deformable code refactor
This commit is contained in:
Xuchen Han
488
src/BulletSoftBody/btDeformableContactProjection.cpp
Normal file
488
src/BulletSoftBody/btDeformableContactProjection.cpp
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//
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// btDeformableContactProjection.cpp
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// BulletSoftBody
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//
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// Created by Xuchen Han on 7/4/19.
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//
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#include "btDeformableContactProjection.h"
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#include "btDeformableRigidDynamicsWorld.h"
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#include <algorithm>
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static void findJacobian(const btMultiBodyLinkCollider* multibodyLinkCol,
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btMultiBodyJacobianData& jacobianData,
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const btVector3& contact_point,
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const btVector3& dir)
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{
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const int ndof = multibodyLinkCol->m_multiBody->getNumDofs() + 6;
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jacobianData.m_jacobians.resize(ndof);
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jacobianData.m_deltaVelocitiesUnitImpulse.resize(ndof);
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btScalar* jac = &jacobianData.m_jacobians[0];
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multibodyLinkCol->m_multiBody->fillContactJacobianMultiDof(multibodyLinkCol->m_link, contact_point, dir, jac, jacobianData.scratch_r, jacobianData.scratch_v, jacobianData.scratch_m);
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multibodyLinkCol->m_multiBody->calcAccelerationDeltasMultiDof(&jacobianData.m_jacobians[0], &jacobianData.m_deltaVelocitiesUnitImpulse[0], jacobianData.scratch_r, jacobianData.scratch_v);
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}
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static btVector3 generateUnitOrthogonalVector(const btVector3& u)
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{
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btScalar ux = u.getX();
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btScalar uy = u.getY();
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btScalar uz = u.getZ();
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btScalar ax = std::abs(ux);
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btScalar ay = std::abs(uy);
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btScalar az = std::abs(uz);
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btVector3 v;
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if (ax <= ay && ax <= az)
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v = btVector3(0, -uz, uy);
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else if (ay <= ax && ay <= az)
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v = btVector3(-uz, 0, ux);
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else
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v = btVector3(-uy, ux, 0);
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v.normalize();
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return v;
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}
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void btDeformableContactProjection::update()
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{
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///solve rigid body constraints
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m_world->getSolverInfo().m_numIterations = 10;
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m_world->btMultiBodyDynamicsWorld::solveConstraints(m_world->getSolverInfo());
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// loop through constraints to set constrained values
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for (auto& it : m_constraints)
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{
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btAlignedObjectArray<DeformableFrictionConstraint>& frictions = m_frictions[it.first];
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btAlignedObjectArray<DeformableContactConstraint>& constraints = it.second;
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for (int i = 0; i < constraints.size(); ++i)
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{
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DeformableContactConstraint& constraint = constraints[i];
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DeformableFrictionConstraint& friction = frictions[i];
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for (int j = 0; j < constraint.m_contact.size(); ++j)
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{
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if (constraint.m_contact[j] == nullptr)
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{
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// nothing needs to be done for dirichelet constraints
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continue;
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}
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const btSoftBody::RContact* c = constraint.m_contact[j];
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const btSoftBody::sCti& cti = c->m_cti;
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// normal jacobian is precompute but tangent jacobian is not
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const btMultiBodyJacobianData& jacobianData_normal = constraint.m_normal_jacobian[j];
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const btMultiBodyJacobianData& jacobianData_complementary = friction.m_complementary_jacobian[j];
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if (cti.m_colObj->hasContactResponse())
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{
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btVector3 va(0, 0, 0);
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btRigidBody* rigidCol = 0;
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btMultiBodyLinkCollider* multibodyLinkCol = 0;
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const btScalar* deltaV_normal;
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// grab the velocity of the rigid body
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if (cti.m_colObj->getInternalType() == btCollisionObject::CO_RIGID_BODY)
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{
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rigidCol = (btRigidBody*)btRigidBody::upcast(cti.m_colObj);
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va = rigidCol ? (rigidCol->getVelocityInLocalPoint(c->m_c1)) * m_dt : btVector3(0, 0, 0);
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}
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else if (cti.m_colObj->getInternalType() == btCollisionObject::CO_FEATHERSTONE_LINK)
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{
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multibodyLinkCol = (btMultiBodyLinkCollider*)btMultiBodyLinkCollider::upcast(cti.m_colObj);
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if (multibodyLinkCol)
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{
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const int ndof = multibodyLinkCol->m_multiBody->getNumDofs() + 6;
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const btScalar* jac_normal = &jacobianData_normal.m_jacobians[0];
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deltaV_normal = &jacobianData_normal.m_deltaVelocitiesUnitImpulse[0];
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// add in the normal component of the va
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btScalar vel = 0.0;
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for (int k = 0; k < ndof; ++k)
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{
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vel += multibodyLinkCol->m_multiBody->getVelocityVector()[k] * jac_normal[k];
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}
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va = cti.m_normal * vel * m_dt;
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// add in complementary direction of va
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const btScalar* jac_complementary = &jacobianData_complementary.m_jacobians[0];
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vel = 0.0;
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for (int k = 0; k < ndof; ++k)
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{
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vel += multibodyLinkCol->m_multiBody->getVelocityVector()[k] * jac_complementary[k];
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}
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va += friction.m_complementaryDirection[j] * vel * m_dt;
