[Mesa-dev] [PATCH 0/4] Removal of point size clamping in st/mesa

[Christoph Bumiller]

On 28.01.2012 01:38, Marek Olšák wrote:
> Hi everyone,
>
> the subject says it all. This series fixes gl_PointSize with transform feedback. There is a new piglit test to verify that a driver does clamping properly during rasterization: vs-point_size-zero

The piglit test is wrong.

GL spec 4.2/3.4 - Points: (and probably earlier specs too)

If program point size mode is enabled, the derived point size is taken
from the (potentially clipped) shader built-in gl_PointSize written by
... and clamped to the implementation-dependent point size range.
If the value written to gl_PointSize is less than or >> equal (this is
what the test does) << to zero, or if no value was written to
gl_PointSize, results are >>> undefined <<<.


> I haven't changed Draw, because softpipe and llvmpipe do the clamping internally somewhere. (I didn't take a look where they do it, but they pass the test, which can't be said about r600 with point size clamping disabled)
>
> The only drivers I am not sure about are i915 and nouveau.
>
> Please review.
>
> Marek
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