1 /*
2 Written by Xuchen Han <xuchenhan2015@u.northwestern.edu>
3
4 Bullet Continuous Collision Detection and Physics Library
5 Copyright (c) 2019 Google Inc. http://bulletphysics.org
6 This software is provided 'as-is', without any express or implied warranty.
7 In no event will the authors be held liable for any damages arising from the use of this software.
8 Permission is granted to anyone to use this software for any purpose,
9 including commercial applications, and to alter it and redistribute it freely,
10 subject to the following restrictions:
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 /* ====== Overview of the Deformable Algorithm ====== */
17
18 /*
19 A single step of the deformable body simulation contains the following main components:
20 Call internalStepSimulation multiple times, to achieve 240Hz (4 steps of 60Hz).
21 1. Deformable maintaintenance of rest lengths and volume preservation. Forces only depend on position: Update velocity to a temporary state v_{n+1}^* = v_n + explicit_force * dt / mass, where explicit forces include gravity and elastic forces.
22 2. Detect discrete collisions between rigid and deformable bodies at position x_{n+1}^* = x_n + dt * v_{n+1}^*.
23
24 3a. Solve all constraints, including LCP. Contact, position correction due to numerical drift, friction, and anchors for deformable.
25
26 3b. 5 Newton steps (multiple step). Conjugent Gradient solves linear system. Deformable Damping: Then velocities of deformable bodies v_{n+1} are solved in
27 M(v_{n+1} - v_{n+1}^*) = damping_force * dt / mass,
28 by a conjugate gradient solver, where the damping force is implicit and depends on v_{n+1}.
29 Make sure contact constraints are not violated in step b by performing velocity projections as in the paper by Baraff and Witkin https://www.cs.cmu.edu/~baraff/papers/sig98.pdf. Dynamic frictions are treated as a force and added to the rhs of the CG solve, whereas static frictions are treated as constraints similar to contact.
30 4. Position is updated via x_{n+1} = x_n + dt * v_{n+1}.
31
32
33 The algorithm also closely resembles the one in http://physbam.stanford.edu/~fedkiw/papers/stanford2008-03.pdf
34 */
35
36 #include <stdio.h>
37 #include "btDeformableMultiBodyDynamicsWorld.h"
38 #include "DeformableBodyInplaceSolverIslandCallback.h"
39 #include "btDeformableBodySolver.h"
40 #include "LinearMath/btQuickprof.h"
41 #include "btSoftBodyInternals.h"
btDeformableMultiBodyDynamicsWorld(btDispatcher * dispatcher,btBroadphaseInterface * pairCache,btDeformableMultiBodyConstraintSolver * constraintSolver,btCollisionConfiguration * collisionConfiguration,btDeformableBodySolver * deformableBodySolver)42 btDeformableMultiBodyDynamicsWorld::btDeformableMultiBodyDynamicsWorld(btDispatcher* dispatcher, btBroadphaseInterface* pairCache, btDeformableMultiBodyConstraintSolver* constraintSolver, btCollisionConfiguration* collisionConfiguration, btDeformableBodySolver* deformableBodySolver)
43 : btMultiBodyDynamicsWorld(dispatcher, pairCache, (btMultiBodyConstraintSolver*)constraintSolver, collisionConfiguration),
44 m_deformableBodySolver(deformableBodySolver),
45 m_solverCallback(0)
46 {
47 m_drawFlags = fDrawFlags::Std;
48 m_drawNodeTree = true;
49 m_drawFaceTree = false;
50 m_drawClusterTree = false;
51 m_sbi.m_broadphase = pairCache;
52 m_sbi.m_dispatcher = dispatcher;
53 m_sbi.m_sparsesdf.Initialize();
54 m_sbi.m_sparsesdf.setDefaultVoxelsz(0.005);
55 m_sbi.m_sparsesdf.Reset();
56
57 m_sbi.air_density = (btScalar)1.2;
58 m_sbi.water_density = 0;
59 m_sbi.water_offset = 0;
60 m_sbi.water_normal = btVector3(0, 0, 0);
