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//
// btDeformableRigidDynamicsWorld.cpp
// BulletSoftBody
//
// Created by Xuchen Han on 7/1/19.
//
#include <stdio.h>
#include "btDeformableRigidDynamicsWorld.h"
#include "btDeformableBodySolver.h"
void btDeformableRigidDynamicsWorld::internalSingleStepSimulation(btScalar timeStep)
{
reinitialize(timeStep);
// beforeSolverCallbacks(timeStep);
// add gravity to velocity of rigid and multi bodys
applyRigidBodyGravity(timeStep);
///apply gravity and explicit force to velocity, predict motion
predictUnconstraintMotion(timeStep);
///perform collision detection
btMultiBodyDynamicsWorld::performDiscreteCollisionDetection();
btMultiBodyDynamicsWorld::calculateSimulationIslands();
beforeSolverCallbacks(timeStep);
///solve deformable bodies constraints
solveDeformableBodiesConstraints(timeStep);
afterSolverCallbacks(timeStep);
integrateTransforms(timeStep);
///update vehicle simulation
btMultiBodyDynamicsWorld::updateActions(timeStep);
btMultiBodyDynamicsWorld::updateActivationState(timeStep);
// End solver-wise simulation step
// ///////////////////////////////
}
void btDeformableRigidDynamicsWorld::positionCorrection(btScalar dt)
{
// perform position correction for all constraints
for (auto& it : m_deformableBodySolver->m_objective->projection.m_constraints)
{
btAlignedObjectArray<DeformableFrictionConstraint>& frictions = m_deformableBodySolver->m_objective->projection.m_frictions[it.first];
btAlignedObjectArray<DeformableContactConstraint>& constraints = it.second;
for (int i = 0; i < constraints.size(); ++i)
{
DeformableContactConstraint& constraint = constraints[i];
DeformableFrictionConstraint& friction = frictions[i];
for (int j = 0; j < constraint.m_contact.size(); ++j)
{
const btSoftBody::RContact* c = constraint.m_contact[j];
// skip anchor points
if (c == nullptr || c->m_node->m_im == 0)
continue;
const btSoftBody::sCti& cti = c->m_cti;
btVector3 va(0, 0, 0);
// grab the velocity of the rigid body
if (cti.m_colObj->getInternalType() == btCollisionObject::CO_RIGID_BODY)
{
btRigidBody* rigidCol = (btRigidBody*)btRigidBody::upcast(cti.m_colObj);
va = rigidCol ? (rigidCol->getVelocityInLocalPoint(c->m_c1)): btVector3(0, 0, 0);
}
else if (cti.m_colObj->getInternalType() == btCollisionObject::CO_FEATHERSTONE_LINK)
{
btMultiBodyLinkCollider* multibodyLinkCol = (btMultiBodyLinkCollider*)btMultiBodyLinkCollider::upcast(cti.m_colObj);
if (multibodyLinkCol)
{
const int ndof = multibodyLinkCol->m_multiBody->getNumDofs() + 6;
const btScalar* J_n = &c->jacobianData_normal.m_jacobians[0];
const btScalar* J_t1 = &c->jacobianData_t1.m_jacobians[0];
const btScalar* J_t2 = &c->jacobianData_t2.m_jacobians[0];
const btScalar* local_v = multibodyLinkCol->m_multiBody->getVelocityVector();
// add in the normal component of the va
btScalar vel = 0.0;
for (int k = 0; k < ndof; ++k)
{
vel += local_v[k] * J_n[k];
}
va = cti.m_normal * vel;
vel = 0.0;
for (int k = 0; k < ndof; ++k)
{
vel += local_v[k] * J_t1[k];
}
va += c->t1 * vel;
vel = 0.0;
for (int k = 0; k < ndof; ++k)
{
vel += local_v[k] * J_t2[k];
}
va += c->t2 * vel;
}
}
else
{
// The object interacting with deformable node is not supported for position correction
btAssert(false);
}
if (cti.m_colObj->hasContactResponse())
{
btScalar dp = cti.m_offset;
if (friction.m_static[j] == true)
{
c->m_node->m_v = va;
}
if (dp < 0)
{
c->m_node->m_v -= dp * cti.m_normal / dt;
}
}
}
}
}
}
