Bullet Collision Detection & Physics Library
btMultiBodyConstraint.cpp
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3 #include "btMultiBodyPoint2Point.h" //for testing (BTMBP2PCONSTRAINT_BLOCK_ANGULAR_MOTION_TEST macro)
4 
5 
6 
7 btMultiBodyConstraint::btMultiBodyConstraint(btMultiBody* bodyA,btMultiBody* bodyB,int linkA, int linkB, int numRows, bool isUnilateral)
8  :m_bodyA(bodyA),
9  m_bodyB(bodyB),
10  m_linkA(linkA),
11  m_linkB(linkB),
12  m_numRows(numRows),
13  m_jacSizeA(0),
14  m_jacSizeBoth(0),
15  m_isUnilateral(isUnilateral),
16  m_numDofsFinalized(-1),
17  m_maxAppliedImpulse(100)
18 {
19 
20 }
21 
23 {
24  if(m_bodyA)
25  {
26  m_jacSizeA = (6 + m_bodyA->getNumDofs());
27  }
28 
29  if(m_bodyB)
30  {
32  }
33  else
35 }
36 
38 {
40 
43 }
44 
46 {
47 }
48 
49 void btMultiBodyConstraint::applyDeltaVee(btMultiBodyJacobianData& data, btScalar* delta_vee, btScalar impulse, int velocityIndex, int ndof)
50 {
51  for (int i = 0; i < ndof; ++i)
52  data.m_deltaVelocities[velocityIndex+i] += delta_vee[i] * impulse;
53 }
54 
57  btScalar* jacOrgA, btScalar* jacOrgB,
58  const btVector3& contactNormalOnB,
59  const btVector3& posAworld, const btVector3& posBworld,
60  btScalar posError,
61  const btContactSolverInfo& infoGlobal,
62  btScalar lowerLimit, btScalar upperLimit,
63  btScalar relaxation,
64  bool isFriction, btScalar desiredVelocity, btScalar cfmSlip)
65 {
66 
67 
68  solverConstraint.m_multiBodyA = m_bodyA;
69  solverConstraint.m_multiBodyB = m_bodyB;
70  solverConstraint.m_linkA = m_linkA;
71  solverConstraint.m_linkB = m_linkB;
72 
73  btMultiBody* multiBodyA = solverConstraint.m_multiBodyA;
74  btMultiBody* multiBodyB = solverConstraint.m_multiBodyB;
75 
76  btSolverBody* bodyA = multiBodyA ? 0 : &data.m_solverBodyPool->at(solverConstraint.m_solverBodyIdA);
77  btSolverBody* bodyB = multiBodyB ? 0 : &data.m_solverBodyPool->at(solverConstraint.m_solverBodyIdB);
78 
79  btRigidBody* rb0 = multiBodyA ? 0 : bodyA->m_originalBody;
80  btRigidBody* rb1 = multiBodyB ? 0 : bodyB->m_originalBody;
81 
82  btVector3 rel_pos1, rel_pos2; //these two used to be inited to posAworld and posBworld (respectively) but it does not seem necessary
83  if (bodyA)
84  rel_pos1 = posAworld - bodyA->getWorldTransform().getOrigin();
85  if (bodyB)
86  rel_pos2 = posBworld - bodyB->getWorldTransform().getOrigin();
87 
88  if (multiBodyA)
89  {
90  if (solverConstraint.m_linkA<0)
91  {
92  rel_pos1 = posAworld - multiBodyA->getBasePos();
93  } else
94  {
95  rel_pos1 = posAworld - multiBodyA->getLink(solverConstraint.m_linkA).m_cachedWorldTransform.getOrigin();
96  }
97 
98  const int ndofA = multiBodyA->getNumDofs() + 6;
99 
100  solverConstraint.m_deltaVelAindex = multiBodyA->getCompanionId();
101 
102  if (solverConstraint.m_deltaVelAindex <0)
103  {
104  solverConstraint.m_deltaVelAindex = data.m_deltaVelocities.size();
105  multiBodyA->setCompanionId(solverConstraint.m_deltaVelAindex);
106  data.m_deltaVelocities.resize(data.m_deltaVelocities.size()+ndofA);
107  } else
108  {
109  btAssert(data.m_deltaVelocities.size() >= solverConstraint.m_deltaVelAindex+ndofA);
110  }
111 
112  //determine jacobian of this 1D constraint in terms of multibodyA's degrees of freedom
113  //resize..
