DRECT</em><br> 17203<em>IIMAGE2DRECT</em><br> 17204<em>UIMAGE2DRECT</em><br> 17205<em>IMAGE2DARRAY</em><br> 17206<em>IIMAGE2DARRAY</em><br> 17207<em>UIMAGE2DARRAY</em><br> 17208<em>IMAGECUBEARRAY</em><br> 17209<em>IIMAGECUBEARRAY</em><br> 17210<em>UIMAGECUBEARRAY</em><br> 17211<em>IMAGE2DMS</em><br> 17212<em>IIMAGE2DMS</em><br> 17213<em>UIMAGE2DMS</em><br> 17214<em>IMAGE2DMSARRAY</em><br> 17215<em>IIMAGE2DMSARRAY</em><br> 17216<em>UIMAGE2DMSARRAY</em><br> 17217<em>struct_specifier</em><br> 17218<em>TYPE_NAME</em></p> 17219</dd> 17220<dt class="hdlist1"><em>precision_qualifier</em> : </dt> 17221<dd> 17222<p><em>HIGH_PRECISION</em><br> 17223<em>MEDIUM_PRECISION</em><br> 17224<em>LOW_PRECISION</em></p> 17225</dd> 17226<dt class="hdlist1"><em>struct_specifier</em> : </dt> 17227<dd> 17228<p><em>STRUCT</em> <em>IDENTIFIER</em> <em>LEFT_BRACE</em> <em>struct_declaration_list</em> 17229<em>RIGHT_BRACE</em><br> 17230<em>STRUCT</em> <em>LEFT_BRACE</em> <em>struct_declaration_list</em> <em>RIGHT_BRACE</em></p> 17231</dd> 17232<dt class="hdlist1"><em>struct_declaration_list</em> : </dt> 17233<dd> 17234<p><em>struct_declaration</em><br> 17235<em>struct_declaration_list</em> <em>struct_declaration</em></p> 17236</dd> 17237<dt class="hdlist1"><em>struct_declaration</em> : </dt> 17238<dd> 17239<p><em>type_specifier</em> <em>struct_declarator_list</em> <em>SEMICOLON</em><br> 17240<em>type_qualifier</em> <em>type_specifier</em> <em>struct_declarator_list</em> <em>SEMICOLON</em></p> 17241</dd> 17242<dt class="hdlist1"><em>struct_declarator_list</em> : </dt> 17243<dd> 17244<p><em>struct_declarator</em><br> 17245<em>struct_declarator_list</em> <em>COMMA</em> <em>struct_declarator</em></p> 17246</dd> 17247<dt class="hdlist1"><em>struct_declarator</em> : </dt> 17248<dd> 17249<p><em>IDENTIFIER</em><br> 17250<em>IDENTIFIER</em> <em>array_specifier</em></p> 17251</dd> 17252<dt class="hdlist1"><em>initializer</em> : </dt> 17253<dd> 17254<p><em>assignment_expression</em><br> 17255<em>LEFT_BRACE</em> <em>initializer_list</em> <em>RIGHT_BRACE</em><br> 17256<em>LEFT_BRACE</em> <em>initializer_list</em> <em>COMMA</em> <em>RIGHT_BRACE</em></p> 17257</dd> 17258<dt class="hdlist1"><em>initializer_list</em> : </dt> 17259<dd> 17260<p><em>initializer</em><br> 17261<em>initializer_list</em> <em>COMMA</em> <em>initializer</em></p> 17262</dd> 17263<dt class="hdlist1"><em>declaration_statement</em> : </dt> 17264<dd> 17265<p><em>declaration</em></p> 17266</dd> 17267<dt class="hdlist1"><em>statement</em> : </dt> 17268<dd> 17269<p><em>compound_statement</em><br> 17270<em>simple_statement</em></p> 17271</dd> 17272</dl> 17273</div> 17274<div class="admonitionblock note"> 17275<table> 17276<tr> 17277<td class="icon"> 17278<i class="fa icon-note" title="Note"></i> 17279</td> 17280<td class="content"> 17281<div class="paragraph"> 17282<p>Grammar Note: labeled statements for SWITCH only; 'goto' is not supported.</p> 17283</div> 17284</td> 17285</tr> 17286</table> 17287</div> 17288<div class="dlist"> 17289<dl> 17290<dt class="hdlist1"><em>simple_statement</em> : </dt> 17291<dd> 17292<p><em>declaration_statement</em><br> 17293<em>expression_statement</em><br> 17294<em>selection_statement</em><br> 17295<em>switch_statement</em><br> 17296<em>case_label</em><br> 17297<em>iteration_statement</em><br> 17298<em>jump_statement</em></p> 17299</dd> 17300<dt class="hdlist1"><em>compound_statement</em> : </dt> 17301<dd> 17302<p><em>LEFT_BRACE</em> <em>RIGHT_BRACE</em><br> 17303<em>LEFT_BRACE</em> <em>statement_list</em> <em>RIGHT_BRACE</em></p> 17304</dd> 17305<dt class="hdlist1"><em>statement_no_new_scope</em> : </dt> 17306<dd> 17307<p><em>compound_statement_no_new_scope</em><br> 17308<em>simple_statement</em></p> 17309</dd> 17310<dt class="hdlist1"><em>compound_statement_no_new_scope</em> : </dt> 17311<dd> 17312<p><em>LEFT_BRACE</em> <em>RIGHT_BRACE</em><br> 17313<em>LEFT_BRACE</em> <em>statement_list</em> <em>RIGHT_BRACE</em></p> 17314</dd> 17315<dt class="hdlist1"><em>statement_list</em> : </dt> 17316<dd> 17317<p><em>statement</em><br> 17318<em>statement_list</em> <em>statement</em></p> 17319</dd> 17320<dt class="hdlist1"><em>expression_statement</em> : </dt> 17321<dd> 17322<p><em>SEMICOLON</em><br> 17323<em>expression</em> <em>SEMICOLON</em></p> 17324</dd> 17325<dt class="hdlist1"><em>selection_statement</em> : </dt> 17326<dd> 17327<p><em>IF</em> <em>LEFT_PAREN</em> <em>expression</em> <em>RIGHT_PAREN</em> <em>selection_rest_statement</em></p> 17328</dd> 17329<dt class="hdlist1"><em>selection_rest_statement</em> : </dt> 17330<dd> 17331<p><em>statement</em> <em>ELSE</em> <em>statement</em><br> 17332<em>statement</em></p> 17333</dd> 17334<dt class="hdlist1"><em>condition</em> : </dt> 17335<dd> 17336<p><em>expression</em><br> 17337<em>fully_specified_type</em> <em>IDENTIFIER</em> <em>EQUAL</em> <em>initializer</em></p> 17338</dd> 17339<dt class="hdlist1"><em>switch_statement</em> : </dt> 17340<dd> 17341<p><em>SWITCH</em> <em>LEFT_PAREN</em> <em>expression</em> <em>RIGHT_PAREN</em> <em>LEFT_BRACE</em> 17342<em>switch_statement_list</em><br> 17343<em>RIGHT_BRACE</em></p> 17344</dd> 17345<dt class="hdlist1"><em>switch_statement_list</em> : </dt> 17346<dd> 17347<p>/* <em>nothing</em> */<br> 17348<em>statement_list</em></p> 17349</dd> 17350<dt class="hdlist1"><em>case_label</em> : </dt> 17351<dd> 17352<p><em>CASE</em> <em>expression</em> <em>COLON</em><br> 17353<em>DEFAULT</em> <em>COLON</em></p> 17354</dd> 17355<dt class="hdlist1"><em>iteration_statement</em> : </dt> 17356<dd> 17357<p><em>WHILE</em> <em>LEFT_PAREN</em> <em>condition</em> <em>RIGHT_PAREN</em> <em>statement_no_new_scope</em><br> 17358<em>DO</em> <em>statement</em> <em>WHILE</em> <em>LEFT_PAREN</em> <em>expression</em> <em>RIGHT_PAREN</em> 17359<em>SEMICOLON</em><br> 17360<em>FOR</em> <em>LEFT_PAREN</em> <em>for_init_statement</em> <em>for_rest_statement</em> 