Bullet Collision Detection & Physics Library
btMultiBodyGearConstraint.cpp
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1/*
2Bullet Continuous Collision Detection and Physics Library
3Copyright (c) 2013 Erwin Coumans http://bulletphysics.org
4
5This software is provided 'as-is', without any express or implied warranty.
6In no event will the authors be held liable for any damages arising from the use of this software.
7Permission is granted to anyone to use this software for any purpose,
8including commercial applications, and to alter it and redistribute it freely,
9subject to the following restrictions:
10
111. 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.
122. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
133. This notice may not be removed or altered from any source distribution.
14*/
15
17
19#include "btMultiBody.h"
22
23btMultiBodyGearConstraint::btMultiBodyGearConstraint(btMultiBody* bodyA, int linkA, btMultiBody* bodyB, int linkB, const btVector3& pivotInA, const btVector3& pivotInB, const btMatrix3x3& frameInA, const btMatrix3x3& frameInB)
24 :btMultiBodyConstraint(bodyA,bodyB,linkA,linkB,1,false),
25 m_gearRatio(1),
26 m_gearAuxLink(-1),
27 m_erp(0),
28 m_relativePositionTarget(0)
29{
30
31}
32
34{
35
37
39}
40
42{
43}
44
45
47{
48
49 if (m_bodyA)
50 {
52 if (col)
53 return col->getIslandTag();
54 for (int i=0;i<m_bodyA->getNumLinks();i++)
55 {
58 }
59 }
60 return -1;
61}
62
64{
65 if (m_bodyB)
66 {
68 if (col)
69 return col->getIslandTag();
70
71 for (int i=0;i<m_bodyB->getNumLinks();i++)
72 {
73 col = m_bodyB->getLink(i).m_collider;
74 if (col)
75 return col->getIslandTag();
76 }
77 }
78 return -1;
79}
80
81
84 const btContactSolverInfo& infoGlobal)
85{
86 // only positions need to be updated -- data.m_jacobians and force
87 // directions were set in the ctor and never change.
88
90 {
92 }
93
94 //don't crash
96 return;
97
98
99 if (m_maxAppliedImpulse==0.f)
100 return;
101
102 // note: we rely on the fact that data.m_jacobians are
103 // always initialized to zero by the Constraint ctor
104 int linkDoF = 0;
105 unsigned int offsetA = 6 + (m_bodyA->getLink(m_linkA).m_dofOffset + linkDoF);
106 unsigned int offsetB = 6 + (m_bodyB->getLink(m_linkB).m_dofOffset + linkDoF);
107
108 // row 0: the lower bound
109 jacobianA(0)[offsetA] = 1;
110 jacobianB(0)[offsetB] = m_gearRatio;
111
112 btScalar posError = 0;
113 const btVector3 dummy(0, 0, 0);
114
115 btScalar kp = 1;
116 btScalar kd = 1;
117 int numRows = getNumRows();
118
119 for (int row=0;row<numRows;row++)
120 {
121 btMultiBodySolverConstraint& constraintRow = constraintRows.expandNonInitializing();
122
123
124 int dof = 0;
125 btScalar currentPosition = m_bodyA->getJointPosMultiDof(m_linkA)[dof];
126 btScalar currentVelocity = m_bodyA->getJointVelMultiDof(m_linkA)[dof];
127 btScalar auxVel = 0;
128
129 if (m_gearAuxLink>=0)
130 {
132 }
133 currentVelocity += auxVel;
134 if (m_erp!=0)
135 {
136 btScalar currentPositionA = m_bodyA->getJointPosMultiDof(m_linkA)[dof];
137 btScalar currentPositionB = m_gearRatio*m_bodyA->getJointPosMultiDof(m_linkB)[dof];
138 btScalar diff = currentPositionB+currentPositionA;
139 btScalar desiredPositionDiff = this->m_relativePositionTarget;
140 posError = -m_erp*(desiredPositionDiff - diff);
141 }
142
143 btScalar desiredRelativeVelocity = auxVel;
144
145 fillMultiBodyConstraint(constraintRow,data,jacobianA(row),jacobianB(row),dummy,dummy,dummy,dummy,posError,infoGlobal,-m_maxAppliedImpulse,m_maxAppliedImpulse,false,1,false,desiredRelativeVelocity);
146
147 constraintRow.m_orgConstraint = this;
148 constraintRow.m_orgDofIndex = row;
149 {
150 //expect either prismatic or revolute joint type for now
153 {
155 {
156 constraintRow.m_contactNormal1.setZero();
157 constraintRow.m_contactNormal2.setZero();
159 constraintRow.m_relpos1CrossNormal=revoluteAxisInWorld;
160 constraintRow.m_relpos2CrossNormal=-revoluteAxisInWorld;
161
162 break;
163 }
165 {
167 constraintRow.m_contactNormal1=prismaticAxisInWorld;
168 constraintRow.m_contactNormal2=-prismaticAxisInWorld;
169 constraintRow.m_relpos1CrossNormal.setZero();
170 constraintRow.m_relpos2CrossNormal.setZero();
171 break;
172 }
173 default:
174 {
175 btAssert(0);
176 }
177 };
178
179 }
180
181 }
182
183}
184
btVector3 quatRotate(const btQuaternion &rotation, const btVector3 &v)
Definition: btQuaternion.h:917
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:292
#define btAssert(x)
Definition: btScalar.h:131
int getIslandTag() const
The btMatrix3x3 class implements a 3x3 rotation matrix, to perform linear algebra in combination with...
Definition: btMatrix3x3.h:48
btScalar * jacobianA(int row)
btScalar * jacobianB(int row)
btScalar fillMultiBodyConstraint(btMultiBodySolverConstraint &solverConstraint, btMultiBodyJacobianData &data, btScalar *jacOrgA, btScalar *jacOrgB, const btVector3 &constraintNormalAng, const btVector3 &constraintNormalLin, const btVector3 &posAworld, const btVector3 &posBworld, btScalar posError, const btContactSolverInfo &infoGlobal, btScalar lowerLimit, btScalar upperLimit, bool angConstraint=false, btScalar relaxation=1.f, bool isFriction=false, btScalar desiredVelocity=0, btScalar cfmSlip=0)
virtual void createConstraintRows(btMultiBodyConstraintArray &constraintRows, btMultiBodyJacobianData &data, const btContactSolverInfo &infoGlobal)
btMultiBodyGearConstraint(btMultiBody *bodyA, int linkA, btMultiBody *bodyB, int linkB, const btVector3 &pivotInA, const btVector3 &pivotInB, const btMatrix3x3 &frameInA, const btMatrix3x3 &frameInB)
This file was written by Erwin Coumans.
btScalar * getJointPosMultiDof(int i)
int getNumLinks() const
Definition: btMultiBody.h:164
const btMultibodyLink & getLink(int index) const
Definition: btMultiBody.h:119
const btMultiBodyLinkCollider * getBaseCollider() const
Definition: btMultiBody.h:134
btScalar * getJointVelMultiDof(int i)
btQuaternion getRotation() const
Return a quaternion representing the rotation.
Definition: btTransform.h:122
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:84
void setZero()
Definition: btVector3.h:683
1D constraint along a normal axis between bodyA and bodyB. It can be combined to solve contact and fr...
btMultiBodyConstraint * m_orgConstraint