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gallium/docs: clarify TGSI_SEMANTIC_SAMPLEMASK, again

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I've since discovered the fragment shader sample mask system value (which
corresponds to gl_SampleMaskIn).

v2: It's a system value, not a shader input.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
This commit is contained in:
Brian Paul 2017-06-12 11:33:30 -06:00
parent 26500c3fad
commit def8d1d23f
1 changed files with 11 additions and 4 deletions
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15
src/gallium/docs/source/tgsi.rst
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@ -3297,10 +3297,17 @@ and Y values are used.
TGSI_SEMANTIC_SAMPLEMASK
""""""""""""""""""""""""
For fragment shaders, this semantic label indicates that an output contains
the sample mask used to disable further sample processing. The output's
type is uint[4] but only the X component is used (i.e. gl_SampleMask[0]).
Each bit corresponds to one sample position (up to 32x MSAA is supported).
For fragment shaders, this semantic label can be applied to either a
shader system value input or output.
For a system value, the sample mask indicates the set of samples covered by
the current primitive. If MSAA is not enabled, the value is (1, 0, 0, 0).
For an output, the sample mask is used to disable further sample processing.
For both, the register type is uint[4] but only the X component is used
(i.e. gl_SampleMask[0]). Each bit corresponds to one sample position (up
to 32x MSAA is supported).
TGSI_SEMANTIC_INVOCATIONID
""""""""""""""""""""""""""