[Bug 53884] New: gl_FragCoord gets corrupted in some camera angles

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=53884

             Bug #: 53884
           Summary: gl_FragCoord gets corrupted in some camera angles
    Classification: Unclassified
           Product: Mesa
           Version: 8.0
          Platform: x86-64 (AMD64)
        OS/Version: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/Gallium/r600
        AssignedTo: dri-devel at lists.freedesktop.org
        ReportedBy: curaga at operamail.com


Created attachment 65891
  --> https://bugs.freedesktop.org/attachment.cgi?id=65891
Screenshot of the issue, bad camera angle

In certain camera angles, gl_FragCoord.xy seem to have bogus/corrupted values.

I tried to make a simple example but couldn't, so uploading an apitrace of the
bigger app and screenshots. The apitrace is 60mb XZ-compressed, that's why the
need to use a third-party service - upload limits here.

This shader:

void main() {
  gl_FragColor = vec4(gl_FragCoord.xy / vec2(640, 480), 0.0, 0.0);
}

should always create values from 0 to 1 in a window of that size. In the
apitrace the only difference is that the size is passed in an uniform.


This bug happens on both r600g and llvmpipe. I didn't have the patience to wait
for softpipe to render it. I don't have anything else on this machine to
compare to (swrast, blobs).

Mesa 8.0.3
Linux 3.2.23

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