17361<em>RIGHT_PAREN</em> <em>statement_no_new_scope</em></p> 17362</dd> 17363<dt class="hdlist1"><em>for_init_statement</em> : </dt> 17364<dd> 17365<p><em>expression_statement</em><br> 17366<em>declaration_statement</em></p> 17367</dd> 17368<dt class="hdlist1"><em>conditionopt</em> : </dt> 17369<dd> 17370<p><em>condition</em><br> 17371/* <em>empty</em> */</p> 17372</dd> 17373<dt class="hdlist1"><em>for_rest_statement</em> : </dt> 17374<dd> 17375<p><em>conditionopt</em> <em>SEMICOLON</em><br> 17376<em>conditionopt</em> <em>SEMICOLON</em> <em>expression</em></p> 17377</dd> 17378<dt class="hdlist1"><em>jump_statement</em> : </dt> 17379<dd> 17380<p><em>CONTINUE</em> <em>SEMICOLON</em><br> 17381<em>BREAK</em> <em>SEMICOLON</em><br> 17382<em>RETURN</em> <em>SEMICOLON</em><br> 17383<em>RETURN</em> <em>expression</em> <em>SEMICOLON</em><br> 17384<em>DISCARD</em> <em>SEMICOLON</em> // Fragment shader only.</p> 17385</dd> 17386</dl> 17387</div> 17388<div class="admonitionblock note"> 17389<table> 17390<tr> 17391<td class="icon"> 17392<i class="fa icon-note" title="Note"></i> 17393</td> 17394<td class="content"> 17395<div class="paragraph"> 17396<p>Grammar Note: No 'goto'. 17397Gotos are not supported.</p> 17398</div> 17399</td> 17400</tr> 17401</table> 17402</div> 17403<div class="dlist"> 17404<dl> 17405<dt class="hdlist1"><em>translation_unit</em> : </dt> 17406<dd> 17407<p><em>external_declaration</em><br> 17408<em>translation_unit</em> <em>external_declaration</em></p> 17409</dd> 17410<dt class="hdlist1"><em>external_declaration</em> : </dt> 17411<dd> 17412<p><em>function_definition</em><br> 17413<em>declaration</em><br> 17414<em>SEMICOLON</em></p> 17415</dd> 17416<dt class="hdlist1"><em>function_definition</em> : </dt> 17417<dd> 17418<p><em>function_prototype</em> <em>compound_statement_no_new_scope</em></p> 17419</dd> 17420</dl> 17421</div> 17422</div> 17423</div> 17424<div class="paragraph"> 17425<p>In general the above grammar describes a super set of the OpenGL Shading Language. 17426Certain constructs that are valid purely in terms of the grammar are 17427disallowed by statements elsewhere in this specification.</p> 17428</div> 17429</div> 17430</div> 17431<div class="sect1"> 17432<h2 id="acknowledgments">10. Acknowledgments</h2> 17433<div class="sectionbody"> 17434<div class="paragraph"> 17435<p>This specification is based on the work of those who contributed to past 17436versions of the Open GL and Open GL ES Language Specifications and the 17437following contributors to this version:</p> 17438</div> 17439<div class="paragraph"> 17440<p>Pat Brown, NVIDIA<br> 17441Jeff Bolz, NVIDIA<br> 17442Frank Chen<br> 17443Pierre Boudier, AMD<br> 17444Piers Daniell, NVIDIA<br> 17445Chris Dodd, NVIDIA<br> 17446Nick Haemel, NVIDIA<br> 17447Jason Green, Transgaming<br> 17448Brent Insko, Intel<br> 17449Jon Leech<br> 17450Bill Licea-Kane, Qualcomm<br> 17451Daniel Koch, NVIDIA<br> 17452Graeme Leese, Broadcom<br> 17453Barthold Lichtenbelt, NVIDIA<br> 17454Bruce Merry, ARM<br> 17455Robert Ohannessian<br> 17456Tom Olson, ARM<br> 17457Brian Paul, VMware<br> 17458Acorn Pooley, NVIDIA<br> 17459Daniel Rakos, AMD<br> 17460Christophe Riccio, AMD<br> 17461Kevin Rogovin<br> 17462Ian Romanick, Intel<br> 17463Greg Roth, NVIDIA<br> 17464Graham Sellers, AMD<br> 17465Dave Shreiner, ARM<br> 17466Jeremy Sandmel, Apple<br> 17467Robert Simpson, Qualcomm<br> 17468Eric Werness, NVIDIA<br> 17469Mark Young, AMD</p> 17470</div> 17471</div> 17472</div> 17473<div class="sect1"> 17474<h2 id="references">11. Normative References</h2> 17475<div class="sectionbody"> 17476<div class="olist arabic"> 17477<ol class="arabic"> 17478<li> 17479<p>International Standard ISO/IEC 14882:1998(E). 17480Programming Languages - C++. Referenced for preprocessor only</p> 17481</li> 17482<li> 17483<p>“OpenGL<sup>R</sup> ES, Version 3.2”, 17484<a href="https://www.khronos.org/registry/OpenGL/index_es.php" class="bare">https://www.khronos.org/registry/OpenGL/index_es.php</a>, November 3, 2016.</p> 17485</li> 17486<li> 17487<p>“The OpenGL<sup>R</sup> Graphics System: A Specification, Version 4.6 (Core 17488Profile)”, <a href="https://www.khronos.org/registry/OpenGL/index_gl.php" class="bare">https://www.khronos.org/registry/OpenGL/index_gl.php</a>, June 174891, 2016.</p> 17490</li> 17491<li> 17492<p>IEEE 754-2008. 17493<em>IEEE Standard for Floating-Point Arithmetic</em></p> 17494</li> 17495<li> 17496<p>“SPIR-V Specification, Version 1.3, Revision 7” , 17497<a href="https://www.khronos.org/registry/spir-v/" class="bare">https://www.khronos.org/registry/spir-v/</a>.</p> 17498</li> 17499<li> 17500<p>“Vulkan<sup>R</sup> 1.1.105 - A Specification”, 17501<a href="https://www.khronos.org/registry/vulkan/" class="bare">https://www.khronos.org/registry/vulkan/</a>, 17502March 19, 2019.</p> 17503</li> 17504</ol> 17505</div> 17506</div> 17507</div> 17508<div class="sect1"> 17509<h2 id="_non_normative_spir_v_mappings">12. Non-Normative SPIR-V Mappings</h2> 17510<div class="sectionbody"> 17511<div class="paragraph"> 17512<p>This appendix includes:</p> 17513</div> 17514<div class="ulist"> 17515<ul> 17516<li> 17517<p>a comparision of feature differences with SPIR-V versus without, for both Vulkan and OpenGL</p> 17518</li> 17519<li> 17520<p>a discussion of how GLSL features logically map to SPIR-V features.