1 /*
2 * Copyright 2017 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "GrCCQuadraticShader.h"
9
10 #include "glsl/GrGLSLVertexGeoBuilder.h"
11 #include "glsl/GrGLSLFragmentShaderBuilder.h"
12 #include "glsl/GrGLSLVertexGeoBuilder.h"
13
14 using Shader = GrCCCoverageProcessor::Shader;
15
emitSetupCode(GrGLSLVertexGeoBuilder * s,const char * pts,const char * repetitionID,const char * wind,GeometryVars * vars) const16 void GrCCQuadraticShader::emitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
17 const char* repetitionID, const char* wind,
18 GeometryVars* vars) const {
19 s->declareGlobal(fCanonicalMatrix);
20 s->codeAppendf("%s = float3x3(0.0, 0, 1, "
21 "0.5, 0, 1, "
22 "1.0, 1, 1) * "
23 "inverse(float3x3(%s[0], 1, "
24 "%s[1], 1, "
25 "%s[2], 1));",
26 fCanonicalMatrix.c_str(), pts, pts, pts);
27
28 s->declareGlobal(fEdgeDistanceEquation);
29 s->codeAppendf("float2 edgept0 = %s[%s > 0 ? 2 : 0];", pts, wind);
30 s->codeAppendf("float2 edgept1 = %s[%s > 0 ? 0 : 2];", pts, wind);
31 Shader::EmitEdgeDistanceEquation(s, "edgept0", "edgept1", fEdgeDistanceEquation.c_str());
32
33 this->onEmitSetupCode(s, pts, repetitionID, vars);
34 }
35
onEmitVaryings(GrGLSLVaryingHandler * varyingHandler,GrGLSLVarying::Scope scope,SkString * code,const char * position,const char * inputCoverage,const char * wind)36 void GrCCQuadraticShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
37 GrGLSLVarying::Scope scope, SkString* code,
38 const char* position, const char* inputCoverage,
39 const char* wind) {
40 SkASSERT(!inputCoverage);
41
42 fXYDW.reset(kFloat4_GrSLType, scope);
43 varyingHandler->addVarying("xydw", &fXYDW);
44 code->appendf("%s.xy = (%s * float3(%s, 1)).xy;",
45 OutName(fXYDW), fCanonicalMatrix.c_str(), position);
46 code->appendf("%s.z = dot(%s.xy, %s) + %s.z;",
47 OutName(fXYDW), fEdgeDistanceEquation.c_str(), position,
48 fEdgeDistanceEquation.c_str());
49 code->appendf("%s.w = %s;", OutName(fXYDW), wind);
50
51 this->onEmitVaryings(varyingHandler, scope, code);
52 }
53
onEmitFragmentCode(GrGLSLFPFragmentBuilder * f,const char * outputCoverage) const54 void GrCCQuadraticShader::onEmitFragmentCode(GrGLSLFPFragmentBuilder* f,
55 const char* outputCoverage) const {
56 this->emitCoverage(f, outputCoverage);
57 f->codeAppendf("%s *= %s.w;", outputCoverage, fXYDW.fsIn()); // Sign by wind.
58 }
59
onEmitSetupCode(GrGLSLVertexGeoBuilder * s,const char * pts,const char *,GeometryVars * vars) const60 void GrCCQuadraticHullShader::onEmitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
61 const char* /*repetitionID*/,
62 GeometryVars* vars) const {
63 // Find the T value whose tangent is halfway between the tangents at the endpionts.
64 s->codeAppendf("float2 tan0 = %s[1] - %s[0];", pts, pts);
65 s->codeAppendf("float2 tan1 = %s[2] - %s[1];", pts, pts);
66 s->codeAppend ("float2 midnorm = normalize(tan0) - normalize(tan1);");
67 s->codeAppend ("float2 T = midnorm * float2x2(tan0 - tan1, tan0);");
68 s->codeAppend ("float t = clamp(T.t / T.s, 0, 1);"); // T.s != 0; we cull flat curves on CPU.
69
70 // Clip the bezier triangle by the tangent at our new t value. This is a simple application for
71 // De Casteljau's algorithm.
