SpotShadow.cpp revision 91a8c7c62913c2597e3bf5a6d59d2ed5fc7ba4e0
1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17#define LOG_TAG "OpenGLRenderer" 18 19#define SHADOW_SHRINK_SCALE 0.1f 20 21#include <math.h> 22#include <stdlib.h> 23#include <utils/Log.h> 24 25#include "ShadowTessellator.h" 26#include "SpotShadow.h" 27#include "Vertex.h" 28 29namespace android { 30namespace uirenderer { 31 32static const double EPSILON = 1e-7; 33 34/** 35 * Calculate the angle between and x and a y coordinate. 36 * The atan2 range from -PI to PI. 37 */ 38static float angle(const Vector2& point, const Vector2& center) { 39 return atan2(point.y - center.y, point.x - center.x); 40} 41 42/** 43 * Calculate the intersection of a ray with the line segment defined by two points. 44 * 45 * Returns a negative value in error conditions. 46 47 * @param rayOrigin The start of the ray 48 * @param dx The x vector of the ray 49 * @param dy The y vector of the ray 50 * @param p1 The first point defining the line segment 51 * @param p2 The second point defining the line segment 52 * @return The distance along the ray if it intersects with the line segment, negative if otherwise 53 */ 54static float rayIntersectPoints(const Vector2& rayOrigin, float dx, float dy, 55 const Vector2& p1, const Vector2& p2) { 56 // The math below is derived from solving this formula, basically the 57 // intersection point should stay on both the ray and the edge of (p1, p2). 58 // solve([p1x+t*(p2x-p1x)=dx*t2+px,p1y+t*(p2y-p1y)=dy*t2+py],[t,t2]); 59 60 double divisor = (dx * (p1.y - p2.y) + dy * p2.x - dy * p1.x); 61 if (divisor == 0) return -1.0f; // error, invalid divisor 62 63#if DEBUG_SHADOW 64 double interpVal = (dx * (p1.y - rayOrigin.y) + dy * rayOrigin.x - dy * p1.x) / divisor; 65 if (interpVal < 0 || interpVal > 1) { 66 ALOGW("rayIntersectPoints is hitting outside the segment %f", interpVal); 67 } 68#endif 69 70 double distance = (p1.x * (rayOrigin.y - p2.y) + p2.x * (p1.y - rayOrigin.y) + 71 rayOrigin.x * (p2.y - p1.y)) / divisor; 72 73 return distance; // may be negative in error cases 74} 75 76/** 77 * Sort points by their X coordinates 78 * 79 * @param points the points as a Vector2 array. 80 * @param pointsLength the number of vertices of the polygon. 81 */ 82void SpotShadow::xsort(Vector2* points, int pointsLength) { 83 quicksortX(points, 0, pointsLength - 1); 84} 85 86/** 87 * compute the convex hull of a collection of Points 88 * 89 * @param points the points as a Vector2 array. 90 * @param pointsLength the number of vertices of the polygon. 91 * @param retPoly pre allocated array of floats to put the vertices 92 * @return the number of points in the polygon 0 if no intersection 93 */ 94int SpotShadow::hull(Vector2* points, int pointsLength, Vector2* retPoly) { 95 xsort(points, pointsLength); 96 int n = pointsLength; 97 Vector2 lUpper[n]; 98 lUpper[0] = points[0]; 99 lUpper[1] = points[1]; 100 101 int lUpperSize = 2; 102 103 for (int i = 2; i < n; i++) { 104 lUpper[lUpperSize] = points[i]; 105 lUpperSize++; 106 107 while (lUpperSize > 2 && !ccw( 108 lUpper[lUpperSize - 3].x, lUpper[lUpperSize - 3].y, 109 lUpper[lUpperSize - 2].x, lUpper[lUpperSize - 2].y, 110 lUpper[lUpperSize - 1].x, lUpper[lUpperSize - 1].y)) { 111 // Remove the middle point of the three last 112 lUpper[lUpperSize - 2].x = lUpper[lUpperSize - 1].x; 113 lUpper[lUpperSize - 2].y = lUpper[lUpperSize - 1].y; 114 lUpperSize--; 115 } 116 } 117 118 Vector2 lLower[n]; 119 lLower[0] = points[n - 1]; 120 lLower[1] = points[n - 2]; 121 122 int lLowerSize = 2; 123 124 for (int i = n - 3; i >= 0; i--) { 125 lLower[lLowerSize] = points[i]; 126 lLowerSize++; 127 128 while (lLowerSize > 2 && !ccw( 129 lLower[lLowerSize - 3].x, lLower[lLowerSize - 3].y, 130 lLower[lLowerSize - 2].x, lLower[lLowerSize - 2].y, 131 lLower[lLowerSize - 1].x, lLower[lLowerSize - 1].y)) { 132 // Remove the middle point of the three