1/*
2 * Copyright 2013 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef GrBezierEffect_DEFINED
9#define GrBezierEffect_DEFINED
10
11#include "GrDrawTargetCaps.h"
12#include "GrEffect.h"
13#include "GrVertexEffect.h"
14#include "GrTypesPriv.h"
15
16/**
17 * Shader is based off of Loop-Blinn Quadratic GPU Rendering
18 * The output of this effect is a hairline edge for conics.
19 * Conics specified by implicit equation K^2 - LM.
20 * K, L, and M, are the first three values of the vertex attribute,
21 * the fourth value is not used. Distance is calculated using a
22 * first order approximation from the taylor series.
23 * Coverage for AA is max(0, 1-distance).
24 *
25 * Test were also run using a second order distance approximation.
26 * There were two versions of the second order approx. The first version
27 * is of roughly the form:
28 * f(q) = |f(p)| - ||f'(p)||*||q-p|| - ||f''(p)||*||q-p||^2.
29 * The second is similar:
30 * f(q) = |f(p)| + ||f'(p)||*||q-p|| + ||f''(p)||*||q-p||^2.
31 * The exact version of the equations can be found in the paper
32 * "Distance Approximations for Rasterizing Implicit Curves" by Gabriel Taubin
33 *
34 * In both versions we solve the quadratic for ||q-p||.
35 * Version 1:
36 * gFM is magnitude of first partials and gFM2 is magnitude of 2nd partials (as derived from paper)
37 * builder->fsCodeAppend("\t\tedgeAlpha = (sqrt(gFM*gFM+4.0*func*gF2M) - gFM)/(2.0*gF2M);\n");
38 * Version 2:
39 * builder->fsCodeAppend("\t\tedgeAlpha = (gFM - sqrt(gFM*gFM-4.0*func*gF2M))/(2.0*gF2M);\n");
40 *
41 * Also note that 2nd partials of k,l,m are zero
42 *
43 * When comparing the two second order approximations to the first order approximations,
44 * the following results were found. Version 1 tends to underestimate the distances, thus it
45 * basically increases all the error that we were already seeing in the first order
46 * approx. So this version is not the one to use. Version 2 has the opposite effect
47 * and tends to overestimate the distances. This is much closer to what we are
48 * looking for. It is able to render ellipses (even thin ones) without the need to chop.
49 * However, it can not handle thin hyperbolas well and thus would still rely on
50 * chopping to tighten the clipping. Another side effect of the overestimating is
51 * that the curves become much thinner and "ropey". If all that was ever rendered
52 * were "not too thin" curves and ellipses then 2nd order may have an advantage since
53 * only one geometry would need to be rendered. However no benches were run comparing
54 * chopped first order and non chopped 2nd order.
55 */
56class GrGLConicEffect;
57
58class GrConicEffect : public GrVertexEffect {
59public:
60    static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
61        GR_CREATE_STATIC_EFFECT(gConicFillAA, GrConicEffect, (kFillAA_GrEffectEdgeType));
62        GR_CREATE_STATIC_EFFECT(gConicHairAA, GrConicEffect, (kHairlineAA_GrEffectEdgeType));
63        GR_CREATE_STATIC_EFFECT(gConicFillBW, GrConicEffect, (kFillBW_GrEffectEdgeType));
64        switch (edgeType) {
65            case kFillAA_GrEffectEdgeType:
66                if (!caps.shaderDerivativeSupport()) {
67                    return NULL;
68                }
69                gConicFillAA->ref();
70                return gConicFillAA;
71            case kHairlineAA_GrEffectEdgeType:
72                if (!caps.shaderDerivativeSupport()) {
73                    return NULL;
74                }
75                gConicHairAA->ref();
76                return gConicHairAA;
77            case kFillBW_GrEffectEdgeType:
78                gConicFillBW->ref();
79                return gConicFillBW;
80            default:
81                return NULL;
82        }
83    }
84
85    virtual ~GrConicEffect();
86
87    static const char* Name() { return "Conic"; }
88
89    inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
90    inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
91    inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
92
93    typedef GrGLConicEffect GLEffect;
94
95    virtual void getConstantColorComponents(GrColor* color,
96                                            uint32_t* validFlags) const SK_OVERRIDE {
97        *validFlags = 0;
98    }
99
100    virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
101
102private:
103    GrConicEffect(GrEffectEdgeType);
104
105    virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
106
107    GrEffectEdgeType fEdgeType;
108
109    GR_DECLARE_EFFECT_TEST;
110
111    typedef GrVertexEffect INHERITED;
112};
113
114///////////////////////////////////////////////////////////////////////////////
115/**
116 * The output of this effect is a hairline edge for quadratics.
117 * Quadratic specified by 0=u^2-v canonical coords. u and v are the first
118 * two components of the vertex attribute. At the three control points that define
119 * the Quadratic, u, v have the values {0,0}, {1/2, 0}, and {1, 1} respectively.
