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 #include "GrCCCoverageProcessor.h" 9 10 #include "GrGpuCommandBuffer.h" 11 #include "GrOpFlushState.h" 12 #include "SkMakeUnique.h" 13 #include "ccpr/GrCCConicShader.h" 14 #include "ccpr/GrCCCubicShader.h" 15 #include "ccpr/GrCCQuadraticShader.h" 16 #include "glsl/GrGLSLVertexGeoBuilder.h" 17 #include "glsl/GrGLSLFragmentShaderBuilder.h" 18 #include "glsl/GrGLSLVertexGeoBuilder.h" 19 20 class GrCCCoverageProcessor::TriangleShader : public GrCCCoverageProcessor::Shader { 21 void onEmitVaryings(GrGLSLVaryingHandler* varyingHandler, GrGLSLVarying::Scope scope, 22 SkString* code, const char* position, const char* coverage, 23 const char* cornerCoverage) override { 24 if (!cornerCoverage) { 25 fCoverages.reset(kHalf_GrSLType, scope); 26 varyingHandler->addVarying("coverage", &fCoverages); 27 code->appendf("%s = %s;", OutName(fCoverages), coverage); 28 } else { 29 fCoverages.reset(kHalf3_GrSLType, scope); 30 varyingHandler->addVarying("coverages", &fCoverages); 31 code->appendf("%s = half3(%s, %s);", OutName(fCoverages), coverage, cornerCoverage); 32 } 33 } 34 35 void onEmitFragmentCode(GrGLSLFPFragmentBuilder* f, const char* outputCoverage) const override { 36 if (kHalf_GrSLType == fCoverages.type()) { 37 f->codeAppendf("%s = %s;", outputCoverage, fCoverages.fsIn()); 38 } else { 39 f->codeAppendf("%s = %s.z * %s.y + %s.x;", 40 outputCoverage, fCoverages.fsIn(), fCoverages.fsIn(), fCoverages.fsIn()); 41 } 42 } 43 44 GrGLSLVarying fCoverages; 45 }; 46 47 void GrCCCoverageProcessor::Shader::CalcWind(const GrCCCoverageProcessor& proc, 48 GrGLSLVertexGeoBuilder* s, const char* pts, 49 const char* outputWind) { 50 if (3 == proc.numInputPoints()) { 51 s->codeAppendf("float2 a = %s[0] - %s[1], " 52 "b = %s[0] - %s[2];", pts, pts, pts, pts); 53 } else { 54 // All inputs are convex, so it's sufficient to just average the middle two input points. 55 SkASSERT(4 == proc.numInputPoints()); 56 s->codeAppendf("float2 p12 = (%s[1] + %s[2]) * .5;", pts, pts); 57 s->codeAppendf("float2 a = %s[0] - p12, " 58 "b = %s[0] - %s[3];", pts, pts, pts); 59 } 60 61 s->codeAppend ("float area_x2 = determinant(float2x2(a, b));"); 62 if (proc.isTriangles()) { 63 // We cull extremely thin triangles by zeroing wind. When a triangle gets too thin it's 64 // possible for FP round-off error to actually give us the wrong winding direction, causing 65 // rendering artifacts. The criteria we choose is "height <~ 1/1024". So we drop a triangle 66 // if the max effect it can have on any single pixel is <~ 1/1024, or 1/4 of a bit in 8888. 67 s->codeAppend ("float2 bbox_size = max(abs(a), abs(b));"); 68 s->codeAppend ("float basewidth = max(bbox_size.x + bbox_size.y, 1);"); 69 s->codeAppendf("%s = (abs(area_x2 * 1024) > basewidth) ? sign(area_x2) : 0;", outputWind); 70 } else { 71 // We already converted nearly-flat curves to lines on the CPU, so no need to worry about 72 // thin curve hulls at this point. 73 s->codeAppendf("%s = sign(area_x2);", outputWind); 74 } 75 } 76 77 void GrCCCoverageProcessor::Shader::EmitEdgeDistanceEquation(GrGLSLVertexGeoBuilder* s, 78 const char* leftPt, 79 const char* rightPt, 80 const char* outputDistanceEquation) { 81 s->codeAppendf("float2 n = float2(%s.y - %s.y, %s.x - %s.x);", 82 rightPt, leftPt, leftPt, rightPt); 83 s->codeAppend ("float nwidth = (abs(n.x) + abs(n.y)) * (bloat * 2);"); 84 // When nwidth=0, wind must also be 0 (and coverage * wind = 0). So it doesn't matter what we 85 // come up with here as long as it isn't NaN or Inf. 86 s->codeAppend ("n /= (0 != nwidth) ? nwidth : 1;"); 87 s->codeAppendf("%s = float3(-n, dot(n, %s) - .5);", outputDistanceEquation, leftPt); 