last 133 lLower[lLowerSize - 2] = lLower[lLowerSize - 1]; 134 lLowerSize--; 135 } 136 } 137 138 // output points in CW ordering 139 const int total = lUpperSize + lLowerSize - 2; 140 int outIndex = total - 1; 141 for (int i = 0; i < lUpperSize; i++) { 142 retPoly[outIndex] = lUpper[i]; 143 outIndex--; 144 } 145 146 for (int i = 1; i < lLowerSize - 1; i++) { 147 retPoly[outIndex] = lLower[i]; 148 outIndex--; 149 } 150 // TODO: Add test harness which verify that all the points are inside the hull. 151 return total; 152} 153 154/** 155 * Test whether the 3 points form a counter clockwise turn. 156 * 157 * @return true if a right hand turn 158 */ 159bool SpotShadow::ccw(double ax, double ay, double bx, double by, 160 double cx, double cy) { 161 return (bx - ax) * (cy - ay) - (by - ay) * (cx - ax) > EPSILON; 162} 163 164/** 165 * Calculates the intersection of poly1 with poly2 and put in poly2. 166 * Note that both poly1 and poly2 must be in CW order already! 167 * 168 * @param poly1 The 1st polygon, as a Vector2 array. 169 * @param poly1Length The number of vertices of 1st polygon. 170 * @param poly2 The 2nd and output polygon, as a Vector2 array. 171 * @param poly2Length The number of vertices of 2nd polygon. 172 * @return number of vertices in output polygon as poly2. 173 */ 174int SpotShadow::intersection(const Vector2* poly1, int poly1Length, 175 Vector2* poly2, int poly2Length) { 176#if DEBUG_SHADOW 177 if (!ShadowTessellator::isClockwise(poly1, poly1Length)) { 178 ALOGW("Poly1 is not clockwise! Intersection is wrong!"); 179 } 180 if (!ShadowTessellator::isClockwise(poly2, poly2Length)) { 181 ALOGW("Poly2 is not clockwise! Intersection is wrong!"); 182 } 183#endif 184 Vector2 poly[poly1Length * poly2Length + 2]; 185 int count = 0; 186 int pcount = 0; 187 188 // If one vertex from one polygon sits inside another polygon, add it and 189 // count them. 190 for (int i = 0; i < poly1Length; i++) { 191 if (testPointInsidePolygon(poly1[i], poly2, poly2Length)) { 192 poly[count] = poly1[i]; 193 count++; 194 pcount++; 195 196 } 197 } 198 199 int insidePoly2 = pcount; 200 for (int i = 0; i < poly2Length; i++) { 201 if (testPointInsidePolygon(poly2[i], poly1, poly1Length)) { 202 poly[count] = poly2[i]; 203 count++; 204 } 205 } 206 207 int insidePoly1 = count - insidePoly2; 208 // If all vertices from poly1 are inside poly2, then just return poly1. 209 if (insidePoly2 == poly1Length) { 210 memcpy(poly2, poly1, poly1Length * sizeof(Vector2)); 211 return poly1Length; 212 } 213 214 // If all vertices from poly2 are inside poly1, then just return poly2. 215 if (insidePoly1 == poly2Length) { 216 return poly2Length; 217 } 218 219 // Since neither polygon fully contain the other one, we need to add all the 220 // intersection points. 221 Vector2 intersection = {0, 0}; 222 for (int i = 0; i < poly2Length; i++) { 223 for (int j = 0; j < poly1Length; j++) { 224 int poly2LineStart = i; 225 int poly2LineEnd = ((i + 1) % poly2Length); 226 int poly1LineStart = j; 227 int poly1LineEnd = ((j + 1) % poly1Length); 228 bool found = lineIntersection( 229 poly2[poly2LineStart].x, poly2[poly2LineStart].y, 230 poly2[poly2LineEnd].x, poly2[poly2LineEnd].y, 231 poly1[poly1LineStart].x, poly1[poly1LineStart].y, 232 poly1[poly1LineEnd].x, poly1[poly1LineEnd].y, 233 intersection); 234 if (found) { 235 poly[count].x = intersection.x; 236 poly[count].y = intersection.y; 237 count++; 238 } else { 239 Vector2 delta = poly2[i] - poly1[j]; 240 if (delta.lengthSquared() < EPSILON) { 241 poly[count] = poly2[i]; 242 count++; 243 } 244 } 245 } 246 } 247 248 if (count == 0) { 249 return 0; 250 } 251 252 // Sort the result polygon around the center. 253 Vector2 center = {0.0f, 0.0f}; 254 for (int i = 0; i < count; i++) { 255 center += poly[i]; 256 } 257 center /= count; 258 sort(poly, count, center); 259 260#if DEBUG_SHADOW 261 // Since poly2 is overwritten as the result, we need to save a copy to do 262 // our verification. 