Mesa (master): gallium/docs: document TGSI_SEMANTIC_EDGEFLAG

[Brian Paul]

Module: Mesa
Branch: master
Commit: 7315300fa5a5e63c16b9e258feb4df76176b5b4b
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=7315300fa5a5e63c16b9e258feb4df76176b5b4b

Author: Brian Paul <brianp at vmware.com>
Date:   Wed Jun 23 17:38:58 2010 -0600

gallium/docs: document TGSI_SEMANTIC_EDGEFLAG

---

 src/gallium/docs/source/tgsi.rst |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index f5678c7..205e7b8 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -1397,7 +1397,15 @@ back-facing.
 TGSI_SEMANTIC_EDGEFLAG
 """"""""""""""""""""""
 
-XXX no clue
+For vertex shaders, this sematic label indicates that an input or
+output is a boolean edge flag.  The register layout is [F, x, x, x]
+where F is 0.0 or 1.0 and x = don't care.  Normally, the vertex shader
+simply copies the edge flag input to the edgeflag output.
+
+Edge flags are used to control which lines or points are actually
+drawn when the polygon mode converts triangles/quads/polygons into
+points or lines.
+
 
 
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