114  solverConstraint.m_jacAindex = data.m_jacobians.size();
115  data.m_jacobians.resize(data.m_jacobians.size()+ndofA);
116  //copy/determine
117  if(jacOrgA)
118  {
119  for (int i=0;i<ndofA;i++)
120  data.m_jacobians[solverConstraint.m_jacAindex+i] = jacOrgA[i];
121  }
122  else
123  {
124  btScalar* jac1=&data.m_jacobians[solverConstraint.m_jacAindex];
125  multiBodyA->fillContactJacobianMultiDof(solverConstraint.m_linkA, posAworld, contactNormalOnB, jac1, data.scratch_r, data.scratch_v, data.scratch_m);
126  }
127 
128  //determine the velocity response of multibodyA to reaction impulses of this constraint (i.e. A[i,i] for i=1,...n_con: multibody's inverse inertia with respect to this 1D constraint)
129  //resize..
130  data.m_deltaVelocitiesUnitImpulse.resize(data.m_deltaVelocitiesUnitImpulse.size()+ndofA); //=> each constraint row has the constrained tree dofs allocated in m_deltaVelocitiesUnitImpulse
132  btScalar* delta = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
133  //determine..
134  multiBodyA->calcAccelerationDeltasMultiDof(&data.m_jacobians[solverConstraint.m_jacAindex],delta,data.scratch_r, data.scratch_v);
135 
136  btVector3 torqueAxis0 = rel_pos1.cross(contactNormalOnB);
137  solverConstraint.m_relpos1CrossNormal = torqueAxis0;
138  solverConstraint.m_contactNormal1 = contactNormalOnB;
139  }
140  else //if(rb0)
141  {
142  btVector3 torqueAxis0 = rel_pos1.cross(contactNormalOnB);
143  solverConstraint.m_angularComponentA = rb0 ? rb0->getInvInertiaTensorWorld()*torqueAxis0*rb0->getAngularFactor() : btVector3(0,0,0);
144  solverConstraint.m_relpos1CrossNormal = torqueAxis0;
145  solverConstraint.m_contactNormal1 = contactNormalOnB;
146  }
147 
148  if (multiBodyB)
149  {
150  if (solverConstraint.m_linkB<0)
151  {
152  rel_pos2 = posBworld - multiBodyB->getBasePos();
153  } else
154  {
155  rel_pos2 = posBworld - multiBodyB->getLink(solverConstraint.m_linkB).m_cachedWorldTransform.getOrigin();
156  }
157 
158  const int ndofB = multiBodyB->getNumDofs() + 6;
159 
160  solverConstraint.m_deltaVelBindex = multiBodyB->getCompanionId();
161  if (solverConstraint.m_deltaVelBindex <0)
162  {
163  solverConstraint.m_deltaVelBindex = data.m_deltaVelocities.size();
164  multiBodyB->setCompanionId(solverConstraint.m_deltaVelBindex);
165  data.m_deltaVelocities.resize(data.m_deltaVelocities.size()+ndofB);
166  }
167 
168  //determine jacobian of this 1D constraint in terms of multibodyB's degrees of freedom
169  //resize..
170  solverConstraint.m_jacBindex = data.m_jacobians.size();
171  data.m_jacobians.resize(data.m_jacobians.size()+ndofB);
172  //copy/determine..
173  if(jacOrgB)
174  {
175  for (int i=0;i<ndofB;i++)
176  data.m_jacobians[solverConstraint.m_jacBindex+i] = jacOrgB[i];
177  }
178  else
179  {
180  multiBodyB->fillContactJacobianMultiDof(solverConstraint.m_linkB, posBworld, -contactNormalOnB, &data.m_jacobians[solverConstraint.m_jacBindex], data.scratch_r, data.scratch_v, data.scratch_m);
181  }
182 
183  //determine velocity response of multibodyB to reaction impulses of this constraint (i.e. A[i,i] for i=1,...n_con: multibody's inverse inertia with respect to this 1D constraint)
184  //resize..
