svn merge ^/trunk/blender -r47023:HEAD
[blender.git] / extern / bullet2 / src / LinearMath / btGrahamScan2dConvexHull.h
1 /*
2 Bullet Continuous Collision Detection and Physics Library
3 Copyright (c) 2011 Advanced Micro Devices, Inc.  http://bulletphysics.org
4
5 This software is provided 'as-is', without any express or implied warranty.
6 In no event will the authors be held liable for any damages arising from the use of this software.
7 Permission is granted to anyone to use this software for any purpose, 
8 including commercial applications, and to alter it and redistribute it freely, 
9 subject to the following restrictions:
10
11 1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
12 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
13 3. This notice may not be removed or altered from any source distribution.
14 */
15
16
17 #ifndef GRAHAM_SCAN_2D_CONVEX_HULL_H
18 #define GRAHAM_SCAN_2D_CONVEX_HULL_H
19
20
21 #include "btVector3.h"
22 #include "btAlignedObjectArray.h"
23
24 struct GrahamVector2 : public btVector3
25 {
26         GrahamVector2(const btVector3& org, int orgIndex)
27                 :btVector3(org),
28                         m_orgIndex(orgIndex)
29         {
30         }
31         btScalar        m_angle;
32         int m_orgIndex;
33 };
34
35
36 struct btAngleCompareFunc {
37         btVector3 m_anchor;
38         btAngleCompareFunc(const btVector3& anchor)
39         : m_anchor(anchor) 
40         {
41         }
42         bool operator()(const GrahamVector2& a, const GrahamVector2& b) const {
43                 if (a.m_angle != b.m_angle)
44                         return a.m_angle < b.m_angle;
45                 else
46                 {
47                         btScalar al = (a-m_anchor).length2();
48                         btScalar bl = (b-m_anchor).length2();
49                         if (al != bl)
50                                 return  al < bl;
51                         else
52                         {
53                                 return a.m_orgIndex < b.m_orgIndex;
54                         }
55                 }
56         }
57 };
58
59 inline void GrahamScanConvexHull2D(btAlignedObjectArray<GrahamVector2>& originalPoints, btAlignedObjectArray<GrahamVector2>& hull)
60 {
61         if (originalPoints.size()<=1)
62         {
63                 for (int i=0;i<originalPoints.size();i++)
64                         hull.push_back(originalPoints[0]);
65                 return;
66         }
67         //step1 : find anchor point with smallest x/y and move it to first location
68         //also precompute angles
69         for (int i=0;i<originalPoints.size();i++)
70         {
71                 const btVector3& left = originalPoints[i];
72                 const btVector3& right = originalPoints[0];
73                 if (left.x() < right.x() || !(right.x() < left.x()) && left.y() < right.y())
74                 {
75                         originalPoints.swap(0,i);
76                 }
77         }
78
79         for (int i=0;i<originalPoints.size();i++)
80         {
81                 btVector3 xvec(1,0,0);
82                 btVector3 ar = originalPoints[i]-originalPoints[0];
83                 originalPoints[i].m_angle = btCross(xvec, ar).dot(btVector3(0,0,1)) / ar.length();
84         }
85
86         //step 2: sort all points, based on 'angle' with this anchor
87         btAngleCompareFunc comp(originalPoints[0]);
88         originalPoints.quickSortInternal(comp,1,originalPoints.size()-1);
89
90         int i;
91         for (i = 0; i<2; i++) 
92                 hull.push_back(originalPoints[i]);
93
94         //step 3: keep all 'convex' points and discard concave points (using back tracking)
95         for (; i != originalPoints.size(); i++) 
96         {
97                 bool isConvex = false;
98                 while (!isConvex&& hull.size()>1) {
99                         btVector3& a = hull[hull.size()-2];
100                         btVector3& b = hull[hull.size()-1];
101                         isConvex = btCross(a-b,a-originalPoints[i]).dot(btVector3(0,0,1))> 0;
102                         if (!isConvex)
103                                 hull.pop_back();
104                         else 
105                                 hull.push_back(originalPoints[i]);
106                 }
107         }
108 }
109
110 #endif //GRAHAM_SCAN_2D_CONVEX_HULL_H