Upgrade Bullet to version 2.83.
[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 GrahamVector3 : public btVector3
25 {
26         GrahamVector3(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 GrahamVector3& a, const GrahamVector3& 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<GrahamVector3>& originalPoints, btAlignedObjectArray<GrahamVector3>& hull, const btVector3& normalAxis)
60 {
61         btVector3 axis0,axis1;
62         btPlaneSpace1(normalAxis,axis0,axis1);
63         
64
65         if (originalPoints.size()<=1)
66         {
67                 for (int i=0;i<originalPoints.size();i++)
68                         hull.push_back(originalPoints[0]);
69                 return;
70         }
71         //step1 : find anchor point with smallest projection on axis0 and move it to first location
72         for (int i=0;i<originalPoints.size();i++)
73         {
74 //              const btVector3& left = originalPoints[i];
75 //              const btVector3& right = originalPoints[0];
76                 btScalar projL = originalPoints[i].dot(axis0);
77                 btScalar projR = originalPoints[0].dot(axis0);
78                 if (projL < projR)
79                 {
80                         originalPoints.swap(0,i);
81                 }
82         }
83
84         //also precompute angles
85         originalPoints[0].m_angle = -1e30f;
86         for (int i=1;i<originalPoints.size();i++)
87         {
88             btVector3 ar = originalPoints[i]-originalPoints[0];
89             btScalar ar1 = axis1.dot(ar);
90             btScalar ar0 = axis0.dot(ar);
91             if( ar1*ar1+ar0*ar0 < FLT_EPSILON ) 
92             {
93               originalPoints[i].m_angle = 0.0f;
94             }
95             else
96             {
97               originalPoints[i].m_angle = btAtan2Fast(ar1, ar0);
98             }
99         }
100
101         //step 2: sort all points, based on 'angle' with this anchor
102         btAngleCompareFunc comp(originalPoints[0]);
103         originalPoints.quickSortInternal(comp,1,originalPoints.size()-1);
104
105         int i;
106         for (i = 0; i<2; i++) 
107                 hull.push_back(originalPoints[i]);
108
109         //step 3: keep all 'convex' points and discard concave points (using back tracking)
110         for (; i != originalPoints.size(); i++) 
111         {
112                 bool isConvex = false;
113                 while (!isConvex&& hull.size()>1) {
114                         btVector3& a = hull[hull.size()-2];
115                         btVector3& b = hull[hull.size()-1];
116                         isConvex = btCross(a-b,a-originalPoints[i]).dot(normalAxis)> 0;
117                         if (!isConvex)
118                                 hull.pop_back();
119                         else 
120                                 hull.push_back(originalPoints[i]);
121                 }
122
123             if( hull.size() == 1 )
124             {
125               hull.push_back( originalPoints[i] );
126             }
127         }
128 }
129
130 #endif //GRAHAM_SCAN_2D_CONVEX_HULL_H