187  btScalar* delta = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
188  //determine..
189  multiBodyB->calcAccelerationDeltasMultiDof(&data.m_jacobians[solverConstraint.m_jacBindex],delta,data.scratch_r, data.scratch_v);
190 
191  btVector3 torqueAxis1 = rel_pos2.cross(contactNormalOnB);
192  solverConstraint.m_relpos2CrossNormal = -torqueAxis1;
193  solverConstraint.m_contactNormal2 = -contactNormalOnB;
194 
195  }
196  else //if(rb1)
197  {
198  btVector3 torqueAxis1 = rel_pos2.cross(contactNormalOnB);
199  solverConstraint.m_angularComponentB = rb1 ? rb1->getInvInertiaTensorWorld()*-torqueAxis1*rb1->getAngularFactor() : btVector3(0,0,0);
200  solverConstraint.m_relpos2CrossNormal = -torqueAxis1;
201  solverConstraint.m_contactNormal2 = -contactNormalOnB;
202  }
203  {
204 
205  btVector3 vec;
206  btScalar denom0 = 0.f;
207  btScalar denom1 = 0.f;
208  btScalar* jacB = 0;
209  btScalar* jacA = 0;
210  btScalar* deltaVelA = 0;
211  btScalar* deltaVelB = 0;
212  int ndofA = 0;
213  //determine the "effective mass" of the constrained multibodyA with respect to this 1D constraint (i.e. 1/A[i,i])
214  if (multiBodyA)
215  {
216  ndofA = multiBodyA->getNumDofs() + 6;
217  jacA = &data.m_jacobians[solverConstraint.m_jacAindex];
218  deltaVelA = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
219  for (int i = 0; i < ndofA; ++i)
220  {
221  btScalar j = jacA[i] ;
222  btScalar l = deltaVelA[i];
223  denom0 += j*l;
224  }
225  }
226  else if(rb0)
227  {
228  vec = ( solverConstraint.m_angularComponentA).cross(rel_pos1);
229  denom0 = rb0->getInvMass() + contactNormalOnB.dot(vec);
230  }
231  //
232  if (multiBodyB)
233  {
234  const int ndofB = multiBodyB->getNumDofs() + 6;
235  jacB = &data.m_jacobians[solverConstraint.m_jacBindex];
236  deltaVelB = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
237  for (int i = 0; i < ndofB; ++i)
238  {
239  btScalar j = jacB[i] ;
240  btScalar l = deltaVelB[i];
241  denom1 += j*l;
242  }
243 
244  }
245  else if(rb1)
246  {
247  vec = ( -solverConstraint.m_angularComponentB).cross(rel_pos2);
248  denom1 = rb1->getInvMass() + contactNormalOnB.dot(vec);
249  }
250 
251  //
252  btScalar d = denom0+denom1;
253  if (d>SIMD_EPSILON)
254  {
255  solverConstraint.m_jacDiagABInv = relaxation/(d);
256  }
257  else
258  {
259  //disable the constraint row to handle singularity/redundant constraint
260  solverConstraint.m_jacDiagABInv = 0.f;
261  }
262  }
263 
264 
265  //compute rhs and remaining solverConstraint fields
266  btScalar penetration = isFriction? 0 : posError+infoGlobal.m_linearSlop;
267 
268  btScalar rel_vel = 0.f;
269  int ndofA = 0;
270  int ndofB = 0;
271  {
272  btVector3 vel1,vel2;
273  if (multiBodyA)
274  {
275  ndofA = multiBodyA->getNumDofs() + 6;
276  btScalar* jacA = &data.m_jacobians[solverConstraint.m_jacAindex];
277  for (int i = 0; i < ndofA ; ++i)
278  rel_vel += multiBodyA->getVelocityVector()[i] * jacA[i];
279  }
280  else if(rb0)
281  {
282  rel_vel += rb0->getVelocityInLocalPoint(rel_pos1).dot(solverConstraint.m_contactNormal1);
283  }
284  if (multiBodyB)
285  {
286  ndofB = multiBodyB->getNumDofs() + 6;
287  btScalar* jacB = &data.m_jacobians[solverConstraint.m_jacBindex];
288  for (int i = 0; i < ndofB ; ++i)
289  rel_vel += multiBodyB->getVelocityVector()[i] * jacB[i];
290 
291  }
292  else if(rb1)
293  {
294  rel_vel += rb1->getVelocityInLocalPoint(rel_pos2).dot(solverConstraint.m_contactNormal2);
295  }
296 
