xref: /third_party/openGLES/extensions/NV/NV_shadow_samplers_array.txt

Name

    NV_shadow_samplers_array

Name Strings

    GL_NV_shadow_samplers_array

Contributors

    Mathias Heyer, NVIDIA
    Greg Roth, NVIDIA

Contacts

    Greg Roth, NVIDIA (groth 'at' nvidia 'dot' com)

Status

    Complete

Version

    Date: Aug 30, 2012
    Revision: 4

Number

    OpenGL ES Extension #146

Dependencies

    Requires OpenGL ES 2.0.

    Written based on the wording of the OpenGL ES 2.0.25 Specification.

    Written based on the wording of The OpenGL ES Shading Language
    1.00.14 Specification.

    Requires NV_texture_array and EXT_shadow_samplers.

Overview

    This extension expands the shadow map capability described in
    EXT_shadow_samplers to include support for shadow samplers of 2D
    array textures.

New Procedures and Functions

    None

New Tokens

    Returned in <type> by glGetActiveUniform:

        GL_SAMPLER_2D_ARRAY_SHADOW_NV                   0x8DC4

New GLSL defines

    #define GL_NV_shadow_samplers_array 1

New GLSL sampler types

    sampler2DArrayShadowNV

New GLSL functions

    float shadow2DArrayNV(sampler2DArrayShadowNV sampler, vec4 coord);

Additions to Chapter 2 of the OpenGL ES 2.0.25 Specification (OpenGL ES
Operation)

    Modify Section 2.10.4 (Shader Variables)

    In the final sentence on p. 36 add "SAMPLER_2D_ARRAY_SHADOW_NV" to
    the list of types that can be returned in the <type> parameter of
    GetActiveUniform.

Additions to OpenGL ES Shading Language 1.00.14 Specification

    Modify Section 4.1, (Basic Types):

    Append the following row to the unnamed table in section 4.1

    Type                  Meaning
    ---------------       ---------------------------------------------------------
    sampler2DArrayShadowNV  a handle for accessing a 2D array depth texture with comparison

    Modify section 4.5.3 (Default Precision Qualifiers):

    Add to the list of predeclared globally scoped default precision
    statements:

    "precision lowp sampler2DArrayShadowNV;"

    Modify section 8.7 (Texture Lookup Functions):

    Add the following new texture lookup function:

    The built-in texture lookup function shadow2DArrayNV is optional,
    and must be enabled by

    #extension GL_NV_shadow_samplers_array : enable

    before being used.

    Syntax:

      float shadow2DArrayNV(sampler2DArrayShadowNV sampler, vec4 coord)

    Description:

    Use texture coordinate (coord.s, coord.t) to do a depth comparison
    lookup on an array layer of the depth texture bound to sampler, as
    described in section 3.7.14.1. The layer to access is indicated by
    the third coordinate (coord.p) and is computed by layer = max (0,
    min(d - 1, floor (coord.p + 0.5)) where 'd' is the depth of the
    texture array. The fourth component of coord (coord.q) is used as
    the R value. The texture bound to sampler must be a depth texture,
    or results are undefined.

Issues

    (1) Should the result of the texture comparison be interpreted as
    a LUMINANCE, INTENSITY or ALPHA texel?

    RESOLVED: A scalar value is returned from the shadow lookup built-in
    function in the fragment shader, so it can be interpreted however
    desired.

Revision History

    Rev.    Date        Author      Changes
    ----  ------------- ---------   ----------------------------------------
     4    30 Aug 2012    groth      Added missing NV suffixes. Corrected a dependency
     3    28 Aug 2012    groth      Minor copy edits
     2    19 Aug 2012    groth      Correct dependency and GLSL enable
     1    12 Aug 2012    groth      Initial GLES2 version from EXT_gpu_shader4.