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 B3_JACOBIAN_ENTRY_H
17 #define B3_JACOBIAN_ENTRY_H
18
19 #include "Bullet3Common/b3Matrix3x3.h"
20
21 //notes:
22 // Another memory optimization would be to store m_1MinvJt in the remaining 3 w components
23 // which makes the b3JacobianEntry 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
B3_ATTRIBUTE_ALIGNED16(class)29 B3_ATTRIBUTE_ALIGNED16(class)
30 b3JacobianEntry
31 {
32 public:
33 b3JacobianEntry(){};
34 //constraint between two different rigidbodies
35 b3JacobianEntry(
36 const b3Matrix3x3& world2A,
37 const b3Matrix3x3& world2B,
38 const b3Vector3& rel_pos1, const b3Vector3& rel_pos2,
39 const b3Vector3& jointAxis,
40 const b3Vector3& inertiaInvA,
41 const b3Scalar massInvA,
42 const b3Vector3& inertiaInvB,
43 const b3Scalar 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 b3Assert(m_Adiag > b3Scalar(0.0));
53 }
54
55 //angular constraint between two different rigidbodies
56 b3JacobianEntry(const b3Vector3& jointAxis,
57 const b3Matrix3x3& world2A,
58 const b3Matrix3x3& world2B,
59 const b3Vector3& inertiaInvA,
60 const b3Vector3& inertiaInvB)
61 : m_linearJointAxis(b3MakeVector3(b3Scalar(0.), b3Scalar(0.), b3Scalar(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 b3Assert(m_Adiag > b3Scalar(0.0));
70 }
71
72 //angular constraint between two different rigidbodies
73 b3JacobianEntry(const b3Vector3& axisInA,
74 const b3Vector3& axisInB,
75 const b3Vector3& inertiaInvA,
76 const b3Vector3& inertiaInvB)
77 : m_linearJointAxis(b3MakeVector3(b3Scalar(0.), b3Scalar(0.), b3Scalar(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 b3Assert(m_Adiag > b3Scalar(0.0));
84 }
85
86 //constraint on one rigidbody
87 b3JacobianEntry(
88 const b3Matrix3x3& world2A,
89 const b3Vector3& rel_pos1, const b3Vector3& rel_pos2,
90 const b3Vector3& jointAxis,
91 const b3Vector3& inertiaInvA,
92 const b3Scalar 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 = b3MakeVector3(b3Scalar(0.), b3Scalar(0.), b3Scalar(0.));
99 m_Adiag = massInvA + m_0MinvJt.dot(m_aJ);
100
101 b3Assert(m_Adiag > b3Scalar(0.0));
102 }
103
104 b3Scalar getDiagonal() const { return m_Adiag; }
105
106 // for two constraints on the same rigidbody (for example vehicle friction)
107 b3Scalar getNonDiagonal(const b3JacobianEntry& jacB, const b3Scalar massInvA) const
108 {
109 const b3JacobianEntry& jacA = *this;
110 b3Scalar lin = massInvA * jacA.m_linearJointAxis.dot(jacB.m_linearJointAxis);
111 b3Scalar 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 b3Scalar getNonDiagonal(const b3JacobianEntry& jacB, const b3Scalar massInvA, const b3Scalar massInvB) const
117 {
118 const b3JacobianEntry& jacA = *this;
119 b3Vector3 lin = jacA.m_linearJointAxis * jacB.m_linearJointAxis;
120 b3Vector3 ang0 = jacA.m_0MinvJt * jacB.m_aJ;
121 b3Vector3 ang1 = jacA.m_1MinvJt * jacB.m_bJ;
122 b3Vector3 lin0 = massInvA * lin;
123 b3Vector3 lin1 = massInvB * lin;
124 b3Vector3 sum = ang0 + ang1 + lin0 + lin1;
125 return sum[0] + sum[1] + sum[2];
126 }
127
128 b3Scalar getRelativeVelocity(const b3Vector3& linvelA, const b3Vector3& angvelA, const b3Vector3& linvelB, const b3Vector3& angvelB)
129 {
130 b3Vector3 linrel = linvelA - linvelB;
131 b3Vector3 angvela = angvelA * m_aJ;
132 b3Vector3 angvelb = angvelB * m_bJ;
133 linrel *= m_linearJointAxis;
134 angvela += angvelb;
135 angvela += linrel;
136 b3Scalar rel_vel2 = angvela[0] + angvela[1] + angvela[2];
137 return rel_vel2 + B3_EPSILON;
138 }
139 //private:
140
141 b3Vector3 m_linearJointAxis;
142 b3Vector3 m_aJ;
143 b3Vector3 m_bJ;
144 b3Vector3 m_0MinvJt;
145 b3Vector3 m_1MinvJt;
146 //Optimization: can be stored in the w/last component of one of the vectors
147 b3Scalar m_Adiag;
148 };
149
150 #endif //B3_JACOBIAN_ENTRY_H
151