1 /*
2 Bullet Continuous Collision Detection and Physics Library
3 Copyright (c) 2003-2006 Erwin Coumans https://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 #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
26 /// Jacobian entry is an abstraction that allows to describe constraints
27 /// it can be used in combination with a constraint solver
28 /// Can be used to relate the effect of an impulse to the constraint error
ATTRIBUTE_ALIGNED16(class)29 ATTRIBUTE_ALIGNED16(class)
30 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.))), 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
87 btJacobianEntry(
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
141 btVector3 m_linearJointAxis;
142 btVector3 m_aJ;
143 btVector3 m_bJ;
144 btVector3 m_0MinvJt;
145 btVector3 m_1MinvJt;
146 //Optimization: can be stored in the w/last component of one of the vectors
147 btScalar m_Adiag;
148 };
149
150 #endif //BT_JACOBIAN_ENTRY_H
151