https://bugs.freedesktop.org/show_bug.cgi?id=97477
Bug ID: 97477
Summary: i915g: gl_FragCoord is always (0.0, max_y)
Product: Mesa
Version: git
Hardware: Other
OS: All
Status: NEW
Severity: normal
Priority: medium
Component: Drivers/Gallium/i915g
Assignee: dri-devel at lists.freedesktop.org
Reporter: nicholasbishop at gmail.com
QA Contact: dri-devel at lists.freedesktop.org
Created attachment 126029
--> https://bugs.freedesktop.org/attachment.cgi?id=126029&action=edit
Patch: Handle I915_SEMANTIC_POS when setting texCoords for gl_FragCoord
On Intel Pineview M hardware, the i915 gallium driver doesn't output the
correct gl_FragCoord. It seems to always have an X coord of 0.0 and a Y coord
of the window's height in pixels, e.g. 600.0f or such.
I believe this is a regression caused in part by commit
afa035031ff9e0c07a2297d864e46c76f7bfff58
(https://lists.freedesktop.org/archives/mesa-commit/2016-January/061181.html)
The old behavior used output zero, while the new behavior uses actual zeroes.
In the case of gl_FragCoord output zero happened to be the correct one.
I've attached a patch that seems to fix the issue for me. I ran the piglit
"quick" tests and observed 17 new tests passing, and one regression. I suspect
the regression is unimportant since it involves derivatives that aren't
implemented for this driver anyway:
"fs-dfdy-accuracy" test failed ... in i915_fpc_translate.c:
case TGSI_OPCODE_DDY:
/* XXX We just output 0 here */
debug_printf("Punting DDX/DDX\n");
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