61 m_sbi.m_gravity.setValue(0, -9.8, 0);
62 m_internalTime = 0.0;
63 m_implicit = false;
64 m_lineSearch = false;
65 m_useProjection = false;
66 m_ccdIterations = 5;
67 m_solverDeformableBodyIslandCallback = new DeformableBodyInplaceSolverIslandCallback(constraintSolver, dispatcher);
68 }
69
~btDeformableMultiBodyDynamicsWorld()70 btDeformableMultiBodyDynamicsWorld::~btDeformableMultiBodyDynamicsWorld()
71 {
72 delete m_solverDeformableBodyIslandCallback;
73 }
74
internalSingleStepSimulation(btScalar timeStep)75 void btDeformableMultiBodyDynamicsWorld::internalSingleStepSimulation(btScalar timeStep)
76 {
77 BT_PROFILE("internalSingleStepSimulation");
78 if (0 != m_internalPreTickCallback)
79 {
80 (*m_internalPreTickCallback)(this, timeStep);
81 }
82 reinitialize(timeStep);
83
84 // add gravity to velocity of rigid and multi bodys
85 applyRigidBodyGravity(timeStep);
86
87 ///apply gravity and explicit force to velocity, predict motion
88 predictUnconstraintMotion(timeStep);
89
90 ///perform collision detection that involves rigid/multi bodies
91 btMultiBodyDynamicsWorld::performDiscreteCollisionDetection();
92
93 btMultiBodyDynamicsWorld::calculateSimulationIslands();
94
95 beforeSolverCallbacks(timeStep);
96
97 ///solve contact constraints and then deformable bodies momemtum equation
98 solveConstraints(timeStep);
99
100 afterSolverCallbacks(timeStep);
101
102 performDeformableCollisionDetection();
103
104 applyRepulsionForce(timeStep);
105
106 performGeometricCollisions(timeStep);
107
108 integrateTransforms(timeStep);
109
110 ///update vehicle simulation
111 btMultiBodyDynamicsWorld::updateActions(timeStep);
112
113 updateActivationState(timeStep);
114 // End solver-wise simulation step
115 // ///////////////////////////////
116 }
117
performDeformableCollisionDetection()118 void btDeformableMultiBodyDynamicsWorld::performDeformableCollisionDetection()
119 {
120 for (int i = 0; i < m_softBodies.size(); ++i)
121 {
122 m_softBodies[i]->m_softSoftCollision = true;
123 }
124
125 for (int i = 0; i < m_softBodies.size(); ++i)
126 {
127 for (int j = i; j < m_softBodies.size(); ++j)
128 {
129 m_softBodies[i]->defaultCollisionHandler(m_softBodies[j]);
130 }
131 }
132
133 for (int i = 0; i < m_softBodies.size(); ++i)
134 {
135 m_softBodies[i]->m_softSoftCollision = false;
136 }
137 }
138
updateActivationState(btScalar timeStep)139 void btDeformableMultiBodyDynamicsWorld::updateActivationState(btScalar timeStep)
140 {
141 for (int i = 0; i < m_softBodies.size(); i++)
142 {
143 btSoftBody* psb = m_softBodies[i];
144 psb->updateDeactivation(timeStep);
145 if (psb->wantsSleeping())
146 {
147 if (psb->getActivationState() == ACTIVE_TAG)
148 psb->setActivationState(WANTS_DEACTIVATION);
149 if (psb->getActivationState() == ISLAND_SLEEPING)
150 {
151 psb->setZeroVelocity();
152 }
153 }
154 else
155 {
156 if (psb->getActivationState() != DISABLE_DEACTIVATION)
157 psb->setActivationState(ACTIVE_TAG);
158 }
159 }
160 btMultiBodyDynamicsWorld::updateActivationState(timeStep);
161 }
162
applyRepulsionForce(btScalar timeStep)163 void btDeformableMultiBodyDynamicsWorld::applyRepulsionForce(btScalar timeStep)
164 {
165 BT_PROFILE("btDeformableMultiBodyDynamicsWorld::applyRepulsionForce");
166 for (int i = 0; i < m_softBodies.size(); i++)
167 {
168 btSoftBody* psb = m_softBodies[i];
169 if (psb->isActive())
170 {
171 psb->applyRepulsionForce(timeStep, true);
172 }
173 }
174 }
175
performGeometricCollisions(btScalar timeStep)176 void btDeformableMultiBodyDynamicsWorld::performGeometricCollisions(btScalar timeStep)
177 {
