/*
* Copyright 2013 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrBezierEffect_DEFINED
#define GrBezierEffect_DEFINED
#include "GrCaps.h"
#include "GrProcessor.h"
#include "GrGeometryProcessor.h"
#include "GrTypesPriv.h"
/**
* 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.
* 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 for AA is max(0, 1-distance).
*
* Test were also run using a second order distance approximation.
* There were two versions of the second order approx. The first version
* is of roughly the form:
* f(q) = |f(p)| - ||f'(p)||*||q-p|| - ||f''(p)||*||q-p||^2.
* The second is similar:
* f(q) = |f(p)| + ||f'(p)||*||q-p|| + ||f''(p)||*||q-p||^2.
* The exact version of the equations can be found in the paper
* "Distance Approximations for Rasterizing Implicit Curves" by Gabriel Taubin
*
* In both versions we solve the quadratic for ||q-p||.
* Version 1:
* gFM is magnitude of first partials and gFM2 is magnitude of 2nd partials (as derived from paper)
* builder->fsCodeAppend("\t\tedgeAlpha = (sqrt(gFM*gFM+4.0*func*gF2M) - gFM)/(2.0*gF2M);\n");
* Version 2:
* builder->fsCodeAppend("\t\tedgeAlpha = (gFM - sqrt(gFM*gFM-4.0*func*gF2M))/(2.0*gF2M);\n");
*
* Also note that 2nd partials of k,l,m are zero
*
* When comparing the two second order approximations to the first order approximations,
* the following results were found. Version 1 tends to underestimate the distances, thus it
* basically increases all the error that we were already seeing in the first order
* approx. So this version is not the one to use. Version 2 has the opposite effect
* and tends to overestimate the distances. This is much closer to what we are
* looking for. It is able to render ellipses (even thin ones) without the need to chop.
* However, it can not handle thin hyperbolas well and thus would still rely on
* chopping to tighten the clipping. Another side effect of the overestimating is
* that the curves become much thinner and "ropey". If all that was ever rendered
* were "not too thin" curves and ellipses then 2nd order may have an advantage since
* only one geometry would need to be rendered. However no benches were run comparing
* chopped first order and non chopped 2nd order.
*/
class GrGLConicEffect;
class GrConicEffect : public GrGeometryProcessor {
public:
static sk_sp<GrGeometryProcessor> Make(const SkPMColor4f& color,
const SkMatrix& viewMatrix,
const GrClipEdgeType edgeType,
const GrCaps& caps,
const SkMatrix& localMatrix,
bool usesLocalCoords,
uint8_t coverage = 0xff) {
switch (edgeType) {
case GrClipEdgeType::kFillAA:
if (!caps.shaderCaps()->shaderDerivativeSupport()) {
return nullptr;
}
return sk_sp<GrGeometryProcessor>(
new GrConicEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillAA,
localMatrix, usesLocalCoords));
case GrClipEdgeType::kHairlineAA:
if (!caps.shaderCaps()->shaderDerivativeSupport()) {
return nullptr;
}
return sk_sp<GrGeometryProcessor>(
new GrConicEffect(color, viewMatrix, coverage,
GrClipEdgeType::kHairlineAA, localMatrix,
usesLocalCoords));
case GrClipEdgeType::kFillBW:
return sk_sp<GrGeometryProcessor>(
new GrConicEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillBW,
localMatrix, usesLocalCoords));
default:
return nullptr;
}
}
~GrConicEffect() override;
const char* name() const override { return "Conic"; }
inline const Attribute& inPosition() const { return kAttributes[0]; }
inline const Attribute& inConicCoeffs() const { return kAttributes[1]; }
inline bool isAntiAliased() const { return GrProcessorEdgeTypeIsAA(fEdgeType); }
inline bool isFilled() const { return GrProcessorEdgeTypeIsFill(fEdgeType); }
inline GrClipEdgeType getEdgeType() const { return fEdgeType; }
const SkPMColor4f& color() const { return fColor; }
const SkMatrix& viewMatrix() const { return fViewMatrix; }
const SkMatrix& localMatrix() const { return fLocalMatrix; }
bool usesLocalCoords() const { return fUsesLocalCoords; }
uint8_t coverageScale() const { return fCoverageScale; }
void getGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override;
GrGLSLPrimitiveProcessor* createGLSLInstance(const GrShaderCaps&) const override;
private:
GrConicEffect(const SkPMColor4f&, const SkMatrix& viewMatrix, uint8_t coverage, GrClipEdgeType,
const SkMatrix& localMatrix, bool usesLocalCoords);
SkPMColor4f fColor;
SkMatrix fViewMatrix;
SkMatrix fLocalMatrix;
bool fUsesLocalCoords;
uint8_t fCoverageScale;
GrClipEdgeType fEdgeType;
static constexpr Attribute kAttributes[] = {
{"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType},
{"inConicCoeffs", kFloat4_GrVertexAttribType, kHalf4_GrSLType}
};
GR_DECLARE_GEOMETRY_PROCESSOR_TEST
typedef GrGeometryProcessor INHERITED;
};
///////////////////////////////////////////////////////////////////////////////
/**
* The output of this effect is a hairline edge for quadratics.