263 Vector2 oldPoly2[poly2Length]; 264 int oldPoly2Length = poly2Length; 265 memcpy(oldPoly2, poly2, sizeof(Vector2) * poly2Length); 266#endif 267 268 // Filter the result out from poly and put it into poly2. 269 poly2[0] = poly[0]; 270 int lastOutputIndex = 0; 271 for (int i = 1; i < count; i++) { 272 Vector2 delta = poly[i] - poly2[lastOutputIndex]; 273 if (delta.lengthSquared() >= EPSILON) { 274 poly2[++lastOutputIndex] = poly[i]; 275 } else { 276 // If the vertices are too close, pick the inner one, because the 277 // inner one is more likely to be an intersection point. 278 Vector2 delta1 = poly[i] - center; 279 Vector2 delta2 = poly2[lastOutputIndex] - center; 280 if (delta1.lengthSquared() < delta2.lengthSquared()) { 281 poly2[lastOutputIndex] = poly[i]; 282 } 283 } 284 } 285 int resultLength = lastOutputIndex + 1; 286 287#if DEBUG_SHADOW 288 testConvex(poly2, resultLength, "intersection"); 289 testConvex(poly1, poly1Length, "input poly1"); 290 testConvex(oldPoly2, oldPoly2Length, "input poly2"); 291 292 testIntersection(poly1, poly1Length, oldPoly2, oldPoly2Length, poly2, resultLength); 293#endif 294 295 return resultLength; 296} 297 298/** 299 * Sort points about a center point 300 * 301 * @param poly The in and out polyogon as a Vector2 array. 302 * @param polyLength The number of vertices of the polygon. 303 * @param center the center ctr[0] = x , ctr[1] = y to sort around. 304 */ 305void SpotShadow::sort(Vector2* poly, int polyLength, const Vector2& center) { 306 quicksortCirc(poly, 0, polyLength - 1, center); 307} 308 309/** 310 * Swap points pointed to by i and j 311 */ 312void SpotShadow::swap(Vector2* points, int i, int j) { 313 Vector2 temp = points[i]; 314 points[i] = points[j]; 315 points[j] = temp; 316} 317 318/** 319 * quick sort implementation about the center. 320 */ 321void SpotShadow::quicksortCirc(Vector2* points, int low, int high, 322 const Vector2& center) { 323 int i = low, j = high; 324 int p = low + (high - low) / 2; 325 float pivot = angle(points[p], center); 326 while (i <= j) { 327 while (angle(points[i], center) > pivot) { 328 i++; 329 } 330 while (angle(points[j], center) < pivot) { 331 j--; 332 } 333 334 if (i <= j) { 335 swap(points, i, j); 336 i++; 337 j--; 338 } 339 } 340 if (low < j) quicksortCirc(points, low, j, center); 341 if (i < high) quicksortCirc(points, i, high, center); 342} 343 344/** 345 * Sort points by x axis 346 * 347 * @param points points to sort 348 * @param low start index 349 * @param high end index 350 */ 351void SpotShadow::quicksortX(Vector2* points, int low, int high) { 352 int i = low, j = high; 353 int p = low + (high - low) / 2; 354 float pivot = points[p].x; 355 while (i <= j) { 356 while (points[i].x < pivot) { 357 i++; 358 } 359 while (points[j].x > pivot) { 360 j--; 361 } 362 363 if (i <= j) { 364 swap(points, i, j); 365 i++; 366 j--; 367 } 368 } 369 if (low < j) quicksortX(points, low, j); 370 if (i < high) quicksortX(points, i, high); 371} 372 373/** 374 * Test whether a point is inside the polygon. 375 * 376 * @param testPoint the point to test 377 * @param poly the polygon 378 * @return true if the testPoint is inside the poly. 379 */ 380bool SpotShadow::testPointInsidePolygon(const Vector2 testPoint, 381 const Vector2* poly, int len) { 382 bool c = false; 383 double testx = testPoint.x; 384 double testy = testPoint.y; 385 for (int i = 0, j = len - 1; i < len; j = i++) { 386 double startX = poly[j].x; 387 double startY = poly[j].y; 388 double endX = poly[i].x; 389 double endY = poly[i].y; 390 391 if (((endY > testy) != (startY > testy)) && 392 (testx < (startX - endX) * (testy - endY) 393 / (startY - endY) + endX)) { 394 c = !c; 395 } 396 } 397 return c; 398} 399 400/** 401 * Make the polygon turn clockwise. 402 * 403 * @param polygon the polygon as a Vector2 array. 