178 BT_PROFILE("btDeformableMultiBodyDynamicsWorld::performGeometricCollisions");
179 // refit the BVH tree for CCD
180 for (int i = 0; i < m_softBodies.size(); ++i)
181 {
182 btSoftBody* psb = m_softBodies[i];
183 if (psb->isActive())
184 {
185 m_softBodies[i]->updateFaceTree(true, false);
186 m_softBodies[i]->updateNodeTree(true, false);
187 for (int j = 0; j < m_softBodies[i]->m_faces.size(); ++j)
188 {
189 btSoftBody::Face& f = m_softBodies[i]->m_faces[j];
190 f.m_n0 = (f.m_n[1]->m_x - f.m_n[0]->m_x).cross(f.m_n[2]->m_x - f.m_n[0]->m_x);
191 }
192 }
193 }
194
195 // clear contact points & update DBVT
196 for (int r = 0; r < m_ccdIterations; ++r)
197 {
198 for (int i = 0; i < m_softBodies.size(); ++i)
199 {
200 btSoftBody* psb = m_softBodies[i];
201 if (psb->isActive())
202 {
203 // clear contact points in the previous iteration
204 psb->m_faceNodeContacts.clear();
205
206 // update m_q and normals for CCD calculation
207 for (int j = 0; j < psb->m_nodes.size(); ++j)
208 {
209 psb->m_nodes[j].m_q = psb->m_nodes[j].m_x + timeStep * psb->m_nodes[j].m_v;
210 }
211 for (int j = 0; j < psb->m_faces.size(); ++j)
212 {
213 btSoftBody::Face& f = psb->m_faces[j];
214 f.m_n1 = (f.m_n[1]->m_q - f.m_n[0]->m_q).cross(f.m_n[2]->m_q - f.m_n[0]->m_q);
215 f.m_vn = (f.m_n[1]->m_v - f.m_n[0]->m_v).cross(f.m_n[2]->m_v - f.m_n[0]->m_v) * timeStep * timeStep;
216 }
217 }
218 }
219
220 // apply CCD to register new contact points
221 for (int i = 0; i < m_softBodies.size(); ++i)
222 {
223 for (int j = i; j < m_softBodies.size(); ++j)
224 {
225 btSoftBody* psb1 = m_softBodies[i];
226 btSoftBody* psb2 = m_softBodies[j];
227 if (psb1->isActive() && psb2->isActive())
228 {
229 m_softBodies[i]->geometricCollisionHandler(m_softBodies[j]);
230 }
231 }
232 }
233
234 int penetration_count = 0;
235 for (int i = 0; i < m_softBodies.size(); ++i)
236 {
237 btSoftBody* psb = m_softBodies[i];
238 if (psb->isActive())
239 {
240 penetration_count += psb->m_faceNodeContacts.size();
241 }
242 }
243 if (penetration_count == 0)
244 {
245 break;
246 }
247
248 // apply inelastic impulse
249 for (int i = 0; i < m_softBodies.size(); ++i)
250 {
251 btSoftBody* psb = m_softBodies[i];
252 if (psb->isActive())
253 {
254 psb->applyRepulsionForce(timeStep, false);
255 }
256 }
257 }
258 }
259
softBodySelfCollision()260 void btDeformableMultiBodyDynamicsWorld::softBodySelfCollision()
261 {
262 BT_PROFILE("btDeformableMultiBodyDynamicsWorld::softBodySelfCollision");
263 for (int i = 0; i < m_softBodies.size(); i++)
264 {
265 btSoftBody* psb = m_softBodies[i];
266 if (psb->isActive())
267 {
268 psb->defaultCollisionHandler(psb);
269 }
270 }
271 }
272
positionCorrection(btScalar timeStep)273 void btDeformableMultiBodyDynamicsWorld::positionCorrection(btScalar timeStep)
274 {
275 // correct the position of rigid bodies with temporary velocity generated from split impulse
276 btContactSolverInfo infoGlobal;
277 btVector3 zero(0, 0, 0);
278 for (int i = 0; i < m_nonStaticRigidBodies.size(); ++i)
279 {
280 btRigidBody* rb = m_nonStaticRigidBodies[i];
281 //correct the position/orientation based on push/turn recovery
282 btTransform newTransform;
283 btVector3 pushVelocity = rb->getPushVelocity();
284 btVector3 turnVelocity = rb->getTurnVelocity();
285 if (pushVelocity[0] != 0.f || pushVelocity[1] != 0 || pushVelocity[2] != 0 || turnVelocity[0] != 0.f || turnVelocity[1] != 0 || turnVelocity[2] != 0)
286 {
287 btTransformUtil::integrateTransform(rb->getWorldTransform(), pushVelocity, turnVelocity * infoGlobal.m_splitImpulseTurnErp, timeStep, newTransform);
288 rb->setWorldTransform(newTransform);
289 rb->setPushVelocity(zero);
