Add direct bezier cubic support for GPU shaders
BUG=
R=bsalomon@google.com, jvanverth@google.com, robertphillips@google.com
Author: egdaniel@google.com
Review URL: https://chromiumcodereview.appspot.com/22900007
git-svn-id: http://skia.googlecode.com/svn/trunk@10814 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrAAHairLinePathRenderer.cpp b/src/gpu/GrAAHairLinePathRenderer.cpp
index 5ef981b..2b5f3cc 100644
--- a/src/gpu/GrAAHairLinePathRenderer.cpp
+++ b/src/gpu/GrAAHairLinePathRenderer.cpp
@@ -738,6 +738,105 @@
}
/**
+ * Shader is based off of "Resolution Independent Curve Rendering using
+ * Programmable Graphics Hardware" by Loop and Blinn.
+ * The output of this effect is a hairline edge for non rational cubics.
+ * Cubics are specified by implicit equation K^3 - LM.
+ * K, L, and M, are the first three values of the vertex attribute,
+ * the fourth value is not used. Distance is calculated using a
+ * first order approximation from the taylor series.
+ * Coverage is max(0, 1-distance).
+ */
+class HairCubicEdgeEffect : public GrEffect {
+public:
+ static GrEffectRef* Create() {
+ GR_CREATE_STATIC_EFFECT(gHairCubicEdgeEffect, HairCubicEdgeEffect, ());
+ gHairCubicEdgeEffect->ref();
+ return gHairCubicEdgeEffect;
+ }
+
+ virtual ~HairCubicEdgeEffect() {}
+
+ static const char* Name() { return "HairCubicEdge"; }
+
+ virtual void getConstantColorComponents(GrColor* color,
+ uint32_t* validFlags) const SK_OVERRIDE {
+ *validFlags = 0;
+ }
+
+ virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE {
+ return GrTBackendEffectFactory<HairCubicEdgeEffect>::getInstance();
+ }
+
+ class GLEffect : public GrGLEffect {
+ public:
+ GLEffect(const GrBackendEffectFactory& factory, const GrDrawEffect&)
+ : INHERITED (factory) {}
+
+ virtual void emitCode(GrGLShaderBuilder* builder,
+ const GrDrawEffect& drawEffect,
+ EffectKey key,
+ const char* outputColor,
+ const char* inputColor,
+ const TextureSamplerArray& samplers) SK_OVERRIDE {
+ const char *vsName, *fsName;
+
+ SkAssertResult(builder->enableFeature(
+ GrGLShaderBuilder::kStandardDerivatives_GLSLFeature));
+ builder->addVarying(kVec4f_GrSLType, "CubicCoeffs",
+ &vsName, &fsName);
+ const SkString* attr0Name =
+ builder->getEffectAttributeName(drawEffect.getVertexAttribIndices()[0]);
+ builder->vsCodeAppendf("\t%s = %s;\n", vsName, attr0Name->c_str());
+
+ builder->fsCodeAppend("\t\tfloat edgeAlpha;\n");
+
+ builder->fsCodeAppendf("\t\tvec3 dklmdx = dFdx(%s.xyz);\n", fsName);
+ builder->fsCodeAppendf("\t\tvec3 dklmdy = dFdy(%s.xyz);\n", fsName);
+ builder->fsCodeAppendf("\t\tfloat dfdx =\n"
+ "\t\t3.0*%s.x*%s.x*dklmdx.x - %s.y*dklmdx.z - %s.z*dklmdx.y;\n",
+ fsName, fsName, fsName, fsName);
+ builder->fsCodeAppendf("\t\tfloat dfdy =\n"
+ "\t\t3.0*%s.x*%s.x*dklmdy.x - %s.y*dklmdy.z - %s.z*dklmdy.y;\n",
+ fsName, fsName, fsName, fsName);
+ builder->fsCodeAppend("\t\tvec2 gF = vec2(dfdx, dfdy);\n");
+ builder->fsCodeAppend("\t\tfloat gFM = sqrt(dot(gF, gF));\n");
+ builder->fsCodeAppendf("\t\tfloat func = abs(%s.x*%s.x*%s.x - %s.y*%s.z);\n",
+ fsName, fsName, fsName, fsName, fsName);
+ builder->fsCodeAppend("\t\tedgeAlpha = func / gFM;\n");
+ builder->fsCodeAppend("\t\tedgeAlpha = max(1.0 - edgeAlpha, 0.0);\n");
+ // Add line below for smooth cubic ramp
+ // builder->fsCodeAppend("\t\tedgeAlpha = edgeAlpha*edgeAlpha*(3.0-2.0*edgeAlpha);\n");
+
+ SkString modulate;
+ GrGLSLModulatef<4>(&modulate, inputColor, "edgeAlpha");
+ builder->fsCodeAppendf("\t%s = %s;\n", outputColor, modulate.c_str());
+ }
+
+ static inline EffectKey GenKey(const GrDrawEffect& drawEffect, const GrGLCaps&) {
+ return 0x0;
+ }
+
+ virtual void setData(const GrGLUniformManager&, const GrDrawEffect&) SK_OVERRIDE {}
+
+ private:
+ typedef GrGLEffect INHERITED;
+ };
+private:
+ HairCubicEdgeEffect() {
+ this->addVertexAttrib(kVec4f_GrSLType);
+ }
+
+ virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE {
+ return true;
+ }
+
+ GR_DECLARE_EFFECT_TEST;
+
+ typedef GrEffect INHERITED;
+};
+
+/**
* Shader is based off of Loop-Blinn Quadratic GPU Rendering
* The output of this effect is a hairline edge for conics.
* Conics specified by implicit equation K^2 - LM.