Refactor CCPR coverage shaders for a vertex impl
Decouples geometry generation and analytic coverage. This paves the
way for a vertex shader implementation.
TBR=egdaniel@google.com
Bug: skia:
Change-Id: I2a183401bfe70b9f14b9b1cf035de6020a2135fa
Reviewed-on: https://skia-review.googlesource.com/60103
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/ccpr/GrCCPRQuadraticShader.h b/src/gpu/ccpr/GrCCPRQuadraticShader.h
new file mode 100644
index 0000000..7441266
--- /dev/null
+++ b/src/gpu/ccpr/GrCCPRQuadraticShader.h
@@ -0,0 +1,87 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrCCPRQuadraticShader_DEFINED
+#define GrCCPRQuadraticShader_DEFINED
+
+#include "ccpr/GrCCPRCoverageProcessor.h"
+
+/**
+ * This class renders the coverage of closed quadratic curves using the techniques outlined in
+ * "Resolution Independent Curve Rendering using Programmable Graphics Hardware" by Charles Loop and
+ * Jim Blinn:
+ *
+ * https://www.microsoft.com/en-us/research/wp-content/uploads/2005/01/p1000-loop.pdf
+ *
+ * The provided curves must be monotonic with respect to the vector of their closing edge [P2 - P0].
+ * (Use GrCCPRGeometry.)
+ */
+class GrCCPRQuadraticShader : public GrCCPRCoverageProcessor::Shader {
+protected:
+ int getNumInputPoints() const final { return 3; }
+
+ void appendInputPointFetch(const GrCCPRCoverageProcessor&, GrGLSLShaderBuilder*,
+ const TexelBufferHandle& pointsBuffer,
+ const char* pointId) const override;
+
+ void emitWind(GrGLSLShaderBuilder*, const char* pts, const char* rtAdjust,
+ const char* outputWind) const final;
+
+ void emitSetupCode(GrGLSLShaderBuilder*, const char* pts, const char* segmentId,
+ const char* bloat, const char* wind, const char* rtAdjust,
+ GeometryVars*) const final;
+
+ virtual void onEmitSetupCode(GrGLSLShaderBuilder*, const char* pts, const char* segmentId,
+ const char* rtAdjust, GeometryVars*) const = 0;
+
+ WindHandling onEmitVaryings(GrGLSLVaryingHandler*, SkString* code, const char* position,
+ const char* coverage, const char* wind) final;
+
+ virtual void onEmitVaryings(GrGLSLVaryingHandler*, SkString* code) = 0;
+
+ const GrShaderVar fCanonicalMatrix{"canonical_matrix", kFloat3x3_GrSLType};
+ const GrShaderVar fCanonicalDerivatives{"canonical_derivatives", kFloat2x2_GrSLType};
+ const GrShaderVar fEdgeDistanceEquation{"edge_distance_equation", kFloat3_GrSLType};
+ GrGLSLGeoToFrag fXYD{kFloat3_GrSLType};
+};
+
+/**
+ * This pass draws a conservative raster hull around the quadratic bezier curve, computes the
+ * curve's coverage using the gradient-based AA technique outlined in the Loop/Blinn paper, and
+ * uses simple distance-to-edge to subtract out coverage for the flat closing edge [P2 -> P0]. Since
+ * the provided curves are monotonic, this will get every pixel right except the two corners.
+ */
+class GrCCPRQuadraticHullShader : public GrCCPRQuadraticShader {
+ int getNumSegments() const final { return 4; } // 4 wedges.
+
+ GeometryType getGeometryType() const override { return GeometryType::kHull; }
+ void onEmitSetupCode(GrGLSLShaderBuilder*, const char* pts, const char* wedgeId,
+ const char* rtAdjust, GeometryVars*) const override;
+ void onEmitVaryings(GrGLSLVaryingHandler*, SkString* code) override;
+ void onEmitFragmentCode(GrGLSLPPFragmentBuilder*, const char* outputCoverage) const override;
+
+ GrGLSLGeoToFrag fGrad{kFloat2_GrSLType};
+};
+
+/**
+ * This pass fixes the corners of a closed quadratic segment with soft MSAA.
+ */
+class GrCCPRQuadraticCornerShader : public GrCCPRQuadraticShader {
+ int getNumSegments() const final { return 2; } // 2 corners.
+
+ GeometryType getGeometryType() const override { return GeometryType::kCorners; }
+ void onEmitSetupCode(GrGLSLShaderBuilder*, const char* pts, const char* cornerId,
+ const char* rtAdjust, GeometryVars*) const override;
+ void onEmitVaryings(GrGLSLVaryingHandler*, SkString* code) override;
+ void onEmitFragmentCode(GrGLSLPPFragmentBuilder*, const char* outputCoverage) const override;
+
+ const GrShaderVar fEdgeDistanceDerivatives{"edge_distance_derivatives", kFloat2_GrSLType};
+ GrGLSLGeoToFrag fdXYDdx{kFloat3_GrSLType};
+ GrGLSLGeoToFrag fdXYDdy{kFloat3_GrSLType};
+};
+
+#endif