</p> 17521</li> 17522</ul> 17523</div> 17524<div class="sect2"> 17525<h3 id="_feature_comparisons">12.1. Feature Comparisons</h3> 17526<div class="paragraph"> 17527<p>The following features are removed for both OpenGL and Vulkan:</p> 17528</div> 17529<div class="ulist"> 17530<ul> 17531<li> 17532<p>subroutines</p> 17533</li> 17534<li> 17535<p>shared and packed block layouts</p> 17536</li> 17537<li> 17538<p>the already deprecated texturing functions (e.g., <code>texture2D()</code>)</p> 17539</li> 17540<li> 17541<p>the already deprecated noise functions (e.g., <code>noise1()</code>)</p> 17542</li> 17543<li> 17544<p>compatibility-profile features</p> 17545</li> 17546<li> 17547<p><em>gl_DepthRangeParameters</em> and <em>gl_NumSamples</em></p> 17548</li> 17549</ul> 17550</div> 17551<div class="paragraph"> 17552<p>Vulkan removed the following features, which are still present for OpenGL:</p> 17553</div> 17554<div class="ulist"> 17555<ul> 17556<li> 17557<p>Default uniforms, for non-opaque types: 17558The <strong>UniformConstant</strong> storage class can be used on individual 17559variables at global scope. (That is, uniforms don’t have to be in a 17560block, unless they are built-in members that are in block in GLSL 17561version 4.5 or above.)</p> 17562</li> 17563<li> 17564<p>GLSL atomic-counter bindings have the <em>offset</em> layout qualifier → 17565SPIR-V <strong>AtomicCounter</strong> storage class using the <strong>Offset</strong> decoration</p> 17566</li> 17567<li> 17568<p>GLSL <em>origin_lower_left</em> → SPIR-V <strong>OriginLowerLeft</strong></p> 17569</li> 17570<li> 17571<p>special rules for locations for input doubles in the vertex shader</p> 17572</li> 17573<li> 17574<p><em>gl_VertexID</em> and <em>gl_InstanceID</em> (more detail follows)</p> 17575</li> 17576</ul> 17577</div> 17578<div class="paragraph"> 17579<p>The following features are added for both OpenGL and Vulkan:</p> 17580</div> 17581<div class="ulist"> 17582<ul> 17583<li> 17584<p>specialization constants</p> 17585</li> 17586<li> 17587<p><em>offset</em> can organize members in a different order than declaration order</p> 17588</li> 17589<li> 17590<p><em>offset</em> and <em>align</em> layout qualifiers for uniform/buffer blocks for 17591versions that did not support them</p> 17592</li> 17593</ul> 17594</div> 17595<div class="paragraph"> 17596<p>Vulkan Only: The following features are added:</p> 17597</div> 17598<div class="ulist"> 17599<ul> 17600<li> 17601<p>push-constant buffers</p> 17602</li> 17603<li> 17604<p>shader combining of separate textures and samplers (SPIR-V <strong>OpTypeSampler</strong>)</p> 17605</li> 17606<li> 17607<p>descriptor sets (<strong>DescriptorSet</strong> must be 0, if present)</p> 17608</li> 17609<li> 17610<p><em>gl_VertexIndex</em> and <em>gl_InstanceIndex</em></p> 17611</li> 17612<li> 17613<p>subpass-input targets and input attachments (<em>input_attachment_index</em>)</p> 17614</li> 17615</ul> 17616</div> 17617<div class="paragraph"> 17618<p>The following features are changed in both OpenGL and Vulkan:</p> 17619</div> 17620<div class="ulist"> 17621<ul> 17622<li> 17623<p><em>gl_FragColor</em> will no longer indicate an implicit broadcast</p> 17624</li> 17625</ul> 17626</div> 17627<div class="paragraph"> 17628<p>Vulkan Only: The following features are changed:</p> 17629</div> 17630<div class="ulist"> 17631<ul> 17632<li> 17633<p>precision qualifiers (<strong>mediump</strong> and <strong>lowp</strong>) will be respected for all 17634versions, not dropped for desktop versions (default precision for 17635desktop versions is <strong>highp</strong> for all types)</p> 17636</li> 17637<li> 17638<p>arrays of uniforms and buffer blocks take only one binding number for 17639the entire object, not one per array element</p> 17640</li> 17641<li> 17642<p>the default origin is <em>origin_upper_left</em> instead of <em>origin_lower_left</em></p> 17643</li> 17644</ul> 17645</div> 17646<div class="paragraph"> 17647<p>Vulkan does not allow multi-dimensional arrays of resources like 17648UBOs and SSBOs in its SPIR-V environment spec. SPIR-V supports 17649it and OpenGL already allows this for GLSL shaders. SPIR-V 17650for OpenGL also allows it.</p> 17651</div> 17652</div> 17653<div class="sect2"> 17654<h3 id="_mapping_from_glsl_to_spir_v">12.2. Mapping from GLSL to SPIR-V</h3> 17655<div class="sect3"> 17656<h4 id="_specialization_constants">12.2.1. Specialization Constants</h4> 17657<div class="paragraph"> 17658<p>SPIR-V specialization constants, which can be set later by the client API, 17659can be declared using <code>layout(constant_id=…​)</code>. For example, to make a 17660specialization constant with a default value of 12:</p> 17661</div> 17662<div class="literalblock"> 17663<div class="content"> 17664<pre>layout(constant_id = 17) const int arraySize = 12;</pre> 17665</div> 17666</div> 17667<div class="paragraph"> 17668<p>Above, <code>17</code> is the ID by which the API or other tools can later refer to 17669this specific specialization constant. The API or an intermediate tool can 17670then change its value to another constant integer before it is fully 17671lowered to executable code. If it is never changed before final lowering, 17672it will retain the value of 12.</p> 17673</div> 17674<div class="paragraph"> 17675<p>Specialization constants have const semantics, except they don’t fold. 17676Hence, an array can be declared with <code>arraySize</code> from above:</p> 17677</div> 17678<div class="literalblock"> 17679<div class="content"> 17680<pre>vec4 data[arraySize]; // legal, even though arraySize might change</pre> 17681</div> 17682</div> 17683<div class="paragraph"> 17684<p>Specialization constants can be in expressions:</p> 17685</div> 17686<div class="literalblock"> 17687<div class="content"> 17688<pre>vec4 data2[arraySize + 2];</pre> 17689</div> 17690</div> 17691<div class="paragraph"> 17692<p>This will make <code>data2</code> be sized by 2 more than whatever constant value 17693<code>arraySize</code> has when it is time to lower the shader to executable code.</p> 17694</div> 17695<div class="paragraph"> 17696<p>An expression formed with specialization constants also behaves in the 17697shader like a specialization constant, not a like a constant.</p> 17698</div> 17699<div class="literalblock"> 17700<div class="content"> 17701<pre>arraySize + 2 // a specialization constant (with no constant_id)</pre> 17702</div> 17703</div> 17704<div class="paragraph"> 17705<p>Such expressions can be used in the same places as a constant.