* Quadratic specified by 0=u^2-v canonical coords. u and v are the first
* two components of the vertex attribute. At the three control points that define
* the Quadratic, u, v have the values {0,0}, {1/2, 0}, and {1, 1} respectively.
* Coverage for AA is min(0, 1-distance). 3rd & 4th cimponent unused.
* Requires shader derivative instruction support.
*/
class GrGLQuadEffect;
class GrQuadEffect : public GrGeometryProcessor {
public:
static sk_sp<GrGeometryProcessor> Make(const SkPMColor4f& color,
const SkMatrix& viewMatrix,
const GrClipEdgeType edgeType,
const GrCaps& caps,
const SkMatrix& localMatrix,
bool usesLocalCoords,
uint8_t coverage = 0xff) {
switch (edgeType) {
case GrClipEdgeType::kFillAA:
if (!caps.shaderCaps()->shaderDerivativeSupport()) {
return nullptr;
}
return sk_sp<GrGeometryProcessor>(
new GrQuadEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillAA,
localMatrix, usesLocalCoords));
case GrClipEdgeType::kHairlineAA:
if (!caps.shaderCaps()->shaderDerivativeSupport()) {
return nullptr;
}
return sk_sp<GrGeometryProcessor>(
new GrQuadEffect(color, viewMatrix, coverage,
GrClipEdgeType::kHairlineAA, localMatrix,
usesLocalCoords));
case GrClipEdgeType::kFillBW:
return sk_sp<GrGeometryProcessor>(
new GrQuadEffect(color, viewMatrix, coverage, GrClipEdgeType::kFillBW,
localMatrix, usesLocalCoords));
default:
return nullptr;
}
}
~GrQuadEffect() override;
const char* name() const override { return "Quad"; }
inline const Attribute& inPosition() const { return kAttributes[0]; }
inline const Attribute& inHairQuadEdge() const { return kAttributes[1]; }
inline bool isAntiAliased() const { return GrProcessorEdgeTypeIsAA(fEdgeType); }
inline bool isFilled() const { return GrProcessorEdgeTypeIsFill(fEdgeType); }
inline GrClipEdgeType getEdgeType() const { return fEdgeType; }
const SkPMColor4f& color() const { return fColor; }
const SkMatrix& viewMatrix() const { return fViewMatrix; }
const SkMatrix& localMatrix() const { return fLocalMatrix; }
bool usesLocalCoords() const { return fUsesLocalCoords; }
uint8_t coverageScale() const { return fCoverageScale; }
void getGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override;
GrGLSLPrimitiveProcessor* createGLSLInstance(const GrShaderCaps&) const override;
private:
GrQuadEffect(const SkPMColor4f&, const SkMatrix& viewMatrix, uint8_t coverage, GrClipEdgeType,
const SkMatrix& localMatrix, bool usesLocalCoords);
SkPMColor4f fColor;
SkMatrix fViewMatrix;
SkMatrix fLocalMatrix;
bool fUsesLocalCoords;
uint8_t fCoverageScale;
GrClipEdgeType fEdgeType;
static constexpr Attribute kAttributes[] = {
{"inPosition", kFloat2_GrVertexAttribType, kFloat2_GrSLType},
{"inHairQuadEdge", kFloat4_GrVertexAttribType, kHalf4_GrSLType}
};
GR_DECLARE_GEOMETRY_PROCESSOR_TEST
typedef GrGeometryProcessor INHERITED;
};
#endif