src/gpu/effects/GrBezierEffect.h - platform/external/skqp - Gitiles

 /*
  * 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"

 enum GrBezierEdgeType {
     kFillAA_GrBezierEdgeType,
     kHairAA_GrBezierEdgeType,
     kFillNoAA_GrBezierEdgeType,
 };

 static inline bool GrBezierEdgeTypeIsFill(const GrBezierEdgeType edgeType) {
     return (kHairAA_GrBezierEdgeType != edgeType);
 }

 static inline bool GrBezierEdgeTypeIsAA(const GrBezierEdgeType edgeType) {
     return (kFillNoAA_GrBezierEdgeType != edgeType);
 }

 /**
  * 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 GrBezierEdgeType edgeType, const GrDrawTargetCaps& caps) {
         GR_CREATE_STATIC_EFFECT(gConicFillAA, GrConicEffect, (kFillAA_GrBezierEdgeType));
         GR_CREATE_STATIC_EFFECT(gConicHairAA, GrConicEffect, (kHairAA_GrBezierEdgeType));
         GR_CREATE_STATIC_EFFECT(gConicFillNoAA, GrConicEffect, (kFillNoAA_GrBezierEdgeType));
         if (kFillAA_GrBezierEdgeType == edgeType) {
             if (!caps.shaderDerivativeSupport()) {
                 return NULL;
             }
             gConicFillAA->ref();
             return gConicFillAA;
         } else if (kHairAA_GrBezierEdgeType == edgeType) {
             if (!caps.shaderDerivativeSupport()) {
                 return NULL;
             }
             gConicHairAA->ref();
             return gConicHairAA;
         } else {
             gConicFillNoAA->ref();
             return gConicFillNoAA;
         }
     }

     virtual ~GrConicEffect();

     static const char* Name() { return "Conic"; }

     inline bool isAntiAliased() const { return GrBezierEdgeTypeIsAA(fEdgeType); }
     inline bool isFilled() const { return GrBezierEdgeTypeIsFill(fEdgeType); }
     inline GrBezierEdgeType 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(GrBezierEdgeType);

     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;

     GrBezierEdgeType 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 GrBezierEdgeType edgeType, const GrDrawTargetCaps& caps) {
         GR_CREATE_STATIC_EFFECT(gQuadFillAA, GrQuadEffect, (kFillAA_GrBezierEdgeType));
         GR_CREATE_STATIC_EFFECT(gQuadHairAA, GrQuadEffect, (kHairAA_GrBezierEdgeType));
         GR_CREATE_STATIC_EFFECT(gQuadFillNoAA, GrQuadEffect, (kFillNoAA_GrBezierEdgeType));
         if (kFillAA_GrBezierEdgeType == edgeType) {
             if (!caps.shaderDerivativeSupport()) {
                 return NULL;
             }
             gQuadFillAA->ref();
             return gQuadFillAA;
         } else if (kHairAA_GrBezierEdgeType == edgeType) {
             if (!caps.shaderDerivativeSupport()) {
                 return NULL;
             }
             gQuadHairAA->ref();
             return gQuadHairAA;
         } else {
             gQuadFillNoAA->ref();
             return gQuadFillNoAA;
         }
     }

     virtual ~GrQuadEffect();

     static const char* Name() { return "Quad"; }

     inline bool isAntiAliased() const { return GrBezierEdgeTypeIsAA(fEdgeType); }
     inline bool isFilled() const { return GrBezierEdgeTypeIsFill(fEdgeType); }
     inline GrBezierEdgeType 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(GrBezierEdgeType);

     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;

     GrBezierEdgeType 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 GrBezierEdgeType edgeType, const GrDrawTargetCaps& caps) {
         GR_CREATE_STATIC_EFFECT(gCubicFillAA, GrCubicEffect, (kFillAA_GrBezierEdgeType));
         GR_CREATE_STATIC_EFFECT(gCubicHairAA, GrCubicEffect, (kHairAA_GrBezierEdgeType));
         GR_CREATE_STATIC_EFFECT(gCubicFillNoAA, GrCubicEffect, (kFillNoAA_GrBezierEdgeType));
         if (kFillAA_GrBezierEdgeType == edgeType) {
             if (!caps.shaderDerivativeSupport()) {
                 return NULL;
             }
             gCubicFillAA->ref();
             return gCubicFillAA;
         } else if (kHairAA_GrBezierEdgeType == edgeType) {
             if (!caps.shaderDerivativeSupport()) {
                 return NULL;
             }
             gCubicHairAA->ref();
             return gCubicHairAA;
         } else {
             gCubicFillNoAA->ref();
             return gCubicFillNoAA;
         }
     }

     virtual ~GrCubicEffect();

     static const char* Name() { return "Cubic"; }

     inline bool isAntiAliased() const { return GrBezierEdgeTypeIsAA(fEdgeType); }
     inline bool isFilled() const { return GrBezierEdgeTypeIsFill(fEdgeType); }
     inline GrBezierEdgeType 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(GrBezierEdgeType);

     virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;

     GrBezierEdgeType fEdgeType;

     GR_DECLARE_EFFECT_TEST;

     typedef GrVertexEffect INHERITED;
 };

