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Incorporate changes related to Tom's post-hoc comments on the convex path renderer.

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git-svn-id: http://skia.googlecode.com/svn/trunk@3045 2bbb7eff-a529-9590-31e7-b0007b416f81
This commit is contained in:
bsalomon@google.com 2012-01-17 16:28:34 +00:00
parent 90d344adc2
commit 5cc90d1322
2 changed files with 24 additions and 9 deletions
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15
gm/convexpaths.cpp
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@ -79,6 +79,8 @@ protected:
20 * SK_Scalar1, 40 * SK_Scalar1,
SkPath::kCCW_Direction);
/*
It turns out arcTos are not automatically marked as convex and they
may in fact be ever so slightly concave.
fPaths.push_back().arcTo(SkRect::MakeXYWH(0, 0,
50 * SK_Scalar1,
100 * SK_Scalar1),
@ -86,9 +88,16 @@ protected:
*/
// point degenerate
fPaths.push_back().lineTo(0,0);
fPaths.push_back().quadTo(0,0,0,0);
fPaths.push_back().cubicTo(0,0,0,0,0,0);
fPaths.push_back().moveTo(50 * SK_Scalar1, 50 * SK_Scalar1);
fPaths.back().lineTo(50 * SK_Scalar1, 50 * SK_Scalar1);
fPaths.push_back().moveTo(50 * SK_Scalar1, 50 * SK_Scalar1);
fPaths.back().quadTo(50 * SK_Scalar1, 50 * SK_Scalar1,
50 * SK_Scalar1, 50 * SK_Scalar1);
fPaths.push_back().moveTo(50 * SK_Scalar1, 50 * SK_Scalar1);
fPaths.back().cubicTo(50 * SK_Scalar1, 50 * SK_Scalar1,
50 * SK_Scalar1, 50 * SK_Scalar1,
50 * SK_Scalar1, 50 * SK_Scalar1);
// line degenerate
fPaths.push_back().lineTo(100 * SK_Scalar1, 100 * SK_Scalar1);

18
src/gpu/GrAAConvexPathRenderer.cpp
View File

@ -87,10 +87,13 @@ bool get_segments(const GrPath& path,
*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 @@ void get_counts(int quadCount, int lineCount, int* vCount, int* iCount) {
*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)