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 "src/gpu/ccpr/GrCCCubicShader.h"
9
10 #include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
11 #include "src/gpu/glsl/GrGLSLProgramBuilder.h"
12 #include "src/gpu/glsl/GrGLSLVertexGeoBuilder.h"
13
14 using Shader = GrCCCoverageProcessor::Shader;
15
emitSetupCode(GrGLSLVertexGeoBuilder * s,const char * pts,const char **) const16 void GrCCCubicShader::emitSetupCode(
17 GrGLSLVertexGeoBuilder* s, const char* pts, const char** /*outHull4*/) const {
18 // Find the cubic's power basis coefficients.
19 s->codeAppendf("float2x4 C = float4x4(-1, 3, -3, 1, "
20 " 3, -6, 3, 0, "
21 "-3, 3, 0, 0, "
22 " 1, 0, 0, 0) * transpose(%s);", pts);
23
24 // Find the cubic's inflection function.
25 s->codeAppend ("float D3 = +determinant(float2x2(C[0].yz, C[1].yz));");
26 s->codeAppend ("float D2 = -determinant(float2x2(C[0].xz, C[1].xz));");
27 s->codeAppend ("float D1 = +determinant(float2x2(C));");
28
29 // Shift the exponents in D so the largest magnitude falls somewhere in 1..2. This protects us
30 // from overflow while solving for roots and KLM functionals.
31 s->codeAppend ("float Dmax = max(max(abs(D1), abs(D2)), abs(D3));");
32 s->codeAppend ("float norm;");
33 if (s->getProgramBuilder()->shaderCaps()->fpManipulationSupport()) {
34 s->codeAppend ("int exp;");
35 s->codeAppend ("frexp(Dmax, exp);");
36 s->codeAppend ("norm = ldexp(1, 1 - exp);");
37 } else {
38 s->codeAppend ("norm = 1/Dmax;"); // Dmax will not be 0 because we cull line cubics on CPU.
39 }
40 s->codeAppend ("D3 *= norm;");
41 s->codeAppend ("D2 *= norm;");
42 s->codeAppend ("D1 *= norm;");
43
44 // Calculate the KLM matrix.
45 s->declareGlobal(fKLMMatrix);
46 s->codeAppend ("float discr = 3*D2*D2 - 4*D1*D3;");
47 s->codeAppend ("float x = discr >= 0 ? 3 : 1;");
48 s->codeAppend ("float q = sqrt(x * abs(discr));");
49 s->codeAppend ("q = x*D2 + (D2 >= 0 ? q : -q);");
50
51 s->codeAppend ("float2 l, m;");
52 s->codeAppend ("l.ts = float2(q, 2*x * D1);");
53 s->codeAppend ("m.ts = float2(2, q) * (discr >= 0 ? float2(D3, 1) "
54 ": float2(D2*D2 - D3*D1, D1));");
55
56 s->codeAppend ("float4 K;");
57 s->codeAppend ("float4 lm = l.sstt * m.stst;");
58 s->codeAppend ("K = float4(0, lm.x, -lm.y - lm.z, lm.w);");
59
60 s->codeAppend ("float4 L, M;");
61 s->codeAppend ("lm.yz += 2*lm.zy;");
62 s->codeAppend ("L = float4(-1,x,-x,1) * l.sstt * (discr >= 0 ? l.ssst * l.sttt : lm);");
63 s->codeAppend ("M = float4(-1,x,-x,1) * m.sstt * (discr >= 0 ? m.ssst * m.sttt : lm.xzyw);");
64
65 s->codeAppend ("int middlerow = abs(D2) > abs(D1) ? 2 : 1;");
66 s->codeAppend ("float3x3 CI = inverse(float3x3(C[0][0], C[0][middlerow], C[0][3], "
67 "C[1][0], C[1][middlerow], C[1][3], "
68 " 0, 0, 1));");
69 s->codeAppendf("%s = CI * float3x3(K[0], K[middlerow], K[3], "
70 "L[0], L[middlerow], L[3], "
71 "M[0], M[middlerow], M[3]);", fKLMMatrix.c_str());
72
73 // Evaluate the cubic at T=.5 for a mid-ish point.
74 s->codeAppendf("float2 midpoint = %s * float4(.125, .375, .375, .125);", pts);
75
76 // Orient the KLM matrix so L & M are both positive on the side of the curve we wish to fill.
77 s->codeAppendf("float2 orientation = sign(float3(midpoint, 1) * float2x3(%s[1], %s[2]));",
78 fKLMMatrix.c_str(), fKLMMatrix.c_str());
79 s->codeAppendf("%s *= float3x3(orientation[0] * orientation[1], 0, 0, "
80 "0, orientation[0], 0, "
81 "0, 0, orientation[1]);", fKLMMatrix.c_str());
82 }
83
onEmitVaryings(GrGLSLVaryingHandler * varyingHandler,GrGLSLVarying::Scope scope,SkString * code,const char * position,const char * coverage,const char * cornerCoverage,const char * wind)84 void GrCCCubicShader::onEmitVaryings(
85 GrGLSLVaryingHandler* varyingHandler, GrGLSLVarying::Scope scope, SkString* code,
86 const char* position, const char* coverage, const char* cornerCoverage, const char* wind) {
87 code->appendf("float3 klm = float3(%s, 1) * %s;", position, fKLMMatrix.c_str());
88 if (coverage) {
89 fKLM_fEdge.reset(kFloat4_GrSLType, scope);
90 varyingHandler->addVarying("klm_and_edge", &fKLM_fEdge);
91 // Give L&M both the same sign as wind, in order to pass this value to the fragment shader.
