michael@0: /*
michael@0:  * Copyright 2013 Google Inc.
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: #ifndef GrBezierEffect_DEFINED
michael@0: #define GrBezierEffect_DEFINED
michael@0: 
michael@0: #include "GrDrawTargetCaps.h"
michael@0: #include "GrEffect.h"
michael@0: #include "GrVertexEffect.h"
michael@0: #include "GrTypesPriv.h"
michael@0: 
michael@0: /**
michael@0:  * Shader is based off of Loop-Blinn Quadratic GPU Rendering
michael@0:  * The output of this effect is a hairline edge for conics.
michael@0:  * Conics specified by implicit equation K^2 - LM.
michael@0:  * K, L, and M, are the first three values of the vertex attribute,
michael@0:  * the fourth value is not used. Distance is calculated using a
michael@0:  * first order approximation from the taylor series.
michael@0:  * Coverage for AA is max(0, 1-distance).
michael@0:  *
michael@0:  * Test were also run using a second order distance approximation.
michael@0:  * There were two versions of the second order approx. The first version
michael@0:  * is of roughly the form:
michael@0:  * f(q) = |f(p)| - ||f'(p)||*||q-p|| - ||f''(p)||*||q-p||^2.
michael@0:  * The second is similar:
michael@0:  * f(q) = |f(p)| + ||f'(p)||*||q-p|| + ||f''(p)||*||q-p||^2.
michael@0:  * The exact version of the equations can be found in the paper
michael@0:  * "Distance Approximations for Rasterizing Implicit Curves" by Gabriel Taubin
michael@0:  *
michael@0:  * In both versions we solve the quadratic for ||q-p||.
michael@0:  * Version 1:
michael@0:  * gFM is magnitude of first partials and gFM2 is magnitude of 2nd partials (as derived from paper)
michael@0:  * builder->fsCodeAppend("\t\tedgeAlpha = (sqrt(gFM*gFM+4.0*func*gF2M) - gFM)/(2.0*gF2M);\n");
michael@0:  * Version 2:
michael@0:  * builder->fsCodeAppend("\t\tedgeAlpha = (gFM - sqrt(gFM*gFM-4.0*func*gF2M))/(2.0*gF2M);\n");
michael@0:  *
michael@0:  * Also note that 2nd partials of k,l,m are zero
michael@0:  *
michael@0:  * When comparing the two second order approximations to the first order approximations,
michael@0:  * the following results were found. Version 1 tends to underestimate the distances, thus it
michael@0:  * basically increases all the error that we were already seeing in the first order
michael@0:  * approx. So this version is not the one to use. Version 2 has the opposite effect
michael@0:  * and tends to overestimate the distances. This is much closer to what we are
michael@0:  * looking for. It is able to render ellipses (even thin ones) without the need to chop.
michael@0:  * However, it can not handle thin hyperbolas well and thus would still rely on
michael@0:  * chopping to tighten the clipping. Another side effect of the overestimating is
michael@0:  * that the curves become much thinner and "ropey". If all that was ever rendered
michael@0:  * were "not too thin" curves and ellipses then 2nd order may have an advantage since
michael@0:  * only one geometry would need to be rendered. However no benches were run comparing
michael@0:  * chopped first order and non chopped 2nd order.
