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 GrCCCubicShader_DEFINED 9 #define GrCCCubicShader_DEFINED 10 11 #include "ccpr/GrCCCoverageProcessor.h" 12 13 /** 14 * This class renders the coverage of convex closed cubic segments 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 curve segments must be convex, monotonic with respect to the vector of their closing 21 * edge [P3 - P0], and must not contain or be near any inflection points or loop intersections. 22 * (Use GrCCGeometry::cubicTo().) 23 */ 24 class GrCCCubicShader : public GrCCCoverageProcessor::Shader { 25 public: 26 void emitSetupCode(GrGLSLVertexGeoBuilder*, const char* pts, const char* wind, 27 const char** outHull4) const override; 28 29 void onEmitVaryings(GrGLSLVaryingHandler*, GrGLSLVarying::Scope, SkString* code, 30 const char* position, const char* coverage, 31 const char* cornerCoverage) override; 32 33 void onEmitFragmentCode(GrGLSLFPFragmentBuilder*, const char* outputCoverage) const override; 34 35 private: 36 void calcHullCoverage(SkString* code, const char* klmAndEdge, const char* gradMatrix, 37 const char* outputCoverage) const; 38 39 const GrShaderVar fKLMMatrix{"klm_matrix", kFloat3x3_GrSLType}; 40 const GrShaderVar fEdgeDistanceEquation{"edge_distance_equation", kFloat3_GrSLType}; 41 GrGLSLVarying fKLM_fEdge; 42 GrGLSLVarying fGradMatrix; 43 GrGLSLVarying fCornerCoverage; 44 }; 45 46 #endif 47