</p> 17706</div> 17707<div class="paragraph"> 17708<p>The <em>constant_id</em> can only be applied to a scalar integer, a scalar floating-point 17709or a scalar Boolean.</p> 17710</div> 17711<div class="paragraph"> 17712<p>Only basic operators and constructors can be applied to a specialization 17713constant and still result in a specialization constant:</p> 17714</div> 17715<div class="literalblock"> 17716<div class="content"> 17717<pre>layout(constant_id = 17) const int arraySize = 12; 17718sin(float(arraySize)); // result is not a specialization constant</pre> 17719</div> 17720</div> 17721<div class="paragraph"> 17722<p>While SPIR-V specialization constants are only for scalars, a vector 17723can be made by operations on scalars:</p> 17724</div> 17725<div class="literalblock"> 17726<div class="content"> 17727<pre>layout(constant_id = 18) const int scX = 1; 17728layout(constant_id = 19) const int scZ = 1; 17729const vec3 scVec = vec3(scX, 1, scZ); // partially specialized vector</pre> 17730</div> 17731</div> 17732<div class="paragraph"> 17733<p>A built-in variable can have a <em>constant_id</em> attached to it:</p> 17734</div> 17735<div class="literalblock"> 17736<div class="content"> 17737<pre>layout(constant_id = 18) gl_MaxImageUnits;</pre> 17738</div> 17739</div> 17740<div class="paragraph"> 17741<p>This makes it behave as a specialization constant. It is not a full 17742redeclaration; all other characteristics are left intact from the 17743original built-in declaration.</p> 17744</div> 17745<div class="paragraph"> 17746<p>The built-in vector <em>gl_WorkGroupSize</em> can be specialized using special 17747layout <code>local_size_{xyz}_id</code> applied to the <strong>in</strong> qualifier. For example:</p> 17748</div> 17749<div class="literalblock"> 17750<div class="content"> 17751<pre>layout(local_size_x_id = 18, local_size_z_id = 19) in;</pre> 17752</div> 17753</div> 17754<div class="paragraph"> 17755<p>This leaves <em>gl_WorkGroupSize.y</em> as a non-specialization constant, with 17756<em>gl_WorkGroupSize</em> being a partially specialized vector. Its <em>x</em> and <em>z</em> 17757components can be later specialized using the ID’s 18 and 19.</p> 17758</div> 17759</div> 17760<div class="sect3"> 17761<h4 id="_vulkan_only_push_constants">12.2.2. Vulkan Only: Push Constants</h4> 17762<div class="paragraph"> 17763<p>Push constants reside in a uniform block declared using the new 17764layout-qualifier-id <em>push_constant</em> applied to a uniform-block declaration. 17765The API writes a set of constants to a push-constant buffer, and the shader 17766reads them from a <em>push_constant</em> block:</p> 17767</div> 17768<div class="literalblock"> 17769<div class="content"> 17770<pre>layout(push_constant) uniform BlockName { 17771 int member1; 17772 float member2; 17773 ... 17774} InstanceName; // optional instance name 17775... = InstanceName.member2; // read a push constant</pre> 17776</div> 17777</div> 17778<div class="paragraph"> 17779<p>The memory accounting used for the <em>push_constant</em> uniform block is different 17780than for other uniform blocks: There is a separate small pool of memory 17781it must fit within. By default, a <em>push_constant</em> buffer follows the std430 17782packing rules.</p> 17783</div> 17784</div> 17785<div class="sect3"> 17786<h4 id="_vulkan_only_descriptor_sets">12.2.3. Vulkan Only: Descriptor Sets</h4> 17787<div class="paragraph"> 17788<p>Each shader resource in a descriptor set is assigned a tuple of (set 17789number, binding number, array element) that defines its location within 17790a descriptor set layout. 17791In GLSL, the set number and binding number are assigned via the <em>set</em> 17792and <em>binding</em> layout qualifiers respectively, and the array element is 17793implicitly assigned consecutively starting with index equal to zero for 17794the first element of an array (and array element is zero for non-array 17795variables):</p> 17796</div> 17797<div class="literalblock"> 17798<div class="content"> 17799<pre>// Assign set number = M, binding number = N, array element = 0 17800layout (set=M, binding=N) uniform sampler2D variableName;</pre> 17801</div> 17802</div> 17803<div class="literalblock"> 17804<div class="content"> 17805<pre>// Assign set number = M, binding number = N for all array elements, 17806// and array element = i for the ith member of an array of size I. 17807layout (set=M, binding=N) uniform sampler2D variableNameArray[I];</pre> 17808</div> 17809</div> 17810<div class="paragraph"> 17811<p>For example, two combined texture/sampler objects can be declared in two 17812different descriptor sets as follows</p> 17813</div> 17814<div class="literalblock"> 17815<div class="content"> 17816<pre>layout(set = 0, binding = 0) uniform sampler2D ts3; 17817layout(set = 1, binding = 0) uniform sampler2D ts4;</pre> 17818</div> 17819</div> 17820<div class="paragraph"> 17821<p>See the API documentation for more detail on the operation model of 17822descriptor sets.</p> 17823</div> 17824</div> 17825<div class="sect3"> 17826<h4 id="_vulkan_only_samplers_images_textures_and_buffers">12.2.4. Vulkan Only: Samplers, Images, Textures, and Buffers</h4> 17827<div class="sect4"> 17828<h5 id="_storage_images">Storage Images</h5> 17829<div class="paragraph"> 17830<p>Storage images are declared in GLSL shader source using uniform image 17831variables of the appropriate dimensionality as well as a format layout 17832qualifier (if necessary):</p> 17833</div> 17834<div class="literalblock"> 17835<div class="content"> 17836<pre>layout (set=m, binding=n, r32f) uniform image2D myStorageImage;</pre> 17837</div> 17838</div> 17839<div class="paragraph"> 17840<p>Which maps to the following SPIR-V:</p> 17841</div> 17842<div class="literalblock"> 17843<div class="content"> 17844<pre> ... 