| caryclark@google.com | 639df89 | 2012-01-10 21:46:10 +0000 | [diff] [blame] | 1 | #include "CubicIntersection.h" |
| 2 | #include "Intersections.h" |
| 3 | #include "LineIntersection.h" |
| 4 | |
| 5 | static bool chop(const Cubic& smaller, const Cubic& larger, |
| 6 | Intersections& intersections, double minT, double maxT); |
| 7 | |
| 8 | static bool intersect(const Cubic& smaller, const Cubic& larger, |
| 9 | Intersections& intersections) { |
| 10 | // FIXME: carry order with cubic so we don't call it repeatedly |
| 11 | Cubic smallResult; |
| 12 | if (reduceOrder(smaller, smallResult, kReduceOrder_NoQuadraticsAllowed) <= 2) { |
| 13 | Cubic largeResult; |
| 14 | if (reduceOrder(larger, largeResult, kReduceOrder_NoQuadraticsAllowed) <= 2) { |
| 15 | _Point pt; |
| 16 | const _Line& smallLine = (const _Line&) smallResult; |
| 17 | const _Line& largeLine = (const _Line&) largeResult; |
| 18 | if (!lineIntersect(smallLine, largeLine, &pt)) { |
| 19 | return false; |
| 20 | } |
| 21 | double smallT = t_at(smallLine, pt); |
| 22 | double largeT = t_at(largeLine, pt); |
| 23 | intersections.add(smallT, largeT); |
| 24 | return true; |
| 25 | } |
| 26 | } |
| 27 | double minT, maxT; |
| 28 | if (!bezier_clip(smaller, larger, minT, maxT)) { |
| 29 | if (minT == maxT) { |
| 30 | intersections.add(minT, 0.5); |
| 31 | return true; |
| 32 | } |
| 33 | return false; |
| 34 | } |
| 35 | return chop(larger, smaller, intersections, minT, maxT); |
| 36 | } |
| 37 | |
| 38 | bool chop(const Cubic& smaller, const Cubic& larger, |
| 39 | Intersections& intersections, double minT, double maxT) { |
| 40 | intersections.swap(); |
| 41 | if (maxT - minT > 0.8) { // http://cagd.cs.byu.edu/~tom/papers/bezclip.pdf Multiple intersections |
| 42 | CubicPair cubicPair; |
| 43 | chop_at(larger, cubicPair, 0.5); |
| 44 | int used = intersections.used(); |
| 45 | if (intersect(cubicPair.first(), smaller, intersections)) { |
| 46 | intersections.offset(used, 0, 0.5); |
| 47 | } |
| 48 | used = intersections.used(); |
| 49 | if (intersect(cubicPair.second(), smaller, intersections)) { |
| 50 | intersections.offset(used, 0.5, 1); |
| 51 | } |
| 52 | intersections.swap(); |
| 53 | return intersections.intersected(); |
| 54 | } |
| 55 | Cubic cut; |
| 56 | sub_divide(smaller, minT, maxT, cut); |
| 57 | int used = intersections.used(); |
| 58 | bool result = intersect(cut, larger, intersections); |
| 59 | if (result) { |
| 60 | intersections.offset(used, minT, maxT); |
| 61 | } |
| 62 | intersections.swap(); |
| 63 | return result; |
| 64 | } |
| 65 | |
| 66 | bool intersectStart(const Cubic& cubic1, const Cubic& cubic2, |
| 67 | Intersections& intersections) { |
| 68 | double minT1, minT2, maxT1, maxT2; |
| 69 | if (!bezier_clip(cubic2, cubic1, minT1, maxT1)) { |
| 70 | return false; |
| 71 | } |
| 72 | if (!bezier_clip(cubic1, cubic2, minT2, maxT2)) { |
| 73 | return false; |
| 74 | } |
| 75 | if (maxT1 - minT1 < maxT2 - minT2) { |
| 76 | intersections.swap(); |
| 77 | return chop(cubic1, cubic2, intersections, minT1, maxT1); |
| 78 | } |
| 79 | return chop(cubic2, cubic1, intersections, minT2, maxT2); |
| 80 | } |