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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 "GrCCPRCubicProcessor.h"
#include "glsl/GrGLSLFragmentShaderBuilder.h"
#include "glsl/GrGLSLGeometryShaderBuilder.h"
#include "glsl/GrGLSLVertexShaderBuilder.h"
void GrCCPRCubicProcessor::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 GrCCPRCubicProcessor::emitWind(GrGLSLGeometryBuilder* g, const char* rtAdjust,
const char* outputWind) const {
// We will define bezierpts in onEmitGeometryShader.
g->codeAppend ("float area_times_2 = "
"determinant(float3x3(1, bezierpts[0], "
"1, bezierpts[2], "
"0, bezierpts[3] - bezierpts[1]));");
// Drop curves that are nearly flat. The KLM math becomes unstable in this case.
g->codeAppendf("if (2 * abs(area_times_2) < length((bezierpts[3] - 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 GrCCPRCubicProcessor::onEmitGeometryShader(GrGLSLGeometryBuilder* g, const char* emitVertexFn,
const char* wind, const char* rtAdjust) const {
// Prepend bezierpts at the start of the shader.
g->codePrependf("float4x2 bezierpts = float4x2(sk_in[0].sk_Position.xy, "
"sk_in[1].sk_Position.xy, "
"sk_in[2].sk_Position.xy, "
"sk_in[3].sk_Position.xy);");
// Evaluate the cubic at T=.5 for an mid-ish point.
g->codeAppendf("float2 midpoint = bezierpts * float4(.125, .375, .375, .125);");
// Find the cubic's power basis coefficients.
g->codeAppend ("float2x4 C = float4x4(-1, 3, -3, 1, "
" 3, -6, 3, 0, "
"-3, 3, 0, 0, "
" 1, 0, 0, 0) * transpose(bezierpts);");
// Find the cubic's inflection function.
g->codeAppend ("float D3 = +determinant(float2x2(C[0].yz, C[1].yz));");
g->codeAppend ("float D2 = -determinant(float2x2(C[0].xz, C[1].xz));");
g->codeAppend ("float D1 = +determinant(float2x2(C));");
// Calculate the KLM matrix.
g->declareGlobal(fKLMMatrix);
g->codeAppend ("float4 K, L, M;");
g->codeAppend ("float2 l, m;");
g->codeAppend ("float discr = 3*D2*D2 - 4*D1*D3;");
if (CubicType::kSerpentine == fCubicType) {
// This math also works out for the "cusp" and "cusp at infinity" cases.
g->codeAppend ("float q = sqrt(max(3*discr, 0));");
g->codeAppend ("q = 3*D2 + (D2 >= 0 ? q : -q);");
g->codeAppend ("l.ts = normalize(float2(q, 6*D1));");
g->codeAppend ("m.ts = discr <= 0 ? l.ts : normalize(float2(2*D3, q));");
g->codeAppend ("K = float4(0, l.s * m.s, -l.t * m.s - m.t * l.s, l.t * m.t);");
g->codeAppend ("L = float4(-1,3,-3,1) * l.ssst * l.sstt * l.sttt;");
g->codeAppend ("M = float4(-1,3,-3,1) * m.ssst * m.sstt * m.sttt;");
} else {
g->codeAppend ("float q = sqrt(max(-discr, 0));");
g->codeAppend ("q = D2 + (D2 >= 0 ? q : -q);");
g->codeAppend ("l.ts = normalize(float2(q, 2*D1));");
g->codeAppend ("m.ts = discr >= 0 ? l.ts : normalize(float2(2 * (D2*D2 - D3*D1), D1*q));");
g->codeAppend ("float4 lxm = float4(l.s * m.s, l.s * m.t, l.t * m.s, l.t * m.t);");
g->codeAppend ("K = float4(0, lxm.x, -lxm.y - lxm.z, lxm.w);");
g->codeAppend ("L = float4(-1,1,-1,1) * l.sstt * (lxm.xyzw + float4(0, 2*lxm.zy, 0));");
g->codeAppend ("M = float4(-1,1,-1,1) * m.sstt * (lxm.xzyw + float4(0, 2*lxm.yz, 0));");
}
g->codeAppend ("short middlerow = abs(D2) > abs(D1) ? 2 : 1;");
g->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));");
g->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());
// Orient the KLM matrix so we fill the correct side of the curve.
g->codeAppendf("float2 orientation = sign(float3(midpoint, 1) * float2x3(%s[1], %s[2]));",
fKLMMatrix.c_str(), fKLMMatrix.c_str());
g->codeAppendf("%s *= float3x3(orientation[0] * orientation[1], 0, 0, "
"0, orientation[0], 0, "
"0, 0, orientation[1]);", fKLMMatrix.c_str());
g->declareGlobal(fKLMDerivatives);
g->codeAppendf("%s[0] = %s[0].xy * %s.xz;",
fKLMDerivatives.c_str(), fKLMMatrix.c_str(), rtAdjust);
g->codeAppendf("%s[1] = %s[1].xy * %s.xz;",
fKLMDerivatives.c_str(), fKLMMatrix.c_str(), rtAdjust);
g->codeAppendf("%s[2] = %s[2].xy * %s.xz;",
fKLMDerivatives.c_str(), fKLMMatrix.c_str(), rtAdjust);
// Determine the amount of additional coverage to subtract out for the flat edge (P3 -> P0).