92 // (Cubics are pre-chopped such that L&M do not change sign within any individual segment.)
93 code->appendf("%s.xyz = klm * float3(1, %s, %s);", OutName(fKLM_fEdge), wind, wind);
94 // Flat edge opposite the curve.
95 code->appendf("%s.w = %s;", OutName(fKLM_fEdge), coverage);
96 } else {
97 fKLM_fEdge.reset(kFloat3_GrSLType, scope);
98 varyingHandler->addVarying("klm", &fKLM_fEdge);
99 code->appendf("%s = klm;", OutName(fKLM_fEdge));
100 }
101
102 fGradMatrix.reset(kFloat4_GrSLType, scope);
103 varyingHandler->addVarying("grad_matrix", &fGradMatrix);
104 code->appendf("%s.xy = 2*bloat * 3 * klm[0] * %s[0].xy;",
105 OutName(fGradMatrix), fKLMMatrix.c_str());
106 code->appendf("%s.zw = -2*bloat * (klm[1] * %s[2].xy + klm[2] * %s[1].xy);",
107 OutName(fGradMatrix), fKLMMatrix.c_str(), fKLMMatrix.c_str());
108
109 if (cornerCoverage) {
110 SkASSERT(coverage);
111 code->appendf("half hull_coverage; {");
112 this->calcHullCoverage(code, OutName(fKLM_fEdge), OutName(fGradMatrix), "hull_coverage");
113 code->appendf("}");
114 fCornerCoverage.reset(kHalf2_GrSLType, scope);
115 varyingHandler->addVarying("corner_coverage", &fCornerCoverage);
116 code->appendf("%s = half2(hull_coverage, 1) * %s;",
117 OutName(fCornerCoverage), cornerCoverage);
118 }
119 }
120
emitFragmentCoverageCode(GrGLSLFPFragmentBuilder * f,const char * outputCoverage) const121 void GrCCCubicShader::emitFragmentCoverageCode(
122 GrGLSLFPFragmentBuilder* f, const char* outputCoverage) const {
123 this->calcHullCoverage(
124 &AccessCodeString(f), fKLM_fEdge.fsIn(), fGradMatrix.fsIn(), outputCoverage);
125
126 // Wind is the sign of both L and/or M. Take the sign of whichever has the larger magnitude.
127 // (In reality, either would be fine because we chop cubics with more than a half pixel of
128 // padding around the L & M lines, so neither should approach zero.)
129 f->codeAppend ("half wind = sign(half(l + m));");
130 f->codeAppendf("%s *= wind;", outputCoverage);
131
132 if (fCornerCoverage.fsIn()) {
133 f->codeAppendf("%s = %s.x * %s.y + %s;", // Attenuated corner coverage.
134 outputCoverage, fCornerCoverage.fsIn(), fCornerCoverage.fsIn(),
135 outputCoverage);
136 }
137 }
138
calcHullCoverage(SkString * code,const char * klmAndEdge,const char * gradMatrix,const char * outputCoverage) const139 void GrCCCubicShader::calcHullCoverage(SkString* code, const char* klmAndEdge,
140 const char* gradMatrix, const char* outputCoverage) const {
141 code->appendf("float k = %s.x, l = %s.y, m = %s.z;", klmAndEdge, klmAndEdge, klmAndEdge);
142 code->append ("float f = k*k*k - l*m;");
143 code->appendf("float2 grad = %s.xy * k + %s.zw;", gradMatrix, gradMatrix);
144 code->append ("float fwidth = abs(grad.x) + abs(grad.y);");
145 code->appendf("float curve_coverage = min(0.5 - f/fwidth, 1);");
146 // Flat edge opposite the curve.
147 code->appendf("float edge_coverage = min(%s.w, 0);", klmAndEdge);
148 // Total hull coverage.
149 code->appendf("%s = max(half(curve_coverage + edge_coverage), 0);", outputCoverage);
150 }
151
emitSampleMaskCode(GrGLSLFPFragmentBuilder * f) const152 void GrCCCubicShader::emitSampleMaskCode(GrGLSLFPFragmentBuilder* f) const {
153 f->codeAppendf("float k = %s.x, l = %s.y, m = %s.z;",
154 fKLM_fEdge.fsIn(), fKLM_fEdge.fsIn(), fKLM_fEdge.fsIn());
155 f->codeAppendf("float f = k*k*k - l*m;");
156 f->codeAppendf("float2x2 grad_matrix = float2x2(%s);", fGradMatrix.fsIn());
157 f->codeAppendf("float2 grad = grad_matrix * float2(k, 1);");
158 f->applyFnToMultisampleMask("f", "grad", GrGLSLFPFragmentBuilder::ScopeFlags::kTopLevel);
159 }
160