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 "GrCCCubicShader.h"
9
10 #include "glsl/GrGLSLFragmentShaderBuilder.h"
11 #include "glsl/GrGLSLVertexGeoBuilder.h"
12
13 using Shader = GrCCCoverageProcessor::Shader;
14
emitSetupCode(GrGLSLVertexGeoBuilder * s,const char * pts,const char * repetitionID,const char * wind,GeometryVars * vars) const15 void GrCCCubicShader::emitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
16 const char* repetitionID, const char* wind,
17 GeometryVars* vars) 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 // Calculate the KLM matrix.
30 s->declareGlobal(fKLMMatrix);
31 s->codeAppend ("float discr = 3*D2*D2 - 4*D1*D3;");
32 s->codeAppend ("float x = discr >= 0 ? 3 : 1;");
33 s->codeAppend ("float q = sqrt(x * abs(discr));");
34 s->codeAppend ("q = x*D2 + (D2 >= 0 ? q : -q);");
35
36 s->codeAppend ("float2 l, m;");
37 s->codeAppend ("l.ts = normalize(float2(q, 2*x * D1));");
38 s->codeAppend ("m.ts = normalize(float2(2, q) * (discr >= 0 ? float2(D3, 1) "
39 ": float2(D2*D2 - D3*D1, D1)));");
40
41 s->codeAppend ("float4 K;");
42 s->codeAppend ("float4 lm = l.sstt * m.stst;");
43 s->codeAppend ("K = float4(0, lm.x, -lm.y - lm.z, lm.w);");
44
45 s->codeAppend ("float4 L, M;");
46 s->codeAppend ("lm.yz += 2*lm.zy;");
47 s->codeAppend ("L = float4(-1,x,-x,1) * l.sstt * (discr >= 0 ? l.ssst * l.sttt : lm);");
48 s->codeAppend ("M = float4(-1,x,-x,1) * m.sstt * (discr >= 0 ? m.ssst * m.sttt : lm.xzyw);");
49
50 s->codeAppend ("short middlerow = abs(D2) > abs(D1) ? 2 : 1;");
51 s->codeAppend ("float3x3 CI = inverse(float3x3(C[0][0], C[0][middlerow], C[0][3], "
52 "C[1][0], C[1][middlerow], C[1][3], "
53 " 0, 0, 1));");
54 s->codeAppendf("%s = CI * float3x3(K[0], K[middlerow], K[3], "
55 "L[0], L[middlerow], L[3], "
56 "M[0], M[middlerow], M[3]);", fKLMMatrix.c_str());
57
58 // Evaluate the cubic at T=.5 for a mid-ish point.
59 s->codeAppendf("float2 midpoint = %s * float4(.125, .375, .375, .125);", pts);
60
61 // Orient the KLM matrix so L & M have matching signs on the side of the curve we wish to fill.
62 // We give L & M both the same sign as wind, in order to pass this value to the fragment shader.
63 // (Cubics are pre-chopped such that L & M do not change sign within any individual segment).
64 s->codeAppendf("float2 orientation = sign(float3(midpoint, 1) * float2x3(%s[1], %s[2]));",
65 fKLMMatrix.c_str(), fKLMMatrix.c_str());
66 s->codeAppendf("%s *= float3x3(orientation[0] * orientation[1], 0, 0, "
67 "0, orientation[0] * %s, 0, "
68 "0, 0, orientation[1] * %s);", fKLMMatrix.c_str(), wind, wind);
69
70 // Determine the amount of additional coverage to subtract out for the flat edge (P3 -> P0).
71 s->declareGlobal(fEdgeDistanceEquation);
72 s->codeAppendf("short edgeidx0 = %s > 0 ? 3 : 0;", wind);
73 s->codeAppendf("float2 edgept0 = %s[edgeidx0];", pts);
74 s->codeAppendf("float2 edgept1 = %s[3 - edgeidx0];", pts);
75 Shader::EmitEdgeDistanceEquation(s, "edgept0", "edgept1", fEdgeDistanceEquation.c_str());
76
77 this->onEmitSetupCode(s, pts, repetitionID, vars);
78 }
79
onEmitVaryings(GrGLSLVaryingHandler * varyingHandler,GrGLSLVarying::Scope scope,SkString * code,const char * position,const char * inputCoverage,const char *)80 void GrCCCubicShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
81 GrGLSLVarying::Scope scope, SkString* code,
82 const char* position, const char* inputCoverage,
83 const char* /*wind*/) {
84 SkASSERT(!inputCoverage);
85
86 fKLMD.reset(kFloat4_GrSLType, scope);
87 varyingHandler->addVarying("klmd", &fKLMD);
88 code->appendf("float3 klm = float3(%s, 1) * %s;", position, fKLMMatrix.c_str());
89 code->appendf("float d = dot(float3(%s, 1), %s);", position, fEdgeDistanceEquation.c_str());
90 code->appendf("%s = float4(klm, d);", OutName(fKLMD));
91
92 this->onEmitVaryings(varyingHandler, scope, code);
93 }
94
onEmitFragmentCode(GrGLSLFPFragmentBuilder * f,const char * outputCoverage) const95 void GrCCCubicShader::onEmitFragmentCode(GrGLSLFPFragmentBuilder* f,
96 const char* outputCoverage) const {
97 f->codeAppendf("float k = %s.x, l = %s.y, m = %s.z, d = %s.w;",
98 fKLMD.fsIn(), fKLMD.fsIn(), fKLMD.fsIn(), fKLMD.fsIn());
99
100 this->emitCoverage(f, outputCoverage);
101
102 // Wind is the sign of both L and/or M. Take the sign of whichever has the larger magnitude.