g->declareGlobal(fEdgeDistanceEquation);
g->codeAppendf("short edgeidx0 = %s > 0 ? 3 : 0;", wind);
g->codeAppendf("float2 edgept0 = bezierpts[edgeidx0];");
g->codeAppendf("float2 edgept1 = bezierpts[3 - edgeidx0];");
this->emitEdgeDistanceEquation(g, "edgept0", "edgept1", fEdgeDistanceEquation.c_str());
this->emitCubicGeometry(g, emitVertexFn, wind, rtAdjust);
}
void GrCCPRCubicProcessor::emitPerVertexGeometryCode(SkString* fnBody, const char* position,
const char* /*coverage*/,
const char* /*wind*/) const {
fnBody->appendf("float3 klm = float3(%s, 1) * %s;", position, fKLMMatrix.c_str());
fnBody->appendf("float d = dot(float3(%s, 1), %s);",
position, fEdgeDistanceEquation.c_str());
fnBody->appendf("%s = float4(klm, d);", fKLMD.gsOut());
this->onEmitPerVertexGeometryCode(fnBody);
}
void GrCCPRCubicHullProcessor::emitCubicGeometry(GrGLSLGeometryBuilder* g, const char* emitVertexFn,
const char* wind, const char* rtAdjust) const {
// FIXME: we should clip this geometry at the tip of the curve.
int maxVertices = this->emitHullGeometry(g, emitVertexFn, "bezierpts", 4, "sk_InvocationID",
"midpoint");
g->configure(GrGLSLGeometryBuilder::InputType::kLinesAdjacency,
GrGLSLGeometryBuilder::OutputType::kTriangleStrip,
maxVertices, 4);
}
void GrCCPRCubicHullProcessor::onEmitPerVertexGeometryCode(SkString* fnBody) const {
// "klm" was just defined by the base class.
fnBody->appendf("%s[0] = 3 * klm[0] * %s[0];", fGradMatrix.gsOut(), fKLMDerivatives.c_str());
fnBody->appendf("%s[1] = -klm[1] * %s[2].xy - klm[2] * %s[1].xy;",
fGradMatrix.gsOut(), fKLMDerivatives.c_str(), fKLMDerivatives.c_str());
}
void GrCCPRCubicHullProcessor::emitShaderCoverage(GrGLSLFragmentBuilder* 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());
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 closing edge.
}
void GrCCPRCubicCornerProcessor::emitCubicGeometry(GrGLSLGeometryBuilder* g,
const char* emitVertexFn, const char* wind,
const char* rtAdjust) const {
// We defined bezierpts in onEmitGeometryShader.
g->declareGlobal(fEdgeDistanceDerivatives);
g->codeAppendf("%s = %s.xy * %s.xz;",
fEdgeDistanceDerivatives.c_str(), fEdgeDistanceEquation.c_str(), rtAdjust);
g->codeAppendf("float2 corner = bezierpts[sk_InvocationID * 3];");
int numVertices = this->emitCornerGeometry(g, emitVertexFn, "corner");
g->configure(GrGLSLGeometryBuilder::InputType::kLinesAdjacency,
GrGLSLGeometryBuilder::OutputType::kTriangleStrip, numVertices, 2);
}
void GrCCPRCubicCornerProcessor::onEmitPerVertexGeometryCode(SkString* fnBody) const {
fnBody->appendf("%s = float4(%s[0].x, %s[1].x, %s[2].x, %s.x);",
fdKLMDdx.gsOut(), fKLMDerivatives.c_str(), fKLMDerivatives.c_str(),
fKLMDerivatives.c_str(), fEdgeDistanceDerivatives.c_str());
fnBody->appendf("%s = float4(%s[0].y, %s[1].y, %s[2].y, %s.y);",
fdKLMDdy.gsOut(), fKLMDerivatives.c_str(), fKLMDerivatives.c_str(),
fKLMDerivatives.c_str(), fEdgeDistanceDerivatives.c_str());
// Otherwise, fEdgeDistances = fEdgeDistances * sign(wind * rtAdjust.x * rdAdjust.z).
GR_STATIC_ASSERT(kTopLeft_GrSurfaceOrigin == GrCCPRCoverageProcessor::kAtlasOrigin);
}
void GrCCPRCubicCornerProcessor::emitShaderCoverage(GrGLSLFragmentBuilder* 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.
f->codeAppendf("float k = %s.x, l = %s.y, m = %s.z, d = %s.w;",
fKLMD.fsIn(), fKLMD.fsIn(), fKLMD.fsIn(), fKLMD.fsIn());
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 = this->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 ("}");
}
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