/*
* 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 "GrCCCubicShader.h"
#include "glsl/GrGLSLFragmentShaderBuilder.h"
#include "glsl/GrGLSLVertexGeoBuilder.h"
using Shader = GrCCCoverageProcessor::Shader;
void GrCCCubicShader::emitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
const char* repetitionID, const char* wind,
GeometryVars* vars) const {
// Find the cubic's power basis coefficients.
s->codeAppendf("float2x4 C = float4x4(-1, 3, -3, 1, "
" 3, -6, 3, 0, "
"-3, 3, 0, 0, "
" 1, 0, 0, 0) * transpose(%s);", pts);
// Find the cubic's inflection function.
s->codeAppend ("float D3 = +determinant(float2x2(C[0].yz, C[1].yz));");
s->codeAppend ("float D2 = -determinant(float2x2(C[0].xz, C[1].xz));");
s->codeAppend ("float D1 = +determinant(float2x2(C));");
// Calculate the KLM matrix.
s->declareGlobal(fKLMMatrix);
s->codeAppend ("float discr = 3*D2*D2 - 4*D1*D3;");
s->codeAppend ("float x = discr >= 0 ? 3 : 1;");
s->codeAppend ("float q = sqrt(x * abs(discr));");
s->codeAppend ("q = x*D2 + (D2 >= 0 ? q : -q);");
s->codeAppend ("float2 l, m;");
s->codeAppend ("l.ts = normalize(float2(q, 2*x * D1));");
s->codeAppend ("m.ts = normalize(float2(2, q) * (discr >= 0 ? float2(D3, 1) "
": float2(D2*D2 - D3*D1, D1)));");
s->codeAppend ("float4 K;");
s->codeAppend ("float4 lm = l.sstt * m.stst;");
s->codeAppend ("K = float4(0, lm.x, -lm.y - lm.z, lm.w);");
s->codeAppend ("float4 L, M;");
s->codeAppend ("lm.yz += 2*lm.zy;");
s->codeAppend ("L = float4(-1,x,-x,1) * l.sstt * (discr >= 0 ? l.ssst * l.sttt : lm);");
s->codeAppend ("M = float4(-1,x,-x,1) * m.sstt * (discr >= 0 ? m.ssst * m.sttt : lm.xzyw);");
s->codeAppend ("short middlerow = abs(D2) > abs(D1) ? 2 : 1;");
s->codeAppend ("float3x3 CI = inverse(float3x3(C[0][0], C[0][middlerow], C[0][3], "
"C[1][0], C[1][middlerow], C[1][3], "
" 0, 0, 1));");
s->codeAppendf("%s = CI * float3x3(K[0], K[middlerow], K[3], "
"L[0], L[middlerow], L[3], "
"M[0], M[middlerow], M[3]);", fKLMMatrix.c_str());
// Evaluate the cubic at T=.5 for a mid-ish point.
s->codeAppendf("float2 midpoint = %s * float4(.125, .375, .375, .125);", pts);
// Orient the KLM matrix so L & M have matching signs on the side of the curve we wish to fill.
// We give L & M both the same sign as wind, in order to pass this value to the fragment shader.
// (Cubics are pre-chopped such that L & M do not change sign within any individual segment).
s->codeAppendf("float2 orientation = sign(float3(midpoint, 1) * float2x3(%s[1], %s[2]));",
fKLMMatrix.c_str(), fKLMMatrix.c_str());
s->codeAppendf("%s *= float3x3(orientation[0] * orientation[1], 0, 0, "
"0, orientation[0] * %s, 0, "
"0, 0, orientation[1] * %s);", fKLMMatrix.c_str(), wind, wind);
// Determine the amount of additional coverage to subtract out for the flat edge (P3 -> P0).
s->declareGlobal(fEdgeDistanceEquation);
s->codeAppendf("short edgeidx0 = %s > 0 ? 3 : 0;", wind);
s->codeAppendf("float2 edgept0 = %s[edgeidx0];", pts);
s->codeAppendf("float2 edgept1 = %s[3 - edgeidx0];", pts);
Shader::EmitEdgeDistanceEquation(s, "edgept0", "edgept1", fEdgeDistanceEquation.c_str());
this->onEmitSetupCode(s, pts, repetitionID, vars);
}
void GrCCCubicShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
GrGLSLVarying::Scope scope, SkString* code,
const char* position, const char* inputCoverage,
const char* /*wind*/) {
SkASSERT(!inputCoverage);
fKLMD.reset(kFloat4_GrSLType, scope);
varyingHandler->addVarying("klmd", &fKLMD);
code->appendf("float3 klm = float3(%s, 1) * %s;", position, fKLMMatrix.c_str());
code->appendf("float d = dot(float3(%s, 1), %s);", position, fEdgeDistanceEquation.c_str());
code->appendf("%s = float4(klm, d);", OutName(fKLMD));
this->onEmitVaryings(varyingHandler, scope, code);
}
void GrCCCubicShader::onEmitFragmentCode(GrGLSLPPFragmentBuilder* f,
const char* outputCoverage) const {
f->codeAppendf("float k = %s.x, l = %s.y, m = %s.z, d = %s.w;",
fKLMD.fsIn(), fKLMD.fsIn(), fKLMD.fsIn(), fKLMD.fsIn());
this->emitCoverage(f, outputCoverage);
// Wind is the sign of both L and/or M. Take the sign of whichever has the larger magnitude.