290 rb->setTurnVelocity(zero);
291 }
292 }
293 }
294
integrateTransforms(btScalar timeStep)295 void btDeformableMultiBodyDynamicsWorld::integrateTransforms(btScalar timeStep)
296 {
297 BT_PROFILE("integrateTransforms");
298 positionCorrection(timeStep);
299 btMultiBodyDynamicsWorld::integrateTransforms(timeStep);
300 for (int i = 0; i < m_softBodies.size(); ++i)
301 {
302 btSoftBody* psb = m_softBodies[i];
303 for (int j = 0; j < psb->m_nodes.size(); ++j)
304 {
305 btSoftBody::Node& node = psb->m_nodes[j];
306 btScalar maxDisplacement = psb->getWorldInfo()->m_maxDisplacement;
307 btScalar clampDeltaV = maxDisplacement / timeStep;
308 for (int c = 0; c < 3; c++)
309 {
310 if (node.m_v[c] > clampDeltaV)
311 {
312 node.m_v[c] = clampDeltaV;
313 }
314 if (node.m_v[c] < -clampDeltaV)
315 {
316 node.m_v[c] = -clampDeltaV;
317 }
318 }
319 node.m_x = node.m_x + timeStep * (node.m_v + node.m_splitv);
320 node.m_q = node.m_x;
321 node.m_vn = node.m_v;
322 }
323 // enforce anchor constraints
324 for (int j = 0; j < psb->m_deformableAnchors.size(); ++j)
325 {
326 btSoftBody::DeformableNodeRigidAnchor& a = psb->m_deformableAnchors[j];
327 btSoftBody::Node* n = a.m_node;
328 n->m_x = a.m_cti.m_colObj->getWorldTransform() * a.m_local;
329
330 // update multibody anchor info
331 if (a.m_cti.m_colObj->getInternalType() == btCollisionObject::CO_FEATHERSTONE_LINK)
332 {
333 btMultiBodyLinkCollider* multibodyLinkCol = (btMultiBodyLinkCollider*)btMultiBodyLinkCollider::upcast(a.m_cti.m_colObj);
334 if (multibodyLinkCol)
335 {
336 btVector3 nrm;
337 const btCollisionShape* shp = multibodyLinkCol->getCollisionShape();
338 const btTransform& wtr = multibodyLinkCol->getWorldTransform();
339 psb->m_worldInfo->m_sparsesdf.Evaluate(
340 wtr.invXform(n->m_x),
341 shp,
342 nrm,
343 0);
344 a.m_cti.m_normal = wtr.getBasis() * nrm;
345 btVector3 normal = a.m_cti.m_normal;
346 btVector3 t1 = generateUnitOrthogonalVector(normal);
347 btVector3 t2 = btCross(normal, t1);
348 btMultiBodyJacobianData jacobianData_normal, jacobianData_t1, jacobianData_t2;
349 findJacobian(multibodyLinkCol, jacobianData_normal, a.m_node->m_x, normal);
350 findJacobian(multibodyLinkCol, jacobianData_t1, a.m_node->m_x, t1);
351 findJacobian(multibodyLinkCol, jacobianData_t2, a.m_node->m_x, t2);
352
353 btScalar* J_n = &jacobianData_normal.m_jacobians[0];
354 btScalar* J_t1 = &jacobianData_t1.m_jacobians[0];
355 btScalar* J_t2 = &jacobianData_t2.m_jacobians[0];
356
357 btScalar* u_n = &jacobianData_normal.m_deltaVelocitiesUnitImpulse[0];
358 btScalar* u_t1 = &jacobianData_t1.m_deltaVelocitiesUnitImpulse[0];
359 btScalar* u_t2 = &jacobianData_t2.m_deltaVelocitiesUnitImpulse[0];
360
361 btMatrix3x3 rot(normal.getX(), normal.getY(), normal.getZ(),
362 t1.getX(), t1.getY(), t1.getZ(),
363 t2.getX(), t2.getY(), t2.getZ()); // world frame to local frame
364 const int ndof = multibodyLinkCol->m_multiBody->getNumDofs() + 6;
365 btMatrix3x3 local_impulse_matrix = (Diagonal(n->m_im) + OuterProduct(J_n, J_t1, J_t2, u_n, u_t1, u_t2, ndof)).inverse();
366 a.m_c0 = rot.transpose() * local_impulse_matrix * rot;
367 a.jacobianData_normal = jacobianData_normal;
368 a.jacobianData_t1 = jacobianData_t1;
369 a.jacobianData_t2 = jacobianData_t2;
370 a.t1 = t1;
371 a.t2 = t2;
372 }
373 }
374 }
375 psb->interpolateRenderMesh();
376 }
377 }
378
solveConstraints(btScalar timeStep)379 void btDeformableMultiBodyDynamicsWorld::solveConstraints(btScalar timeStep)
380 {
381 BT_PROFILE("btDeformableMultiBodyDynamicsWorld::solveConstraints");
382 // save v_{n+1}^* velocity after explicit forces
383 m_deformableBodySolver->backupVelocity();
