Conformance Test

    GL_ARB_fragment_shader_interlock

Contributors

    Adam Czupryna, Mobica

Contacts

    Adam Czupryna, Mobica (adam.czupryna 'at' mobica.com)

Status

    In review

Version

    January 31, 2017 (version 1)

Dependencies

    OpenGL 4.5 is required.

    ARB_fragment_shader_interlock extension is required.

    This specification is written against:
    - OpenGL 4.5 Core Profile Specification,
    - version 4.50 (revision 5) Shading Language Specification,
    - ARB_fragment_shader_interlock extension Specification.

Overview

    This test verifies if new GLSL built-in functions
    beginInvocationInterlockARB() and endInvocationInterlockARB() provides
    functionality for pairs of shader invocations with "overlapping"
    coverage in a given pixel, which guarantee that the critical section of
    the fragment shader will be executed for only one fragment at a time.
    Test verifies also two ordered interlock modes supported by this
    extension because testing unordered interlock modes would be
    undeterministic.

Tests

    Shader Extension Test

      * Create shader that require GL_ARB_fragment_shader_interlock extension
        and check if GL_ARB_fragment_shader_interlock is defined and equal 1.
        Check if shader compiles with no error.

    Shader Execution Ordering Test

      * Create 8x8 R8 texture and clear it.

      * Create fragment shader for ordered layout qualifiers added by this
        extension. Shader should read pixel value from the texture at current
        position and compare it with gl_PrimitiveID value. If value read from
        texture is lower then gl_PrimitiveID write (1, 1, 1, 1) into
        renderbuffer and store gl_PrimitiveID in the texture at current
        position, otherwise write (0, 0, 0, 0) into renderbuffer and value 255
        into texture at current position. All operations should be executed
        between beginInvocationInterlockARB and endInvocationInterlockARB
        functions calls.

      * Iterate through the fragment shaders, clear texture and for each shader
        draw three triangles at once in the same position.

      Expected result for ordered layout qualifires is renderbuffer filled with
      (1, 1, 1, 1) if test passed.

      In case of sample_interlock_* qualifier multisampled texture has to be
      used.

      There is no method to test if unordered qualifiers works correctly
      because for those qualifiers fragment shader invocations are generally
      executed in undefined order, which means that it could be either
      ordered or unordered. Tests for unordered qualifiers would be
      undeterministic.

    Shader Critical Section Execution Test

      * Create 1x1 R8UI texture.

      * Create two fragment shaders for all layout qualifiers added by this
        extension. Shader should read pixel value from the texture, increase it
        and store. In first fragment shader all operations should be executed
        between beginInvocationInterlockARB and endInvocationInterlockARB
        functions calls, in second one those calls should be missed.

      * Clear texture and draw 8x8 pixel sized polygon to the renderbuffer.

      The expected result is value 64 stored in the texture if
      beginInvocationInterlockARB and endInvocationInterlockARB functions were
      used.

      In case of sample_interlock_* qualifier multisampled texture has to be
      used.

Revision History

    Revision 1, 31 January, 2016 (Adam Czupryna)
     - Initial version.