// (In reality, either would be fine because we chop cubics with more than a half pixel of
// padding around the L & M lines, so neither should approach zero.)
f->codeAppend ("half wind = sign(l + m);");
f->codeAppendf("%s *= wind;", outputCoverage);
}
void GrCCCubicHullShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
GrGLSLVarying::Scope scope, SkString* code) {
fGradMatrix.reset(kFloat2x2_GrSLType, scope);
varyingHandler->addVarying("grad_matrix", &fGradMatrix);
// "klm" was just defined by the base class.
code->appendf("%s[0] = 3 * klm[0] * %s[0].xy;", OutName(fGradMatrix), fKLMMatrix.c_str());
code->appendf("%s[1] = -klm[1] * %s[2].xy - klm[2] * %s[1].xy;",
OutName(fGradMatrix), fKLMMatrix.c_str(), fKLMMatrix.c_str());
}
void GrCCCubicHullShader::emitCoverage(GrGLSLPPFragmentBuilder* f,
const char* outputCoverage) const {
// k,l,m,d are defined by the base class.
f->codeAppend ("float f = k*k*k - l*m;");
f->codeAppendf("float2 grad_f = %s * float2(k, 1);", fGradMatrix.fsIn());
f->codeAppendf("%s = clamp(0.5 - f * inversesqrt(dot(grad_f, grad_f)), 0, 1);", outputCoverage);
f->codeAppendf("%s += min(d, 0);", outputCoverage); // Flat edge opposite the curve.
}
void GrCCCubicCornerShader::onEmitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
const char* repetitionID, GeometryVars* vars) const {
s->codeAppendf("float2 corner = %s[%s * 3];", pts, repetitionID);
vars->fCornerVars.fPoint = "corner";
}
void GrCCCubicCornerShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
GrGLSLVarying::Scope scope, SkString* code) {
fdKLMDdx.reset(kFloat4_GrSLType, scope);
varyingHandler->addFlatVarying("dklmddx", &fdKLMDdx);
code->appendf("%s = float4(%s[0].x, %s[1].x, %s[2].x, %s.x);",
OutName(fdKLMDdx), fKLMMatrix.c_str(), fKLMMatrix.c_str(),
fKLMMatrix.c_str(), fEdgeDistanceEquation.c_str());
fdKLMDdy.reset(kFloat4_GrSLType, scope);
varyingHandler->addFlatVarying("dklmddy", &fdKLMDdy);
code->appendf("%s = float4(%s[0].y, %s[1].y, %s[2].y, %s.y);",
OutName(fdKLMDdy), fKLMMatrix.c_str(), fKLMMatrix.c_str(),
fKLMMatrix.c_str(), fEdgeDistanceEquation.c_str());
}
void GrCCCubicCornerShader::emitCoverage(GrGLSLPPFragmentBuilder* f,
const char* outputCoverage) const {
f->codeAppendf("float2x4 grad_klmd = float2x4(%s, %s);", fdKLMDdx.fsIn(), fdKLMDdy.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.
// k,l,m,d are defined by the base class.
f->codeAppend ("float f = k*k*k - l*m;");
f->codeAppend ("float2 grad_f = float3(3*k*k, -m, -l) * float2x3(grad_klmd);");
f->codeAppendf("%s = -clamp(0.5 - f * inversesqrt(dot(grad_f, grad_f)), 0, 1);",
outputCoverage);
f->codeAppendf("%s -= d;", outputCoverage);
// Use software msaa to estimate actual coverage at the corner pixels.
const int sampleCount = Shader::DefineSoftSampleLocations(f, "samples");
f->codeAppendf("float4 klmd_center = float4(%s.xyz, %s.w + 0.5);",
fKLMD.fsIn(), fKLMD.fsIn());
f->codeAppendf("for (int i = 0; i < %i; ++i) {", sampleCount);
f->codeAppend ( "float4 klmd = grad_klmd * samples[i] + klmd_center;");
f->codeAppend ( "half f = klmd.y * klmd.z - klmd.x * klmd.x * klmd.x;");
f->codeAppendf( "%s += all(greaterThan(half4(f, klmd.y, klmd.z, klmd.w), "
"half4(0))) ? %f : 0;",
outputCoverage, 1.0 / sampleCount);
f->codeAppend ("}");
}