GLSL_HUAWEI_subpass_shading

Name

    HUAWEI_subpass_shading

Name Strings

    GL_HUAWEI_subpass_shading

Contact

    Hueilong Wang (wyvernathuawei), HUAWEI

Contributors

    Hueilong Wang, HUAWEI

Status

    Draft

Version

    Last Modified Date: 2021-04-26
    Revision: 1

Dependencies

    This extension can be applied to OpenGL GLSL versions 4.60
    (#version 460) and higher.

    This extension can be applied to OpenGL ES ESSL versions 3.20
    (#version 320) and higher.

    This extension is written against revision 7 of the OpenGL Shading Language
    version 4.60, dated July 10, 2019, and can be applied to OpenGL ES ESSL
    version 3.20, dated July 10, 2019.

    This extension interacts with revision 43 of the GL_KHR_vulkan_glsl
    extension, dated October 25, 2017.

Overview

    This extension allows a subpass shading shader to delcare subpass inputs and use subpass input functions.

Modifications to the OpenGL Shading Language Specification, Version 4.60

    Including the following line in a shader can be used to control the
    language features described in this extension:

      #extension GL_HUAWEI_subpass_shading                          : 

    where  is as specified in section 3.3.
    New preprocessor #defines are added:

      #define GL_HUAWEI_subpass_shading

Additions to Chapter 2 of the OpenGL Shading Language Specification, Version 4.60

    Add Section 2.7. Subpass Shading Processor

    The subpass shading processor is a programmable unit that operates the subpass inputs. It runs independently
    from the other shader processors. Compilation units written in the OpenGL Shading Language to run on this
    processor are called subpass shading shaders. When a set of subpass shading shaders are successfully compiled
    and linked, they result in a subpass shading shader executable that runs on the subpass shading processor.

    A subpass shading shader is almost identical to a compute shader except the following
    differences.

        * A subpass shading shader must be dispatched in a dedicated subpass
        * A subpass shading shader is allowed to read fragment froms input attachments
        * The work dimension is defined by the size of render area and the number of layers of the framebuffer

Changes to Chapter 4 of The OpenGL Shading Language Specification, Version 4.60

    Modify Section 4.1.7, (Opaque Types)

    Change the "Subpass-input types are only available in fragment shaders." to

    Subpass-input types are only available in fragment or subpass shading shaders.

Changes to Chapter 8 of The OpenGL Shading Language Specification, Version 4.60

    Modify Section 8.18, (Subpass-Input Functions)

    Change the "Subpass-input functions are only available when targeting a Vulkan fragment stage." to

    Subpass-input functions are only available when targeting a Vulkan fragment or subpass shading stage.

Changes to Chapter 12 of The OpenGL Shading Language Specification, Version 4.60

    Modify Section 12.2.4, (Vulkan Only: Samplers, Images, Textures, and Buffers)

    Change the "Subpass inputs are read through a new set of types, available only to fragment shaders:" to

    Subpass inputs are read through a new set of types, available only to fragment or subpass shading shaders:

Issues

    TBD

Revision History

    Rev.  Date          Author             Changes
    ----  -----------   --------------     -------------------------------------------
     1    2021-04-26    wyvernathuawei     Initial draft