bsalomon@google.com | 69cc6ad | 2012-01-17 14:25:10 +0000 | [diff] [blame^] | 1 | |
| 2 | /* |
| 3 | * Copyright 2012 Google Inc. |
| 4 | * |
| 5 | * Use of this source code is governed by a BSD-style license that can be |
| 6 | * found in the LICENSE file. |
| 7 | */ |
| 8 | |
| 9 | #include "GrAAConvexPathRenderer.h" |
| 10 | |
| 11 | #include "GrContext.h" |
| 12 | #include "GrDrawState.h" |
| 13 | #include "GrPathUtils.h" |
| 14 | #include "SkString.h" |
| 15 | #include "SkTrace.h" |
| 16 | |
| 17 | |
| 18 | GrAAConvexPathRenderer::GrAAConvexPathRenderer() { |
| 19 | } |
| 20 | |
| 21 | bool GrAAConvexPathRenderer::canDrawPath(const GrDrawTarget::Caps& targetCaps, |
| 22 | const SkPath& path, |
| 23 | GrPathFill fill, |
| 24 | bool antiAlias) const { |
| 25 | return targetCaps.fShaderDerivativeSupport && antiAlias && |
| 26 | kHairLine_PathFill != fill && !GrIsFillInverted(fill) && |
| 27 | path.isConvex(); |
| 28 | } |
| 29 | |
| 30 | namespace { |
| 31 | |
| 32 | |
| 33 | struct Segment { |
| 34 | enum { |
| 35 | kLine, |
| 36 | kQuad |
| 37 | } fType; |
| 38 | // line uses a, quad uses a and b (first point comes from prev. segment) |
| 39 | GrPoint fA, fB; |
| 40 | // normal to edge ending at a and b |
| 41 | GrVec fANorm, fBNorm; |
| 42 | // mid vector at a that splits angle with previous edge |
| 43 | GrVec fPrevMid; |
| 44 | }; |
| 45 | |
| 46 | typedef SkTArray<Segment, true> SegmentArray; |
| 47 | |
| 48 | bool is_path_degenerate(const GrPath& path) { |
| 49 | int n = path.countPoints(); |
| 50 | if (n < 3) { |
| 51 | return true; |
| 52 | } |
| 53 | |
| 54 | // compute a line from the first two points that are not equal, look for |
| 55 | // a third pt that is off the line. |
| 56 | static const SkScalar TOL = (SK_Scalar1 / 16); |
| 57 | bool foundLine = false; |
| 58 | GrPoint firstPoint = path.getPoint(0); |
| 59 | GrVec lineV; |
| 60 | SkScalar lineC; |
| 61 | int i = 1; |
| 62 | |
| 63 | do { |
| 64 | GrPoint pt = path.getPoint(i); |
| 65 | if (!foundLine) { |
| 66 | if (pt != firstPoint) { |
| 67 | lineV = pt - firstPoint; |
| 68 | lineV.normalize(); |
| 69 | lineV.setOrthog(lineV); |
| 70 | lineC = lineV.dot(firstPoint); |
| 71 | foundLine = true; |
| 72 | } |
| 73 | } else { |
| 74 | if (SkScalarAbs(lineV.dot(pt) - lineC) > TOL) { |
| 75 | return false; |
| 76 | } |
| 77 | } |
| 78 | ++i; |
| 79 | } while (i < n); |
| 80 | return true; |
| 81 | } |
| 82 | |
| 83 | bool get_segments(const GrPath& path, |
| 84 | SegmentArray* segments, |
| 85 | int* quadCnt, |
| 86 | int* lineCnt) { |
| 87 | *quadCnt = 0; |
| 88 | *lineCnt = 0; |
| 89 | SkPath::Iter iter(path, true); |