384
385 // set up constraints among multibodies and between multibodies and deformable bodies
386 setupConstraints();
387
388 // solve contact constraints
389 solveContactConstraints();
390
391 // set up the directions in which the velocity does not change in the momentum solve
392 if (m_useProjection)
393 m_deformableBodySolver->m_objective->m_projection.setProjection();
394 else
395 m_deformableBodySolver->m_objective->m_projection.setLagrangeMultiplier();
396
397 // for explicit scheme, m_backupVelocity = v_{n+1}^*
398 // for implicit scheme, m_backupVelocity = v_n
399 // Here, set dv = v_{n+1} - v_n for nodes in contact
400 m_deformableBodySolver->setupDeformableSolve(m_implicit);
401
402 // At this point, dv should be golden for nodes in contact
403 // proceed to solve deformable momentum equation
404 m_deformableBodySolver->solveDeformableConstraints(timeStep);
405 }
406
setupConstraints()407 void btDeformableMultiBodyDynamicsWorld::setupConstraints()
408 {
409 // set up constraints between multibody and deformable bodies
410 m_deformableBodySolver->setConstraints(m_solverInfo);
411
412 // set up constraints among multibodies
413 {
414 sortConstraints();
415 // setup the solver callback
416 btMultiBodyConstraint** sortedMultiBodyConstraints = m_sortedMultiBodyConstraints.size() ? &m_sortedMultiBodyConstraints[0] : 0;
417 btTypedConstraint** constraintsPtr = getNumConstraints() ? &m_sortedConstraints[0] : 0;
418 m_solverDeformableBodyIslandCallback->setup(&m_solverInfo, constraintsPtr, m_sortedConstraints.size(), sortedMultiBodyConstraints, m_sortedMultiBodyConstraints.size(), getDebugDrawer());
419
420 // build islands
421 m_islandManager->buildIslands(getCollisionWorld()->getDispatcher(), getCollisionWorld());
422 }
423 }
424
sortConstraints()425 void btDeformableMultiBodyDynamicsWorld::sortConstraints()
426 {
427 m_sortedConstraints.resize(m_constraints.size());
428 int i;
429 for (i = 0; i < getNumConstraints(); i++)
430 {
431 m_sortedConstraints[i] = m_constraints[i];
432 }
433 m_sortedConstraints.quickSort(btSortConstraintOnIslandPredicate2());
434
435 m_sortedMultiBodyConstraints.resize(m_multiBodyConstraints.size());
436 for (i = 0; i < m_multiBodyConstraints.size(); i++)
437 {
438 m_sortedMultiBodyConstraints[i] = m_multiBodyConstraints[i];
439 }
440 m_sortedMultiBodyConstraints.quickSort(btSortMultiBodyConstraintOnIslandPredicate());
441 }
442
solveContactConstraints()443 void btDeformableMultiBodyDynamicsWorld::solveContactConstraints()
444 {
445 // process constraints on each island
446 m_islandManager->processIslands(getCollisionWorld()->getDispatcher(), getCollisionWorld(), m_solverDeformableBodyIslandCallback);
447
448 // process deferred
449 m_solverDeformableBodyIslandCallback->processConstraints();
450 m_constraintSolver->allSolved(m_solverInfo, m_debugDrawer);
451
452 // write joint feedback
453 {
454 for (int i = 0; i < this->m_multiBodies.size(); i++)
455 {
456 btMultiBody* bod = m_multiBodies[i];
457
458 bool isSleeping = false;
459
460 if (bod->getBaseCollider() && bod->getBaseCollider()->getActivationState() == ISLAND_SLEEPING)
461 {
462 isSleeping = true;
463 }
464 for (int b = 0; b < bod->getNumLinks(); b++)
465 {
466 if (bod->getLink(b).m_collider && bod->getLink(b).m_collider->getActivationState() == ISLAND_SLEEPING)
467 isSleeping = true;
468 }
469
470 if (!isSleeping)
471 {
472 //useless? they get resized in stepVelocities once again (AND DIFFERENTLY)
473 m_scratch_r.resize(bod->getNumLinks() + 1); //multidof? ("Y"s use it and it is used to store qdd)
474 m_scratch_v.resize(bod->getNumLinks() + 1);