17845%1 = OpExtInstImport "GLSL.std.450" 17846 ... 17847 OpName %9 "myStorageImage" 17848 OpDecorate %9 DescriptorSet m 17849 OpDecorate %9 Binding n 17850%2 = OpTypeVoid 17851%3 = OpTypeFunction %2 17852%6 = OpTypeFloat 32 17853%7 = OpTypeImage %6 2D 0 0 0 2 R32f 17854%8 = OpTypePointer UniformConstant %7 17855%9 = OpVariable %8 UniformConstant 17856 ...</pre> 17857</div> 17858</div> 17859</div> 17860<div class="sect4"> 17861<h5 id="_samplers">Samplers</h5> 17862<div class="paragraph"> 17863<p>SPIR-V samplers are declared in GLSL shader source using uniform <strong>sampler</strong> and 17864<strong>samplerShadow</strong> types:</p> 17865</div> 17866<div class="literalblock"> 17867<div class="content"> 17868<pre>layout (set=m, binding=n) uniform sampler mySampler;</pre> 17869</div> 17870</div> 17871<div class="paragraph"> 17872<p>Which maps to the following SPIR-V:</p> 17873</div> 17874<div class="literalblock"> 17875<div class="content"> 17876<pre> ... 17877%1 = OpExtInstImport "GLSL.std.450" 17878 ... 17879 OpName %8 "mySampler" 17880 OpDecorate %8 DescriptorSet m 17881 OpDecorate %8 Binding n 17882%2 = OpTypeVoid 17883%3 = OpTypeFunction %2 17884%6 = OpTypeSampler 17885%7 = OpTypePointer UniformConstant %6 17886%8 = OpVariable %7 UniformConstant 17887 ...</pre> 17888</div> 17889</div> 17890</div> 17891<div class="sect4"> 17892<h5 id="_textures_sampled_images">Textures (Sampled Images)</h5> 17893<div class="paragraph"> 17894<p>Textures are declared in GLSL shader source using uniform texture 17895variables of the appropriate dimensionality:</p> 17896</div> 17897<div class="literalblock"> 17898<div class="content"> 17899<pre>layout (set=m, binding=n) uniform texture2D mySampledImage;</pre> 17900</div> 17901</div> 17902<div class="paragraph"> 17903<p>Which maps to the following SPIR-V:</p> 17904</div> 17905<div class="literalblock"> 17906<div class="content"> 17907<pre> ... 17908%1 = OpExtInstImport "GLSL.std.450" 17909 ... 17910 OpName %9 "mySampledImage" 17911 OpDecorate %9 DescriptorSet m 17912 OpDecorate %9 Binding n 17913%2 = OpTypeVoid 17914%3 = OpTypeFunction %2 17915%6 = OpTypeFloat 32 17916%7 = OpTypeImage %6 2D 0 0 0 1 Unknown 17917%8 = OpTypePointer UniformConstant %7 17918%9 = OpVariable %8 UniformConstant 17919 ...</pre> 17920</div> 17921</div> 17922</div> 17923<div class="sect4"> 17924<h5 id="_combined_texture_and_samplers">Combined Texture and Samplers</h5> 17925<div class="paragraph"> 17926<p>Combined textures and samplers are declared in GLSL shader source using 17927uniform texture-combined sampler variables of the appropriate dimensionality:</p> 17928</div> 17929<div class="literalblock"> 17930<div class="content"> 17931<pre>layout (set=m, binding=n) uniform sampler2D myCombinedImageSampler;</pre> 17932</div> 17933</div> 17934<div class="paragraph"> 17935<p>Which maps to the following SPIR-V:</p> 17936</div> 17937<div class="literalblock"> 17938<div class="content"> 17939<pre> ... 17940%1 = OpExtInstImport "GLSL.std.450" 17941 ... 17942 OpName %10 "myCombinedImageSampler" 17943 OpDecorate %10 DescriptorSet m 17944 OpDecorate %10 Binding n 17945%2 = OpTypeVoid 17946%3 = OpTypeFunction %2 17947%6 = OpTypeFloat 32 17948%7 = OpTypeImage %6 2D 0 0 0 1 Unknown 17949%8 = OpTypeSampledImage %7 17950%9 = OpTypePointer UniformConstant %8 17951%10 = OpVariable %9 UniformConstant 17952 ...</pre> 17953</div> 17954</div> 17955<div class="paragraph"> 17956<p>Note that a combined image sampler descriptor can be referred to as just 17957an image or sampler in the shader as per the above sections.</p> 17958</div> 17959</div> 17960<div class="sect4"> 17961<h5 id="_combining_separate_samplers_and_textures">Combining Separate Samplers and Textures</h5> 17962<div class="paragraph"> 17963<p>A sampler, declared with the keyword <strong>sampler</strong>, contains just filtering 17964information, containing neither a texture nor an image:</p> 17965</div> 17966<div class="literalblock"> 17967<div class="content"> 17968<pre>uniform sampler s; // a handle to filtering information</pre> 17969</div> 17970</div> 17971<div class="paragraph"> 17972<p>A texture, declared with keywords like <strong>texture2D</strong>, contains just image 17973information, not filtering information:</p> 17974</div> 17975<div class="literalblock"> 17976<div class="content"> 17977<pre>uniform texture2D t; // a handle to a texture (an image in SPIR-V)</pre> 17978</div> 17979</div> 17980<div class="paragraph"> 17981<p>Constructors can then be used to combine a sampler and a texture at the 17982point of making a texture lookup call:</p> 17983</div> 17984<div class="literalblock"> 17985<div class="content"> 17986<pre>texture(sampler2D(t, s), ...);</pre> 17987</div> 17988</div> 17989<div class="paragraph"> 17990<p>Note, <code>layout()</code> information is omitted above for clarity of this feature.</p> 17991</div> 17992</div> 17993<div class="sect4"> 17994<h5 id="_texture_buffers_uniform_texel_buffers">Texture Buffers (Uniform Texel Buffers)</h5> 17995<div class="paragraph"> 17996<p>Texture buffers are declared in GLSL shader source using uniform 17997textureBuffer variables:</p> 17998</div> 17999<div class="literalblock"> 18000<div class="content"> 18001<pre>layout (set=m, binding=n) uniform textureBuffer myUniformTexelBuffer;</pre> 18002</div> 18003</div> 18004<div class="paragraph"> 18005<p>Which maps to the following SPIR-V:</p> 18006</div> 18007<div class="literalblock"> 18008<div class="content"> 18009<pre> ... 18010%1 = OpExtInstImport "GLSL.std.450" 18011 ... 18012 OpName %9 "myUniformTexelBuffer" 18013 OpDecorate %9 DescriptorSet m 18014 OpDecorate %9 Binding n 18015%2 = OpTypeVoid 18016%3 = OpTypeFunction %2 18017%6 = OpTypeFloat 32 18018%7 = OpTypeImage %6 Buffer 0 0 0 1 Unknown 18019%8 = OpTypePointer UniformConstant %7 18020%9 = OpVariable %8 UniformConstant 18021 ...