88 } 89 90 void GrCCCoverageProcessor::Shader::CalcEdgeCoverageAtBloatVertex(GrGLSLVertexGeoBuilder* s, 91 const char* leftPt, 92 const char* rightPt, 93 const char* rasterVertexDir, 94 const char* outputCoverage) { 95 // Here we find an edge's coverage at one corner of a conservative raster bloat box whose center 96 // falls on the edge in question. (A bloat box is axis-aligned and the size of one pixel.) We 97 // always set up coverage so it is -1 at the outermost corner, 0 at the innermost, and -.5 at 98 // the center. Interpolated, these coverage values convert jagged conservative raster edges into 99 // smooth antialiased edges. 100 // 101 // d1 == (P + sign(n) * bloat) dot n (Distance at the bloat box vertex whose 102 // == P dot n + (abs(n.x) + abs(n.y)) * bloatSize coverage=-1, where the bloat box is 103 // centered on P.) 104 // 105 // d0 == (P - sign(n) * bloat) dot n (Distance at the bloat box vertex whose 106 // == P dot n - (abs(n.x) + abs(n.y)) * bloatSize coverage=0, where the bloat box is 107 // centered on P.) 108 // 109 // d == (P + rasterVertexDir * bloatSize) dot n (Distance at the bloat box vertex whose 110 // == P dot n + (rasterVertexDir dot n) * bloatSize coverage we wish to calculate.) 111 // 112 // coverage == -(d - d0) / (d1 - d0) (coverage=-1 at d=d1; coverage=0 at d=d0) 113 // 114 // == (rasterVertexDir dot n) / (abs(n.x) + abs(n.y)) * -.5 - .5 115 // 116 s->codeAppendf("float2 n = float2(%s.y - %s.y, %s.x - %s.x);", 117 rightPt, leftPt, leftPt, rightPt); 118 s->codeAppend ("float nwidth = abs(n.x) + abs(n.y);"); 119 s->codeAppendf("float t = dot(%s, n);", rasterVertexDir); 120 // The below conditional guarantees we get exactly 1 on the divide when nwidth=t (in case the 121 // GPU divides by multiplying by the reciprocal?) It also guards against NaN when nwidth=0. 122 s->codeAppendf("%s = (abs(t) != nwidth ? t / nwidth : sign(t)) * -.5 - .5;", outputCoverage); 123 } 124 125 void GrCCCoverageProcessor::Shader::CalcEdgeCoveragesAtBloatVertices(GrGLSLVertexGeoBuilder* s, 126 const char* leftPt, 127 const char* rightPt, 128 const char* bloatDir1, 129 const char* bloatDir2, 130 const char* outputCoverages) { 131 // See comments in CalcEdgeCoverageAtBloatVertex. 132 s->codeAppendf("float2 n = float2(%s.y - %s.y, %s.x - %s.x);", 133 rightPt, leftPt, leftPt, rightPt); 134 s->codeAppend ("float nwidth = abs(n.x) + abs(n.y);"); 135 s->codeAppendf("float2 t = n * float2x2(%s, %s);", bloatDir1, bloatDir2); 136 s->codeAppendf("for (int i = 0; i < 2; ++i) {"); 137 s->codeAppendf( "%s[i] = (abs(t[i]) != nwidth ? t[i] / nwidth : sign(t[i])) * -.5 - .5;", 138 outputCoverages); 139 s->codeAppendf("}"); 140 } 141 142 void GrCCCoverageProcessor::Shader::CalcCornerAttenuation(GrGLSLVertexGeoBuilder* s, 143 const char* leftDir, const char* rightDir, 144 const char* outputAttenuation) { 145 // obtuseness = cos(corner_angle) if corner_angle > 90 degrees 146 // 0 if corner_angle <= 90 degrees 147 // 148 // NOTE: leftDir and rightDir are normalized and point in the same direction the path was 149 // defined with, i.e., leftDir points into the corner and rightDir points away from the corner. 150 s->codeAppendf("half obtuseness = max(dot(%s, %s), 0);", leftDir, rightDir); 151 152 // axis_alignedness = 1 - tan(angle_to_nearest_axis_from_corner_bisector) 153 // (i.e., 1 when the corner bisector is aligned with the x- or y-axis 154 // 0 when the corner bisector falls on a 45 degree angle 155 // 0..1 when the corner bisector falls somewhere in between 156 s->codeAppendf("half2 abs_bisect_maybe_transpose = abs((0 == obtuseness) ? %s - %s : %s + %s);", 157 leftDir, rightDir, leftDir, rightDir); 158 s->codeAppend ("half axis_alignedness = " 159 "1 - min(abs_bisect_maybe_transpose.y, abs_bisect_maybe_transpose.x) / " 160 "max(abs_bisect_maybe_transpose.x, abs_bisect_maybe_transpose.y);"); 161 162 // ninety_degreesness = sin^2(corner_angle) 163 // sin^2 just because... it's always positive and the results looked better than plain sine... ? 