Mesa (master): tgsi: update documents with some info on texture lookup

[Dave Airlie]

Module: Mesa
Branch: master
Commit: 35db326de5b173b06344c1a50321a02c2e6e7d93
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=35db326de5b173b06344c1a50321a02c2e6e7d93

Author: Dave Airlie <airlied at redhat.com>
Date:   Mon Dec 19 16:40:05 2011 +0000

tgsi: update documents with some info on texture lookup

this mentions which channels are used for slice and depth comparison values.

Signed-off-by: Dave Airlie <airlied at redhat.com>
Reviewed-by: Brian Paul <brianp at vmware.com>

---

 src/gallium/docs/source/tgsi.rst |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index d7f50b1..45af528 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -585,6 +585,17 @@ This instruction replicates its result.
 
   dst = texture_sample(unit, coord, bias)
 
+  for array textures src0.y contains the slice for 1D,
+  and src0.z contain the slice for 2D.
+  for shadow textures with no arrays, src0.z contains
+  the reference value.
+  for shadow textures with arrays, src0.z contains
+  the reference value for 1D arrays, and src0.w contains
+  the reference value for 2D arrays.
+  There is no way to pass a bias in the .w value for
+  shadow arrays, and GLSL doesn't allow this.
+  GLSL does allow cube shadows maps to take a bias value,
+  and we have to determine how this will look in TGSI.
 
 .. opcode:: TXD - Texture Lookup with Derivatives