72 s->codeAppendf("float4x2 quadratic_hull = float4x2(%s[0], "
73 "%s[0] + tan0 * t, "
74 "%s[1] + tan1 * t, "
75 "%s[2]);", pts, pts, pts, pts);
76 vars->fHullVars.fAlternatePoints = "quadratic_hull";
77 }
78
onEmitVaryings(GrGLSLVaryingHandler * varyingHandler,GrGLSLVarying::Scope scope,SkString * code)79 void GrCCQuadraticHullShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
80 GrGLSLVarying::Scope scope, SkString* code) {
81 fGrad.reset(kFloat2_GrSLType, scope);
82 varyingHandler->addVarying("grad", &fGrad);
83 code->appendf("%s = float2(2 * %s.x, -1) * float2x2(%s);",
84 OutName(fGrad), OutName(fXYDW), fCanonicalMatrix.c_str());
85 }
86
emitCoverage(GrGLSLFPFragmentBuilder * f,const char * outputCoverage) const87 void GrCCQuadraticHullShader::emitCoverage(GrGLSLFPFragmentBuilder* f,
88 const char* outputCoverage) const {
89 f->codeAppendf("float d = (%s.x * %s.x - %s.y) * inversesqrt(dot(%s, %s));",
90 fXYDW.fsIn(), fXYDW.fsIn(), fXYDW.fsIn(), fGrad.fsIn(), fGrad.fsIn());
91 f->codeAppendf("%s = clamp(0.5 - d, 0, 1);", outputCoverage);
92 f->codeAppendf("%s += min(%s.z, 0);", outputCoverage, fXYDW.fsIn()); // Flat closing edge.
93 }
94
onEmitSetupCode(GrGLSLVertexGeoBuilder * s,const char * pts,const char * repetitionID,GeometryVars * vars) const95 void GrCCQuadraticCornerShader::onEmitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
96 const char* repetitionID,
97 GeometryVars* vars) const {
98 s->codeAppendf("float2 corner = %s[%s * 2];", pts, repetitionID);
99 vars->fCornerVars.fPoint = "corner";
100 }
101
onEmitVaryings(GrGLSLVaryingHandler * varyingHandler,GrGLSLVarying::Scope scope,SkString * code)102 void GrCCQuadraticCornerShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
103 GrGLSLVarying::Scope scope, SkString* code) {
104 using Interpolation = GrGLSLVaryingHandler::Interpolation;
105
106 fdXYDdx.reset(kFloat3_GrSLType, scope);
107 varyingHandler->addVarying("dXYDdx", &fdXYDdx, Interpolation::kCanBeFlat);
108 code->appendf("%s = float3(%s[0].x, %s[0].y, %s.x);",
109 OutName(fdXYDdx), fCanonicalMatrix.c_str(), fCanonicalMatrix.c_str(),
110 fEdgeDistanceEquation.c_str());
111
112 fdXYDdy.reset(kFloat3_GrSLType, scope);
113 varyingHandler->addVarying("dXYDdy", &fdXYDdy, Interpolation::kCanBeFlat);
114 code->appendf("%s = float3(%s[1].x, %s[1].y, %s.y);",
115 OutName(fdXYDdy), fCanonicalMatrix.c_str(), fCanonicalMatrix.c_str(),
116 fEdgeDistanceEquation.c_str());
117 }
118
emitCoverage(GrGLSLFPFragmentBuilder * f,const char * outputCoverage) const119 void GrCCQuadraticCornerShader::emitCoverage(GrGLSLFPFragmentBuilder* f,
120 const char* outputCoverage) const {
121 f->codeAppendf("float x = %s.x, y = %s.y, d = %s.z;",
122 fXYDW.fsIn(), fXYDW.fsIn(), fXYDW.fsIn());
123 f->codeAppendf("float2x3 grad_xyd = float2x3(%s, %s);", fdXYDdx.fsIn(), fdXYDdy.fsIn());
124
125 // Erase what the previous hull shader wrote. We don't worry about the two corners falling on
126 // the same pixel because those cases should have been weeded out by this point.
127 f->codeAppend ("float f = x*x - y;");
128 f->codeAppend ("float2 grad_f = float2(2*x, -1) * float2x2(grad_xyd);");
129 f->codeAppendf("%s = -(0.5 - f * inversesqrt(dot(grad_f, grad_f)));", outputCoverage);
130 f->codeAppendf("%s -= d;", outputCoverage);
131
132 // Use software msaa to approximate coverage at the corner pixels.
133 int sampleCount = Shader::DefineSoftSampleLocations(f, "samples");
134 f->codeAppendf("float3 xyd_center = float3(%s.xy, %s.z + 0.5);", fXYDW.fsIn(), fXYDW.fsIn());
135 f->codeAppendf("for (int i = 0; i < %i; ++i) {", sampleCount);
136 f->codeAppend ( "float3 xyd = grad_xyd * samples[i] + xyd_center;");
137 f->codeAppend ( "half f = xyd.y - xyd.x * xyd.x;"); // f > 0 -> inside curve.
138 f->codeAppendf( "%s += all(greaterThan(float2(f,xyd.z), float2(0))) ? %f : 0;",
139 outputCoverage, 1.0 / sampleCount);
140 f->codeAppendf("}");
141 }
142