475 m_scratch_m.resize(bod->getNumLinks() + 1);
476
477 if (bod->internalNeedsJointFeedback())
478 {
479 if (!bod->isUsingRK4Integration())
480 {
481 if (bod->internalNeedsJointFeedback())
482 {
483 bool isConstraintPass = true;
484 bod->computeAccelerationsArticulatedBodyAlgorithmMultiDof(m_solverInfo.m_timeStep, m_scratch_r, m_scratch_v, m_scratch_m, isConstraintPass,
485 getSolverInfo().m_jointFeedbackInWorldSpace,
486 getSolverInfo().m_jointFeedbackInJointFrame);
487 }
488 }
489 }
490 }
491 }
492 }
493
494 for (int i = 0; i < this->m_multiBodies.size(); i++)
495 {
496 btMultiBody* bod = m_multiBodies[i];
497 bod->processDeltaVeeMultiDof2();
498 }
499 }
500
addSoftBody(btSoftBody * body,int collisionFilterGroup,int collisionFilterMask)501 void btDeformableMultiBodyDynamicsWorld::addSoftBody(btSoftBody* body, int collisionFilterGroup, int collisionFilterMask)
502 {
503 m_softBodies.push_back(body);
504
505 // Set the soft body solver that will deal with this body
506 // to be the world's solver
507 body->setSoftBodySolver(m_deformableBodySolver);
508
509 btCollisionWorld::addCollisionObject(body,
510 collisionFilterGroup,
511 collisionFilterMask);
512 }
513
predictUnconstraintMotion(btScalar timeStep)514 void btDeformableMultiBodyDynamicsWorld::predictUnconstraintMotion(btScalar timeStep)
515 {
516 BT_PROFILE("predictUnconstraintMotion");
517 btMultiBodyDynamicsWorld::predictUnconstraintMotion(timeStep);
518 m_deformableBodySolver->predictMotion(timeStep);
519 }
520
reinitialize(btScalar timeStep)521 void btDeformableMultiBodyDynamicsWorld::reinitialize(btScalar timeStep)
522 {
523 m_internalTime += timeStep;
524 m_deformableBodySolver->setImplicit(m_implicit);
525 m_deformableBodySolver->setLineSearch(m_lineSearch);
526 m_deformableBodySolver->reinitialize(m_softBodies, timeStep);
527 btDispatcherInfo& dispatchInfo = btMultiBodyDynamicsWorld::getDispatchInfo();
528 dispatchInfo.m_timeStep = timeStep;
529 dispatchInfo.m_stepCount = 0;
530 dispatchInfo.m_debugDraw = btMultiBodyDynamicsWorld::getDebugDrawer();
531 btMultiBodyDynamicsWorld::getSolverInfo().m_timeStep = timeStep;
532 if (m_useProjection)
533 {
534 m_deformableBodySolver->m_useProjection = true;
535 m_deformableBodySolver->m_objective->m_projection.m_useStrainLimiting = true;
536 m_deformableBodySolver->m_objective->m_preconditioner = m_deformableBodySolver->m_objective->m_massPreconditioner;
537 }
538 else
539 {
540 m_deformableBodySolver->m_useProjection = false;
541 m_deformableBodySolver->m_objective->m_projection.m_useStrainLimiting = false;
542 m_deformableBodySolver->m_objective->m_preconditioner = m_deformableBodySolver->m_objective->m_KKTPreconditioner;
543 }
544 }
545
debugDrawWorld()546 void btDeformableMultiBodyDynamicsWorld::debugDrawWorld()
547 {
548 btMultiBodyDynamicsWorld::debugDrawWorld();
549
550 for (int i = 0; i < getSoftBodyArray().size(); i++)
551 {
552 btSoftBody* psb = (btSoftBody*)getSoftBodyArray()[i];
553 {
554 btSoftBodyHelpers::DrawFrame(psb, getDebugDrawer());
555 btSoftBodyHelpers::Draw(psb, getDebugDrawer(), getDrawFlags());
556 }
557 }
558 }
559
applyRigidBodyGravity(btScalar timeStep)560 void btDeformableMultiBodyDynamicsWorld::applyRigidBodyGravity(btScalar timeStep)
561 {
562 // Gravity is applied in stepSimulation and then cleared here and then applied here and then cleared here again
563 // so that 1) gravity is applied to velocity before constraint solve and 2) gravity is applied in each substep
564 // when there are multiple substeps
565 btMultiBodyDynamicsWorld::applyGravity();
566 // integrate rigid body gravity
