external/openglcts/docs/specs/CTS_ARB_post_depth_coverage.txt

Conformance Test

    GL_ARB_post_depth_coverage

Contributors

    Michal Butterweck, Mobica

Contacts

    Michal Butterweck, Mobica (michal.butterweck 'at' mobica.com)

Status

    In review

Version

    August 31, 2016 (version 1)

Dependencies

    This specification is written against:
    - OpenGL 4.5 Core Profile specification,
    - ARB_post_depth_coverage extension specification.

Overview

    The test verifies that when ARB_post_depth_coverage is available one can
    use post_depth_coverage layout and gl_SampleMaskIn​ is affected according
    to the extension specification.

Tests

    Shader

        Check that macro construction:
            #extension GL_ARB_post_depth_coverage : <behavior>
        is allowed in the shader.

        Check that a new preprocessor #define GL_ARB_post_depth_coverage is
        available and equal to 1.

        Prepare a proper shader with following layout setup:
            layout(early_fragment_tests) in;
            layout(post_depth_coverage) in;
        Expect it builds without error.

        Prepare a proper shader with following layout setup:
            layout(post_depth_coverage) in;
        Expect it builds without error.

    Sample Mask

        Prepare multisample framebuffer with integer color and depth attachments
		1x1 pixels in size. A color attachment must be a texture. Clear it.

        Prepare framebuffer with integer color attachment 1x(number of samples)
        pixels in size. Clear it.

		Prepare shader program which passes gl_SampleMaskIn to the output as a
		color.

		Prepare shader program which passes samples from multisample texture to
		the output fragment.

        Turn on depth test.

        Enable multisampling.

        Use multisample framebuffer.

		Use first program.

        Draw a figure which partially covers the pixels samples but does not
        cover the pixel center. The dimensions of the figure may be dependent
        on the results of GetMultisamplefv called with SAMPLE_POSITION pname.
        The figure shall be placed at near view (eg. depth equal 0.25).

		Clear the color attachment.

        Draw a figure which fully covers the pixel area but is placed behind the
        previous polygon (eg. at depth equal to 0.75). Do not use post depth
        coverage. Output gl_SampleMaskIn to the the fragment.

		Turn off depth test.

		Use second framebuffer.

		Use second program.

		Bind first's frambuffer color attachment texture as an input to the
		fragment shader.

		Copy data from the multisample framebuffer to the second framebuffer
		using the second program and draw call.	Fetch value of gl_SampleMaskIn
		from the second framebuffer using ReadPixels. Expect that for all
		enabled samples corresponding gl_SampleMaskIn bit is set.

        Repeat the test using post depth coverage layout for the second draw
        call. Expect that bits in the gl_SampleMaskIn are only set for the
        samples which are not covered by the first primitive.

        Repeat both test cases substituting the depth test with the stencil
        test.

Revision History

    Revision 1, 31 August, 2016 (Michal Butterweck)
     - Initial version.