1 /* 2 * Copyright 2017 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef GrCCQuadraticShader_DEFINED 9 #define GrCCQuadraticShader_DEFINED 10 11 #include "ccpr/GrCCCoverageProcessor.h" 12 13 /** 14 * This class renders the coverage of closed quadratic curves using the techniques outlined in 15 * "Resolution Independent Curve Rendering using Programmable Graphics Hardware" by Charles Loop and 16 * Jim Blinn: 17 * 18 * https://www.microsoft.com/en-us/research/wp-content/uploads/2005/01/p1000-loop.pdf 19 * 20 * The provided curves must be monotonic with respect to the vector of their closing edge [P2 - P0]. 21 * (Use GrCCGeometry.) 22 */ 23 class GrCCQuadraticShader : public GrCCCoverageProcessor::Shader { 24 protected: 25 void emitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID, 26 const char* wind, GeometryVars*) const final; 27 virtual void onEmitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID, 28 GeometryVars*) const = 0; 29 30 void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code, 31 const char* position, const char* inputCoverage, const char* wind) final; onEmitVaryings(GrGLSLVaryingHandler *,GrGLSLVarying::Scope,SkString * code)32 virtual void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code) {} 33 34 void onEmitFragmentCode(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const final; 35 virtual void emitCoverage(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const = 0; 36 37 const GrShaderVar fCanonicalMatrix{"canonical_matrix", kFloat3x3_GrSLType}; 38 const GrShaderVar fEdgeDistanceEquation{"edge_distance_equation", kFloat3_GrSLType}; 39 GrGLSLVarying fXYDW; 40 }; 41 42 /** 43 * This pass draws a conservative raster hull around the quadratic bezier curve, computes the 44 * curve's coverage using the gradient-based AA technique outlined in the Loop/Blinn paper, and 45 * uses simple distance-to-edge to subtract out coverage for the flat closing edge [P2 -> P0]. Since 46 * the provided curves are monotonic, this will get every pixel right except the two corners. 47 */ 48 class GrCCQuadraticHullShader : public GrCCQuadraticShader { 49 void onEmitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID, 50 GeometryVars*) const override; 51 void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code) override; 52 void emitCoverage(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override; 53 54 GrGLSLVarying fGrad; 55 }; 56 57 /** 58 * This pass fixes the corners of a closed quadratic segment with soft MSAA. 59 */ 60 class GrCCQuadraticCornerShader : public GrCCQuadraticShader { 61 void onEmitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* repetitionID, 62 GeometryVars*) const override; 63 void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code) override; 64 void emitCoverage(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override; 65 66 GrGLSLVarying fdXYDdx; 67 GrGLSLVarying fdXYDdy; 68 }; 69 70 #endif 71