src/gpu/effects/GrBezierEffect.h

   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 "GrProcessor.h"
  13 #include "GrGeometryProcessor.h"
  14 #include "GrInvariantOutput.h"
  15 #include "GrTypesPriv.h"
  16
  17 /**
  18  * Shader is based off of Loop-Blinn Quadratic GPU Rendering
  19  * The output of this effect is a hairline edge for conics.
  20  * Conics specified by implicit equation K^2 - LM.
  21  * K, L, and M, are the first three values of the vertex attribute,
  22  * the fourth value is not used. Distance is calculated using a
  23  * first order approximation from the taylor series.
  24  * Coverage for AA is max(0, 1-distance).
  25  *
  26  * Test were also run using a second order distance approximation.
  27  * There were two versions of the second order approx. The first version
  28  * is of roughly the form:
  29  * f(q) = |f(p)| - ||f'(p)||*||q-p|| - ||f''(p)||*||q-p||^2.
  30  * The second is similar:
  31  * f(q) = |f(p)| + ||f'(p)||*||q-p|| + ||f''(p)||*||q-p||^2.
  32  * The exact version of the equations can be found in the paper
  33  * "Distance Approximations for Rasterizing Implicit Curves" by Gabriel Taubin
  34  *
  35  * In both versions we solve the quadratic for ||q-p||.
  36  * Version 1:
  37  * gFM is magnitude of first partials and gFM2 is magnitude of 2nd partials (as derived from paper)
  38  * builder->fsCodeAppend("\t\tedgeAlpha = (sqrt(gFM*gFM+4.0*func*gF2M) - gFM)/(2.0*gF2M);\n");
  39  * Version 2:
  40  * builder->fsCodeAppend("\t\tedgeAlpha = (gFM - sqrt(gFM*gFM-4.0*func*gF2M))/(2.0*gF2M);\n");
  41  *
  42  * Also note that 2nd partials of k,l,m are zero
  43  *
  44  * When comparing the two second order approximations to the first order approximations,
  45  * the following results were found. Version 1 tends to underestimate the distances, thus it
  46  * basically increases all the error that we were already seeing in the first order
  47  * approx. So this version is not the one to use. Version 2 has the opposite effect
  48  * and tends to overestimate the distances. This is much closer to what we are
  49  * looking for. It is able to render ellipses (even thin ones) without the need to chop.
  50  * However, it can not handle thin hyperbolas well and thus would still rely on
  51  * chopping to tighten the clipping. Another side effect of the overestimating is
  52  * that the curves become much thinner and "ropey". If all that was ever rendered
  53  * were "not too thin" curves and ellipses then 2nd order may have an advantage since
  54  * only one geometry would need to be rendered. However no benches were run comparing
  55  * chopped first order and non chopped 2nd order.
  56  */
  57 class GrGLConicEffect;
  58
  59 class GrConicEffect : public GrGeometryProcessor {
  60 public:
  61     static GrGeometryProcessor* Create(GrColor color,
  62                                        const SkMatrix& viewMatrix,
  63                                        const GrPrimitiveEdgeType edgeType,
  64                                        const GrDrawTargetCaps& caps,
  65                                        const SkMatrix& localMatrix,
  66                                        uint8_t coverage = 0xff) {
  67         switch (edgeType) {
  68             case kFillAA_GrProcessorEdgeType:
  69                 if (!caps.shaderDerivativeSupport()) {
  70                     return NULL;
  71                 }
  72                 return SkNEW_ARGS(GrConicEffect, (color, viewMatrix, coverage,
  73                                                   kFillAA_GrProcessorEdgeType,
  74                                                   localMatrix));
  75             case kHairlineAA_GrProcessorEdgeType:
  76                 if (!caps.shaderDerivativeSupport()) {
  77                     return NULL;
  78                 }
  79                 return SkNEW_ARGS(GrConicEffect, (color, viewMatrix, coverage,
  80                                                   kHairlineAA_GrProcessorEdgeType,
  81                                                   localMatrix));
  82             case kFillBW_GrProcessorEdgeType:
  83                 return SkNEW_ARGS(GrConicEffect, (color, viewMatrix, coverage,
  84                                                   kFillBW_GrProcessorEdgeType,
  85                                                   localMatrix));
  86             default:
  87                 return NULL;
  88         }
  89     }
  90
  91     virtual ~GrConicEffect();
  92
  93     const char* name() const SK_OVERRIDE { return "Conic"; }
  94
  95     inline const Attribute* inPosition() const { return fInPosition; }
  96     inline const Attribute* inConicCoeffs() const { return fInConicCoeffs; }
  97     inline bool isAntiAliased() const { return GrProcessorEdgeTypeIsAA(fEdgeType); }
  98     inline bool isFilled() const { return GrProcessorEdgeTypeIsFill(fEdgeType); }
  99     inline GrPrimitiveEdgeType getEdgeType() const { return fEdgeType; }
 100
 101     virtual void getGLProcessorKey(const GrBatchTracker& bt,
 102                                    const GrGLCaps& caps,
 103                                    GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 104
 105     virtual GrGLPrimitiveProcessor* createGLInstance(const GrBatchTracker& bt,
 106                                                      const GrGLCaps&) const SK_OVERRIDE;
 107