michael@0:  */
michael@0: class GrGLConicEffect;
michael@0: 
michael@0: class GrConicEffect : public GrVertexEffect {
michael@0: public:
michael@0:     static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
michael@0:         GR_CREATE_STATIC_EFFECT(gConicFillAA, GrConicEffect, (kFillAA_GrEffectEdgeType));
michael@0:         GR_CREATE_STATIC_EFFECT(gConicHairAA, GrConicEffect, (kHairlineAA_GrEffectEdgeType));
michael@0:         GR_CREATE_STATIC_EFFECT(gConicFillBW, GrConicEffect, (kFillBW_GrEffectEdgeType));
michael@0:         switch (edgeType) {
michael@0:             case kFillAA_GrEffectEdgeType:
michael@0:                 if (!caps.shaderDerivativeSupport()) {
michael@0:                     return NULL;
michael@0:                 }
michael@0:                 gConicFillAA->ref();
michael@0:                 return gConicFillAA;
michael@0:             case kHairlineAA_GrEffectEdgeType:
michael@0:                 if (!caps.shaderDerivativeSupport()) {
michael@0:                     return NULL;
michael@0:                 }
michael@0:                 gConicHairAA->ref();
michael@0:                 return gConicHairAA;
michael@0:             case kFillBW_GrEffectEdgeType:
michael@0:                 gConicFillBW->ref();
michael@0:                 return gConicFillBW;
michael@0:             default:
michael@0:                 return NULL;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     virtual ~GrConicEffect();
michael@0: 
michael@0:     static const char* Name() { return "Conic"; }
michael@0: 
michael@0:     inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
michael@0:     inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
michael@0:     inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
michael@0: 
michael@0:     typedef GrGLConicEffect GLEffect;
michael@0: 
michael@0:     virtual void getConstantColorComponents(GrColor* color,
michael@0:                                             uint32_t* validFlags) const SK_OVERRIDE {
michael@0:         *validFlags = 0;
michael@0:     }
michael@0: 
michael@0:     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
michael@0: 
michael@0: private:
michael@0:     GrConicEffect(GrEffectEdgeType);
michael@0: 
michael@0:     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
michael@0: 
michael@0:     GrEffectEdgeType fEdgeType;
michael@0: 
michael@0:     GR_DECLARE_EFFECT_TEST;
michael@0: 
michael@0:     typedef GrVertexEffect INHERITED;
michael@0: };
michael@0: 
michael@0: ///////////////////////////////////////////////////////////////////////////////
michael@0: /**
michael@0:  * The output of this effect is a hairline edge for quadratics.
michael@0:  * Quadratic specified by 0=u^2-v canonical coords. u and v are the first
michael@0:  * two components of the vertex attribute. At the three control points that define
michael@0:  * the Quadratic, u, v have the values {0,0}, {1/2, 0}, and {1, 1} respectively.
michael@0:  * Coverage for AA is min(0, 1-distance). 3rd & 4th cimponent unused.
michael@0:  * Requires shader derivative instruction support.
michael@0:  */
michael@0: class GrGLQuadEffect;
michael@0: 
michael@0: class GrQuadEffect : public GrVertexEffect {
michael@0: public:
michael@0:     static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
michael@0:         GR_CREATE_STATIC_EFFECT(gQuadFillAA, GrQuadEffect, (kFillAA_GrEffectEdgeType));
michael@0:         GR_CREATE_STATIC_EFFECT(gQuadHairAA, GrQuadEffect, (kHairlineAA_GrEffectEdgeType));
michael@0:         GR_CREATE_STATIC_EFFECT(gQuadFillBW, GrQuadEffect, (kFillBW_GrEffectEdgeType));
michael@0:         switch (edgeType) {
michael@0:             case kFillAA_GrEffectEdgeType:
michael@0:                 if (!caps.shaderDerivativeSupport()) {
michael@0:                     return NULL;
michael@0:                 }
michael@0:                 gQuadFillAA->ref();
michael@0:                 return gQuadFillAA;
michael@0:             case kHairlineAA_GrEffectEdgeType:
michael@0:                 if (!caps.shaderDerivativeSupport()) {
michael@0:                     return NULL;
michael@0:                 }
michael@0:                 gQuadHairAA->ref();
michael@0:                 return gQuadHairAA;
michael@0:             case kFillBW_GrEffectEdgeType:
michael@0:                 gQuadFillBW->ref();
michael@0:                 return gQuadFillBW;
michael@0:             default:
michael@0:                 return NULL;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     virtual ~GrQuadEffect();
michael@0: 
michael@0:     static const char* Name() { return "Quad"; }
michael@0: 
michael@0:     inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
michael@0:     inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
michael@0:     inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
michael@0: 
michael@0:     typedef GrGLQuadEffect GLEffect;
michael@0: 
michael@0:     virtual void getConstantColorComponents(GrColor* color,
michael@0:                                             uint32_t* validFlags) const SK_OVERRIDE {
michael@0:         *validFlags = 0;
michael@0:     }
michael@0: 
michael@0:     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
michael@0: 
michael@0: private:
michael@0:     GrQuadEffect(GrEffectEdgeType);
michael@0: 
michael@0:     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
michael@0: 
michael@0:     GrEffectEdgeType fEdgeType;
michael@0: 
michael@0:     GR_DECLARE_EFFECT_TEST;
michael@0: 
michael@0:     typedef GrVertexEffect INHERITED;
michael@0: };
michael@0: 
michael@0: //////////////////////////////////////////////////////////////////////////////
michael@0: /**
michael@0:  * Shader is based off of "Resolution Independent Curve Rendering using
michael@0:  * Programmable Graphics Hardware" by Loop and Blinn.
