Bullet Collision Detection & Physics Library
SphereTriangleDetector.cpp
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1 /*
2 Bullet Continuous Collision Detection and Physics Library
3 Copyright (c) 2003-2006 Erwin Coumans http://continuousphysics.com/Bullet/
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 #include "LinearMath/btScalar.h"
17 #include "SphereTriangleDetector.h"
20 
21 
23 :m_sphere(sphere),
24 m_triangle(triangle),
25 m_contactBreakingThreshold(contactBreakingThreshold)
26 {
27 
28 }
29 
30 void SphereTriangleDetector::getClosestPoints(const ClosestPointInput& input,Result& output,class btIDebugDraw* debugDraw,bool swapResults)
31 {
32 
33  (void)debugDraw;
34  const btTransform& transformA = input.m_transformA;
35  const btTransform& transformB = input.m_transformB;
36 
37  btVector3 point,normal;
38  btScalar timeOfImpact = btScalar(1.);
39  btScalar depth = btScalar(0.);
40 // output.m_distance = btScalar(BT_LARGE_FLOAT);
41  //move sphere into triangle space
42  btTransform sphereInTr = transformB.inverseTimes(transformA);
43 
44  if (collide(sphereInTr.getOrigin(),point,normal,depth,timeOfImpact,m_contactBreakingThreshold))
45  {
46  if (swapResults)
47  {
48  btVector3 normalOnB = transformB.getBasis()*normal;
49  btVector3 normalOnA = -normalOnB;
50  btVector3 pointOnA = transformB*point+normalOnB*depth;
51  output.addContactPoint(normalOnA,pointOnA,depth);
52  } else
53  {
54  output.addContactPoint(transformB.getBasis()*normal,transformB*point,depth);
55  }
56  }
57 
58 }
59 
60 
61 
62 // See also geometrictools.com
63 // Basic idea: D = |p - (lo + t0*lv)| where t0 = lv . (p - lo) / lv . lv
64 btScalar SegmentSqrDistance(const btVector3& from, const btVector3& to,const btVector3 &p, btVector3 &nearest);
65 
66 btScalar SegmentSqrDistance(const btVector3& from, const btVector3& to,const btVector3 &p, btVector3 &nearest) {
67  btVector3 diff = p - from;
68  btVector3 v = to - from;
69  btScalar t = v.dot(diff);
70 
71  if (t > 0) {
72  btScalar dotVV = v.dot(v);
73  if (t < dotVV) {
74  t /= dotVV;
75  diff -= t*v;
76  } else {
77  t = 1;
78  diff -= v;
79  }
80  } else
81  t = 0;
82 
83  nearest = from + t*v;
84  return diff.dot(diff);
85 }
86 
87 bool SphereTriangleDetector::facecontains(const btVector3 &p,const btVector3* vertices,btVector3& normal) {
88  btVector3 lp(p);
89  btVector3 lnormal(normal);
90 
91  return pointInTriangle(vertices, lnormal, &lp);
92 }
93 
94 bool SphereTriangleDetector::collide(const btVector3& sphereCenter,btVector3 &point, btVector3& resultNormal, btScalar& depth, btScalar &timeOfImpact, btScalar contactBreakingThreshold)
95 {
96 
97  const btVector3* vertices = &m_triangle->getVertexPtr(0);
98 
99  btScalar radius = m_sphere->getRadius();
100  btScalar radiusWithThreshold = radius + contactBreakingThreshold;
101 
102  btVector3 normal = (vertices[1]-vertices[0]).cross(vertices[2]-vertices[0]);
103 
104  btScalar l2 = normal.length2();
105  bool hasContact = false;
106  btVector3 contactPoint;
107 
108  if (l2 >= SIMD_EPSILON*SIMD_EPSILON)
109  {
110  normal /= btSqrt(l2);
111 
112  btVector3 p1ToCentre = sphereCenter - vertices[0];
113  btScalar distanceFromPlane = p1ToCentre.dot(normal);
114 
115  if (distanceFromPlane < btScalar(0.))