 108     void initBatchTracker(GrBatchTracker*, const GrPipelineInfo&) const SK_OVERRIDE;
 109     bool onCanMakeEqual(const GrBatchTracker&,
 110                         const GrGeometryProcessor&,
 111                         const GrBatchTracker&) const SK_OVERRIDE;
 112
 113 private:
 114     GrConicEffect(GrColor, const SkMatrix& viewMatrix, uint8_t coverage, GrPrimitiveEdgeType,
 115                   const SkMatrix& localMatrix);
 116
 117     bool onIsEqual(const GrGeometryProcessor& other) const SK_OVERRIDE;
 118
 119     void onGetInvariantOutputCoverage(GrInitInvariantOutput* out) const SK_OVERRIDE {
 120         out->setUnknownSingleComponent();
 121     }
 122
 123     uint8_t               fCoverageScale;
 124     GrPrimitiveEdgeType   fEdgeType;
 125     const Attribute*    fInPosition;
 126     const Attribute*    fInConicCoeffs;
 127
 128     GR_DECLARE_GEOMETRY_PROCESSOR_TEST;
 129
 130     typedef GrGeometryProcessor INHERITED;
 131 };
 132
 133 ///////////////////////////////////////////////////////////////////////////////
 134 /**
 135  * The output of this effect is a hairline edge for quadratics.
 136  * Quadratic specified by 0=u^2-v canonical coords. u and v are the first
 137  * two components of the vertex attribute. At the three control points that define
 138  * the Quadratic, u, v have the values {0,0}, {1/2, 0}, and {1, 1} respectively.
 139  * Coverage for AA is min(0, 1-distance). 3rd & 4th cimponent unused.
 140  * Requires shader derivative instruction support.
 141  */
 142 class GrGLQuadEffect;
 143
 144 class GrQuadEffect : public GrGeometryProcessor {
 145 public:
 146     static GrGeometryProcessor* Create(GrColor color,
 147                                        const SkMatrix& viewMatrix,
 148                                        const GrPrimitiveEdgeType edgeType,
 149                                        const GrDrawTargetCaps& caps,
 150                                        const SkMatrix& localMatrix,
 151                                        uint8_t coverage = 0xff) {
 152         switch (edgeType) {
 153             case kFillAA_GrProcessorEdgeType:
 154                 if (!caps.shaderDerivativeSupport()) {
 155                     return NULL;
 156                 }
 157                 return SkNEW_ARGS(GrQuadEffect, (color, viewMatrix, coverage,
 158                                                  kFillAA_GrProcessorEdgeType,
 159                                                  localMatrix));
 160             case kHairlineAA_GrProcessorEdgeType:
 161                 if (!caps.shaderDerivativeSupport()) {
 162                     return NULL;
 163                 }
 164                 return SkNEW_ARGS(GrQuadEffect, (color, viewMatrix, coverage,
 165                                                  kHairlineAA_GrProcessorEdgeType,
 166                                                  localMatrix));
 167             case kFillBW_GrProcessorEdgeType:
 168                 return SkNEW_ARGS(GrQuadEffect, (color, viewMatrix, coverage,
 169                                                  kFillBW_GrProcessorEdgeType,
 170                                                  localMatrix));
 171             default:
 172                 return NULL;
 173         }
 174     }
 175
 176     virtual ~GrQuadEffect();
 177
 178     const char* name() const SK_OVERRIDE { return "Quad"; }
 179
 180     inline const Attribute* inPosition() const { return fInPosition; }
 181     inline const Attribute* inHairQuadEdge() const { return fInHairQuadEdge; }
 182     inline bool isAntiAliased() const { return GrProcessorEdgeTypeIsAA(fEdgeType); }
 183     inline bool isFilled() const { return GrProcessorEdgeTypeIsFill(fEdgeType); }
 184     inline GrPrimitiveEdgeType getEdgeType() const { return fEdgeType; }
 185
 186     virtual void getGLProcessorKey(const GrBatchTracker& bt,
 187                                    const GrGLCaps& caps,
 188                                    GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 189
 190     virtual GrGLPrimitiveProcessor* createGLInstance(const GrBatchTracker& bt,
 191                                                      const GrGLCaps&) const SK_OVERRIDE;
 192
 193     void initBatchTracker(GrBatchTracker*, const GrPipelineInfo&) const SK_OVERRIDE;
 194     bool onCanMakeEqual(const GrBatchTracker&,
 195                         const GrGeometryProcessor&,
 196                         const GrBatchTracker&) const SK_OVERRIDE;
 197
 198 private:
 199     GrQuadEffect(GrColor, const SkMatrix& viewMatrix, uint8_t coverage, GrPrimitiveEdgeType,
 200                  const SkMatrix& localMatrix);
 201
 202     bool onIsEqual(const GrGeometryProcessor& other) const SK_OVERRIDE;
 203
 204     void onGetInvariantOutputCoverage(GrInitInvariantOutput* out) const SK_OVERRIDE {
 205         out->setUnknownSingleComponent();
 206     }
 207
 208     uint8_t               fCoverageScale;
 209     GrPrimitiveEdgeType   fEdgeType;
 210     const Attribute*    fInPosition;
 211     const Attribute*    fInHairQuadEdge;
 212
 213     GR_DECLARE_GEOMETRY_PROCESSOR_TEST;
 214
 215     typedef GrGeometryProcessor INHERITED;
 216 };
 217
 218 //////////////////////////////////////////////////////////////////////////////
 219 /**
 220  * Shader is based off of "Resolution Independent Curve Rendering using
 221  * Programmable Graphics Hardware" by Loop and Blinn.