michael@0:  * The output of this effect is a hairline edge for non rational cubics.
michael@0:  * Cubics are specified by implicit equation K^3 - LM.
michael@0:  * K, L, and M, are the first three values of the vertex attribute,
michael@0:  * the fourth value is not used. Distance is calculated using a
michael@0:  * first order approximation from the taylor series.
michael@0:  * Coverage for AA is max(0, 1-distance).
michael@0:  */
michael@0: class GrGLCubicEffect;
michael@0: 
michael@0: class GrCubicEffect : public GrVertexEffect {
michael@0: public:
michael@0:     static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
michael@0:         GR_CREATE_STATIC_EFFECT(gCubicFillAA, GrCubicEffect, (kFillAA_GrEffectEdgeType));
michael@0:         GR_CREATE_STATIC_EFFECT(gCubicHairAA, GrCubicEffect, (kHairlineAA_GrEffectEdgeType));
michael@0:         GR_CREATE_STATIC_EFFECT(gCubicFillBW, GrCubicEffect, (kFillBW_GrEffectEdgeType));
michael@0:         switch (edgeType) {
michael@0:             case kFillAA_GrEffectEdgeType:
michael@0:                 if (!caps.shaderDerivativeSupport()) {
michael@0:                     return NULL;
michael@0:                 }
michael@0:                 gCubicFillAA->ref();
michael@0:                 return gCubicFillAA;
michael@0:             case kHairlineAA_GrEffectEdgeType:
michael@0:                 if (!caps.shaderDerivativeSupport()) {
michael@0:                     return NULL;
michael@0:                 }
michael@0:                 gCubicHairAA->ref();
michael@0:                 return gCubicHairAA;
michael@0:             case kFillBW_GrEffectEdgeType:
michael@0:                 gCubicFillBW->ref();
michael@0:                 return gCubicFillBW;
michael@0:             default:
michael@0:                 return NULL;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     virtual ~GrCubicEffect();
michael@0: 
michael@0:     static const char* Name() { return "Cubic"; }
michael@0: 
michael@0:     inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
michael@0:     inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
michael@0:     inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
michael@0: 
michael@0:     typedef GrGLCubicEffect GLEffect;
michael@0: 
michael@0:     virtual void getConstantColorComponents(GrColor* color,
michael@0:                                             uint32_t* validFlags) const SK_OVERRIDE {
michael@0:         *validFlags = 0;
michael@0:     }
michael@0: 
michael@0:     virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
michael@0: 
michael@0: private:
michael@0:     GrCubicEffect(GrEffectEdgeType);
michael@0: 
michael@0:     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
michael@0: 
michael@0:     GrEffectEdgeType fEdgeType;
michael@0: 
michael@0:     GR_DECLARE_EFFECT_TEST;
michael@0: 
michael@0:     typedef GrVertexEffect INHERITED;
michael@0: };
michael@0: 
michael@0: #endif