| /* |
| * Copyright 2017 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "GrCCQuadraticShader.h" |
| |
| #include "glsl/GrGLSLFragmentShaderBuilder.h" |
| #include "glsl/GrGLSLVertexGeoBuilder.h" |
| |
| void GrCCQuadraticShader::emitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts, |
| const char* wind, const char** outHull4) const { |
| s->declareGlobal(fQCoordMatrix); |
| s->codeAppendf("%s = float2x2(1, 1, .5, 0) * inverse(float2x2(%s[2] - %s[0], %s[1] - %s[0]));", |
| fQCoordMatrix.c_str(), pts, pts, pts, pts); |
| |
| s->declareGlobal(fQCoord0); |
| s->codeAppendf("%s = %s[0];", fQCoord0.c_str(), pts); |
| |
| s->declareGlobal(fEdgeDistanceEquation); |
| s->codeAppendf("float2 edgept0 = %s[%s > 0 ? 2 : 0];", pts, wind); |
| s->codeAppendf("float2 edgept1 = %s[%s > 0 ? 0 : 2];", pts, wind); |
| Shader::EmitEdgeDistanceEquation(s, "edgept0", "edgept1", fEdgeDistanceEquation.c_str()); |
| |
| if (outHull4) { |
| // Clip the bezier triangle by the tangent line at maximum height. Quadratics have the nice |
| // property that maximum height always occurs at T=.5. This is a simple application for |
| // De Casteljau's algorithm. |
| s->codeAppend ("float2 quadratic_hull[4];"); |
| s->codeAppendf("quadratic_hull[0] = %s[0];", pts); |
| s->codeAppendf("quadratic_hull[1] = (%s[0] + %s[1]) * .5;", pts, pts); |
| s->codeAppendf("quadratic_hull[2] = (%s[1] + %s[2]) * .5;", pts, pts); |
| s->codeAppendf("quadratic_hull[3] = %s[2];", pts); |
| *outHull4 = "quadratic_hull"; |
| } |
| } |
| |
| void GrCCQuadraticShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler, |
| GrGLSLVarying::Scope scope, SkString* code, |
| const char* position, const char* coverage, |
| const char* cornerCoverage) { |
| fCoord_fGrad.reset(kFloat4_GrSLType, scope); |
| varyingHandler->addVarying("coord_and_grad", &fCoord_fGrad); |
| code->appendf("%s.xy = %s * (%s - %s);", // Quadratic coords. |
| OutName(fCoord_fGrad), fQCoordMatrix.c_str(), position, fQCoord0.c_str()); |
| code->appendf("%s.zw = 2*bloat * float2(2 * %s.x, -1) * %s;", // Gradient. |
| OutName(fCoord_fGrad), OutName(fCoord_fGrad), fQCoordMatrix.c_str()); |
| |
| // Coverages need full precision since distance to the opposite edge can be large. |
| fEdge_fWind_fCorner.reset(cornerCoverage ? kFloat4_GrSLType : kFloat2_GrSLType, scope); |
| varyingHandler->addVarying("edge_and_wind_and_corner", &fEdge_fWind_fCorner); |
| code->appendf("float edge = dot(%s, float3(%s, 1));", // Distance to flat opposite edge. |
| fEdgeDistanceEquation.c_str(), position); |
| code->appendf("%s.x = edge;", OutName(fEdge_fWind_fCorner)); |
| code->appendf("%s.y = %s;", OutName(fEdge_fWind_fCorner), coverage); // coverage == wind. |
| |
| if (cornerCoverage) { |
| code->appendf("half hull_coverage;"); |
| this->calcHullCoverage(code, OutName(fCoord_fGrad), "edge", "hull_coverage"); |
| code->appendf("%s.zw = half2(hull_coverage, 1) * %s;", |
| OutName(fEdge_fWind_fCorner), cornerCoverage); |
| } |
| } |
| |
| void GrCCQuadraticShader::onEmitFragmentCode(GrGLSLFPFragmentBuilder* f, |
| const char* outputCoverage) const { |
| this->calcHullCoverage(&AccessCodeString(f), fCoord_fGrad.fsIn(), |
| SkStringPrintf("%s.x", fEdge_fWind_fCorner.fsIn()).c_str(), |
| outputCoverage); |
| f->codeAppendf("%s *= %s.y;", outputCoverage, fEdge_fWind_fCorner.fsIn()); // Wind. |
| |
| if (kFloat4_GrSLType == fEdge_fWind_fCorner.type()) { |
| f->codeAppendf("%s = %s.z * %s.w + %s;",// Attenuated corner coverage. |
| outputCoverage, fEdge_fWind_fCorner.fsIn(), fEdge_fWind_fCorner.fsIn(), |
| outputCoverage); |
| } |
| } |
| |
| void GrCCQuadraticShader::calcHullCoverage(SkString* code, const char* coordAndGrad, |
| const char* edge, const char* outputCoverage) const { |
| code->appendf("float x = %s.x, y = %s.y;", coordAndGrad, coordAndGrad); |
| code->appendf("float2 grad = %s.zw;", coordAndGrad); |
| code->append ("float f = x*x - y;"); |
| code->append ("float fwidth = abs(grad.x) + abs(grad.y);"); |
| code->appendf("%s = min(0.5 - f/fwidth, 1);", outputCoverage); // Curve coverage. |
| code->appendf("half d = min(%s, 0);", edge); // Flat edge opposite the curve. |
| code->appendf("%s = max(%s + d, 0);", outputCoverage, outputCoverage); // Total hull coverage. |
| } |