 222  * The output of this effect is a hairline edge for non rational cubics.
 223  * Cubics are specified by implicit equation K^3 - LM.
 224  * K, L, and M, are the first three values of the vertex attribute,
 225  * the fourth value is not used. Distance is calculated using a
 226  * first order approximation from the taylor series.
 227  * Coverage for AA is max(0, 1-distance).
 228  */
 229 class GrGLCubicEffect;
 230
 231 class GrCubicEffect : public GrGeometryProcessor {
 232 public:
 233     static GrGeometryProcessor* Create(GrColor color,
 234                                        const SkMatrix& viewMatrix,
 235                                        const GrPrimitiveEdgeType edgeType,
 236                                        const GrDrawTargetCaps& caps) {
 237         switch (edgeType) {
 238             case kFillAA_GrProcessorEdgeType:
 239                 if (!caps.shaderDerivativeSupport()) {
 240                     return NULL;
 241                 }
 242                 return SkNEW_ARGS(GrCubicEffect, (color, viewMatrix, kFillAA_GrProcessorEdgeType));
 243             case kHairlineAA_GrProcessorEdgeType:
 244                 if (!caps.shaderDerivativeSupport()) {
 245                     return NULL;
 246                 }
 247                 return SkNEW_ARGS(GrCubicEffect, (color, viewMatrix,
 248                                                   kHairlineAA_GrProcessorEdgeType));
 249             case kFillBW_GrProcessorEdgeType:
 250                 return SkNEW_ARGS(GrCubicEffect, (color, viewMatrix,
 251                                                   kFillBW_GrProcessorEdgeType));
 252             default:
 253                 return NULL;
 254         }
 255     }
 256
 257     virtual ~GrCubicEffect();
 258
 259     const char* name() const SK_OVERRIDE { return "Cubic"; }
 260
 261     inline const Attribute* inPosition() const { return fInPosition; }
 262     inline const Attribute* inCubicCoeffs() const { return fInCubicCoeffs; }
 263     inline bool isAntiAliased() const { return GrProcessorEdgeTypeIsAA(fEdgeType); }
 264     inline bool isFilled() const { return GrProcessorEdgeTypeIsFill(fEdgeType); }
 265     inline GrPrimitiveEdgeType getEdgeType() const { return fEdgeType; }
 266
 267     virtual void getGLProcessorKey(const GrBatchTracker& bt,
 268                                    const GrGLCaps& caps,
 269                                    GrProcessorKeyBuilder* b) const SK_OVERRIDE;
 270
 271     virtual GrGLPrimitiveProcessor* createGLInstance(const GrBatchTracker& bt,
 272                                                      const GrGLCaps&) const SK_OVERRIDE;
 273
 274     void initBatchTracker(GrBatchTracker*, const GrPipelineInfo&) const SK_OVERRIDE;
 275     bool onCanMakeEqual(const GrBatchTracker&,
 276                         const GrGeometryProcessor&,
 277                         const GrBatchTracker&) const SK_OVERRIDE;
 278
 279 private:
 280     GrCubicEffect(GrColor, const SkMatrix& viewMatrix, GrPrimitiveEdgeType);
 281
 282     bool onIsEqual(const GrGeometryProcessor& other) const SK_OVERRIDE;
 283
 284     void onGetInvariantOutputCoverage(GrInitInvariantOutput* out) const SK_OVERRIDE {
 285         out->setUnknownSingleComponent();
 286     }
 287
 288     GrPrimitiveEdgeType   fEdgeType;
 289     const Attribute*    fInPosition;
 290     const Attribute*    fInCubicCoeffs;
 291
 292     GR_DECLARE_GEOMETRY_PROCESSOR_TEST;
 293
 294     typedef GrGeometryProcessor INHERITED;
 295 };
 296
 297 #endif