Incorporate changes related to Tom's post-hoc comments on the convex path renderer.
git-svn-id: http://skia.googlecode.com/svn/trunk@3045 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrAAConvexPathRenderer.cpp b/src/gpu/GrAAConvexPathRenderer.cpp
index 7260962..8cf6c77 100644
--- a/src/gpu/GrAAConvexPathRenderer.cpp
+++ b/src/gpu/GrAAConvexPathRenderer.cpp
@@ -87,10 +87,13 @@
*quadCnt = 0;
*lineCnt = 0;
SkPath::Iter iter(path, true);
- // This renderer overemphasis very thin paths (every pixel intersected by
- // the path will be at least 1/2 on). When the path degenerates to a line
- // this makes the path draw as a hairline. This is a pretty glaring error
- // so we detect this case and will not draw.
+ // This renderer overemphasises very thin path regions. We use the distance
+ // to the path from the sample to compute coverage. Every pixel intersected
+ // by the path will be hit and the maximum distance is sqrt(2)/2. We don't
+ // notice that the sample may be close to a very thin area of the path and
+ // thus should be very light. This is particularly egregious for degenerate
+ // line paths. We detect paths that are very close to a line (zero area) and
+ // draw nothing.
if (is_path_degenerate(path)) {
return false;
}
@@ -147,8 +150,11 @@
*iCount = 15 * lineCount + 24 * quadCount;
}
-// for visual debugging, exagerate the AA smear at the edges
-// requires modifying the distance calc in the shader actually shade differently
+// This macro can be defined for visual debugging purposes. It exagerates the AA
+// smear at the edges by increasing the size of the extruded geometry used for
+// AA. However, the coverage value computed in the shader will still go to zero
+// at distance > .5 outside the curves. So, the shader code has be modified as
+// well to stretch out the AA smear.
//#define STRETCH_AA
#define STRETCH_FACTOR (20 * SK_Scalar1)