xref: /third_party/openGLES/extensions/NV/NV_deep_texture3D.txt

Name

    NV_deep_texture3D

Name Strings

    GL_NV_deep_texture3D

Contact

    Eric Werness, NVIDIA Corporation (ewerness 'at' nvidia.com)

Status

    Shipping.

Version

    Last Modified Date:         April 12, 2010
    Revision:                   1

Number

    424

Dependencies

    This extension is written against the OpenGL 3.2 specification (Core
    Profile).

Overview

    Some applications require 3D textures that have a significant number of
    slices, but less resolution in width and height. In the current spec, the
    maximum value for the size of all three dimensions is specified by a
    single value. This extension adds a second set of limits against which 3D
    textures can be checked if an application needs deeper textures than would
    be allowed by the symmetric texture limits.

New Procedures and Functions

    None

New Tokens

    Accepted by the <pname> parameter of GetBooleanv, GetDoublev, GetIntegerv
    and GetFloatv:

        MAX_DEEP_3D_TEXTURE_WIDTH_HEIGHT_NV              0x90D0
        MAX_DEEP_3D_TEXTURE_DEPTH_NV                     0x90D1

Additions to Chapter 2 of the OpenGL 3.2 Specification (OpenGL Operation)

    None

Additions to Chapter 3 of the OpenGL 3.2 Specification (Rasterization)

    (modify 3.8.1 Texture Image Specification on p. 141

    (add to the discussion of the maximum allowable size of a 3D texture)

    If the width and height of the texel array for a three-dimensional texture
    are both less than pow(2, j-lod) + 2Bt where j is the log base 2 of
    MAX_DEEP_3D_TEXTURE_WIDTH_HEIGHT_NV, then the depth may be up to pow(2,
    m-lod) + 2Bt where m is the log base 2 of MAX_DEEP_3D_TEXTURE_DEPTH_NV.
    The error INVALID_VALUE is generated if the specified image is too large
    to be stored under any conditions.

Additions to Chapter 4 of the OpenGL 3.2 Specification (Per-Fragment Operations
and the Frame Buffer)

    (modify the discussion of FramebufferTexture in 4.4 on p. 228)
    
    If textarget is TEXTURE_3D, then level must be greater than or equal to zero
    and less than or equal to log2 of the larger of the values of
    MAX_3D_TEXTURE_SIZE and MAX_DEEP_3D_TEXTURE_DEPTH_NV.

    ...

    layer specifies the layer of a 2-dimensional image within a 3-dimensional
    texture.  An INVALID_VALUE error is generated if layer is larger than the
    larger of the value of MAX_DEEP_3D_TEXTURE_DEPTH_NV-1 and the value of
    MAX_3D_TEXTURE_SIZE-1.

Additions to Chapter 5 of the OpenGL 3.2 Specification (Special Functions)

    None

Additions to Chapter 6 of the OpenGL 3.2 Specification (State and
State Requests)

    None

Additions to the AGL/GLX/WGL Specifications

    None

Errors

    None

New State

    None

New Implementation Dependent State

    (add to Table 6.37, p. 302)

                                                    Minimum
    Get Value                            Type  Get Command  Value  Description         Sec.  Attribute
    ----------------------------         ----  ----------- ------- ------------------  ----- ---------
    MAX_DEEP_3D_TEXTURE_WIDTH_HEIGHT_NV   Z+   GetIntegerv   64    maximum width and   3.8.1     -
                                                                   height for deep 3D
                                                                   textures
    MAX_DEEP_3D_TEXTURE_DEPTH_NV          Z+   GetIntegerv   64    maximum depth for   3.8.1     -
                                                                   deep 3D textures


Issues

    1) Does this spec require that the texture exposed actually be deep?

    RESOLVED: No. The spec doesn't require that MAX_DEEP_3D_TEXTURE_DEPTH is
    actually greater than MAX_DEEP_3D_TEXTURE_WIDTH_HEIGHT, though the spec is
    pointless if that isn't the case.

    2) Does the spec guarantee that the entire 3D texture can be bound for
       rendering?

    RESOLVED: No. The framebuffer may be unsupported at the implementation's
    discretion. Rendering to a single layer at a time may be supported even if
    binding the entire 3D texture is unsupported. This is the case with the
    initial NVIDIA implementation.

Revision History

    Rev.    Date    Author    Changes
    ----  --------  --------  -----------------------------------------
    1               ewerness  Internal spec development.