/*
* 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 "GrDrawTargetCaps.h"
#include "GrEffect.h"
#include "GrVertexEffect.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 GrVertexEffect {
public:
static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
GR_CREATE_STATIC_EFFECT(gConicFillAA, GrConicEffect, (kFillAA_GrEffectEdgeType));
GR_CREATE_STATIC_EFFECT(gConicHairAA, GrConicEffect, (kHairlineAA_GrEffectEdgeType));
GR_CREATE_STATIC_EFFECT(gConicFillBW, GrConicEffect, (kFillBW_GrEffectEdgeType));
switch (edgeType) {
case kFillAA_GrEffectEdgeType:
if (!caps.shaderDerivativeSupport()) {
return NULL;
}
gConicFillAA->ref();
return gConicFillAA;
case kHairlineAA_GrEffectEdgeType:
if (!caps.shaderDerivativeSupport()) {
return NULL;
}
gConicHairAA->ref();
return gConicHairAA;
case kFillBW_GrEffectEdgeType:
gConicFillBW->ref();
return gConicFillBW;
default:
return NULL;
}
}
virtual ~GrConicEffect();
static const char* Name() { return "Conic"; }
inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
typedef GrGLConicEffect GLEffect;
virtual void getConstantColorComponents(GrColor* color,
uint32_t* validFlags) const SK_OVERRIDE {
*validFlags = 0;
}
virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
private:
GrConicEffect(GrEffectEdgeType);
virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
GrEffectEdgeType fEdgeType;
GR_DECLARE_EFFECT_TEST;
typedef GrVertexEffect 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 GrVertexEffect {
public:
static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
GR_CREATE_STATIC_EFFECT(gQuadFillAA, GrQuadEffect, (kFillAA_GrEffectEdgeType));
GR_CREATE_STATIC_EFFECT(gQuadHairAA, GrQuadEffect, (kHairlineAA_GrEffectEdgeType));
GR_CREATE_STATIC_EFFECT(gQuadFillBW, GrQuadEffect, (kFillBW_GrEffectEdgeType));
switch (edgeType) {
case kFillAA_GrEffectEdgeType:
if (!caps.shaderDerivativeSupport()) {
return NULL;
}
gQuadFillAA->ref();
return gQuadFillAA;
case kHairlineAA_GrEffectEdgeType:
if (!caps.shaderDerivativeSupport()) {
return NULL;
}
gQuadHairAA->ref();
return gQuadHairAA;
case kFillBW_GrEffectEdgeType:
gQuadFillBW->ref();
return gQuadFillBW;
default:
return NULL;
}
}
virtual ~GrQuadEffect();
static const char* Name() { return "Quad"; }
inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
typedef GrGLQuadEffect GLEffect;
virtual void getConstantColorComponents(GrColor* color,
uint32_t* validFlags) const SK_OVERRIDE {
*validFlags = 0;
}
virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
private:
GrQuadEffect(GrEffectEdgeType);
virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
GrEffectEdgeType fEdgeType;
GR_DECLARE_EFFECT_TEST;
typedef GrVertexEffect INHERITED;
};
//////////////////////////////////////////////////////////////////////////////
/**
* 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 for AA is max(0, 1-distance).
*/
class GrGLCubicEffect;
class GrCubicEffect : public GrVertexEffect {
public:
static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
GR_CREATE_STATIC_EFFECT(gCubicFillAA, GrCubicEffect, (kFillAA_GrEffectEdgeType));
GR_CREATE_STATIC_EFFECT(gCubicHairAA, GrCubicEffect, (kHairlineAA_GrEffectEdgeType));
GR_CREATE_STATIC_EFFECT(gCubicFillBW, GrCubicEffect, (kFillBW_GrEffectEdgeType));
switch (edgeType) {
case kFillAA_GrEffectEdgeType:
if (!caps.shaderDerivativeSupport()) {
return NULL;
}
gCubicFillAA->ref();
return gCubicFillAA;
case kHairlineAA_GrEffectEdgeType:
if (!caps.shaderDerivativeSupport()) {
return NULL;
}
gCubicHairAA->ref();
return gCubicHairAA;
case kFillBW_GrEffectEdgeType:
gCubicFillBW->ref();
return gCubicFillBW;
default:
return NULL;
}
}
virtual ~GrCubicEffect();
static const char* Name() { return "Cubic"; }
inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
typedef GrGLCubicEffect GLEffect;
virtual void getConstantColorComponents(GrColor* color,
uint32_t* validFlags) const SK_OVERRIDE {
*validFlags = 0;
}
virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
private:
GrCubicEffect(GrEffectEdgeType);
virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
GrEffectEdgeType fEdgeType;
GR_DECLARE_EFFECT_TEST;
typedef GrVertexEffect INHERITED;
};
#endif