164 s->codeAppendf("half ninety_degreesness = determinant(half2x2(%s, %s));", leftDir, rightDir); 165 s->codeAppend ("ninety_degreesness = ninety_degreesness * ninety_degreesness;"); 166 167 // The below formula is not smart. It was just arrived at by considering the following 168 // observations: 169 // 170 // 1. 90-degree, axis-aligned corners have full attenuation along the bisector. 171 // (i.e. coverage = 1 - distance_to_corner^2) 172 // (i.e. outputAttenuation = 0) 173 // 174 // 2. 180-degree corners always have zero attenuation. 175 // (i.e. coverage = 1 - distance_to_corner) 176 // (i.e. outputAttenuation = 1) 177 // 178 // 3. 90-degree corners whose bisector falls on a 45 degree angle also do not attenuate. 179 // (i.e. outputAttenuation = 1) 180 s->codeAppendf("%s = max(obtuseness, axis_alignedness * ninety_degreesness);", 181 outputAttenuation); 182 } 183 184 void GrCCCoverageProcessor::getGLSLProcessorKey(const GrShaderCaps&, 185 GrProcessorKeyBuilder* b) const { 186 int key = (int)fPrimitiveType << 2; 187 if (GSSubpass::kCorners == fGSSubpass) { 188 key |= 2; 189 } 190 if (Impl::kVertexShader == fImpl) { 191 key |= 1; 192 } 193 #ifdef SK_DEBUG 194 uint32_t bloatBits; 195 memcpy(&bloatBits, &fDebugBloat, 4); 196 b->add32(bloatBits); 197 #endif 198 b->add32(key); 199 } 200 201 GrGLSLPrimitiveProcessor* GrCCCoverageProcessor::createGLSLInstance(const GrShaderCaps&) const { 202 std::unique_ptr<Shader> shader; 203 switch (fPrimitiveType) { 204 case PrimitiveType::kTriangles: 205 case PrimitiveType::kWeightedTriangles: 206 shader = skstd::make_unique<TriangleShader>(); 207 break; 208 case PrimitiveType::kQuadratics: 209 shader = skstd::make_unique<GrCCQuadraticShader>(); 210 break; 211 case PrimitiveType::kCubics: 212 shader = skstd::make_unique<GrCCCubicShader>(); 213 break; 214 case PrimitiveType::kConics: 215 shader = skstd::make_unique<GrCCConicShader>(); 216 break; 217 } 218 return Impl::kGeometryShader == fImpl ? this->createGSImpl(std::move(shader)) 219 : this->createVSImpl(std::move(shader)); 220 } 221 222 void GrCCCoverageProcessor::Shader::emitFragmentCode(const GrCCCoverageProcessor& proc, 223 GrGLSLFPFragmentBuilder* f, 224 const char* skOutputColor, 225 const char* skOutputCoverage) const { 226 f->codeAppendf("half coverage = 0;"); 227 this->onEmitFragmentCode(f, "coverage"); 228 f->codeAppendf("%s.a = coverage;", skOutputColor); 229 f->codeAppendf("%s = half4(1);", skOutputCoverage); 230 } 231 232 void GrCCCoverageProcessor::draw(GrOpFlushState* flushState, const GrPipeline& pipeline, 233 const SkIRect scissorRects[], const GrMesh meshes[], int meshCount, 234 const SkRect& drawBounds) const { 235 GrPipeline::DynamicStateArrays dynamicStateArrays; 236 dynamicStateArrays.fScissorRects = scissorRects; 237 GrGpuRTCommandBuffer* cmdBuff = flushState->rtCommandBuffer(); 238 cmdBuff->draw(*this, pipeline, nullptr, &dynamicStateArrays, meshes, meshCount, drawBounds); 239 240 // Geometry shader backend draws primitives in two subpasses. 241 if (Impl::kGeometryShader == fImpl) { 242 SkASSERT(GSSubpass::kHulls == fGSSubpass); 243 GrCCCoverageProcessor cornerProc(*this, GSSubpass::kCorners); 244 cmdBuff->draw(cornerProc, pipeline, nullptr, &dynamicStateArrays, meshes, meshCount, 245 drawBounds); 246 } 247 } 248