| 90 | // This renderer overemphasis very thin paths (every pixel intersected by |
| 91 | // the path will be at least 1/2 on). When the path degenerates to a line |
| 92 | // this makes the path draw as a hairline. This is a pretty glaring error |
| 93 | // so we detect this case and will not draw. |
| 94 | if (is_path_degenerate(path)) { |
| 95 | return false; |
| 96 | } |
| 97 | for (;;) { |
| 98 | GrPoint pts[4]; |
| 99 | GrPathCmd cmd = (GrPathCmd)iter.next(pts); |
| 100 | switch (cmd) { |
| 101 | case kLine_PathCmd: { |
| 102 | segments->push_back(); |
| 103 | segments->back().fType = Segment::kLine; |
| 104 | segments->back().fA = pts[1]; |
| 105 | ++(*lineCnt); |
| 106 | break; |
| 107 | } |
| 108 | case kQuadratic_PathCmd: |
| 109 | segments->push_back(); |
| 110 | segments->back().fType = Segment::kQuad; |
| 111 | segments->back().fA = pts[1]; |
| 112 | segments->back().fB = pts[2]; |
| 113 | ++(*quadCnt); |
| 114 | break; |
| 115 | case kCubic_PathCmd: { |
| 116 | SkSTArray<15, SkPoint, true> quads; |
| 117 | GrPathUtils::convertCubicToQuads(pts, SK_Scalar1, &quads); |
| 118 | int count = quads.count(); |
| 119 | for (int q = 0; q < count; q += 3) { |
| 120 | segments->push_back(); |
| 121 | segments->back().fType = Segment::kQuad; |
| 122 | segments->back().fA = quads[q + 1]; |
| 123 | segments->back().fB = quads[q + 2]; |
| 124 | ++(*quadCnt); |
| 125 | } |
| 126 | break; |
| 127 | }; |
| 128 | case kEnd_PathCmd: |
| 129 | GrAssert(*quadCnt + *lineCnt == segments->count()); |
| 130 | return true; |
| 131 | default: |
| 132 | break; |
| 133 | } |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | struct QuadVertex { |
| 138 | GrPoint fPos; |
| 139 | union { |
| 140 | GrPoint fQuadUV; |
| 141 | GrScalar fEdge[4]; |
| 142 | }; |
| 143 | }; |
| 144 | |
| 145 | void get_counts(int quadCount, int lineCount, int* vCount, int* iCount) { |
| 146 | *vCount = 9 * lineCount + 11 * quadCount; |
| 147 | *iCount = 15 * lineCount + 24 * quadCount; |
| 148 | } |
| 149 | |
| 150 | // for visual debugging, exagerate the AA smear at the edges |
| 151 | // requires modifying the distance calc in the shader actually shade differently |
| 152 | //#define STRETCH_AA |
| 153 | #define STRETCH_FACTOR (20 * SK_Scalar1) |
| 154 | |
| 155 | void create_vertices(SegmentArray* segments, |
| 156 | const GrPoint& fanPt, |
| 157 | QuadVertex* verts, |
| 158 | uint16_t* idxs) { |
| 159 | int count = segments->count(); |
| 160 | GrAssert(count > 1); |
| 161 | int prevS = count - 1; |
| 162 | const Segment& lastSeg = (*segments)[prevS]; |
| 163 | |
| 164 | // walk the segments and compute normals to each edge and |
| 165 | // bisectors at vertices. The loop relies on having the end point and normal |