103 // (In reality, either would be fine because we chop cubics with more than a half pixel of
104 // padding around the L & M lines, so neither should approach zero.)
105 f->codeAppend ("half wind = sign(l + m);");
106 f->codeAppendf("%s *= wind;", outputCoverage);
107 }
108
onEmitVaryings(GrGLSLVaryingHandler * varyingHandler,GrGLSLVarying::Scope scope,SkString * code)109 void GrCCCubicHullShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
110 GrGLSLVarying::Scope scope, SkString* code) {
111 fGradMatrix.reset(kFloat2x2_GrSLType, scope);
112 varyingHandler->addVarying("grad_matrix", &fGradMatrix);
113 // "klm" was just defined by the base class.
114 code->appendf("%s[0] = 3 * klm[0] * %s[0].xy;", OutName(fGradMatrix), fKLMMatrix.c_str());
115 code->appendf("%s[1] = -klm[1] * %s[2].xy - klm[2] * %s[1].xy;",
116 OutName(fGradMatrix), fKLMMatrix.c_str(), fKLMMatrix.c_str());
117 }
118
emitCoverage(GrGLSLFPFragmentBuilder * f,const char * outputCoverage) const119 void GrCCCubicHullShader::emitCoverage(GrGLSLFPFragmentBuilder* f,
120 const char* outputCoverage) const {
121 // k,l,m,d are defined by the base class.
122 f->codeAppend ("float f = k*k*k - l*m;");
123 f->codeAppendf("float2 grad_f = %s * float2(k, 1);", fGradMatrix.fsIn());
124 f->codeAppendf("%s = clamp(0.5 - f * inversesqrt(dot(grad_f, grad_f)), 0, 1);", outputCoverage);
125 f->codeAppendf("%s += min(d, 0);", outputCoverage); // Flat edge opposite the curve.
126 }
127
onEmitSetupCode(GrGLSLVertexGeoBuilder * s,const char * pts,const char * repetitionID,GeometryVars * vars) const128 void GrCCCubicCornerShader::onEmitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts,
129 const char* repetitionID, GeometryVars* vars) const {
130 s->codeAppendf("float2 corner = %s[%s * 3];", pts, repetitionID);
131 vars->fCornerVars.fPoint = "corner";
132 }
133
onEmitVaryings(GrGLSLVaryingHandler * varyingHandler,GrGLSLVarying::Scope scope,SkString * code)134 void GrCCCubicCornerShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
135 GrGLSLVarying::Scope scope, SkString* code) {
136 using Interpolation = GrGLSLVaryingHandler::Interpolation;
137
138 fdKLMDdx.reset(kFloat4_GrSLType, scope);
139 varyingHandler->addVarying("dklmddx", &fdKLMDdx, Interpolation::kCanBeFlat);
140 code->appendf("%s = float4(%s[0].x, %s[1].x, %s[2].x, %s.x);",
141 OutName(fdKLMDdx), fKLMMatrix.c_str(), fKLMMatrix.c_str(),
142 fKLMMatrix.c_str(), fEdgeDistanceEquation.c_str());
143
144 fdKLMDdy.reset(kFloat4_GrSLType, scope);
145 varyingHandler->addVarying("dklmddy", &fdKLMDdy, Interpolation::kCanBeFlat);
146 code->appendf("%s = float4(%s[0].y, %s[1].y, %s[2].y, %s.y);",
147 OutName(fdKLMDdy), fKLMMatrix.c_str(), fKLMMatrix.c_str(),
148 fKLMMatrix.c_str(), fEdgeDistanceEquation.c_str());
149 }
150
emitCoverage(GrGLSLFPFragmentBuilder * f,const char * outputCoverage) const151 void GrCCCubicCornerShader::emitCoverage(GrGLSLFPFragmentBuilder* f,
152 const char* outputCoverage) const {
153 f->codeAppendf("float2x4 grad_klmd = float2x4(%s, %s);", fdKLMDdx.fsIn(), fdKLMDdy.fsIn());
154
155 // Erase what the previous hull shader wrote. We don't worry about the two corners falling on
156 // the same pixel because those cases should have been weeded out by this point.
157 // k,l,m,d are defined by the base class.
158 f->codeAppend ("float f = k*k*k - l*m;");
159 f->codeAppend ("float2 grad_f = float3(3*k*k, -m, -l) * float2x3(grad_klmd);");
160 f->codeAppendf("%s = -clamp(0.5 - f * inversesqrt(dot(grad_f, grad_f)), 0, 1);",
161 outputCoverage);
162 f->codeAppendf("%s -= d;", outputCoverage);
163
164 // Use software msaa to estimate actual coverage at the corner pixels.
165 const int sampleCount = Shader::DefineSoftSampleLocations(f, "samples");
166 f->codeAppendf("float4 klmd_center = float4(%s.xyz, %s.w + 0.5);",
167 fKLMD.fsIn(), fKLMD.fsIn());
168 f->codeAppendf("for (int i = 0; i < %i; ++i) {", sampleCount);
169 f->codeAppend ( "float4 klmd = grad_klmd * samples[i] + klmd_center;");
170 f->codeAppend ( "half f = klmd.y * klmd.z - klmd.x * klmd.x * klmd.x;");
171 f->codeAppendf( "%s += all(greaterThan(half4(f, klmd.y, klmd.z, klmd.w), "
172 "half4(0))) ? %f : 0;",
173 outputCoverage, 1.0 / sampleCount);
174 f->codeAppend ("}");
175 }
176