</pre> 18022</div> 18023</div> 18024</div> 18025<div class="sect4"> 18026<h5 id="_image_buffers_storage_texel_buffers">Image Buffers (Storage Texel Buffers)</h5> 18027<div class="paragraph"> 18028<p>Image buffers are declared in GLSL shader source using uniform 18029imageBuffer variables:</p> 18030</div> 18031<div class="literalblock"> 18032<div class="content"> 18033<pre>layout (set=m, binding=n, r32f) uniform imageBuffer myStorageTexelBuffer;</pre> 18034</div> 18035</div> 18036<div class="paragraph"> 18037<p>Which maps to the following SPIR-V:</p> 18038</div> 18039<div class="literalblock"> 18040<div class="content"> 18041<pre> ... 18042%1 = OpExtInstImport "GLSL.std.450" 18043 ... 18044 OpName %9 "myStorageTexelBuffer" 18045 OpDecorate %9 DescriptorSet m 18046 OpDecorate %9 Binding n 18047%2 = OpTypeVoid 18048%3 = OpTypeFunction %2 18049%6 = OpTypeFloat 32 18050%7 = OpTypeImage %6 Buffer 0 0 0 2 R32f 18051%8 = OpTypePointer UniformConstant %7 18052%9 = OpVariable %8 UniformConstant 18053 ...</pre> 18054</div> 18055</div> 18056</div> 18057<div class="sect4"> 18058<h5 id="_storage_buffers">Storage Buffers</h5> 18059<div class="paragraph"> 18060<p>Storage buffers are declared in GLSL shader source using buffer storage 18061qualifier and block syntax:</p> 18062</div> 18063<div class="literalblock"> 18064<div class="content"> 18065<pre>layout (set=m, binding=n) buffer myStorageBuffer 18066{ 18067 vec4 myElement[]; 18068};</pre> 18069</div> 18070</div> 18071<div class="paragraph"> 18072<p>Which maps to the following SPIR-V:</p> 18073</div> 18074<div class="literalblock"> 18075<div class="content"> 18076<pre> ... 18077%1 = OpExtInstImport "GLSL.std.450" 18078 ... 18079 OpName %9 "myStorageBuffer" 18080 OpMemberName %9 0 "myElement" 18081 OpName %11 "" 18082 OpDecorate %8 ArrayStride 16 18083 OpMemberDecorate %9 0 Offset 0 18084 OpDecorate %9 BufferBlock 18085 OpDecorate %11 DescriptorSet m 18086 OpDecorate %11 Binding n 18087%2 = OpTypeVoid 18088%3 = OpTypeFunction %2 18089%6 = OpTypeFloat 32 18090%7 = OpTypeVector %6 4 18091%8 = OpTypeRuntimeArray %7 18092%9 = OpTypeStruct %8 18093%10 = OpTypePointer Uniform %9 18094%11 = OpVariable %10 Uniform 18095 ...</pre> 18096</div> 18097</div> 18098</div> 18099<div class="sect4"> 18100<h5 id="_uniform_buffers">Uniform Buffers</h5> 18101<div class="paragraph"> 18102<p>Uniform buffers are declared in GLSL shader source using the uniform storage 18103qualifier and block syntax:</p> 18104</div> 18105<div class="literalblock"> 18106<div class="content"> 18107<pre>layout (set=m, binding=n) uniform myUniformBuffer 18108{ 18109 vec4 myElement[32]; 18110};</pre> 18111</div> 18112</div> 18113<div class="paragraph"> 18114<p>Which maps to the following SPIR-V:</p> 18115</div> 18116<div class="literalblock"> 18117<div class="content"> 18118<pre> ... 18119%1 = OpExtInstImport "GLSL.std.450" 18120 ... 18121 OpName %11 "myUniformBuffer" 18122 OpMemberName %11 0 "myElement" 18123 OpName %13 "" 18124 OpDecorate %10 ArrayStride 16 18125 OpMemberDecorate %11 0 Offset 0 18126 OpDecorate %11 Block 18127 OpDecorate %13 DescriptorSet m 18128 OpDecorate %13 Binding n 18129%2 = OpTypeVoid 18130%3 = OpTypeFunction %2 18131%6 = OpTypeFloat 32 18132%7 = OpTypeVector %6 4 18133%8 = OpTypeInt 32 0 18134%9 = OpConstant %8 32 18135%10 = OpTypeArray %7 %9 18136%11 = OpTypeStruct %10 18137%12 = OpTypePointer Uniform %11 18138%13 = OpVariable %12 Uniform 18139 ...</pre> 18140</div> 18141</div> 18142</div> 18143<div class="sect4"> 18144<h5 id="_subpass_inputs_2">Subpass Inputs</h5> 18145<div class="paragraph"> 18146<p>Within a rendering pass, a subpass can write results to an output target 18147that can then be read by the next subpass as an input subpass. The 18148"Subpass Input" feature regards the ability to read an output target.</p> 18149</div> 18150<div class="paragraph"> 18151<p>Subpass inputs are read through a new set of types, available only 18152to fragment shaders:</p> 18153</div> 18154<div class="literalblock"> 18155<div class="content"> 18156<pre>subpassInput 18157subpassInputMS 18158isubpassInput 18159isubpassInputMS 18160usubpassInput 18161usubpassInputMS</pre> 18162</div> 18163</div> 18164<div class="paragraph"> 18165<p>Unlike sampler and image objects, subpass inputs are implicitly addressed 18166by the fragment’s (<em>x</em>, <em>y</em>, <em>layer</em>) coordinate.</p> 18167</div> 18168<div class="paragraph"> 18169<p>Input attachments are decorated with their input attachment index in 18170addition to descriptor set and binding numbers.</p> 18171</div> 18172<div class="literalblock"> 18173<div class="content"> 18174<pre>layout (input_attachment_index=i, set=m, binding=n) uniform subpassInput myInputAttachment;</pre> 18175</div> 18176</div> 18177<div class="paragraph"> 18178<p>Which maps to the following SPIR-V:</p> 18179</div> 18180<div class="literalblock"> 18181<div class="content"> 18182<pre> ... 18183%1 = OpExtInstImport "GLSL.std.450" 18184 ... 18185 OpName %9 "myInputAttachment" 18186 OpDecorate %9 DescriptorSet m 18187 OpDecorate %9 Binding n 18188 OpDecorate %9 InputAttachmentIndex i 18189%2 = OpTypeVoid 18190%3 = OpTypeFunction %2 18191%6 = OpTypeFloat 32 18192%7 = OpTypeImage %6 SubpassData 0 0 0 2 Unknown 18193%8 = OpTypePointer UniformConstant %7 18194%9 = OpVariable %8 UniformConstant 18195 ...</pre> 18196</div> 18197</div> 18198<div class="paragraph"> 18199<p>An <em>input_attachment_index</em> of i selects the ith entry in the input pass 18200list. (See API specification for more information.)