567 for (int i = 0; i < m_nonStaticRigidBodies.size(); ++i)
568 {
569 btRigidBody* rb = m_nonStaticRigidBodies[i];
570 rb->integrateVelocities(timeStep);
571 }
572
573 // integrate multibody gravity
574 {
575 forwardKinematics();
576 clearMultiBodyConstraintForces();
577 {
578 for (int i = 0; i < this->m_multiBodies.size(); i++)
579 {
580 btMultiBody* bod = m_multiBodies[i];
581
582 bool isSleeping = false;
583
584 if (bod->getBaseCollider() && bod->getBaseCollider()->getActivationState() == ISLAND_SLEEPING)
585 {
586 isSleeping = true;
587 }
588 for (int b = 0; b < bod->getNumLinks(); b++)
589 {
590 if (bod->getLink(b).m_collider && bod->getLink(b).m_collider->getActivationState() == ISLAND_SLEEPING)
591 isSleeping = true;
592 }
593
594 if (!isSleeping)
595 {
596 m_scratch_r.resize(bod->getNumLinks() + 1);
597 m_scratch_v.resize(bod->getNumLinks() + 1);
598 m_scratch_m.resize(bod->getNumLinks() + 1);
599 bool isConstraintPass = false;
600 {
601 if (!bod->isUsingRK4Integration())
602 {
603 bod->computeAccelerationsArticulatedBodyAlgorithmMultiDof(m_solverInfo.m_timeStep,
604 m_scratch_r, m_scratch_v, m_scratch_m, isConstraintPass,
605 getSolverInfo().m_jointFeedbackInWorldSpace,
606 getSolverInfo().m_jointFeedbackInJointFrame);
607 }
608 else
609 {
610 btAssert(" RK4Integration is not supported");
611 }
612 }
613 }
614 }
615 }
616 }
617 clearGravity();
618 }
619
clearGravity()620 void btDeformableMultiBodyDynamicsWorld::clearGravity()
621 {
622 BT_PROFILE("btMultiBody clearGravity");
623 // clear rigid body gravity
624 for (int i = 0; i < m_nonStaticRigidBodies.size(); i++)
625 {
626 btRigidBody* body = m_nonStaticRigidBodies[i];
627 if (body->isActive())
628 {
629 body->clearGravity();
630 }
631 }
632 // clear multibody gravity
633 for (int i = 0; i < this->m_multiBodies.size(); i++)
634 {
635 btMultiBody* bod = m_multiBodies[i];
636
637 bool isSleeping = false;
638
639 if (bod->getBaseCollider() && bod->getBaseCollider()->getActivationState() == ISLAND_SLEEPING)
640 {
641 isSleeping = true;
642 }
643 for (int b = 0; b < bod->getNumLinks(); b++)
644 {
645 if (bod->getLink(b).m_collider && bod->getLink(b).m_collider->getActivationState() == ISLAND_SLEEPING)
646 isSleeping = true;
647 }
648
649 if (!isSleeping)
650 {
651 bod->addBaseForce(-m_gravity * bod->getBaseMass());
652
653 for (int j = 0; j < bod->getNumLinks(); ++j)
654 {
655 bod->addLinkForce(j, -m_gravity * bod->getLinkMass(j));
656 }
657 }
658 }
659 }
660
beforeSolverCallbacks(btScalar timeStep)661 void btDeformableMultiBodyDynamicsWorld::beforeSolverCallbacks(btScalar timeStep)
662 {
663 if (0 != m_internalTickCallback)
664 {
665 (*m_internalTickCallback)(this, timeStep);
666 }
667
668 if (0 != m_solverCallback)
669 {
670 (*m_solverCallback)(m_internalTime, this);
671 }
672 }
673
afterSolverCallbacks(btScalar timeStep)674 void btDeformableMultiBodyDynamicsWorld::afterSolverCallbacks(btScalar timeStep)
675 {
676 if (0 != m_solverCallback)
677 {
678 (*m_solverCallback)(m_internalTime, this);
679 }
680 }
681
addForce(btSoftBody * psb,btDeformableLagrangianForce * force)682 void btDeformableMultiBodyDynamicsWorld::addForce(btSoftBody* psb, btDeformableLagrangianForce* force)
683 {
684 btAlignedObjectArray<btDeformableLagrangianForce*>& forces = m_deformableBodySolver->m_objective->m_lf;
685 bool added = false;
686 for (int i = 0; i < forces.size(); ++i)
687 {
688 if (forces[i]->getForceType() == force->getForceType())
689 {
690 forces[i]->addSoftBody(psb);
691 added = true;
692 break;
693 }
694 }
695 if (!added)
696 {
697 force->addSoftBody(psb);
698 force->setIndices(m_deformableBodySolver->m_objective->getIndices());
