For the SAMPLE_POS and SAMPLE_INFO opcodes, clarify resource vs. render
target queries, range of postion values, swizzling, etc. We basically
follow the DX10.1 conventions.
For the TXQS opcode and TGSI_SEMANTIC_SAMPLEID, clarify return value
and type.
For the TGSI_SEMANTIC_SAMPLEPOS system value, clarify the range of
positions returned.
---
src/gallium/docs/source/tgsi.rst | 53 +++++++++++++++++++++++++++++++---------
1 file changed, 42 insertions(+), 11 deletions(-)
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index 7fb963f..310b49d 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -982,7 +982,9 @@ XXX doesn't look like most of the opcodes really belong
here.
.. opcode:: TXQS - Texture Samples Query
This retrieves the number of samples in the texture, and stores it
- into the x component. The other components are undefined.
+ into the x component as an unsigned integer. The other components are
+ undefined. If the texture is not multisampled, this function returns
+ (1, 0, 0, 0).
.. math::
@@ -2538,14 +2540,40 @@ after lookup.
.. opcode:: SAMPLE_POS
- Query the position of a given sample. dst receives float4 (x, y, 0, 0)
- indicated where the sample is located. If the resource is not a multi-sample
- resource and not a render target, the result is 0.
+ Query the position of a sample in the given resource or render target
+ when per-sample fragment shading is in effect.
+
+ Syntax: ``SAMPLE_POS dst, source, sample_index``
+
+ dst receives float4 (x, y, 0, 0) indicated where the sample is located.
+ Sample locations are in the range [0, 1] where 0.5 is the center of the
+ fragment.
+
+ source is either a sampler view (to indicate a shader resource) or temp
+ register (to indicate the render target). The source register may have
+ an optional swizzle to apply to the returned result
+
+ sample_index is an integer scalar indicating which sample position is to
+ be queried.
+
+ If per-sample shading is not in effect or the source resource or render
+ target is not multisampled, the result is (0, 0, 0, 0).
.. opcode:: SAMPLE_INFO
- dst receives number of samples in x. If the resource is not a multi-sample
- resource and not a render target, the result is 0.
+ Query the number of samples in a multisampled resource or render target.
+
+ Syntax: ``SAMPLE_INFO dst, source``
+
+ dst receives int4 (n, 0, 0, 0) where n is the number of samples in a
+ resource or the render target.
+
+ source is either a sampler view (to indicate a shader resource) or temp
+ register (to indicate the render target). The source register may have
+ an optional swizzle to apply to the returned result
+
+ If per-sample shading is not in effect or the source resource or render
+ target is not multisampled, the result is (1, 0, 0, 0).
.. _resourceopcodes:
@@ -3284,15 +3312,18 @@ TGSI_SEMANTIC_SAMPLEID
""""""""""""""""""""""
For fragment shaders, this semantic label indicates that a system value
-contains the current sample id (i.e. gl_SampleID).
-This is an integer value, and only the X component is used.
+contains the current sample id (i.e. gl_SampleID) as an unsigned int.
+Only the X component is used. If per-sample shading is not enabled,
+the result is (0, 0, 0, 0).
TGSI_SEMANTIC_SAMPLEPOS
"""""""""""""""""""""""
-For fragment shaders, this semantic label indicates that a system value
-contains the current sample's position (i.e. gl_SamplePosition). Only the X
-and Y values are used.
+For fragment shaders, this semantic label indicates that a system
+value contains the current sample's position as float4(x, y, 0, 0) in
+the render target (i.e. gl_SamplePosition) when per-fragment shading
+is in effect. Position values are in the range [0, 1] where 0.5 is
+the center of the fragment.
TGSI_SEMANTIC_SAMPLEMASK
""""""""""""""""""""""""
--
1.9.1
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