297  solverConstraint.m_friction = 0.f;//cp.m_combinedFriction;
298  }
299 
300 
302  /*
303  if (infoGlobal.m_solverMode & SOLVER_USE_WARMSTARTING)
304  {
305  solverConstraint.m_appliedImpulse = isFriction ? 0 : cp.m_appliedImpulse * infoGlobal.m_warmstartingFactor;
306 
307  if (solverConstraint.m_appliedImpulse)
308  {
309  if (multiBodyA)
310  {
311  btScalar impulse = solverConstraint.m_appliedImpulse;
312  btScalar* deltaV = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
313  multiBodyA->applyDeltaVee(deltaV,impulse);
314  applyDeltaVee(data,deltaV,impulse,solverConstraint.m_deltaVelAindex,ndofA);
315  } else
316  {
317  if (rb0)
318  bodyA->internalApplyImpulse(solverConstraint.m_contactNormal1*bodyA->internalGetInvMass()*rb0->getLinearFactor(),solverConstraint.m_angularComponentA,solverConstraint.m_appliedImpulse);
319  }
320  if (multiBodyB)
321  {
322  btScalar impulse = solverConstraint.m_appliedImpulse;
323  btScalar* deltaV = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
324  multiBodyB->applyDeltaVee(deltaV,impulse);
325  applyDeltaVee(data,deltaV,impulse,solverConstraint.m_deltaVelBindex,ndofB);
326  } else
327  {
328  if (rb1)
329  bodyB->internalApplyImpulse(-solverConstraint.m_contactNormal2*bodyB->internalGetInvMass()*rb1->getLinearFactor(),-solverConstraint.m_angularComponentB,-(btScalar)solverConstraint.m_appliedImpulse);
330  }
331  }
332  } else
333  */
334 
335  solverConstraint.m_appliedImpulse = 0.f;
336  solverConstraint.m_appliedPushImpulse = 0.f;
337 
338  {
339 
340  btScalar positionalError = 0.f;
341  btScalar velocityError = desiredVelocity - rel_vel;// * damping;
342 
343 
344  btScalar erp = infoGlobal.m_erp2;
345  if (!infoGlobal.m_splitImpulse || (penetration > infoGlobal.m_splitImpulsePenetrationThreshold))
346  {
347  erp = infoGlobal.m_erp;
348  }
349 
350  positionalError = -penetration * erp/infoGlobal.m_timeStep;
351 
352  btScalar penetrationImpulse = positionalError*solverConstraint.m_jacDiagABInv;
353  btScalar velocityImpulse = velocityError *solverConstraint.m_jacDiagABInv;
354 
355  if (!infoGlobal.m_splitImpulse || (penetration > infoGlobal.m_splitImpulsePenetrationThreshold))
356  {
357  //combine position and velocity into rhs
358  solverConstraint.m_rhs = penetrationImpulse+velocityImpulse;
359  solverConstraint.m_rhsPenetration = 0.f;
360 
361  } else
362  {
363  //split position and velocity into rhs and m_rhsPenetration
364  solverConstraint.m_rhs = velocityImpulse;
365  solverConstraint.m_rhsPenetration = penetrationImpulse;
366  }
367 
368  solverConstraint.m_cfm = 0.f;
369  solverConstraint.m_lowerLimit = lowerLimit;
370  solverConstraint.m_upperLimit = upperLimit;
371  }
372 
373  return rel_vel;
374 
375 }
btScalar getInvMass() const
Definition: btRigidBody.h:270
#define SIMD_EPSILON
Definition: btScalar.h:494
btScalar fillMultiBodyConstraint(btMultiBodySolverConstraint &solverConstraint, btMultiBodyJacobianData &data, btScalar *jacOrgA, btScalar *jacOrgB, const btVector3 &contactNormalOnB, const btVector3 &posAworld, const btVector3 &posBworld, btScalar posError, const btContactSolverInfo &infoGlobal, btScalar lowerLimit, btScalar upperLimit, btScalar relaxation=1.f, bool isFriction=false, btScalar desiredVelocity=0, btScalar cfmSlip=0)
const btMultibodyLink & getLink(int index) const
Definition: btMultiBody.h:119
1D constraint along a normal axis between bodyA and bodyB. It can be combined to solve contact and fr...
