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/*
* 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.
}
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