ccpr: Implement conics
TBR=egdaniel@google.com
Bug: skia:
Change-Id: Idf7811dc285961db52db41c9ff145afda40c274d
Reviewed-on: https://skia-review.googlesource.com/122127
Reviewed-by: Chris Dalton <csmartdalton@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/ccpr/GrCCConicShader.cpp b/src/gpu/ccpr/GrCCConicShader.cpp
new file mode 100644
index 0000000..01568de
--- /dev/null
+++ b/src/gpu/ccpr/GrCCConicShader.cpp
@@ -0,0 +1,93 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrCCConicShader.h"
+
+#include "glsl/GrGLSLFragmentShaderBuilder.h"
+#include "glsl/GrGLSLVertexGeoBuilder.h"
+
+void GrCCConicShader::emitSetupCode(GrGLSLVertexGeoBuilder* s, const char* pts, const char* wind,
+ const char** outHull4) const {
+ // K is distance from the line P2 -> P0. L is distance from the line P0 -> P1, scaled by 2w.
+ // M is distance from the line P1 -> P2, scaled by 2w. We do this in a space where P1=0.
+ s->declareGlobal(fKLMMatrix);
+ s->codeAppendf("float x0 = %s[0].x - %s[1].x, x2 = %s[2].x - %s[1].x;", pts, pts, pts, pts);
+ s->codeAppendf("float y0 = %s[0].y - %s[1].y, y2 = %s[2].y - %s[1].y;", pts, pts, pts, pts);
+ s->codeAppendf("float w = %s[3].x;", pts);
+ s->codeAppendf("%s = float3x3(y2 - y0, x0 - x2, x2*y0 - x0*y2, "
+ "2*w * float2(+y0, -x0), 0, "
+ "2*w * float2(-y2, +x2), 0);", fKLMMatrix.c_str());
+
+ s->declareGlobal(fControlPoint);
+ s->codeAppendf("%s = %s[1];", fControlPoint.c_str(), pts);
+
+ // Scale KLM by the inverse Manhattan width of K. This allows K to double as the flat opposite
+ // edge AA. kwidth will not be 0 because we cull degenerate conics on the CPU.
+ s->codeAppendf("float kwidth = 2*bloat * %s * (abs(%s[0].x) + abs(%s[0].y));",
+ wind, fKLMMatrix.c_str(), fKLMMatrix.c_str());
+ s->codeAppendf("%s *= 1/kwidth;", fKLMMatrix.c_str());
+
+ if (outHull4) {
+ // Clip the conic triangle by the tangent line at maximum height. Conics have the nice
+ // property that maximum height always occurs at T=.5. This is a simple application for
+ // De Casteljau's algorithm.
+ s->codeAppendf("float2 p1w = %s[1]*w;", pts);
+ s->codeAppend ("float r = 1 / (1 + w);");
+ s->codeAppendf("float2 conic_hull[4] = float2[4](%s[0], "
+ "(%s[0] + p1w) * r, "
+ "(p1w + %s[2]) * r, "
+ "%s[2]);", pts, pts, pts, pts);
+ *outHull4 = "conic_hull";
+ }
+}
+
+void GrCCConicShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler,
+ GrGLSLVarying::Scope scope, SkString* code,
+ const char* position, const char* coverage,
+ const char* cornerCoverage) {
+ fKLM_fWind.reset(kFloat4_GrSLType, scope);
+ varyingHandler->addVarying("klm_and_wind", &fKLM_fWind);
+ code->appendf("float3 klm = float3(%s - %s, 1) * %s;",
+ position, fControlPoint.c_str(), fKLMMatrix.c_str());
+ code->appendf("%s.xyz = klm;", OutName(fKLM_fWind));
+ code->appendf("%s.w = %s;", OutName(fKLM_fWind), coverage); // coverage == wind.
+
+ fGrad_fCorner.reset(cornerCoverage ? kFloat4_GrSLType : kFloat2_GrSLType, scope);
+ varyingHandler->addVarying(cornerCoverage ? "grad_and_corner" : "grad", &fGrad_fCorner);
+ code->appendf("%s.xy = 2*bloat * (float3x2(%s) * float3(2*klm[0], -klm[2], -klm[1]));",
+ OutName(fGrad_fCorner), fKLMMatrix.c_str());
+
+ if (cornerCoverage) {
+ code->appendf("half hull_coverage;");
+ this->calcHullCoverage(code, "klm", OutName(fGrad_fCorner), "hull_coverage");
+ code->appendf("%s.zw = half2(hull_coverage, 1) * %s;",
+ OutName(fGrad_fCorner), cornerCoverage);
+ }
+}
+
+void GrCCConicShader::onEmitFragmentCode(GrGLSLFPFragmentBuilder* f,
+ const char* outputCoverage) const {
+ this->calcHullCoverage(&AccessCodeString(f), fKLM_fWind.fsIn(), fGrad_fCorner.fsIn(),
+ outputCoverage);
+ f->codeAppendf("%s *= %s.w;", outputCoverage, fKLM_fWind.fsIn()); // Wind.
+
+ if (kFloat4_GrSLType == fGrad_fCorner.type()) {
+ f->codeAppendf("%s = %s.z * %s.w + %s;", // Attenuated corner coverage.
+ outputCoverage, fGrad_fCorner.fsIn(), fGrad_fCorner.fsIn(),
+ outputCoverage);
+ }
+}
+
+void GrCCConicShader::calcHullCoverage(SkString* code, const char* klm, const char* grad,
+ const char* outputCoverage) const {
+ code->appendf("float k = %s.x, l = %s.y, m = %s.z;", klm, klm, klm);
+ code->append ("float f = k*k - l*m;");
+ code->appendf("float fwidth = abs(%s.x) + abs(%s.y);", grad, grad);
+ code->appendf("%s = min(0.5 - f/fwidth, 1);", outputCoverage); // Curve coverage.
+ code->append ("half d = min(k - 0.5, 0);"); // K doubles as the flat opposite edge's AA.
+ code->appendf("%s = max(%s + d, 0);", outputCoverage, outputCoverage); // Total hull coverage.
+}