ccpr: Calculate edge coverage in the coverage processor
Does the opposite-edge coverage calculation for curves in the coverage
processor, rather than the Shader class. This allows the vertex shader
implementation to do it more clean and directly, as well as allowing
the future sample mask implementation to disregard edge coverage
entirely.
Bug: skia:
Change-Id: Idaddfff8b22e3223f2a4e286900941969f975c6a
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208990
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/ccpr/GrVSCoverageProcessor.cpp b/src/gpu/ccpr/GrVSCoverageProcessor.cpp
index dc00b96..aa87dd7 100644
--- a/src/gpu/ccpr/GrVSCoverageProcessor.cpp
+++ b/src/gpu/ccpr/GrVSCoverageProcessor.cpp
@@ -280,7 +280,7 @@
v->defineConstant("bloat", bloat);
const char* hullPts = "pts";
- fShader->emitSetupCode(v, "pts", "wind", (4 == fNumSides) ? &hullPts : nullptr);
+ fShader->emitSetupCode(v, "pts", (4 == fNumSides) ? &hullPts : nullptr);
// Reverse all indices if the wind is counter-clockwise: [0, 1, 2] -> [2, 1, 0].
v->codeAppendf("int clockwise_indices = wind > 0 ? %s : 0x%x - %s;",
@@ -360,8 +360,8 @@
// fallthru.
v->codeAppend ("}");
- v->codeAppend ("float2 vertex = fma(bloatdir, float2(bloat), corner);");
- gpArgs->fPositionVar.set(kFloat2_GrSLType, "vertex");
+ v->codeAppend ("float2 vertexpos = fma(bloatdir, float2(bloat), corner);");
+ gpArgs->fPositionVar.set(kFloat2_GrSLType, "vertexpos");
// Hulls have a coverage of +1 all around.
v->codeAppend ("half coverage = +1;");
@@ -385,6 +385,16 @@
kVertexData_InvertNegativeCoverageBit);
v->codeAppend ( "coverage = -1 - coverage;");
v->codeAppend ("}");
+ } else if (!fShader->calculatesOwnEdgeCoverage()) {
+ // Determine the amount of coverage to subtract out for the flat edge of the curve.
+ v->codeAppendf("float2 p0 = pts[0], p1 = pts[%i];", numInputPoints - 1);
+ v->codeAppendf("float2 n = float2(p0.y - p1.y, p1.x - p0.x);");
+ v->codeAppend ("float nwidth = bloat*2 * (abs(n.x) + abs(n.y));");
+ // When nwidth=0, wind must also be 0 (and coverage * wind = 0). So it doesn't matter
+ // what we come up with here as long as it isn't NaN or Inf.
+ v->codeAppend ("float d = dot(p0 - vertexpos, n);");
+ v->codeAppend ("d /= (0 != nwidth) ? nwidth : 1;");
+ v->codeAppend ("coverage = half(d) - .5*sign(wind);");
}
// Non-corner geometry should have zero effect from corner coverage.
@@ -392,16 +402,12 @@
v->codeAppendf("if (0 != (%s & %i)) {", // Are we a corner?
proc.fPerVertexData.name(), kVertexData_IsCornerBit);
- // We use coverage=-1 to erase what the hull geometry wrote.
- //
- // In the context of curves, this effectively means "wind = -wind" and
- // causes the Shader to erase what it had written previously for the hull.
- //
- // For triangles it just erases the "+1" value written by the hull geometry.
- v->codeAppend ( "coverage = -1;");
+ // Erase what the previous geometry wrote.
+ v->codeAppend ( "wind = -wind;");
if (3 == fNumSides) {
- // Triangle corners also have to erase what the edge geometry wrote.
- v->codeAppend ("coverage -= left_coverage + right_coverage;");
+ v->codeAppend ("coverage = 1 + left_coverage + right_coverage;");
+ } else if (!fShader->calculatesOwnEdgeCoverage()) {
+ v->codeAppend ("coverage = -coverage;");
}
// Corner boxes require attenuated coverage.
@@ -414,16 +420,16 @@
// Shader will calculate the curve's local coverage value, interpolate it
// alongside our attenuation parameter, and multiply the two together for a
// final coverage value.
- v->codeAppend ( "corner_coverage = (0 == bloatidx) ? half2(0, attenuation) : half2(1);");
+ v->codeAppend ( "corner_coverage = (0 == bloatidx) ? half2(0, attenuation) : half2(-1,+1);");
if (3 == fNumSides) {
// For triangles we also provide the actual coverage values at each vertex of
// the corner box.
v->codeAppend ("if (1 == bloatidx || 2 == bloatidx) {");
- v->codeAppend ( "corner_coverage.x += right_coverage;");
+ v->codeAppend ( "corner_coverage.x -= right_coverage;");
v->codeAppend ("}");
v->codeAppend ("if (bloatidx >= 2) {");
- v->codeAppend ( "corner_coverage.x += left_coverage;");
+ v->codeAppend ( "corner_coverage.x -= left_coverage;");
v->codeAppend ("}");
}
v->codeAppend ("}");
@@ -432,7 +438,7 @@
v->codeAppend ("coverage *= wind;");
v->codeAppend ("corner_coverage.x *= wind;");
fShader->emitVaryings(varyingHandler, GrGLSLVarying::Scope::kVertToFrag, &AccessCodeString(v),
- gpArgs->fPositionVar.c_str(), "coverage", "corner_coverage");
+ "vertexpos", "coverage", "corner_coverage", "wind");
varyingHandler->emitAttributes(proc);
SkASSERT(!args.fFPCoordTransformHandler->nextCoordTransform());