</p> 18201</div> 18202<div class="paragraph"> 18203<p>These objects support reading the subpass input through the following 18204functions:</p> 18205</div> 18206<div class="literalblock"> 18207<div class="content"> 18208<pre>gvec4 subpassLoad(gsubpassInput subpass); 18209gvec4 subpassLoad(gsubpassInputMS subpass, int sample);</pre> 18210</div> 18211</div> 18212</div> 18213</div> 18214<div class="sect3"> 18215<h4 id="_mapping_variables">12.2.5. Mapping Variables</h4> 18216<div class="sect4"> 18217<h5 id="_gl_fragcolor"><em>gl_FragColor</em></h5> 18218<div class="paragraph"> 18219<p>The fragment-stage built-in <em>gl_FragColor</em>, which implies a broadcast to all 18220outputs, is not present in SPIR-V. Shaders where writing to <em>gl_FragColor</em> 18221is allowed can still write to it, but it only means to write to an output:</p> 18222</div> 18223<div class="ulist"> 18224<ul> 18225<li> 18226<p>of the same type as <em>gl_FragColor</em></p> 18227</li> 18228<li> 18229<p>decorated with location 0</p> 18230</li> 18231<li> 18232<p>not decorated as a built-in variable.</p> 18233</li> 18234</ul> 18235</div> 18236<div class="paragraph"> 18237<p>There is no implicit broadcast.</p> 18238</div> 18239</div> 18240<div class="sect4"> 18241<h5 id="_vulkan_gl_vertexindex_and_gl_instanceindex">Vulkan <em>gl_VertexIndex</em> and <em>gl_InstanceIndex</em></h5> 18242<div class="paragraph"> 18243<p>Adds two new built-in variables, <em>gl_VertexIndex</em> and <em>gl_InstanceIndex</em> to 18244replace the existing built-in variables <em>gl_VertexID</em> and <em>gl_InstanceID</em>.</p> 18245</div> 18246<div class="paragraph"> 18247<p>In the situations where the indexing is relative to some base offset, 18248these built-in variables are defined, for Vulkan, to take on values as 18249follows:</p> 18250</div> 18251<div class="literalblock"> 18252<div class="content"> 18253<pre>gl_VertexIndex base, base+1, base+2, ... 18254gl_InstanceIndex base, base+1, base+2, ...</pre> 18255</div> 18256</div> 18257<div class="paragraph"> 18258<p>Where it depends on the situation what the base actually is.</p> 18259</div> 18260</div> 18261<div class="sect4"> 18262<h5 id="_storage_classes">Storage Classes:</h5> 18263<div class="literalblock"> 18264<div class="content"> 18265<pre>uniform sampler2D...; -> UniformConstant 18266uniform blockN { ... } ...; -> Uniform, with Block decoration 18267in / out variable -> Input/Output, possibly with block (below) 18268in / out block... -> Input/Output, with Block decoration 18269buffer blockN { ... } ...; -> Uniform, with BufferBlock decoration 18270shared -> Workgroup 18271<normal global> -> Private</pre> 18272</div> 18273</div> 18274<div class="literalblock"> 18275<div class="content"> 18276<pre>Vulkan Only: buffer blockN { ... } ...; -> StorageBuffer, when requested 18277OpenGL Only: uniform variable (non-block) -> UniformConstant 18278OpenGL Only: ... uniform atomic_uint ... -> AtomicCounter</pre> 18279</div> 18280</div> 18281</div> 18282<div class="sect4"> 18283<h5 id="_inputoutput">Input/Output</h5> 18284<div class="paragraph"> 18285<p>Mapping of input/output blocks or variables is the same for all versions 18286of GLSL or ESSL. To the extent variables or members are available in a 18287version, its location is as follows:</p> 18288</div> 18289<div class="paragraph"> 18290<p>These are mapped to SPIR-V individual variables, with similarly spelled 18291built-in decorations (except as noted):</p> 18292</div> 18293<div class="paragraph"> 18294<p>Any stage:</p> 18295</div> 18296<div class="literalblock"> 18297<div class="content"> 18298<pre>in gl_VertexIndex (Vulkan only) 18299in gl_VertexID (OpenGL only) 18300in gl_InstanceIndex (Vulkan only) 18301in gl_InstanceID (OpenGL only) 18302in gl_InvocationID 18303in gl_PatchVerticesIn (PatchVertices) 18304in gl_PrimitiveIDIn (PrimitiveID) 18305in/out gl_PrimitiveID (in/out based only on storage qualifier) 18306in gl_TessCoord</pre> 18307</div> 18308</div> 18309<div class="literalblock"> 18310<div class="content"> 18311<pre>in/out gl_Layer 18312in/out gl_ViewportIndex</pre> 18313</div> 18314</div> 18315<div class="literalblock"> 18316<div class="content"> 18317<pre>patch in/out gl_TessLevelOuter (uses Patch decoration) 18318patch in/out gl_TessLevelInner (uses Patch decoration)</pre> 18319</div> 18320</div> 18321<div class="paragraph"> 18322<p>Compute stage only:</p> 18323</div> 18324<div class="literalblock"> 18325<div class="content"> 18326<pre>in gl_NumWorkGroups 18327in gl_WorkGroupSize 18328in gl_WorkGroupID 18329in gl_LocalInvocationID 18330in gl_GlobalInvocationID 18331in gl_LocalInvocationIndex</pre> 18332</div> 18333</div> 18334<div class="paragraph"> 18335<p>Fragment stage only:</p> 18336</div> 18337<div class="literalblock"> 18338<div class="content"> 18339<pre>in gl_FragCoord 18340in gl_FrontFacing 18341in gl_ClipDistance 18342in gl_CullDistance 18343in gl_PointCoord 18344in gl_SampleID 18345in gl_SamplePosition 18346in gl_HelperInvocation 18347out gl_FragDepth 18348in gl_SampleMaskIn (SampleMask) 18349out gl_SampleMask (in/out based only on storage qualifier)</pre> 18350</div> 18351</div> 18352<div class="paragraph"> 18353<p>These are mapped to SPIR-V blocks, as implied by the pseudo code, with 18354the members decorated with similarly spelled built-in decorations:</p> 18355</div> 18356<div class="paragraph"> 18357<p>Non-fragment stage:</p> 18358</div> 18359<div class="literalblock"> 18360<div class="content"> 18361<pre>in/out gl_PerVertex { // some subset of these members will be used 18362 gl_Position 18363 gl_PointSize 18364 gl_ClipDistance 18365 gl_CullDistance 18366} // name of block is for debug only</pre> 18367</div> 18368</div> 18369<div class="paragraph"> 18370<p>There is at most one input and one output block per stage in SPIR-V. 18371The subset and order of members will match between stages sharing an 18372interface.