2 Bullet Continuous Collision Detection and Physics Library
3 Copyright (c) 2003-2006 Erwin Coumans https://bulletphysics.org
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16 #ifndef BT_JACOBIAN_ENTRY_H
17 #define BT_JACOBIAN_ENTRY_H
19 #include "LinearMath/btMatrix3x3.h"
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
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
29 ATTRIBUTE_ALIGNED16(class)
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)
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);
52 btAssert(m_Adiag > btScalar(0.0));
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.)))
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);
69 btAssert(m_Adiag > btScalar(0.0));
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)
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);
83 btAssert(m_Adiag > btScalar(0.0));
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)
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);
101 btAssert(m_Adiag > btScalar(0.0));
104 btScalar getDiagonal() const { return m_Adiag; }
106 // for two constraints on the same rigidbody (for example vehicle friction)
107 btScalar getNonDiagonal(const btJacobianEntry& jacB, const btScalar massInvA) const
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);
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
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];
128 btScalar getRelativeVelocity(const btVector3& linvelA, const btVector3& angvelA, const btVector3& linvelB, const btVector3& angvelB)
130 btVector3 linrel = linvelA - linvelB;
131 btVector3 angvela = angvelA * m_aJ;
132 btVector3 angvelb = angvelB * m_bJ;
133 linrel *= m_linearJointAxis;
136 btScalar rel_vel2 = angvela[0] + angvela[1] + angvela[2];
137 return rel_vel2 + SIMD_EPSILON;
141 btVector3 m_linearJointAxis;
146 //Optimization: can be stored in the w/last component of one of the vectors
150 #endif //BT_JACOBIAN_ENTRY_H