[Mesa-dev] Mesa (master): r300g: fix gl_PointCoord
idr at freedesktop.org
Thu Aug 26 12:09:32 PDT 2010
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Marek Olšák wrote:
> On Thu, Aug 26, 2010 at 4:08 AM, Luca Barbieri <luca at luca-barbieri.com
> <mailto:luca at luca-barbieri.com>> wrote:
> Also, doesn't sprite coord replacement also affect gl_TexCoord in GLSL?
> I suspect it does.
Why would it? gl_TexCoord is a set of varyings written by the vertex
shader. gl_PointCoord is a magic varying generated during
rasterization. Neither has anything to do with the other in GLSL. Like
all varyings (except the magic varyings gl_PointCoord and gl_FragCoord)
in points, the fragment shader gets the same value at every fragment.
I think there is a piglit test for this. If it's not
Getting all the cases of fixed-function, assembly fragment programs, and
GLSL fragment shaders correct is hard. I worked on this a bit for 965
and got really frustrated. The fixed-function and assembly program
support (with the per-texture coordinate replacement bits) forces
state-based recompiles on most hardware.
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