404 * @param len the number of points of the polygon 405 */ 406void SpotShadow::makeClockwise(Vector2* polygon, int len) { 407 if (polygon == 0 || len == 0) { 408 return; 409 } 410 if (!ShadowTessellator::isClockwise(polygon, len)) { 411 reverse(polygon, len); 412 } 413} 414 415/** 416 * Reverse the polygon 417 * 418 * @param polygon the polygon as a Vector2 array 419 * @param len the number of points of the polygon 420 */ 421void SpotShadow::reverse(Vector2* polygon, int len) { 422 int n = len / 2; 423 for (int i = 0; i < n; i++) { 424 Vector2 tmp = polygon[i]; 425 int k = len - 1 - i; 426 polygon[i] = polygon[k]; 427 polygon[k] = tmp; 428 } 429} 430 431/** 432 * Intersects two lines in parametric form. This function is called in a tight 433 * loop, and we need double precision to get things right. 434 * 435 * @param x1 the x coordinate point 1 of line 1 436 * @param y1 the y coordinate point 1 of line 1 437 * @param x2 the x coordinate point 2 of line 1 438 * @param y2 the y coordinate point 2 of line 1 439 * @param x3 the x coordinate point 1 of line 2 440 * @param y3 the y coordinate point 1 of line 2 441 * @param x4 the x coordinate point 2 of line 2 442 * @param y4 the y coordinate point 2 of line 2 443 * @param ret the x,y location of the intersection 444 * @return true if it found an intersection 445 */ 446inline bool SpotShadow::lineIntersection(double x1, double y1, double x2, double y2, 447 double x3, double y3, double x4, double y4, Vector2& ret) { 448 double d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4); 449 if (d == 0.0) return false; 450 451 double dx = (x1 * y2 - y1 * x2); 452 double dy = (x3 * y4 - y3 * x4); 453 double x = (dx * (x3 - x4) - (x1 - x2) * dy) / d; 454 double y = (dx * (y3 - y4) - (y1 - y2) * dy) / d; 455 456 // The intersection should be in the middle of the point 1 and point 2, 457 // likewise point 3 and point 4. 458 if (((x - x1) * (x - x2) > EPSILON) 459 || ((x - x3) * (x - x4) > EPSILON) 460 || ((y - y1) * (y - y2) > EPSILON) 461 || ((y - y3) * (y - y4) > EPSILON)) { 462 // Not interesected 463 return false; 464 } 465 ret.x = x; 466 ret.y = y; 467 return true; 468 469} 470 471/** 472 * Compute a horizontal circular polygon about point (x , y , height) of radius 473 * (size) 474 * 475 * @param points number of the points of the output polygon. 476 * @param lightCenter the center of the light. 477 * @param size the light size. 478 * @param ret result polygon. 479 */ 480void SpotShadow::computeLightPolygon(int points, const Vector3& lightCenter, 481 float size, Vector3* ret) { 482 // TODO: Caching all the sin / cos values and store them in a look up table. 483 for (int i = 0; i < points; i++) { 484 double angle = 2 * i * M_PI / points; 485 ret[i].x = cosf(angle) * size + lightCenter.x; 486 ret[i].y = sinf(angle) * size + lightCenter.y; 487 ret[i].z = lightCenter.z; 488 } 489} 490 491/** 492* Generate the shadow from a spot light. 493* 494* @param poly x,y,z vertexes of a convex polygon that occludes the light source 495* @param polyLength number of vertexes of the occluding polygon 496* @param lightCenter the center of the light 497* @param lightSize the radius of the light source 498* @param lightVertexCount the vertex counter for the light polygon 499* @param shadowTriangleStrip return an (x,y,alpha) triangle strip representing the shadow. Return 500* empty strip if error. 501* 502*/ 503void SpotShadow::createSpotShadow(bool isCasterOpaque, const Vector3* poly, 504 int polyLength, const Vector3& lightCenter, float lightSize, 505 int lightVertexCount, VertexBuffer& retStrips) { 506 Vector3 light[lightVertexCount * 3]; 507 computeLightPolygon(lightVertexCount, lightCenter, lightSize, light); 508 computeSpotShadow(isCasterOpaque, light, lightVertexCount, lightCenter, poly, 509 polyLength, retStrips); 510} 511 512/** 513 * Generate the shadow spot light of shape lightPoly and a object poly 514 * 515 * @param lightPoly x,y,z vertex of a convex polygon that is the light source 516 * @param lightPolyLength number of vertexes of the light source polygon 517 * @param poly x,y,z vertexes of a convex polygon that occludes the light source 518 * @param polyLength number of vertexes of the occluding polygon 519 * @param shadowTriangleStrip return an (x,y,alpha) triangle strip representing the shadow. Return 520 * empty strip if error. 