void btDeformableRigidDynamicsWorld::integrateTransforms(btScalar dt)
{
m_deformableBodySolver->backupVelocity();
positionCorrection(dt);
btMultiBodyDynamicsWorld::integrateTransforms(dt);
for (int i = 0; i < m_softBodies.size(); ++i)
{
btSoftBody* psb = m_softBodies[i];
for (int j = 0; j < psb->m_nodes.size(); ++j)
{
auto& node = psb->m_nodes[j];
node.m_x = node.m_q + dt * node.m_v;
}
}
m_deformableBodySolver->revertVelocity();
}
void btDeformableRigidDynamicsWorld::solveDeformableBodiesConstraints(btScalar timeStep)
{
m_deformableBodySolver->solveConstraints(timeStep);
}
void btDeformableRigidDynamicsWorld::addSoftBody(btSoftBody* body, int collisionFilterGroup, int collisionFilterMask)
{
m_softBodies.push_back(body);
// Set the soft body solver that will deal with this body
// to be the world's solver
body->setSoftBodySolver(m_deformableBodySolver);
btCollisionWorld::addCollisionObject(body,
collisionFilterGroup,
collisionFilterMask);
}
void btDeformableRigidDynamicsWorld::predictUnconstraintMotion(btScalar timeStep)
{
btDiscreteDynamicsWorld::predictUnconstraintMotion(timeStep);
m_deformableBodySolver->predictMotion(float(timeStep));
}
void btDeformableRigidDynamicsWorld::reinitialize(btScalar timeStep)
{
m_internalTime += timeStep;
m_deformableBodySolver->reinitialize(m_softBodies);
btDispatcherInfo& dispatchInfo = btMultiBodyDynamicsWorld::getDispatchInfo();
dispatchInfo.m_timeStep = timeStep;
dispatchInfo.m_stepCount = 0;
dispatchInfo.m_debugDraw = btMultiBodyDynamicsWorld::getDebugDrawer();
btMultiBodyDynamicsWorld::getSolverInfo().m_timeStep = timeStep;
}
void btDeformableRigidDynamicsWorld::applyRigidBodyGravity(btScalar timeStep)
{
// TODO: This is an ugly hack to get the desired gravity behavior.
// gravity is applied in stepSimulation and then cleared here and then applied here and then cleared here again
// so that 1) gravity is applied to velocity before constraint solve and 2) gravity is applied in each substep
// when there are multiple substeps
clearForces();
clearMultiBodyForces();
btMultiBodyDynamicsWorld::applyGravity();
// integrate rigid body gravity
for (int i = 0; i < m_nonStaticRigidBodies.size(); ++i)
{
btRigidBody* rb = m_nonStaticRigidBodies[i];
rb->integrateVelocities(timeStep);
}
// integrate multibody gravity
btMultiBodyDynamicsWorld::solveExternalForces(btMultiBodyDynamicsWorld::getSolverInfo());
clearForces();
clearMultiBodyForces();
}
void btDeformableRigidDynamicsWorld::beforeSolverCallbacks(btScalar timeStep)
{
if (0 != m_internalTickCallback)
{
(*m_internalTickCallback)(this, timeStep);
}
for (int i = 0; i < m_beforeSolverCallbacks.size(); ++i)
m_beforeSolverCallbacks[i](m_internalTime, this);
}
void btDeformableRigidDynamicsWorld::afterSolverCallbacks(btScalar timeStep)
{
for (int i = 0; i < m_beforeSolverCallbacks.size(); ++i)
m_beforeSolverCallbacks[i](m_internalTime, this);
}
void btDeformableRigidDynamicsWorld::addForce(btSoftBody* psb, btDeformableLagrangianForce* force)
{
btAlignedObjectArray<btDeformableLagrangianForce*>& forces = m_deformableBodySolver->m_objective->m_lf;
bool added = false;
for (int i = 0; i < forces.size(); ++i)
{
if (forces[i]->getForceType() == force->getForceType())
{
forces[i]->addSoftBody(psb);
added = true;
break;
}
}
if (!added)
{
force->addSoftBody(psb);
force->setIndices(m_deformableBodySolver->m_objective->getIndices());
forces.push_back(force);
}
}
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