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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 "GrCCPRQuadraticProcessor.h"
#include "glsl/GrGLSLFragmentShaderBuilder.h"
#include "glsl/GrGLSLGeometryShaderBuilder.h"
#include "glsl/GrGLSLVertexShaderBuilder.h"
void GrCCPRQuadraticProcessor::onEmitVertexShader(const GrCCPRCoverageProcessor& proc,
GrGLSLVertexBuilder* v,
const TexelBufferHandle& pointsBuffer,
const char* atlasOffset, const char* rtAdjust,
GrGPArgs* gpArgs) const {
v->codeAppend ("float2 self = ");
v->appendTexelFetch(pointsBuffer,
SkStringPrintf("%s.x + sk_VertexID", proc.instanceAttrib()).c_str());
v->codeAppendf(".xy + %s;", atlasOffset);
gpArgs->fPositionVar.set(kFloat2_GrSLType, "self");
}
void GrCCPRQuadraticProcessor::emitWind(GrGLSLGeometryBuilder* g, const char* rtAdjust,
const char* outputWind) const {
// We will define bezierpts in onEmitGeometryShader.
g->codeAppend ("float area_times_2 = determinant(float2x2(bezierpts[1] - bezierpts[0], "
"bezierpts[2] - bezierpts[0]));");
// Drop curves that are nearly flat, in favor of the higher quality triangle antialiasing.
g->codeAppendf("if (2 * abs(area_times_2) < length((bezierpts[2] - bezierpts[0]) * %s.zx)) {",
rtAdjust);
#ifndef SK_BUILD_FOR_MAC
g->codeAppend ( "return;");
#else
// Returning from this geometry shader makes Mac very unhappy. Instead we make wind 0.
g->codeAppend ( "area_times_2 = 0;");
#endif
g->codeAppend ("}");
g->codeAppendf("%s = sign(area_times_2);", outputWind);
}
void GrCCPRQuadraticProcessor::onEmitGeometryShader(GrGLSLGeometryBuilder* g,
const char* emitVertexFn, const char* wind,
const char* rtAdjust) const {
// Prepend bezierpts at the start of the shader.
g->codePrependf("float3x2 bezierpts = float3x2(sk_in[0].gl_Position.xy, "
"sk_in[1].gl_Position.xy, "
"sk_in[2].gl_Position.xy);");
g->declareGlobal(fCanonicalMatrix);
g->codeAppendf("%s = float3x3(0.0, 0, 1, "
"0.5, 0, 1, "
"1.0, 1, 1) * "
"inverse(float3x3(bezierpts[0], 1, "
"bezierpts[1], 1, "
"bezierpts[2], 1));",
fCanonicalMatrix.c_str());
g->declareGlobal(fCanonicalDerivatives);
g->codeAppendf("%s = float2x2(%s) * float2x2(%s.x, 0, 0, %s.z);",
fCanonicalDerivatives.c_str(), fCanonicalMatrix.c_str(), rtAdjust, rtAdjust);
g->declareGlobal(fEdgeDistanceEquation);
g->codeAppendf("float2 edgept0 = bezierpts[%s > 0 ? 2 : 0];", wind);
g->codeAppendf("float2 edgept1 = bezierpts[%s > 0 ? 0 : 2];", wind);
this->emitEdgeDistanceEquation(g, "edgept0", "edgept1", fEdgeDistanceEquation.c_str());
this->emitQuadraticGeometry(g, emitVertexFn, rtAdjust);
}
void GrCCPRQuadraticProcessor::emitPerVertexGeometryCode(SkString* fnBody, const char* position,
const char* /*coverage*/,
const char* /*wind*/) const {
fnBody->appendf("%s.xy = (%s * float3(%s, 1)).xy;",
fXYD.gsOut(), fCanonicalMatrix.c_str(), position);
fnBody->appendf("%s.z = dot(%s.xy, %s) + %s.z;",
fXYD.gsOut(), fEdgeDistanceEquation.c_str(), position,
fEdgeDistanceEquation.c_str());
this->onEmitPerVertexGeometryCode(fnBody);
}
void GrCCPRQuadraticHullProcessor::emitQuadraticGeometry(GrGLSLGeometryBuilder* g,
const char* emitVertexFn,
const char* /*rtAdjust*/) const {
// Find the t value whose tangent is halfway between the tangents at the endpionts.
// (We defined bezierpts in onEmitGeometryShader.)
g->codeAppend ("float2 tan0 = bezierpts[1] - bezierpts[0];");
g->codeAppend ("float2 tan1 = bezierpts[2] - bezierpts[1];");
g->codeAppend ("float2 midnorm = normalize(tan0) - normalize(tan1);");
g->codeAppend ("float2 T = midnorm * float2x2(tan0 - tan1, tan0);");
g->codeAppend ("float t = clamp(T.t / T.s, 0, 1);"); // T.s=0 is weeded out by this point.
