commit 91a8c7c62913c2597e3bf5a6d59d2ed5fc7ba4e0
author Chris Craik <ccraik@google.com> Tue Aug 12 14:31:35 2014 -0700
committer Chris Craik <ccraik@google.com> Tue Aug 12 16:00:09 2014 -0700
tree 22f6e0e41bccc3df2b4b053a5decddabe5382c95
parent ddc122ee5015f9ca0cc124a53c175aadf85f50ad

Switch to cos interpolation of shadow alpha

bug:16852257

Updates default shadow opacities to compensate.

Also, update variable/constant naming related to vertex alpha.

Change-Id: I9055b4ac3c9ac305ca9d515f21b52d6aa6dc9c5c

libs/hwui/AmbientShadow.cpp

diff --git a/libs/hwui/AmbientShadow.cpp b/libs/hwui/AmbientShadow.cpp
index 181230a..9cc83ed 100644
--- a/libs/hwui/AmbientShadow.cpp
+++ b/libs/hwui/AmbientShadow.cpp
@@ -117,10 +117,13 @@
 
         // inner ring of points
         float opacity = 1.0 / (1 + rayHeight[rayIndex] * heightFactor);
+        // NOTE: Shadow alpha values are transformed when stored in alphavertices,
+        // so that they can be consumed directly by gFS_Main_ApplyVertexAlphaShadowInterp
+        float transformedOpacity = acos(1.0f - 2.0f * opacity);
         AlphaVertex::set(&shadowVertices[rays + rayIndex],
                 intersection.x,
                 intersection.y,
-                opacity);
+                transformedOpacity);
     }
 
     if (isCasterOpaque) {