116  {
117  //triangle facing the other way
118  distanceFromPlane *= btScalar(-1.);
119  normal *= btScalar(-1.);
120  }
121 
122  bool isInsideContactPlane = distanceFromPlane < radiusWithThreshold;
123 
124  // Check for contact / intersection
125 
126  if (isInsideContactPlane) {
127  if (facecontains(sphereCenter, vertices, normal)) {
128  // Inside the contact wedge - touches a point on the shell plane
129  hasContact = true;
130  contactPoint = sphereCenter - normal*distanceFromPlane;
131  }
132  else {
133  // Could be inside one of the contact capsules
134  btScalar contactCapsuleRadiusSqr = radiusWithThreshold*radiusWithThreshold;
135  btVector3 nearestOnEdge;
136  for (int i = 0; i < m_triangle->getNumEdges(); i++) {
137 
138  btVector3 pa;
139  btVector3 pb;
140 
141  m_triangle->getEdge(i, pa, pb);
142 
143  btScalar distanceSqr = SegmentSqrDistance(pa, pb, sphereCenter, nearestOnEdge);
144  if (distanceSqr < contactCapsuleRadiusSqr) {
145  // Yep, we're inside a capsule
146  hasContact = true;
147  contactPoint = nearestOnEdge;
148  }
149 
150  }
151  }
152  }
153  }
154 
155  if (hasContact) {
156  btVector3 contactToCentre = sphereCenter - contactPoint;
157  btScalar distanceSqr = contactToCentre.length2();
158 
159  if (distanceSqr < radiusWithThreshold*radiusWithThreshold)
160  {
161  if (distanceSqr>SIMD_EPSILON)
162  {
163  btScalar distance = btSqrt(distanceSqr);
164  resultNormal = contactToCentre;
165  resultNormal.normalize();
166  point = contactPoint;
167  depth = -(radius-distance);
168  } else
169  {
170  resultNormal = normal;
171  point = contactPoint;
172  depth = -radius;
173  }
174  return true;
175  }
176  }
177 
178  return false;
179 }
180 
181 
182 bool SphereTriangleDetector::pointInTriangle(const btVector3 vertices[], const btVector3 &normal, btVector3 *p )
183 {
184  const btVector3* p1 = &vertices[0];
185  const btVector3* p2 = &vertices[1];
186  const btVector3* p3 = &vertices[2];
187 
188  btVector3 edge1( *p2 - *p1 );
189  btVector3 edge2( *p3 - *p2 );
190  btVector3 edge3( *p1 - *p3 );
191 
192  btVector3 p1_to_p( *p - *p1 );
193  btVector3 p2_to_p( *p - *p2 );
194  btVector3 p3_to_p( *p - *p3 );
195 
196  btVector3 edge1_normal( edge1.cross(normal));
197  btVector3 edge2_normal( edge2.cross(normal));
198  btVector3 edge3_normal( edge3.cross(normal));
199 
200  btScalar r1, r2, r3;
201  r1 = edge1_normal.dot( p1_to_p );
202  r2 = edge2_normal.dot( p2_to_p );
203  r3 = edge3_normal.dot( p3_to_p );
204  if ( ( r1 > 0 && r2 > 0 && r3 > 0 ) ||
205  ( r1 <= 0 && r2 <= 0 && r3 <= 0 ) )
206  return true;
207  return false;
208 
209 }
#define SIMD_EPSILON
Definition: btScalar.h:521
btScalar length2() const
Return the length of the vector squared.
Definition: btVector3.h:257
btScalar btSqrt(btScalar y)
Definition: btScalar.h:444
The btSphereShape implements an implicit sphere, centered around a local origin with radius.
Definition: btSphereShape.h:22
btVector3 & normalize()
Normalize this vector x^2 + y^2 + z^2 = 1.
Definition: btVector3.h:309
bool facecontains(const btVector3 &p, const btVector3 *vertices, btVector3 &normal)
virtual void getClosestPoints(const ClosestPointInput &input, Result &output, class btIDebugDraw *debugDraw, bool swapResults=false)
btVector3 & getOrigin()
Return the origin vector translation.
Definition: btTransform.h:117
btVector3 cross(const btVector3 &v) const
Return the cross product between this and another vector.
Definition: btVector3.h:389
btScalar dot(const btVector3 &v) const
Return the dot product.
Definition: btVector3.h:235
btScalar getRadius() const
Definition: btSphereShape.h:50
btTransform inverseTimes(const btTransform &t) const
Return the inverse of this transform times the other transform.
Definition: btTransform.h:230
btVector3 & getVertexPtr(int index)
#define output
bool collide(const btVector3 &sphereCenter, btVector3 &point, btVector3 &resultNormal, btScalar &depth, btScalar &timeOfImpact, btScalar contactBreakingThreshold)
SphereTriangleDetector(btSphereShape *sphere, btTriangleShape *triangle, btScalar contactBreakingThreshold)
btMatrix3x3 & getBasis()
Return the basis matrix for the rotation.
Definition: btTransform.h:112
The btIDebugDraw interface class allows hooking up a debug renderer to visually debug simulations.
Definition: btIDebugDraw.h:29
bool pointInTriangle(const btVector3 vertices[], const btVector3 &normal, btVector3 *p)
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:83
The btTransform class supports rigid transforms with only translation and rotation and no scaling/she...
Definition: btTransform.h:34
virtual void getEdge(int i, btVector3 &pa, btVector3 &pb) const
btScalar SegmentSqrDistance(const btVector3 &from, const btVector3 &to, const btVector3 &p, btVector3 &nearest)
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:292
virtual int getNumEdges() const