521 */ 522void SpotShadow::computeSpotShadow(bool isCasterOpaque, const Vector3* lightPoly, 523 int lightPolyLength, const Vector3& lightCenter, const Vector3* poly, 524 int polyLength, VertexBuffer& shadowTriangleStrip) { 525 // Point clouds for all the shadowed vertices 526 Vector2 shadowRegion[lightPolyLength * polyLength]; 527 // Shadow polygon from one point light. 528 Vector2 outline[polyLength]; 529 Vector2 umbraMem[polyLength * lightPolyLength]; 530 Vector2* umbra = umbraMem; 531 532 int umbraLength = 0; 533 534 // Validate input, receiver is always at z = 0 plane. 535 bool inputPolyPositionValid = true; 536 for (int i = 0; i < polyLength; i++) { 537 if (poly[i].z >= lightPoly[0].z) { 538 inputPolyPositionValid = false; 539 ALOGW("polygon above the light"); 540 break; 541 } 542 } 543 544 // If the caster's position is invalid, don't draw anything. 545 if (!inputPolyPositionValid) { 546 return; 547 } 548 549 // Calculate the umbra polygon based on intersections of all outlines 550 int k = 0; 551 for (int j = 0; j < lightPolyLength; j++) { 552 int m = 0; 553 for (int i = 0; i < polyLength; i++) { 554 // After validating the input, deltaZ is guaranteed to be positive. 555 float deltaZ = lightPoly[j].z - poly[i].z; 556 float ratioZ = lightPoly[j].z / deltaZ; 557 float x = lightPoly[j].x - ratioZ * (lightPoly[j].x - poly[i].x); 558 float y = lightPoly[j].y - ratioZ * (lightPoly[j].y - poly[i].y); 559 560 Vector2 newPoint = {x, y}; 561 shadowRegion[k] = newPoint; 562 outline[m] = newPoint; 563 564 k++; 565 m++; 566 } 567 568 // For the first light polygon's vertex, use the outline as the umbra. 569 // Later on, use the intersection of the outline and existing umbra. 570 if (umbraLength == 0) { 571 for (int i = 0; i < polyLength; i++) { 572 umbra[i] = outline[i]; 573 } 574 umbraLength = polyLength; 575 } else { 576 int col = ((j * 255) / lightPolyLength); 577 umbraLength = intersection(outline, polyLength, umbra, umbraLength); 578 if (umbraLength == 0) { 579 break; 580 } 581 } 582 } 583 584 // Generate the penumbra area using the hull of all shadow regions. 585 int shadowRegionLength = k; 586 Vector2 penumbra[k]; 587 int penumbraLength = hull(shadowRegion, shadowRegionLength, penumbra); 588 589 Vector2 fakeUmbra[polyLength]; 590 if (umbraLength < 3) { 591 // If there is no real umbra, make a fake one. 592 for (int i = 0; i < polyLength; i++) { 593 float deltaZ = lightCenter.z - poly[i].z; 594 float ratioZ = lightCenter.z / deltaZ; 595 float x = lightCenter.x - ratioZ * (lightCenter.x - poly[i].x); 596 float y = lightCenter.y - ratioZ * (lightCenter.y - poly[i].y); 597 598 fakeUmbra[i].x = x; 599 fakeUmbra[i].y = y; 600 } 601 602 // Shrink the centroid's shadow by 10%. 603 // TODO: Study the magic number of 10%. 604 Vector2 shadowCentroid = 605 ShadowTessellator::centroid2d(fakeUmbra, polyLength); 606 for (int i = 0; i < polyLength; i++) { 607 fakeUmbra[i] = shadowCentroid * (1.0f - SHADOW_SHRINK_SCALE) + 608 fakeUmbra[i] * SHADOW_SHRINK_SCALE; 609 } 610#if DEBUG_SHADOW 611 ALOGD("No real umbra make a fake one, centroid2d = %f , %f", 612 shadowCentroid.x, shadowCentroid.y); 613#endif 614 // Set the fake umbra, whose size is the same as the original polygon. 615 umbra = fakeUmbra; 616 umbraLength = polyLength; 617 } 618 619 generateTriangleStrip(isCasterOpaque, penumbra, penumbraLength, umbra, 620 umbraLength, poly, polyLength, shadowTriangleStrip); 621} 622 623/** 624 * Converts a polygon specified with CW vertices into an array of distance-from-centroid values. 