 #endif
	/*
	* 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"

	enum GrBezierEdgeType {
	kFillAA_GrBezierEdgeType,
	kHairAA_GrBezierEdgeType,
	kFillNoAA_GrBezierEdgeType,
	};

	static inline bool GrBezierEdgeTypeIsFill(const GrBezierEdgeType edgeType) {
	return (kHairAA_GrBezierEdgeType != edgeType);
	}

	static inline bool GrBezierEdgeTypeIsAA(const GrBezierEdgeType edgeType) {
	return (kFillNoAA_GrBezierEdgeType != edgeType);
	}

	/**
	* 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(gFMgFM+4.0funcgF2M) - gFM)/(2.0gF2M);\n");
	* Version 2:
	* builder->fsCodeAppend("\t\tedgeAlpha = (gFM - sqrt(gFMgFM-4.0funcgF2M))/(2.0gF2M);\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 GrBezierEdgeType edgeType, const GrDrawTargetCaps& caps) {
	GR_CREATE_STATIC_EFFECT(gConicFillAA, GrConicEffect, (kFillAA_GrBezierEdgeType));
	GR_CREATE_STATIC_EFFECT(gConicHairAA, GrConicEffect, (kHairAA_GrBezierEdgeType));
	GR_CREATE_STATIC_EFFECT(gConicFillNoAA, GrConicEffect, (kFillNoAA_GrBezierEdgeType));
	if (kFillAA_GrBezierEdgeType == edgeType) {
	if (!caps.shaderDerivativeSupport()) {
	return NULL;
	}
	gConicFillAA->ref();
	return gConicFillAA;
	} else if (kHairAA_GrBezierEdgeType == edgeType) {
	if (!caps.shaderDerivativeSupport()) {
	return NULL;
	}
	gConicHairAA->ref();
	return gConicHairAA;
	} else {
	gConicFillNoAA->ref();
	return gConicFillNoAA;
	}
	}

	virtual ~GrConicEffect();

	static const char* Name() { return "Conic"; }

	inline bool isAntiAliased() const { return GrBezierEdgeTypeIsAA(fEdgeType); }
	inline bool isFilled() const { return GrBezierEdgeTypeIsFill(fEdgeType); }
	inline GrBezierEdgeType 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(GrBezierEdgeType);

	virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;

	GrBezierEdgeType 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 GrBezierEdgeType edgeType, const GrDrawTargetCaps& caps) {
	GR_CREATE_STATIC_EFFECT(gQuadFillAA, GrQuadEffect, (kFillAA_GrBezierEdgeType));
	GR_CREATE_STATIC_EFFECT(gQuadHairAA, GrQuadEffect, (kHairAA_GrBezierEdgeType));
	GR_CREATE_STATIC_EFFECT(gQuadFillNoAA, GrQuadEffect, (kFillNoAA_GrBezierEdgeType));
	if (kFillAA_GrBezierEdgeType == edgeType) {
	if (!caps.shaderDerivativeSupport()) {
	return NULL;
	}
	gQuadFillAA->ref();
	return gQuadFillAA;
	} else if (kHairAA_GrBezierEdgeType == edgeType) {
	if (!caps.shaderDerivativeSupport()) {
	return NULL;
	}
	gQuadHairAA->ref();
	return gQuadHairAA;
	} else {
	gQuadFillNoAA->ref();
	return gQuadFillNoAA;
	}
	}

	virtual ~GrQuadEffect();

	static const char* Name() { return "Quad"; }

	inline bool isAntiAliased() const { return GrBezierEdgeTypeIsAA(fEdgeType); }
	inline bool isFilled() const { return GrBezierEdgeTypeIsFill(fEdgeType); }
	inline GrBezierEdgeType 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(GrBezierEdgeType);

	virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;

	GrBezierEdgeType 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 GrBezierEdgeType edgeType, const GrDrawTargetCaps& caps) {
	GR_CREATE_STATIC_EFFECT(gCubicFillAA, GrCubicEffect, (kFillAA_GrBezierEdgeType));
	GR_CREATE_STATIC_EFFECT(gCubicHairAA, GrCubicEffect, (kHairAA_GrBezierEdgeType));
	GR_CREATE_STATIC_EFFECT(gCubicFillNoAA, GrCubicEffect, (kFillNoAA_GrBezierEdgeType));
	if (kFillAA_GrBezierEdgeType == edgeType) {
	if (!caps.shaderDerivativeSupport()) {
	return NULL;
	}
	gCubicFillAA->ref();
	return gCubicFillAA;
	} else if (kHairAA_GrBezierEdgeType == edgeType) {
	if (!caps.shaderDerivativeSupport()) {
	return NULL;
	}
	gCubicHairAA->ref();
	return gCubicHairAA;
	} else {
	gCubicFillNoAA->ref();
	return gCubicFillNoAA;
	}
	}

	virtual ~GrCubicEffect();

	static const char* Name() { return "Cubic"; }

	inline bool isAntiAliased() const { return GrBezierEdgeTypeIsAA(fEdgeType); }
	inline bool isFilled() const { return GrBezierEdgeTypeIsFill(fEdgeType); }
	inline GrBezierEdgeType 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(GrBezierEdgeType);

	virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;

	GrBezierEdgeType fEdgeType;

	GR_DECLARE_EFFECT_TEST;

	typedef GrVertexEffect INHERITED;
	};

	#endif