external/openglcts/docs/specs/CTS_ARB_shader_draw_parameters.txt

Conformance Test

    GL_ARB_shader_draw_parameters

Contributors

    Adam Czupryna, Mobica

Contacts

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

Status

    In review

Version

    March 22, 2017 (version 1)

Dependencies

    OpenGL 3.1 is required.

    ARB_shader_draw_parameters extension is required.

    This specification is written against:
    - OpenGL 4.3 Core Profile Specification,
    - version 4.30 Shading Language Specification,
    - ARB_shader_draw_parameters extension Specification.

    The ARB_multi_draw_indirect and ARB_indirect_parameters affects
    definition of this test.

Overview

    This test verifies if new GLSL built-in variables added by this
    extension contain correct data.

    It is expected that:
    gl_BaseVertexARB - contain value passed in baseVertex parameter,
    gl_BaseInstanceARB - contain value passed in baseInstance parameter.
    gl_DrawIDARB - contain the index of the draw currently being
      processed by a Multi* variant of drawing command.

Tests

    Shader Extension Test

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

    Draw Paramaters Test

      * Create vertex shader that adds offset to currently processed
        vertex using gl_baseVertexARB and gl_baseInstanceARB for x and y
        dimensions respectively. Additionally color variable which components
        are function of gl_DrawIDARB value should be passed to the fragment
        shader.

        Color components function could be:
        color.r = (gl_DrawIDARB % 3 == 0 ? 1.0 : 0.0);
        color.g = (gl_DrawIDARB % 3 == 1 ? 1.0 : 0.0);
        color.b = (gl_DrawIDARB % 3 == 2 ? 1.0 : 0.0);

      * Create fragment shader that puts out color passed by vertex shader.

      * Set clear color to black, enable blending and perform different
        drawing commands to draw triangle strips. Use different parameters
        values for each command. Create separated test cases for each drawing
        command.

        List of drawing commands:

          - drawArrays/drawElements
          - drawArraysIndirect/drawElementsIndirect
          - drawArraysInstanced/drawElementsInstanced
          - multiDrawArrays/multiDrawElements
          - multiDrawArraysIndirect/multiDrawElementsIndirect
          - multiDrawArraysIndirectCountARB/multiDrawElementsIndirectCountARB

        Verify if drawing result is as expected by reading pixels from the
        framebuffer. Make sure that each triangle is drawn with correct offset
        and with proper color value.

Revision History

    Revision 1, 22 March, 2017 (Adam Czupryna)
     - Initial version.

    Revision 2, 3 April, 2017 (Adam Czupryna)
     - Changed Draw Parameters Test definition,
     - Updated list of drawing commands.