Blender  V3.3
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 //notes:
22 // Another memory optimization would be to store m_1MinvJt in the remaining 3 w components
23 // which makes the btJacobianEntry memory layout 16 bytes
24 // if you only are interested in angular part, just feed massInvA and massInvB zero
25 
31 {
32 public:
33  btJacobianEntry(){};
34  //constraint between two different rigidbodies
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)
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.))), m_aJ(axisInA), m_bJ(-axisInB)
78  {
79  m_0MinvJt = inertiaInvA * m_aJ;
80  m_1MinvJt = inertiaInvB * m_bJ;
81  m_Adiag = m_0MinvJt.dot(m_aJ) + m_1MinvJt.dot(m_bJ);
82 
83  btAssert(m_Adiag > btScalar(0.0));
84  }
85 
86  //constraint on one rigidbody
88  const btMatrix3x3& world2A,
89  const btVector3& rel_pos1, const btVector3& rel_pos2,
90  const btVector3& jointAxis,
91  const btVector3& inertiaInvA,
92  const btScalar massInvA)
93  : m_linearJointAxis(jointAxis)
94  {
95  m_aJ = world2A * (rel_pos1.cross(jointAxis));
96  m_bJ = world2A * (rel_pos2.cross(-jointAxis));
97  m_0MinvJt = inertiaInvA * m_aJ;
98  m_1MinvJt = btVector3(btScalar(0.), btScalar(0.), btScalar(0.));
99  m_Adiag = massInvA + m_0MinvJt.dot(m_aJ);
100 
101  btAssert(m_Adiag > btScalar(0.0));
102  }
103 
104  btScalar getDiagonal() const { return m_Adiag; }
105 
106  // for two constraints on the same rigidbody (for example vehicle friction)
107  btScalar getNonDiagonal(const btJacobianEntry& jacB, const btScalar massInvA) const
108  {
109  const btJacobianEntry& jacA = *this;
110  btScalar lin = massInvA * jacA.m_linearJointAxis.dot(jacB.m_linearJointAxis);
111  btScalar ang = jacA.m_0MinvJt.dot(jacB.m_aJ);
112  return lin + ang;
113  }
114 
115  // for two constraints on sharing two same rigidbodies (for example two contact points between two rigidbodies)
116  btScalar getNonDiagonal(const btJacobianEntry& jacB, const btScalar massInvA, const btScalar massInvB) const
117  {
118  const btJacobianEntry& jacA = *this;
119  btVector3 lin = jacA.m_linearJointAxis * jacB.m_linearJointAxis;
120  btVector3 ang0 = jacA.m_0MinvJt * jacB.m_aJ;
121  btVector3 ang1 = jacA.m_1MinvJt * jacB.m_bJ;
122  btVector3 lin0 = massInvA * lin;
123  btVector3 lin1 = massInvB * lin;
124  btVector3 sum = ang0 + ang1 + lin0 + lin1;
125  return sum[0] + sum[1] + sum[2];
126  }
127 
128  btScalar getRelativeVelocity(const btVector3& linvelA, const btVector3& angvelA, const btVector3& linvelB, const btVector3& angvelB)
129  {
130  btVector3 linrel = linvelA - linvelB;
131  btVector3 angvela = angvelA * m_aJ;
132  btVector3 angvelb = angvelB * m_bJ;
133  linrel *= m_linearJointAxis;
134  angvela += angvelb;
135  angvela += linrel;
136  btScalar rel_vel2 = angvela[0] + angvela[1] + angvela[2];
137  return rel_vel2 + SIMD_EPSILON;
138  }
139  //private:
140 
146  //Optimization: can be stored in the w/last component of one of the vectors
148 };
149 
150 #endif //BT_JACOBIAN_ENTRY_H
btVector3 m_aJ
btScalar getNonDiagonal(const btJacobianEntry &jacB, const btScalar massInvA) const
btScalar m_Adiag
btScalar getRelativeVelocity(const btVector3 &linvelA, const btVector3 &angvelA, const btVector3 &linvelB, const btVector3 &angvelB)
btScalar getDiagonal() const
btJacobianEntry
btVector3 m_linearJointAxis
btVector3 m_bJ
btVector3 m_0MinvJt
btVector3 m_1MinvJt
btMatrix3x3
The btMatrix3x3 class implements a 3x3 rotation matrix, to perform linear algebra in combination with...
Definition: btMatrix3x3.h:50
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:314
#define ATTRIBUTE_ALIGNED16(a)
Definition: btScalar.h:285
#define SIMD_EPSILON
Definition: btScalar.h:543
#define btAssert(x)
Definition: btScalar.h:295
static T sum(const btAlignedObjectArray< T > &items)
btVector3
btVector3 can be used to represent 3D points and vectors. It has an un-used w component to suit 16-by...
Definition: btVector3.h:82