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 #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
27 /// Jacobian entry is an abstraction that allows to describe constraints
28 /// it can be used in combination with a constraint solver
29 /// Can be used to relate the effect of an impulse to the constraint error
ATTRIBUTE_ALIGNED16(class)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
156