https://bugs.freedesktop.org/show_bug.cgi?id=95130
Bug ID: 95130
Summary: Derivatives of gl_Color wrong when helper pixels used
Product: Mesa
Version: git
Hardware: Other
OS: All
Status: NEW
Severity: normal
Priority: medium
Component: Drivers/Gallium/radeonsi
Assignee: dri-devel at lists.freedesktop.org
Reporter: jlegg at feralinteractive.com
QA Contact: dri-devel at lists.freedesktop.org
Created attachment 123239
--> https://bugs.freedesktop.org/attachment.cgi?id=123239&action=edit
Test program
Along the edges of triangles and around where fragments are rejected due to
depth testing, the GLSL functions dFdx, dFdy, and fwidth return incorrect
values when the argument is dependant on gl_Color or gl_SecondaryColor.
I've attached a program reproducing the issue. It takes derivatives of a
constant, which should be 0. It is expected to produce a black window. However,
the edges of the triangle it draws are visible because of this bug.
The error does not occur when environment variable LIBGL_ALWAYS_SOFTWARE is set
to 1.
I'm using Mesa git 0831eb9 with an AMD R9 270 on x86_64 Fedora 22.
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