Bullet Collision Detection & Physics Library
btJacobianEntry.h
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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:
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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 #ifndef BT_JACOBIAN_ENTRY_H
17 #define BT_JACOBIAN_ENTRY_H
18 
19 #include "LinearMath/btMatrix3x3.h"
20 
21 
22 //notes:
23 // Another memory optimization would be to store m_1MinvJt in the remaining 3 w components
24 // which makes the btJacobianEntry memory layout 16 bytes
25 // if you only are interested in angular part, just feed massInvA and massInvB zero
26 
30 ATTRIBUTE_ALIGNED16(class) btJacobianEntry
31 {
32 public:
33  btJacobianEntry() {};
34  //constraint between two different rigidbodies
35  btJacobianEntry(
36  const btMatrix3x3& world2A,
37  const btMatrix3x3& world2B,
38  const btVector3& rel_pos1,const btVector3& rel_pos2,
39  const btVector3& jointAxis,
40  const btVector3& inertiaInvA,
41  const btScalar massInvA,
42  const btVector3& inertiaInvB,
43  const btScalar massInvB)
44  :m_linearJointAxis(jointAxis)
45  {
46  m_aJ = world2A*(rel_pos1.cross(m_linearJointAxis));
47  m_bJ = world2B*(rel_pos2.cross(-m_linearJointAxis));
48  m_0MinvJt = inertiaInvA * m_aJ;
49  m_1MinvJt = inertiaInvB * m_bJ;
50  m_Adiag = massInvA + m_0MinvJt.dot(m_aJ) + massInvB + m_1MinvJt.dot(m_bJ);
51 
52  btAssert(m_Adiag > btScalar(0.0));
53  }
54 
55  //angular constraint between two different rigidbodies
56  btJacobianEntry(const btVector3& jointAxis,
57  const btMatrix3x3& world2A,
58  const btMatrix3x3& world2B,
59  const btVector3& inertiaInvA,
60  const btVector3& inertiaInvB)
61  :m_linearJointAxis(btVector3(btScalar(0.),btScalar(0.),btScalar(0.)))
62  {
63  m_aJ= world2A*jointAxis;
64  m_bJ = world2B*-jointAxis;
65  m_0MinvJt = inertiaInvA * m_aJ;
66  m_1MinvJt = inertiaInvB * m_bJ;
67  m_Adiag = m_0MinvJt.dot(m_aJ) + m_1MinvJt.dot(m_bJ);
68 
69  btAssert(m_Adiag > btScalar(0.0));
70  }
71 
72  //angular constraint between two different rigidbodies
73  btJacobianEntry(const btVector3& axisInA,
74  const btVector3& axisInB,
75  const btVector3& inertiaInvA,
76  const btVector3& inertiaInvB)
77  : m_linearJointAxis(btVector3(btScalar(0.),btScalar(0.),btScalar(0.)))
78  , m_aJ(axisInA)
79  , m_bJ(-axisInB)
80  {
81  m_0MinvJt = inertiaInvA * m_aJ;
82  m_1MinvJt = inertiaInvB * m_bJ;
83  m_Adiag = m_0MinvJt.dot(m_aJ) + m_1MinvJt.dot(m_bJ);
84 
85  btAssert(m_Adiag > btScalar(0.0));
86  }
87 
88  //constraint on one rigidbody
89  btJacobianEntry(
90  const btMatrix3x3& world2A,
91  const btVector3& rel_pos1,const btVector3& rel_pos2,
92  const btVector3& jointAxis,
93  const btVector3& inertiaInvA,
94  const btScalar massInvA)
95  :m_linearJointAxis(jointAxis)
96  {
97  m_aJ= world2A*(rel_pos1.cross(jointAxis));
98  m_bJ = world2A*(rel_pos2.cross(-jointAxis));
99  m_0MinvJt = inertiaInvA * m_aJ;
100  m_1MinvJt = btVector3(btScalar(0.),btScalar(0.),btScalar(0.));
101  m_Adiag = massInvA + m_0MinvJt.dot(m_aJ);
102 
103  btAssert(m_Adiag > btScalar(0.0));
104  }
105 
106  btScalar getDiagonal() const { return m_Adiag; }
107 
108  // for two constraints on the same rigidbody (for example vehicle friction)
109  btScalar getNonDiagonal(const btJacobianEntry& jacB, const btScalar massInvA) const
110  {
111  const btJacobianEntry& jacA = *this;
112  btScalar lin = massInvA * jacA.m_linearJointAxis.dot(jacB.m_linearJointAxis);
113  btScalar ang = jacA.m_0MinvJt.dot(jacB.m_aJ);
114  return lin + ang;
115  }
116 
117 
118 
119  // for two constraints on sharing two same rigidbodies (for example two contact points between two rigidbodies)
120  btScalar getNonDiagonal(const btJacobianEntry& jacB,const btScalar massInvA,const btScalar massInvB) const
121  {
122  const btJacobianEntry& jacA = *this;
123  btVector3 lin = jacA.m_linearJointAxis * jacB.m_linearJointAxis;
124  btVector3 ang0 = jacA.m_0MinvJt * jacB.m_aJ;
125  btVector3 ang1 = jacA.m_1MinvJt * jacB.m_bJ;
126  btVector3 lin0 = massInvA * lin ;
127  btVector3 lin1 = massInvB * lin;
128  btVector3 sum = ang0+ang1+lin0+lin1;
129  return sum[0]+sum[1]+sum[2];
130  }
131 
132  btScalar getRelativeVelocity(const btVector3& linvelA,const btVector3& angvelA,const btVector3& linvelB,const btVector3& angvelB)
133  {
134  btVector3 linrel = linvelA - linvelB;
135  btVector3 angvela = angvelA * m_aJ;
136  btVector3 angvelb = angvelB * m_bJ;
137  linrel *= m_linearJointAxis;
138  angvela += angvelb;
139  angvela += linrel;
140  btScalar rel_vel2 = angvela[0]+angvela[1]+angvela[2];
141  return rel_vel2 + SIMD_EPSILON;
142  }
143 //private:
144 
145  btVector3 m_linearJointAxis;
146  btVector3 m_aJ;
147  btVector3 m_bJ;
148  btVector3 m_0MinvJt;
149  btVector3 m_1MinvJt;
150  //Optimization: can be stored in the w/last component of one of the vectors
151  btScalar m_Adiag;
152 
153 };
154 
155 #endif //BT_JACOBIAN_ENTRY_H
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