btAlignedObjectArray< btScalar > scratch_r
btAlignedObjectArray< btScalar > m_deltaVelocities
const btVector3 & getAngularFactor() const
Definition: btRigidBody.h:501
btAlignedObjectArray< btSolverBody > * m_solverBodyPool
const T & at(int n) const
#define btAssert(x)
Definition: btScalar.h:113
btAlignedObjectArray< btMatrix3x3 > scratch_m
btScalar dot(const btVector3 &v) const
Return the dot product.
Definition: btVector3.h:235
btVector3 getVelocityInLocalPoint(const btVector3 &rel_pos) const
Definition: btRigidBody.h:379
btAlignedObjectArray< btScalar > m_deltaVelocitiesUnitImpulse
int size() const
return the number of elements in the array
btVector3 & getOrigin()
Return the origin vector translation.
Definition: btTransform.h:117
void setCompanionId(int id)
Definition: btMultiBody.h:473
btVector3 cross(const btVector3 &v) const
Return the cross product between this and another vector.
Definition: btVector3.h:377
The btRigidBody is the main class for rigid body objects.
Definition: btRigidBody.h:62
btAlignedObjectArray< btScalar > m_data
btAlignedObjectArray< btScalar > m_jacobians
btVector3 can be used to represent 3D points and vectors.
Definition: btVector3.h:83
btAlignedObjectArray< btVector3 > scratch_v
void calcAccelerationDeltasMultiDof(const btScalar *force, btScalar *output, btAlignedObjectArray< btScalar > &scratch_r, btAlignedObjectArray< btVector3 > &scratch_v) const
The btSolverBody is an internal datastructure for the constraint solver. Only necessary data is packe...
Definition: btSolverBody.h:108
int getCompanionId() const
Definition: btMultiBody.h:469
void fillContactJacobianMultiDof(int link, const btVector3 &contact_point, const btVector3 &normal, btScalar *jac, btAlignedObjectArray< btScalar > &scratch_r, btAlignedObjectArray< btVector3 > &scratch_v, btAlignedObjectArray< btMatrix3x3 > &scratch_m) const
Definition: btMultiBody.h:426
void resize(int newsize, const T &fillData=T())
btRigidBody * m_originalBody
Definition: btSolverBody.h:124
const btMatrix3x3 & getInvInertiaTensorWorld() const
Definition: btRigidBody.h:271
const btTransform & getWorldTransform() const
Definition: btSolverBody.h:130
btMultiBodyConstraint(btMultiBody *bodyA, btMultiBody *bodyB, int linkA, int linkB, int numRows, bool isUnilateral)
const btVector3 & getBasePos() const
Definition: btMultiBody.h:177
int getNumDofs() const
Definition: btMultiBody.h:156
void applyDeltaVee(btMultiBodyJacobianData &data, btScalar *delta_vee, btScalar impulse, int velocityIndex, int ndof)
const btScalar * getVelocityVector() const
Definition: btMultiBody.h:249
float btScalar
The btScalar type abstracts floating point numbers, to easily switch between double and single floati...
Definition: btScalar.h:278