| 166 | // from previous segment so we first compute that. Also, we determine |
| 167 | // whether normals point left or right to face outside the path. |
| 168 | GrVec prevPt; |
| 169 | GrPoint prevPrevPt; |
| 170 | GrVec prevNorm; |
| 171 | if (Segment::kLine == lastSeg.fType) { |
| 172 | prevPt = lastSeg.fA; |
| 173 | const Segment& secondLastSeg = (*segments)[prevS - 1]; |
| 174 | prevPrevPt = (Segment::kLine == secondLastSeg.fType) ? |
| 175 | secondLastSeg.fA : |
| 176 | secondLastSeg.fB; |
| 177 | } else { |
| 178 | prevPt = lastSeg.fB; |
| 179 | prevPrevPt = lastSeg.fA; |
| 180 | } |
| 181 | GrVec::Side outside; |
| 182 | // we will compute our edge vectors so that they are pointing along the |
| 183 | // direction in which we are iterating the path. So here we take an opposite |
| 184 | // vector and get the side that the fan pt lies relative to it. |
| 185 | fanPt.distanceToLineBetweenSqd(prevPrevPt, prevPt, &outside); |
| 186 | prevNorm = prevPt - prevPrevPt; |
| 187 | prevNorm.normalize(); |
| 188 | prevNorm.setOrthog(prevNorm, outside); |
| 189 | #ifdef STRETCH_AA |
| 190 | prevNorm.scale(STRETCH_FACTOR); |
| 191 | #endif |
| 192 | |
| 193 | // compute the normals and bisectors |
| 194 | for (int s = 0; s < count; ++s, ++prevS) { |
| 195 | Segment& curr = (*segments)[s]; |
| 196 | |
| 197 | GrVec currVec = curr.fA - prevPt; |
| 198 | currVec.normalize(); |
| 199 | curr.fANorm.setOrthog(currVec, outside); |
| 200 | #ifdef STRETCH_AA |
| 201 | curr.fANorm.scale(STRETCH_FACTOR); |
| 202 | #endif |
| 203 | curr.fPrevMid = prevNorm + curr.fANorm; |
| 204 | curr.fPrevMid.normalize(); |
| 205 | #ifdef STRETCH_AA |
| 206 | curr.fPrevMid.scale(STRETCH_FACTOR); |
| 207 | #endif |
| 208 | if (Segment::kLine == curr.fType) { |
| 209 | prevPt = curr.fA; |
| 210 | prevNorm = curr.fANorm; |
| 211 | } else { |
| 212 | currVec = curr.fB - curr.fA; |
| 213 | currVec.normalize(); |
| 214 | curr.fBNorm.setOrthog(currVec, outside); |
| 215 | #ifdef STRETCH_AA |
| 216 | curr.fBNorm.scale(STRETCH_FACTOR); |
| 217 | #endif |
| 218 | prevPt = curr.fB; |
| 219 | prevNorm = curr.fBNorm; |
| 220 | } |
| 221 | } |
| 222 | |
| 223 | // compute the vertices / indices |
| 224 | if (Segment::kLine == lastSeg.fType) { |
| 225 | prevPt = lastSeg.fA; |
| 226 | prevNorm = lastSeg.fANorm; |
| 227 | } else { |
| 228 | prevPt = lastSeg.fB; |
| 229 | prevNorm = lastSeg.fBNorm; |
| 230 | } |
| 231 | int v = 0; |
| 232 | int i = 0; |
| 233 | for (int s = 0; s < count; ++s, ++prevS) { |
| 234 | Segment& curr = (*segments)[s]; |
| 235 | verts[v + 0].fPos = prevPt; |
| 236 | verts[v + 1].fPos = prevPt + prevNorm; |
| 237 | verts[v + 2].fPos = prevPt + curr.fPrevMid; |
