From: Roland Scheidegger Date: Mon, 8 Dec 2014 18:07:10 +0000 (+0100) Subject: gallium/docs: clarify fragment shader position input w component. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=fe7e6b248f4f97e10adb26db2836ff5accbff94a;p=mesa.git gallium/docs: clarify fragment shader position input w component. The previous language was a bit misleading, since it sounded like w was interpolated then the reciprocal calculated which isn't what should be happening. Reviewed-by: Jose Fonseca --- 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