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-rw-r--r--src/gallium/docs/source/tgsi.rst6
1 files changed, 4 insertions, 2 deletions
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index 6f850bf29fb..cbb8f74ab89 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -2512,8 +2512,10 @@ The Y component starts at zero and always increases but Y=0 may either
indicate the top of the window or the bottom depending on the fragment
coordinate origin convention (see TGSI_PROPERTY_FS_COORD_ORIGIN).
The Z coordinate ranges from 0 to 1 to represent depth from the front
-to the back of the Z buffer. The W component contains the reciprocol
-of the interpolated vertex position W component.
+to the back of the Z buffer. The W component contains the interpolated
+reciprocal of the vertex position W component (corresponding to gl_Fragcoord,
+but unlike d3d10 which interpolates the same 1/w but then gives back
+the reciprocal of the interpolated value).
Fragment shaders may also declare an output register with
TGSI_SEMANTIC_POSITION. Only the Z component is writable. This allows