| 238 | verts[v + 3].fPos = prevPt + curr.fANorm; |
| 239 | verts[v + 0].fQuadUV.set(0, 0); |
| 240 | verts[v + 1].fQuadUV.set(0, -SK_Scalar1); |
| 241 | verts[v + 2].fQuadUV.set(0, -SK_Scalar1); |
| 242 | verts[v + 3].fQuadUV.set(0, -SK_Scalar1); |
| 243 | |
| 244 | idxs[i + 0] = v + 0; |
| 245 | idxs[i + 1] = v + 1; |
| 246 | idxs[i + 2] = v + 2; |
| 247 | idxs[i + 3] = v + 0; |
| 248 | idxs[i + 4] = v + 2; |
| 249 | idxs[i + 5] = v + 3; |
| 250 | |
| 251 | v += 4; |
| 252 | i += 6; |
| 253 | |
| 254 | if (Segment::kLine == curr.fType) { |
| 255 | verts[v + 0].fPos = fanPt; |
| 256 | verts[v + 1].fPos = prevPt; |
| 257 | verts[v + 2].fPos = curr.fA; |
| 258 | verts[v + 3].fPos = prevPt + curr.fANorm; |
| 259 | verts[v + 4].fPos = curr.fA + curr.fANorm; |
| 260 | GrScalar lineC = -curr.fANorm.dot(curr.fA); |
| 261 | GrScalar fanDist = curr.fANorm.dot(fanPt) - lineC; |
| 262 | verts[v + 0].fQuadUV.set(0, SkScalarAbs(fanDist)); |
| 263 | verts[v + 1].fQuadUV.set(0, 0); |
| 264 | verts[v + 2].fQuadUV.set(0, 0); |
| 265 | verts[v + 3].fQuadUV.set(0, -GR_Scalar1); |
| 266 | verts[v + 4].fQuadUV.set(0, -GR_Scalar1); |
| 267 | |
| 268 | idxs[i + 0] = v + 0; |
| 269 | idxs[i + 1] = v + 1; |
| 270 | idxs[i + 2] = v + 2; |
| 271 | idxs[i + 3] = v + 1; |
| 272 | idxs[i + 4] = v + 3; |
| 273 | idxs[i + 5] = v + 4; |
| 274 | idxs[i + 6] = v + 1; |
| 275 | idxs[i + 7] = v + 4; |
| 276 | idxs[i + 8] = v + 2; |
| 277 | |
| 278 | i += 9; |
| 279 | v += 5; |
| 280 | |
| 281 | prevPt = curr.fA; |
| 282 | prevNorm = curr.fANorm; |
| 283 | } else { |
| 284 | GrVec splitVec = curr.fANorm + curr.fBNorm; |
| 285 | splitVec.normalize(); |
| 286 | #ifdef STRETCH_AA |
| 287 | splitVec.scale(STRETCH_FACTOR); |
| 288 | #endif |
| 289 | |
| 290 | verts[v + 0].fPos = prevPt; |
| 291 | verts[v + 1].fPos = curr.fA; |
| 292 | verts[v + 2].fPos = curr.fB; |
| 293 | verts[v + 3].fPos = fanPt; |
| 294 | verts[v + 4].fPos = prevPt + curr.fANorm; |
| 295 | verts[v + 5].fPos = curr.fA + splitVec; |
| 296 | verts[v + 6].fPos = curr.fB + curr.fBNorm; |
| 297 | |
| 298 | verts[v + 0].fQuadUV.set(0, 0); |
| 299 | verts[v + 1].fQuadUV.set(GR_ScalarHalf, 0); |
| 300 | verts[v + 2].fQuadUV.set(GR_Scalar1, GR_Scalar1); |
| 301 | GrMatrix toUV; |
| 302 | GrPoint pts[] = {prevPt, curr.fA, curr.fB}; |
| 303 | GrPathUtils::quadDesignSpaceToUVCoordsMatrix(pts, &toUV); |
| 304 | toUV.mapPointsWithStride(&verts[v + 3].fQuadUV, |
| 305 | &verts[v + 3].fPos, |
| 306 | sizeof(QuadVertex), 4); |
| 307 | |
| 308 | idxs[i + 0] = v + 3; |
| 309 | idxs[i + 1] = v + 0; |
| 310 | idxs[i + 2] = v + 1; |
| 311 | idxs[i + 3] = v + 3; |
| 312 | idxs[i + 4] = v + 1; |