625 * 626 * Returns false in error conditions 627 * 628 * @param poly Array of vertices. Note that these *must* be CW. 629 * @param polyLength The number of vertices in the polygon. 630 * @param polyCentroid The centroid of the polygon, from which rays will be cast 631 * @param rayDist The output array for the calculated distances, must be SHADOW_RAY_COUNT in size 632 */ 633bool convertPolyToRayDist(const Vector2* poly, int polyLength, const Vector2& polyCentroid, 634 float* rayDist) { 635 const int rays = SHADOW_RAY_COUNT; 636 const float step = M_PI * 2 / rays; 637 638 const Vector2* lastVertex = &(poly[polyLength - 1]); 639 float startAngle = angle(*lastVertex, polyCentroid); 640 641 // Start with the ray that's closest to and less than startAngle 642 int rayIndex = floor((startAngle - EPSILON) / step); 643 rayIndex = (rayIndex + rays) % rays; // ensure positive 644 645 for (int polyIndex = 0; polyIndex < polyLength; polyIndex++) { 646 /* 647 * For a given pair of vertices on the polygon, poly[i-1] and poly[i], the rays that 648 * intersect these will be those that are between the two angles from the centroid that the 649 * vertices define. 650 * 651 * Because the polygon vertices are stored clockwise, the closest ray with an angle 652 * *smaller* than that defined by angle(poly[i], centroid) will be the first ray that does 653 * not intersect with poly[i-1], poly[i]. 654 */ 655 float currentAngle = angle(poly[polyIndex], polyCentroid); 656 657 // find first ray that will not intersect the line segment poly[i-1] & poly[i] 658 int firstRayIndexOnNextSegment = floor((currentAngle - EPSILON) / step); 659 firstRayIndexOnNextSegment = (firstRayIndexOnNextSegment + rays) % rays; // ensure positive 660 661 // Iterate through all rays that intersect with poly[i-1], poly[i] line segment. 662 // This may be 0 rays. 663 while (rayIndex != firstRayIndexOnNextSegment) { 664 float distanceToIntersect = rayIntersectPoints(polyCentroid, 665 cos(rayIndex * step), 666 sin(rayIndex * step), 667 *lastVertex, poly[polyIndex]); 668 if (distanceToIntersect < 0) { 669#if DEBUG_SHADOW 670 ALOGW("ERROR: convertPolyToRayDist failed"); 671#endif 672 return false; // error case, abort 673 } 674 675 rayDist[rayIndex] = distanceToIntersect; 676 677 rayIndex = (rayIndex - 1 + rays) % rays; 678 } 679 lastVertex = &poly[polyIndex]; 680 } 681 682 return true; 683} 684 685int SpotShadow::calculateOccludedUmbra(const Vector2* umbra, int umbraLength, 686 const Vector3* poly, int polyLength, Vector2* occludedUmbra) { 687 // Occluded umbra area is computed as the intersection of the projected 2D 688 // poly and umbra. 689 for (int i = 0; i < polyLength; i++) { 690 occludedUmbra[i].x = poly[i].x; 691 occludedUmbra[i].y = poly[i].y; 692 } 693 694 // Both umbra and incoming polygon are guaranteed to be CW, so we can call 695 // intersection() directly. 696 return intersection(umbra, umbraLength, 697 occludedUmbra, polyLength); 698} 699 700#define OCLLUDED_UMBRA_SHRINK_FACTOR 0.95f 701/** 702 * Generate a triangle strip given two convex polygons 703 * 704 * @param penumbra The outer polygon x,y vertexes 705 * @param penumbraLength The number of vertexes in the outer polygon 706 * @param umbra The inner outer polygon x,y vertexes 707 * @param umbraLength The number of vertexes in the inner polygon 708 * @param shadowTriangleStrip return an (x,y,alpha) triangle strip representing the shadow. Return 709 * empty strip if error. 710**/ 711void SpotShadow::generateTriangleStrip(bool isCasterOpaque, const Vector2* penumbra, 712 int penumbraLength, const Vector2* umbra, int umbraLength, 713 const Vector3* poly, int polyLength, VertexBuffer& shadowTriangleStrip) { 714 const int rays = SHADOW_RAY_COUNT; 715 const int size = 2 * rays; 716 const float step = M_PI * 2 / rays; 717 // Centroid of the umbra. 