120 * Coverage for AA is min(0, 1-distance). 3rd & 4th cimponent unused.
121 * Requires shader derivative instruction support.
122 */
123class GrGLQuadEffect;
124
125class GrQuadEffect : public GrVertexEffect {
126public:
127    static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
128        GR_CREATE_STATIC_EFFECT(gQuadFillAA, GrQuadEffect, (kFillAA_GrEffectEdgeType));
129        GR_CREATE_STATIC_EFFECT(gQuadHairAA, GrQuadEffect, (kHairlineAA_GrEffectEdgeType));
130        GR_CREATE_STATIC_EFFECT(gQuadFillBW, GrQuadEffect, (kFillBW_GrEffectEdgeType));
131        switch (edgeType) {
132            case kFillAA_GrEffectEdgeType:
133                if (!caps.shaderDerivativeSupport()) {
134                    return NULL;
135                }
136                gQuadFillAA->ref();
137                return gQuadFillAA;
138            case kHairlineAA_GrEffectEdgeType:
139                if (!caps.shaderDerivativeSupport()) {
140                    return NULL;
141                }
142                gQuadHairAA->ref();
143                return gQuadHairAA;
144            case kFillBW_GrEffectEdgeType:
145                gQuadFillBW->ref();
146                return gQuadFillBW;
147            default:
148                return NULL;
149        }
150    }
151
152    virtual ~GrQuadEffect();
153
154    static const char* Name() { return "Quad"; }
155
156    inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
157    inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
158    inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
159
160    typedef GrGLQuadEffect GLEffect;
161
162    virtual void getConstantColorComponents(GrColor* color,
163                                            uint32_t* validFlags) const SK_OVERRIDE {
164        *validFlags = 0;
165    }
166
167    virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
168
169private:
170    GrQuadEffect(GrEffectEdgeType);
171
172    virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
173
174    GrEffectEdgeType fEdgeType;
175
176    GR_DECLARE_EFFECT_TEST;
177
178    typedef GrVertexEffect INHERITED;
179};
180
181//////////////////////////////////////////////////////////////////////////////
182/**
183 * Shader is based off of "Resolution Independent Curve Rendering using
184 * Programmable Graphics Hardware" by Loop and Blinn.
185 * The output of this effect is a hairline edge for non rational cubics.
186 * Cubics are specified by implicit equation K^3 - LM.
187 * K, L, and M, are the first three values of the vertex attribute,
188 * the fourth value is not used. Distance is calculated using a
189 * first order approximation from the taylor series.
190 * Coverage for AA is max(0, 1-distance).
191 */
192class GrGLCubicEffect;
193
194class GrCubicEffect : public GrVertexEffect {
195public:
196    static GrEffectRef* Create(const GrEffectEdgeType edgeType, const GrDrawTargetCaps& caps) {
197        GR_CREATE_STATIC_EFFECT(gCubicFillAA, GrCubicEffect, (kFillAA_GrEffectEdgeType));
198        GR_CREATE_STATIC_EFFECT(gCubicHairAA, GrCubicEffect, (kHairlineAA_GrEffectEdgeType));
199        GR_CREATE_STATIC_EFFECT(gCubicFillBW, GrCubicEffect, (kFillBW_GrEffectEdgeType));
200        switch (edgeType) {
201            case kFillAA_GrEffectEdgeType:
202                if (!caps.shaderDerivativeSupport()) {
203                    return NULL;
204                }
205                gCubicFillAA->ref();
206                return gCubicFillAA;
207            case kHairlineAA_GrEffectEdgeType:
208                if (!caps.shaderDerivativeSupport()) {
209                    return NULL;
210                }
211                gCubicHairAA->ref();
212                return gCubicHairAA;
213            case kFillBW_GrEffectEdgeType:
214                gCubicFillBW->ref();
215                return gCubicFillBW;
216            default:
217                return NULL;
218        }
219    }
220
221    virtual ~GrCubicEffect();
222
223    static const char* Name() { return "Cubic"; }
224
225    inline bool isAntiAliased() const { return GrEffectEdgeTypeIsAA(fEdgeType); }
226    inline bool isFilled() const { return GrEffectEdgeTypeIsFill(fEdgeType); }
227    inline GrEffectEdgeType getEdgeType() const { return fEdgeType; }
228
229    typedef GrGLCubicEffect GLEffect;
230
231    virtual void getConstantColorComponents(GrColor* color,
232                                            uint32_t* validFlags) const SK_OVERRIDE {
233        *validFlags = 0;
234    }
235
236    virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE;
237
238private:
239    GrCubicEffect(GrEffectEdgeType);
240
241    virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE;
242
243    GrEffectEdgeType fEdgeType;
244
245    GR_DECLARE_EFFECT_TEST;
246
247    typedef GrVertexEffect INHERITED;
248};
249
250#endif
251