| 313 | idxs[i + 5] = v + 2; |
| 314 | idxs[i + 6] = v + 0; |
| 315 | idxs[i + 7] = v + 4; |
| 316 | idxs[i + 8] = v + 1; |
| 317 | idxs[i + 9] = v + 4; |
| 318 | idxs[i + 10] = v + 1; |
| 319 | idxs[i + 11] = v + 5; |
| 320 | idxs[i + 12] = v + 5; |
| 321 | idxs[i + 13] = v + 1; |
| 322 | idxs[i + 14] = v + 2; |
| 323 | idxs[i + 15] = v + 5; |
| 324 | idxs[i + 16] = v + 2; |
| 325 | idxs[i + 17] = v + 6; |
| 326 | |
| 327 | i += 18; |
| 328 | v += 7; |
| 329 | prevPt = curr.fB; |
| 330 | prevNorm = curr.fBNorm; |
| 331 | } |
| 332 | } |
| 333 | } |
| 334 | |
| 335 | } |
| 336 | |
| 337 | void GrAAConvexPathRenderer::drawPath(GrDrawState::StageMask stageMask) { |
| 338 | GrAssert(fPath->isConvex()); |
| 339 | if (fPath->isEmpty()) { |
| 340 | return; |
| 341 | } |
| 342 | GrDrawState* drawState = fTarget->drawState(); |
| 343 | |
| 344 | GrDrawTarget::AutoStateRestore asr; |
| 345 | GrMatrix vm = drawState->getViewMatrix(); |
| 346 | vm.postTranslate(fTranslate.fX, fTranslate.fY); |
| 347 | asr.set(fTarget); |
| 348 | GrMatrix ivm; |
| 349 | if (vm.invert(&ivm)) { |
| 350 | drawState->preConcatSamplerMatrices(stageMask, ivm); |
| 351 | } |
| 352 | drawState->setViewMatrix(GrMatrix::I()); |
| 353 | |
| 354 | |
| 355 | SkPath path; |
| 356 | fPath->transform(vm, &path); |
| 357 | |
| 358 | SkPoint fanPt = {path.getBounds().centerX(), |
| 359 | path.getBounds().centerY()}; |
| 360 | |
| 361 | GrVertexLayout layout = 0; |
| 362 | for (int s = 0; s < GrDrawState::kNumStages; ++s) { |
| 363 | if ((1 << s) & stageMask) { |
| 364 | layout |= GrDrawTarget::StagePosAsTexCoordVertexLayoutBit(s); |
| 365 | } |
| 366 | } |
| 367 | layout |= GrDrawTarget::kEdge_VertexLayoutBit; |
| 368 | |
| 369 | QuadVertex *verts; |
| 370 | uint16_t* idxs; |
| 371 | |
| 372 | int nQuads; |
| 373 | int nLines; |
| 374 | SegmentArray segments; |
| 375 | if (!get_segments(path, &segments, &nQuads, &nLines)) { |
| 376 | return; |
| 377 | } |
| 378 | int vCount; |
| 379 | int iCount; |
| 380 | get_counts(nQuads, nLines, &vCount, &iCount); |
| 381 | |
| 382 | if (!fTarget->reserveVertexSpace(layout, |
| 383 | vCount, |
| 384 | reinterpret_cast<void**>(&verts))) { |
| 385 | return; |
| 386 | } |
| 387 | if (!fTarget->reserveIndexSpace(iCount, reinterpret_cast<void**>(&idxs))) { |
| 388 | fTarget->resetVertexSource(); |
| 389 | return; |
| 390 | } |
| 391 | |
| 392 | create_vertices(&segments, fanPt, verts, idxs); |
| 393 | |
| 394 | drawState->setVertexEdgeType(GrDrawState::kQuad_EdgeType); |
| 395 | fTarget->drawIndexed(kTriangles_PrimitiveType, |
| 396 | 0, // start vertex |
| 397 | 0, // start index |
| 398 | vCount, |
| 399 | iCount); |
| 400 | } |
| 401 | |