718 Vector2 centroid = ShadowTessellator::centroid2d(umbra, umbraLength); 719#if DEBUG_SHADOW 720 ALOGD("centroid2d = %f , %f", centroid.x, centroid.y); 721#endif 722 // Intersection to the penumbra. 723 float penumbraDistPerRay[rays]; 724 // Intersection to the umbra. 725 float umbraDistPerRay[rays]; 726 // Intersection to the occluded umbra area. 727 float occludedUmbraDistPerRay[rays]; 728 729 // convert CW polygons to ray distance encoding, aborting on conversion failure 730 if (!convertPolyToRayDist(umbra, umbraLength, centroid, umbraDistPerRay)) return; 731 if (!convertPolyToRayDist(penumbra, penumbraLength, centroid, penumbraDistPerRay)) return; 732 733 bool hasOccludedUmbraArea = false; 734 if (isCasterOpaque) { 735 Vector2 occludedUmbra[polyLength + umbraLength]; 736 int occludedUmbraLength = calculateOccludedUmbra(umbra, umbraLength, poly, polyLength, 737 occludedUmbra); 738 // Make sure the centroid is inside the umbra, otherwise, fall back to the 739 // approach as if there is no occluded umbra area. 740 if (testPointInsidePolygon(centroid, occludedUmbra, occludedUmbraLength)) { 741 hasOccludedUmbraArea = true; 742 // Shrink the occluded umbra area to avoid pixel level artifacts. 743 for (int i = 0; i < occludedUmbraLength; i ++) { 744 occludedUmbra[i] = centroid + (occludedUmbra[i] - centroid) * 745 OCLLUDED_UMBRA_SHRINK_FACTOR; 746 } 747 if (!convertPolyToRayDist(occludedUmbra, occludedUmbraLength, centroid, 748 occludedUmbraDistPerRay)) { 749 return; 750 } 751 } 752 } 753 754 AlphaVertex* shadowVertices = 755 shadowTriangleStrip.alloc<AlphaVertex>(SHADOW_VERTEX_COUNT); 756 757 // NOTE: Shadow alpha values are transformed when stored in alphavertices, 758 // so that they can be consumed directly by gFS_Main_ApplyVertexAlphaShadowInterp 759 float transformedMaxAlpha = M_PI; 760 761 // Calculate the vertices (x, y, alpha) in the shadow area. 762 AlphaVertex centroidXYA; 763 AlphaVertex::set(¢roidXYA, centroid.x, centroid.y, transformedMaxAlpha); 764 for (int rayIndex = 0; rayIndex < rays; rayIndex++) { 765 float dx = cosf(step * rayIndex); 766 float dy = sinf(step * rayIndex); 767 768 // penumbra ring 769 float penumbraDistance = penumbraDistPerRay[rayIndex]; 770 AlphaVertex::set(&shadowVertices[rayIndex], 771 dx * penumbraDistance + centroid.x, 772 dy * penumbraDistance + centroid.y, 0.0f); 773 774 // umbra ring 775 float umbraDistance = umbraDistPerRay[rayIndex]; 776 AlphaVertex::set(&shadowVertices[rays + rayIndex], 777 dx * umbraDistance + centroid.x, 778 dy * umbraDistance + centroid.y, 779 transformedMaxAlpha); 780 781 // occluded umbra ring 782 if (hasOccludedUmbraArea) { 783 float occludedUmbraDistance = occludedUmbraDistPerRay[rayIndex]; 784 AlphaVertex::set(&shadowVertices[2 * rays + rayIndex], 785 dx * occludedUmbraDistance + centroid.x, 786 dy * occludedUmbraDistance + centroid.y, transformedMaxAlpha); 787 } else { 788 // Put all vertices of the occluded umbra ring at the centroid. 789 shadowVertices[2 * rays + rayIndex] = centroidXYA; 790 } 791 } 792 793 shadowTriangleStrip.setMode(VertexBuffer::kTwoPolyRingShadow); 794 shadowTriangleStrip.computeBounds<AlphaVertex>(); 795} 796 797/** 798 * This is only for experimental purpose. 799 * After intersections are calculated, we could smooth the polygon if needed. 800 * So far, we don't think it is more appealing yet. 801 * 802 * @param level The level of smoothness. 803 * @param rays The total number of rays. 804 * @param rayDist (In and Out) The distance for each ray. 805 * 806 */ 807void SpotShadow::smoothPolygon(int level, int rays, float* rayDist) { 808 for (int k = 0; k < level; k++) { 809 for (int i = 0; i < rays; i++) { 810 float p1 = rayDist[(rays - 1 + i) % rays]; 811 float p2 = rayDist[i]; 812 float p3 = rayDist[(i + 1) % rays]; 813 rayDist[i] = (p1 + p2 * 2 + p3) / 4; 814 } 815 } 816} 817 818#if DEBUG_SHADOW 819 820#define TEST_POINT_NUMBER 128 821 822/** 823 * Calculate the bounds for generating random test points. 