[Mesa-dev] [Bug 45913] New: [bisected] piglit vs-clip-vertex-const-reject fails

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri Feb 10 13:57:38 PST 2012


             Bug #: 45913
           Summary: [bisected] piglit vs-clip-vertex-const-reject fails
    Classification: Unclassified
           Product: Mesa
           Version: git
          Platform: Other
        OS/Version: All
            Status: NEW
          Keywords: regression
          Severity: normal
          Priority: medium
         Component: Mesa core
        AssignedTo: mesa-dev at lists.freedesktop.org
        ReportedBy: pavel.ondracka at email.cz
                CC: stereotype441 at gmail.com

Found while comparing piglit runs on r300g RV530 between 7.11 and 8.0. 
llvmpipe is also affected.

7d68c639ddb0f9df45cf698b8e8227bf1860b5fe is the first bad commit
commit 7d68c639ddb0f9df45cf698b8e8227bf1860b5fe
Author: Paul Berry <stereotype441 at gmail.com>
Date:   Mon Sep 26 13:15:57 2011 -0700

    mesa: Add a gl_vert_result for gl_ClipVertex.

    Before this patch, clip planes didn't work properly in Mesa when using
    vertex shaders, because Mesa assigned both gl_ClipVertex and
    gl_Position to the same gl_vert_result (VERT_RESULT_HPOS).  As a
    result, backends couldn't distinguish between the two variables, so
    any shader that wrote different values to them would fail to work

    This patch paves the way for proper support of gl_ClipVertex by
    creating a new enumerated value in gl_vert_result for it
    (VERT_RESULT_CLIP_VERTEX).  After this patch, a back-end may add
    support for gl_ClipVertex using the following algorithm:

    - If using a user-supplied GLSL vertex shader:
      - If the bit corresponding to VERT_RESULT_CLIP_VERTEX is set in
        - Clip using the vertex shader output VERT_RESULT_CLIP_VERTEX and
          the clip planes defined in gl_context::Transform.EyeUserPlane.
      - Else:
        - Clip using the vertex shader output VERT_RESULT_HPOS and the
          clip planes defined in gl_context::Transform.EyeUserPlane.
    - Else (either using fixed function or an ARB vertex program):
      - Clip using the vertex shader output VERT_RESULT_HPOS and the clip
        planes defined in gl_context::Transform._ClipUserPlane (*)

    where (*) represents the normal Mesa behavior before this patch.

    An example of implementing the above algorithm can be found in the
    patch that follows this one, which implements gl_ClipVertex in i965

    Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

My system:
GPU: RV530
Mesa: a8cc228edd1dd6328f8b9086d768b52f821c6575
Kernel: 3.2.3
Libdrm 2.4.31

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