</p> 18373</div> 18374</div> 18375</div> 18376<div class="sect3"> 18377<h4 id="_vulkan_only_mapping_of_precision_qualifiers">12.2.6. Vulkan Only: Mapping of Precision Qualifiers</h4> 18378<div class="literalblock"> 18379<div class="content"> 18380<pre>lowp -> RelaxedPrecision, on storage variable and operation 18381mediump -> RelaxedPrecision, on storage variable and operation 18382highp -> 32-bit, same as int or float</pre> 18383</div> 18384</div> 18385<div class="literalblock"> 18386<div class="content"> 18387<pre>portability tool/mode -> OpQuantizeToF16</pre> 18388</div> 18389</div> 18390</div> 18391<div class="sect3"> 18392<h4 id="_mapping_of_precise">12.2.7. Mapping of <strong>precise</strong>:</h4> 18393<div class="literalblock"> 18394<div class="content"> 18395<pre>precise -> NoContraction</pre> 18396</div> 18397</div> 18398</div> 18399<div class="sect3"> 18400<h4 id="_opengl_mapping_of_atomic_uint_offset_layout_qualifier">12.2.8. OpenGL Mapping of <strong>atomic_uint</strong> <em>offset</em> layout qualifier</h4> 18401<div class="literalblock"> 18402<div class="content"> 18403<pre>offset -> Offset (decoration)</pre> 18404</div> 18405</div> 18406</div> 18407<div class="sect3"> 18408<h4 id="_mapping_of_images">12.2.9. Mapping of Images</h4> 18409<div class="literalblock"> 18410<div class="content"> 18411<pre>imageLoad() -> OpImageRead 18412imageStore() -> OpImageWrite 18413texelFetch() -> OpImageFetch 18414subpassInput -> OpTypeImage with Dim of SubpassData (Vulkan only) 18415subpassLoad() -> OpImageRead (Vulkan only)</pre> 18416</div> 18417</div> 18418<div class="literalblock"> 18419<div class="content"> 18420<pre>imageAtomicXXX(params, data) -> %ptr = OpImageTexelPointer params 18421 OpAtomicXXX %ptr, data</pre> 18422</div> 18423</div> 18424<div class="literalblock"> 18425<div class="content"> 18426<pre>XXXQueryXXX(combined) -> %image = OpImage combined 18427 OpXXXQueryXXX %image</pre> 18428</div> 18429</div> 18430</div> 18431<div class="sect3"> 18432<h4 id="_mapping_of_layouts">12.2.10. Mapping of Layouts</h4> 18433<div class="literalblock"> 18434<div class="content"> 18435<pre>std140/std430 -> explicit Offset, ArrayStride, and MatrixStride 18436 Decoration on struct members 18437shared/packed -> not allowed 18438<default> -> not shared, but std140 or std430 18439xfb_offset -> Offset Decoration on the object or struct member 18440xfb_buffer -> XfbBuffer Decoration on the object 18441xfb_stride -> XfbStride Decoration on the object 18442any xfb_* -> the Xfb Execution Mode is set 18443captured XFB -> has both XfbBuffer and Offset 18444non-captured -> lacking XfbBuffer or Offset</pre> 18445</div> 18446</div> 18447<div class="literalblock"> 18448<div class="content"> 18449<pre>max_vertices -> OutputVertices</pre> 18450</div> 18451</div> 18452</div> 18453<div class="sect3"> 18454<h4 id="_mapping_of_barriers">12.2.11. Mapping of barriers</h4> 18455<div class="literalblock"> 18456<div class="content"> 18457<pre>barrier() (compute) -> OpControlBarrier(/*Execution*/Workgroup, 18458 /*Memory*/Workgroup, 18459 /*Semantics*/AcquireRelease | 18460 WorkgroupMemory)</pre> 18461</div> 18462</div> 18463<div class="literalblock"> 18464<div class="content"> 18465<pre>barrier() (tess control) -> OpControlBarrier(/*Execution*/Workgroup, 18466 /*Memory*/Invocation, 18467 /*Semantics*/None)</pre> 18468</div> 18469</div> 18470<div class="literalblock"> 18471<div class="content"> 18472<pre>memoryBarrier() -> OpMemoryBarrier(/*Memory*/Device, 18473 /*Semantics*/AcquireRelease | 18474 UniformMemory | 18475 WorkgroupMemory | 18476 ImageMemory)</pre> 18477</div> 18478</div> 18479<div class="literalblock"> 18480<div class="content"> 18481<pre>memoryBarrierBuffer() -> OpMemoryBarrier(/*Memory*/Device, 18482 /*Semantics*/AcquireRelease | 18483 UniformMemory)</pre> 18484</div> 18485</div> 18486<div class="literalblock"> 18487<div class="content"> 18488<pre>memoryBarrierShared() -> OpMemoryBarrier(/*Memory*/Device, 18489 /*Semantics*/AcquireRelease | 18490 WorkgroupMemory)</pre> 18491</div> 18492</div> 18493<div class="literalblock"> 18494<div class="content"> 18495<pre>memoryBarrierImage() -> OpMemoryBarrier(/*Memory*/Device, 18496 /*Semantics*/AcquireRelease | 18497 ImageMemory)</pre> 18498</div> 18499</div> 18500<div class="literalblock"> 18501<div class="content"> 18502<pre>groupMemoryBarrier() -> OpMemoryBarrier(/*Memory*/Workgroup, 18503 /*Semantics*/AcquireRelease | 18504 UniformMemory | 18505 WorkgroupMemory | 18506 ImageMemory)</pre> 18507</div> 18508</div> 18509</div> 18510<div class="sect3"> 18511<h4 id="_mapping_of_atomics">12.2.12. Mapping of atomics</h4> 18512<div class="literalblock"> 18513<div class="content"> 18514<pre>all atomic builtin functions -> Semantics = None(Relaxed)</pre> 18515</div> 18516</div> 18517<div class="literalblock"> 18518<div class="content"> 18519<pre>atomicExchange() -> OpAtomicExchange 18520imageAtomicExchange() -> OpAtomicExchange 18521atomicCompSwap() -> OpAtomicCompareExchange 18522imageAtomicCompSwap() -> OpAtomicCompareExchange 18523N/A -> OpAtomicCompareExchangeWeak</pre> 18524</div> 18525</div> 18526</div> 18527<div class="sect3"> 18528<h4 id="_opengl_only_mapping_of_atomics">12.2.13. OpenGL Only: Mapping of Atomics</h4> 18529<div class="literalblock"> 18530<div class="content"> 18531<pre>atomicCounterIncrement -> OpAtomicIIncrement 18532atomicCounterDecrement -> OpAtomicIDecrement 18533atomicCounter -> OpAtomicLoad</pre> 18534</div> 18535</div> 18536</div> 18537<div class="sect3"> 18538<h4 id="_mapping_of_other_instructions">12.2.14. Mapping of other instructions</h4> 18539<div class="literalblock"> 18540<div class="content"> 18541<pre>% -> OpUMod/OpSMod 18542mod() -> OpFMod 18543N/A -> OpSRem/OpFRem</pre> 18544</div> 18545</div> 18546<div class="literalblock"> 18547<div class="content"> 18548<pre>pack/unpack (conversion) -> pack/unpack in GLSL extended instructions 18549pack/unpack (no conversion) -> OpBitcast</pre> 18550</div> 18551</div> 18552</div> 18553</div> 18554</div> 18555</div> 18556</div> 18557<div id="footer"> 18558<div id="footer-text"> 18559Version 4.60.7<br> 18560Last updated 2019-07-10 14:42:53 MDT 18561</div> 18562</div> 18563 18564<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.4/MathJax.js?config=TeX-MML-AM_HTMLorMML"></script> 18565</body> 18566</html>