824 */ 825void SpotShadow::updateBound(const Vector2 inVector, Vector2& lowerBound, 826 Vector2& upperBound ) { 827 if (inVector.x < lowerBound.x) { 828 lowerBound.x = inVector.x; 829 } 830 831 if (inVector.y < lowerBound.y) { 832 lowerBound.y = inVector.y; 833 } 834 835 if (inVector.x > upperBound.x) { 836 upperBound.x = inVector.x; 837 } 838 839 if (inVector.y > upperBound.y) { 840 upperBound.y = inVector.y; 841 } 842} 843 844/** 845 * For debug purpose, when things go wrong, dump the whole polygon data. 846 */ 847static void dumpPolygon(const Vector2* poly, int polyLength, const char* polyName) { 848 for (int i = 0; i < polyLength; i++) { 849 ALOGD("polygon %s i %d x %f y %f", polyName, i, poly[i].x, poly[i].y); 850 } 851} 852 853/** 854 * Test whether the polygon is convex. 855 */ 856bool SpotShadow::testConvex(const Vector2* polygon, int polygonLength, 857 const char* name) { 858 bool isConvex = true; 859 for (int i = 0; i < polygonLength; i++) { 860 Vector2 start = polygon[i]; 861 Vector2 middle = polygon[(i + 1) % polygonLength]; 862 Vector2 end = polygon[(i + 2) % polygonLength]; 863 864 double delta = (double(middle.x) - start.x) * (double(end.y) - start.y) - 865 (double(middle.y) - start.y) * (double(end.x) - start.x); 866 bool isCCWOrCoLinear = (delta >= EPSILON); 867 868 if (isCCWOrCoLinear) { 869 ALOGW("(Error Type 2): polygon (%s) is not a convex b/c start (x %f, y %f)," 870 "middle (x %f, y %f) and end (x %f, y %f) , delta is %f !!!", 871 name, start.x, start.y, middle.x, middle.y, end.x, end.y, delta); 872 isConvex = false; 873 break; 874 } 875 } 876 return isConvex; 877} 878 879/** 880 * Test whether or not the polygon (intersection) is within the 2 input polygons. 881 * Using Marte Carlo method, we generate a random point, and if it is inside the 882 * intersection, then it must be inside both source polygons. 883 */ 884void SpotShadow::testIntersection(const Vector2* poly1, int poly1Length, 885 const Vector2* poly2, int poly2Length, 886 const Vector2* intersection, int intersectionLength) { 887 // Find the min and max of x and y. 888 Vector2 lowerBound(FLT_MAX, FLT_MAX); 889 Vector2 upperBound(-FLT_MAX, -FLT_MAX); 890 for (int i = 0; i < poly1Length; i++) { 891 updateBound(poly1[i], lowerBound, upperBound); 892 } 893 for (int i = 0; i < poly2Length; i++) { 894 updateBound(poly2[i], lowerBound, upperBound); 895 } 896 897 bool dumpPoly = false; 898 for (int k = 0; k < TEST_POINT_NUMBER; k++) { 899 // Generate a random point between minX, minY and maxX, maxY. 900 double randomX = rand() / double(RAND_MAX); 901 double randomY = rand() / double(RAND_MAX); 902 903 Vector2 testPoint; 904 testPoint.x = lowerBound.x + randomX * (upperBound.x - lowerBound.x); 905 testPoint.y = lowerBound.y + randomY * (upperBound.y - lowerBound.y); 906 907 // If the random point is in both poly 1 and 2, then it must be intersection. 908 if (testPointInsidePolygon(testPoint, intersection, intersectionLength)) { 909 if (!testPointInsidePolygon(testPoint, poly1, poly1Length)) { 910 dumpPoly = true; 911 ALOGW("(Error Type 1): one point (%f, %f) in the intersection is" 912 " not in the poly1", 913 testPoint.x, testPoint.y); 914 } 915 916 if (!testPointInsidePolygon(testPoint, poly2, poly2Length)) { 917 dumpPoly = true; 918 ALOGW("(Error Type 1): one point (%f, %f) in the intersection is" 919 " not in the poly2", 920 testPoint.x, testPoint.y); 921 } 922 } 923 } 924 925 if (dumpPoly) { 926 dumpPolygon(intersection, intersectionLength, "intersection"); 927 for (int i = 1; i < intersectionLength; i++) { 928 Vector2 delta = intersection[i] - intersection[i - 1]; 929 ALOGD("Intersetion i, %d Vs i-1 is delta %f", i, delta.lengthSquared()); 930 } 931 932 dumpPolygon(poly1, poly1Length, "poly 1"); 933 dumpPolygon(poly2, poly2Length, "poly 2"); 934 } 935} 936#endif 937 938}; // namespace uirenderer 939}; // namespace android 940