1 /* 2 * Copyright 2013 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 GrBezierEffect_DEFINED 9 #define GrBezierEffect_DEFINED 10 11 #include "GrCaps.h" 12 #include "GrProcessor.h" 13 #include "GrGeometryProcessor.h" 14 #include "GrTypesPriv.h" 15 16 /** 17 * Shader is based off of Loop-Blinn Quadratic GPU Rendering 18 * The output of this effect is a hairline edge for conics. 19 * Conics specified by implicit equation K^2 - LM. 20 * K, L, and M, are the first three values of the vertex attribute, 21 * the fourth value is not used. Distance is calculated using a 22 * first order approximation from the taylor series. 23 * Coverage for AA is max(0, 1-distance). 24 * 25 * Test were also run using a second order distance approximation. 26 * There were two versions of the second order approx. The first version 27 * is of roughly the form: 28 * f(q) = |f(p)| - ||f'(p)||*||q-p|| - ||f''(p)||*||q-p||^2. 29 * The second is similar: 30 * f(q) = |f(p)| + ||f'(p)||*||q-p|| + ||f''(p)||*||q-p||^2. 31 * The exact version of the equations can be found in the paper 32 * "Distance Approximations for Rasterizing Implicit Curves" by Gabriel Taubin 33 * 34 * In both versions we solve the quadratic for ||q-p||. 35 * Version 1: 36 * gFM is magnitude of first partials and gFM2 is magnitude of 2nd partials (as derived from paper) 37 * builder->fsCodeAppend("\t\tedgeAlpha = (sqrt(gFM*gFM+4.0*func*gF2M) - gFM)/(2.0*gF2M);\n"); 38 * Version 2: 39 * builder->fsCodeAppend("\t\tedgeAlpha = (gFM - sqrt(gFM*gFM-4.0*func*gF2M))/(2.0*gF2M);\n"); 40 * 41 * Also note that 2nd partials of k,l,m are zero 42 * 43 * When comparing the two second order approximations to the first order approximations, 44 * the following results were found. Version 1 tends to underestimate the distances, thus it 45 * basically increases all the error that we were already seeing in the first order 46 * approx. So this version is not the one to use. Version 2 has the opposite effect 47 * and tends to overestimate the distances. This is much closer to what we are 48 * looking for. It is able to render ellipses (even thin ones) without the need to chop. 49 * However, it can not handle thin hyperbolas well and thus would still rely on 50 * chopping to tighten the clipping. Another side effect of the overestimating is 51 * that the curves become much thinner and "ropey". If all that was ever rendered 52 * were "not too thin" curves and ellipses then 2nd order may have an advantage since 53 * only one geometry would need to be rendered. However no benches were run comparing 54 * chopped first order and non chopped 2nd order. 55 */ 56 class GrGLConicEffect; 57 58 class GrConicEffect : public GrGeometryProcessor { 59 public: 60 static sk_sp<GrGeometryProcessor> Make(const SkPMColor4f& color, 61 const SkMatrix& viewMatrix, 62 const GrClipEdgeType edgeType, 63 const GrCaps& caps, 64 const SkMatrix& localMatrix, 65 bool usesLocalCoords, 66 uint8_t coverage = 0xff) { 67 switch (edgeType) { 68 case GrClipEdgeType::kFillAA: 69 if (!caps.shaderCaps()->shaderDerivativeSupport()) { 70 return nullptr; 71 } 72 return sk_sp<GrGeometryProcessor>( 73 new GrConicEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillAA, 74 localMatrix, usesLocalCoords)); 75 case GrClipEdgeType::kHairlineAA: 76 if (!caps.shaderCaps()->shaderDerivativeSupport()) { 77 return nullptr; 78 } 79 return sk_sp<GrGeometryProcessor>( 80 new GrConicEffect(color, viewMatrix, coverage, 81 GrClipEdgeType::kHairlineAA, localMatrix, 82 usesLocalCoords)); 83 case GrClipEdgeType::kFillBW: 84 return sk_sp<GrGeometryProcessor>( 85 new GrConicEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillBW, 86 localMatrix, usesLocalCoords)); 87 default: 88 return nullptr; 89 } 90 } 91 92 ~GrConicEffect() override; 93 94 const char* name() const override { return "Conic"; } 95 96 inline const Attribute& inPosition() const { return kAttributes[0]; } 97 inline const Attribute& inConicCoeffs() const { return kAttributes[1]; } 98 inline bool isAntiAliased() const { return GrProcessorEdgeTypeIsAA(fEdgeType); } 99 inline bool isFilled() const { return GrProcessorEdgeTypeIsFill(fEdgeType); } 100 inline GrClipEdgeType getEdgeType() const { return fEdgeType; } 101 const SkPMColor4f& color() const { return fColor; } 102 const SkMatrix& viewMatrix() const { return fViewMatrix; } 103 const SkMatrix& localMatrix() const { return fLocalMatrix; } 104 bool usesLocalCoords() const { return fUsesLocalCoords; } 105 uint8_t coverageScale() const { return fCoverageScale; } 106 107 void getGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override; 108 109 GrGLSLPrimitiveProcessor* createGLSLInstance(const GrShaderCaps&) const override; 110 111 private: 112 GrConicEffect(const SkPMColor4f&, const SkMatrix& viewMatrix, uint8_t coverage, GrClipEdgeType, 113 const SkMatrix& localMatrix, bool usesLocalCoords); 114 115 SkPMColor4f fColor; 116 SkMatrix fViewMatrix; 117 SkMatrix fLocalMatrix; 118 bool fUsesLocalCoords; 119 uint8_t fCoverageScale; 120 GrClipEdgeType fEdgeType; 121 static constexpr Attribute kAttributes[] = { 122 {"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType}, 123 {"inConicCoeffs", kFloat4_GrVertexAttribType, kHalf4_GrSLType} 124 }; 125 126 GR_DECLARE_GEOMETRY_PROCESSOR_TEST 127 128 typedef GrGeometryProcessor INHERITED; 129 }; 130 131 /////////////////////////////////////////////////////////////////////////////// 132 /** 133 * The output of this effect is a hairline edge for quadratics. 134 * Quadratic specified by 0=u^2-v canonical coords. u and v are the first 135 * two components of the vertex attribute. At the three control points that define 136 * the Quadratic, u, v have the values {0,0}, {1/2, 0}, and {1, 1} respectively. 137 * Coverage for AA is min(0, 1-distance). 3rd & 4th cimponent unused. 138 * Requires shader derivative instruction support. 139 */ 140 class GrGLQuadEffect; 141 142 class GrQuadEffect : public GrGeometryProcessor { 143 public: 144 static sk_sp<GrGeometryProcessor> Make(const SkPMColor4f& color, 145 const SkMatrix& viewMatrix, 146 const GrClipEdgeType edgeType, 147 const GrCaps& caps, 148 const SkMatrix& localMatrix, 149 bool usesLocalCoords, 150 uint8_t coverage = 0xff) { 151 switch (edgeType) { 152 case GrClipEdgeType::kFillAA: 153 if (!caps.shaderCaps()->shaderDerivativeSupport()) { 154 return nullptr; 155 } 156 return sk_sp<GrGeometryProcessor>( 157 new GrQuadEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillAA, 158 localMatrix, usesLocalCoords)); 159 case GrClipEdgeType::kHairlineAA: 160 if (!caps.shaderCaps()->shaderDerivativeSupport()) { 161 return nullptr; 162 } 163 return sk_sp<GrGeometryProcessor>( 164 new GrQuadEffect(color, viewMatrix, coverage, 165 GrClipEdgeType::kHairlineAA, localMatrix, 166 usesLocalCoords)); 167 case GrClipEdgeType::kFillBW: 168 return sk_sp<GrGeometryProcessor>( 169 new GrQuadEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillBW, 170 localMatrix, usesLocalCoords)); 171 default: 172 return nullptr; 173 } 174 } 175 176 ~GrQuadEffect() override; 177 178 const char* name() const override { return "Quad"; } 179 180 inline const Attribute& inPosition() const { return kAttributes[0]; } 181 inline const Attribute& inHairQuadEdge() const { return kAttributes[1]; } 182 inline bool isAntiAliased() const { return GrProcessorEdgeTypeIsAA(fEdgeType); } 183 inline bool isFilled() const { return GrProcessorEdgeTypeIsFill(fEdgeType); } 184 inline GrClipEdgeType getEdgeType() const { return fEdgeType; } 185 const SkPMColor4f& color() const { return fColor; } 186 const SkMatrix& viewMatrix() const { return fViewMatrix; } 187 const SkMatrix& localMatrix() const { return fLocalMatrix; } 188 bool usesLocalCoords() const { return fUsesLocalCoords; } 189 uint8_t coverageScale() const { return fCoverageScale; } 190 191 void getGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override; 192 193 GrGLSLPrimitiveProcessor* createGLSLInstance(const GrShaderCaps&) const override; 194 195 private: 196 GrQuadEffect(const SkPMColor4f&, const SkMatrix& viewMatrix, uint8_t coverage, GrClipEdgeType, 197 const SkMatrix& localMatrix, bool usesLocalCoords); 198 199 SkPMColor4f fColor; 200 SkMatrix fViewMatrix; 201 SkMatrix fLocalMatrix; 202 bool fUsesLocalCoords; 203 uint8_t fCoverageScale; 204 GrClipEdgeType fEdgeType; 205 206 static constexpr Attribute kAttributes[] = { 207 {"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType}, 208 {"inHairQuadEdge", kFloat4_GrVertexAttribType, kHalf4_GrSLType} 209 }; 210 211 GR_DECLARE_GEOMETRY_PROCESSOR_TEST 212 213 typedef GrGeometryProcessor INHERITED; 214 }; 215 216 #endif 217