699 forces.push_back(force);
700 }
701 }
702
removeForce(btSoftBody * psb,btDeformableLagrangianForce * force)703 void btDeformableMultiBodyDynamicsWorld::removeForce(btSoftBody* psb, btDeformableLagrangianForce* force)
704 {
705 btAlignedObjectArray<btDeformableLagrangianForce*>& forces = m_deformableBodySolver->m_objective->m_lf;
706 int removed_index = -1;
707 for (int i = 0; i < forces.size(); ++i)
708 {
709 if (forces[i]->getForceType() == force->getForceType())
710 {
711 forces[i]->removeSoftBody(psb);
712 if (forces[i]->m_softBodies.size() == 0)
713 removed_index = i;
714 break;
715 }
716 }
717 if (removed_index >= 0)
718 forces.removeAtIndex(removed_index);
719 }
720
removeSoftBodyForce(btSoftBody * psb)721 void btDeformableMultiBodyDynamicsWorld::removeSoftBodyForce(btSoftBody* psb)
722 {
723 btAlignedObjectArray<btDeformableLagrangianForce*>& forces = m_deformableBodySolver->m_objective->m_lf;
724 for (int i = 0; i < forces.size(); ++i)
725 {
726 forces[i]->removeSoftBody(psb);
727 }
728 }
729
removeSoftBody(btSoftBody * body)730 void btDeformableMultiBodyDynamicsWorld::removeSoftBody(btSoftBody* body)
731 {
732 removeSoftBodyForce(body);
733 m_softBodies.remove(body);
734 btCollisionWorld::removeCollisionObject(body);
735 // force a reinitialize so that node indices get updated.
736 m_deformableBodySolver->reinitialize(m_softBodies, btScalar(-1));
737 }
738
removeCollisionObject(btCollisionObject * collisionObject)739 void btDeformableMultiBodyDynamicsWorld::removeCollisionObject(btCollisionObject* collisionObject)
740 {
741 btSoftBody* body = btSoftBody::upcast(collisionObject);
742 if (body)
743 removeSoftBody(body);
744 else
745 btDiscreteDynamicsWorld::removeCollisionObject(collisionObject);
746 }
747
stepSimulation(btScalar timeStep,int maxSubSteps,btScalar fixedTimeStep)748 int btDeformableMultiBodyDynamicsWorld::stepSimulation(btScalar timeStep, int maxSubSteps, btScalar fixedTimeStep)
749 {
750 startProfiling(timeStep);
751
752 int numSimulationSubSteps = 0;
753
754 if (maxSubSteps)
755 {
756 //fixed timestep with interpolation
757 m_fixedTimeStep = fixedTimeStep;
758 m_localTime += timeStep;
759 if (m_localTime >= fixedTimeStep)
760 {
761 numSimulationSubSteps = int(m_localTime / fixedTimeStep);
762 m_localTime -= numSimulationSubSteps * fixedTimeStep;
763 }
764 }
765 else
766 {
767 //variable timestep
768 fixedTimeStep = timeStep;
769 m_localTime = m_latencyMotionStateInterpolation ? 0 : timeStep;
770 m_fixedTimeStep = 0;
771 if (btFuzzyZero(timeStep))
772 {
773 numSimulationSubSteps = 0;
774 maxSubSteps = 0;
775 }
776 else
777 {
778 numSimulationSubSteps = 1;
779 maxSubSteps = 1;
780 }
781 }
782
783 //process some debugging flags
784 if (getDebugDrawer())
785 {
786 btIDebugDraw* debugDrawer = getDebugDrawer();
787 gDisableDeactivation = (debugDrawer->getDebugMode() & btIDebugDraw::DBG_NoDeactivation) != 0;
788 }
789 if (numSimulationSubSteps)
790 {
791 //clamp the number of substeps, to prevent simulation grinding spiralling down to a halt
792 int clampedSimulationSteps = (numSimulationSubSteps > maxSubSteps) ? maxSubSteps : numSimulationSubSteps;
793
794 saveKinematicState(fixedTimeStep * clampedSimulationSteps);
795
796 for (int i = 0; i < clampedSimulationSteps; i++)
797 {
798 internalSingleStepSimulation(fixedTimeStep);
799 synchronizeMotionStates();
800 }
801 }
802 else
803 {
804 synchronizeMotionStates();
805 }
806
807 clearForces();
808
809 #ifndef BT_NO_PROFILE
810 CProfileManager::Increment_Frame_Counter();
811 #endif //BT_NO_PROFILE
812
813 return numSimulationSubSteps;
814 }
815