// Clip the bezier triangle by the tangent at our new t value. This is a simple application for
// De Casteljau's algorithm.
g->codeAppendf("float4x2 quadratic_hull = float4x2(bezierpts[0], "
"bezierpts[0] + tan0 * t, "
"bezierpts[1] + tan1 * t, "
"bezierpts[2]);");
int maxVerts = this->emitHullGeometry(g, emitVertexFn, "quadratic_hull", 4, "sk_InvocationID");
g->configure(GrGLSLGeometryBuilder::InputType::kTriangles,
GrGLSLGeometryBuilder::OutputType::kTriangleStrip,
maxVerts, 4);
}
void GrCCPRQuadraticHullProcessor::onEmitPerVertexGeometryCode(SkString* fnBody) const {
fnBody->appendf("%s = float2(2 * %s.x, -1) * %s;",
fGradXY.gsOut(), fXYD.gsOut(), fCanonicalDerivatives.c_str());
}
void GrCCPRQuadraticHullProcessor::emitShaderCoverage(GrGLSLFragmentBuilder* f,
const char* outputCoverage) const {
f->codeAppendf("float d = (%s.x * %s.x - %s.y) * inversesqrt(dot(%s, %s));",
fXYD.fsIn(), fXYD.fsIn(), fXYD.fsIn(), fGradXY.fsIn(), fGradXY.fsIn());
f->codeAppendf("%s = clamp(0.5 - d, 0, 1);", outputCoverage);
f->codeAppendf("%s += min(%s.z, 0);", outputCoverage, fXYD.fsIn()); // Flat closing edge.
}
void GrCCPRQuadraticCornerProcessor::emitQuadraticGeometry(GrGLSLGeometryBuilder* g,
const char* emitVertexFn,
const char* rtAdjust) const {
g->declareGlobal(fEdgeDistanceDerivatives);
g->codeAppendf("%s = %s.xy * %s.xz;",
fEdgeDistanceDerivatives.c_str(), fEdgeDistanceEquation.c_str(), rtAdjust);
g->codeAppendf("float2 corner = bezierpts[sk_InvocationID * 2];");
int numVertices = this->emitCornerGeometry(g, emitVertexFn, "corner");
g->configure(GrGLSLGeometryBuilder::InputType::kTriangles,
GrGLSLGeometryBuilder::OutputType::kTriangleStrip, numVertices, 2);
}
void GrCCPRQuadraticCornerProcessor::onEmitPerVertexGeometryCode(SkString* fnBody) const {
fnBody->appendf("%s = float3(%s[0].x, %s[0].y, %s.x);",
fdXYDdx.gsOut(), fCanonicalDerivatives.c_str(), fCanonicalDerivatives.c_str(),
fEdgeDistanceDerivatives.c_str());
fnBody->appendf("%s = float3(%s[1].x, %s[1].y, %s.y);",
fdXYDdy.gsOut(), fCanonicalDerivatives.c_str(), fCanonicalDerivatives.c_str(),
fEdgeDistanceDerivatives.c_str());
}
void GrCCPRQuadraticCornerProcessor::emitShaderCoverage(GrGLSLFragmentBuilder* f,
const char* outputCoverage) const {
f->codeAppendf("float x = %s.x, y = %s.y, d = %s.z;",
fXYD.fsIn(), fXYD.fsIn(), fXYD.fsIn());
f->codeAppendf("float2x3 grad_xyd = float2x3(%s, %s);", fdXYDdx.fsIn(), fdXYDdy.fsIn());
// Erase what the previous hull shader wrote. We don't worry about the two corners falling on
// the same pixel because those cases should have been weeded out by this point.
f->codeAppend ("float f = x*x - y;");
f->codeAppend ("float2 grad_f = float2(2*x, -1) * float2x2(grad_xyd);");
f->codeAppendf("%s = -(0.5 - f * inversesqrt(dot(grad_f, grad_f)));", outputCoverage);
f->codeAppendf("%s -= d;", outputCoverage);
// Use software msaa to approximate coverage at the corner pixels.
int sampleCount = this->defineSoftSampleLocations(f, "samples");
f->codeAppendf("float3 xyd_center = float3(%s.xy, %s.z + 0.5);",
fXYD.fsIn(), fXYD.fsIn());
f->codeAppendf("for (int i = 0; i < %i; ++i) {", sampleCount);
f->codeAppend ( "float3 xyd = grad_xyd * samples[i] + xyd_center;");
f->codeAppend ( "half f = xyd.y - xyd.x * xyd.x;"); // f > 0 -> inside curve.
f->codeAppendf( "%s += all(greaterThan(float2(f,xyd.z), float2(0))) ? %f : 0;",
outputCoverage, 1.0 / sampleCount);
f->codeAppendf("}");
}
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