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1 /* | |
2 * Copyright 2012 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 #include "SkPathOpsTriangle.h" | |
9 | |
10 // http://www.blackpawn.com/texts/pointinpoly/default.html | |
11 // return true if pt is inside triangle; false if outside or on the line | |
12 bool SkDTriangle::contains(const SkDPoint& pt) const { | |
13 // Compute vectors | |
14 SkDVector v0 = fPts[2] - fPts[0]; | |
15 SkDVector v1 = fPts[1] - fPts[0]; | |
16 SkDVector v2 = pt - fPts[0]; | |
17 | |
18 // Compute dot products | |
19 double dot00 = v0.dot(v0); | |
20 double dot01 = v0.dot(v1); | |
21 double dot02 = v0.dot(v2); | |
22 double dot11 = v1.dot(v1); | |
23 double dot12 = v1.dot(v2); | |
24 | |
25 // original code doesn't handle degenerate input; isn't symmetric with inclusion
of corner pts; | |
26 // introduces error with divide; doesn't short circuit on early answer | |
27 #if 0 | |
28 // Compute barycentric coordinates | |
29 double invDenom = 1 / (dot00 * dot11 - dot01 * dot01); | |
30 double u = (dot11 * dot02 - dot01 * dot12) * invDenom; | |
31 double v = (dot00 * dot12 - dot01 * dot02) * invDenom; | |
32 | |
33 // Check if point is in triangle | |
34 return (u >= 0) && (v >= 0) && (u + v <= 1); | |
35 #else | |
36 double w = dot00 * dot11 - dot01 * dot01; | |
37 if (w == 0) { | |
38 return false; | |
39 } | |
40 double wSign = w < 0 ? -1 : 1; | |
41 double u = (dot11 * dot02 - dot01 * dot12) * wSign; | |
42 if (u <= 0) { | |
43 return false; | |
44 } | |
45 double v = (dot00 * dot12 - dot01 * dot02) * wSign; | |
46 if (v <= 0) { | |
47 return false; | |
48 } | |
49 return u + v < w * wSign; | |
50 #endif | |
51 } | |
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