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 13using Shader = GrCCCoverageProcessor::Shader; 14 15void 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 80void 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 95void 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 109void 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 119void 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 128void 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 134void 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 151void 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