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}
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}
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const btVector3 vb = c->m_node->m_v * m_dt;
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const btVector3 vr = vb - va;
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const btScalar dn = btDot(vr, cti.m_normal);
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btVector3 impulse = c->m_c0 * vr;
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const btVector3 impulse_normal = c->m_c0 * (cti.m_normal * dn);
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const btVector3 impulse_tangent = impulse - impulse_normal;
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// start friction handling
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// copy old data
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friction.m_impulse_prev[j] = friction.m_impulse[j];
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friction.m_dv_prev[j] = friction.m_dv[j];
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friction.m_static_prev[j] = friction.m_static[j];
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// get the current tangent direction
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btScalar local_tangent_norm = impulse_tangent.norm();
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btVector3 local_tangent_dir = btVector3(0,0,0);
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if (local_tangent_norm > SIMD_EPSILON)
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local_tangent_dir = impulse_tangent.normalized();
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// accumulated impulse on the rb in this and all prev cg iterations
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constraint.m_accumulated_normal_impulse[j] += impulse_normal.dot(cti.m_normal);
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const btScalar& accumulated_normal = constraint.m_accumulated_normal_impulse[j];
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// the total tangential impulse required to stop sliding
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btVector3 tangent = friction.m_accumulated_tangent_impulse[j] + impulse_tangent;
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btScalar tangent_norm = tangent.norm();
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if (accumulated_normal < 0)
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{
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friction.m_direction[j] = -local_tangent_dir;
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// do not allow switching from static friction to dynamic friction
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// it causes cg to explode
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if (-accumulated_normal*c->m_c3 < tangent_norm && friction.m_static_prev[j] == false && friction.m_released[j] == false)
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{
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friction.m_static[j] = false;
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friction.m_impulse[j] = -accumulated_normal*c->m_c3;
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}
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else
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{
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friction.m_static[j] = true;
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friction.m_impulse[j] = tangent_norm;
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}
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}
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else
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{
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friction.m_released[j] = true;
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friction.m_static[j] = false;
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friction.m_impulse[j] = 0;
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friction.m_direction[j] = btVector3(0,0,0);
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}
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friction.m_dv[j] = friction.m_impulse[j] * c->m_c2/m_dt;
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friction.m_accumulated_tangent_impulse[j] = -friction.m_impulse[j] * friction.m_direction[j];
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// the incremental impulse applied to rb in the tangential direction
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btVector3 incremental_tangent = (friction.m_impulse_prev[j] * friction.m_direction_prev[j])-(friction.m_impulse[j] * friction.m_direction[j]);
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// TODO cleanup
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if (1) // in the same CG solve, the set of constraits doesn't change
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{
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// c0 is the impulse matrix, c3 is 1 - the friction coefficient or 0, c4 is the contact hardness coefficient
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// dv = new_impulse + accumulated velocity change in previous CG iterations
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// so we have the invariant node->m_v = backupVelocity + dv;
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btScalar dvn = -accumulated_normal * c->m_c2/m_dt;
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// the following is equivalent
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/*
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btVector3 dv = -impulse_normal * c->m_c2/m_dt + c->m_node->m_v - backupVelocity[m_indices[c->m_node]];
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btScalar dvn = dv.dot(cti.m_normal);
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*/
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constraint.m_value[j] = dvn;
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// the incremental impulse:
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// in the normal direction it's the normal component of "impulse"
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// in the tangent direction it's the difference between the frictional impulse in the iteration and the previous iteration
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impulse = impulse_normal + incremental_tangent;
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if (cti.m_colObj->getInternalType() == btCollisionObject::CO_RIGID_BODY)
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{
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if (rigidCol)
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rigidCol->applyImpulse(impulse, c->m_c1);
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}
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else if (cti.m_colObj->getInternalType() == btCollisionObject::CO_FEATHERSTONE_LINK)
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{
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if (multibodyLinkCol)
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{
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double multiplier = 1;
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multibodyLinkCol->m_multiBody->applyDeltaVeeMultiDof(deltaV_normal, -impulse_normal.length() * multiplier);
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if (incremental_tangent.norm() > SIMD_EPSILON)
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{
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btMultiBodyJacobianData jacobian_tangent;
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btVector3 tangent = incremental_tangent.normalized();
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findJacobian(multibodyLinkCol, jacobian_tangent, c->m_node->m_x, tangent);
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const btScalar* deltaV_tangent = &jacobian_tangent.m_deltaVelocitiesUnitImpulse[0];
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multibodyLinkCol->m_multiBody->applyDeltaVeeMultiDof(deltaV_tangent, incremental_tangent.length() * multiplier);
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}
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}
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}
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}
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}
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}
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}
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}
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}
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void btDeformableContactProjection::setConstraints()
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{
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// set Dirichlet constraint
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for (int i = 0; i < m_softBodies.size(); ++i)
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{
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btSoftBody* psb = m_softBodies[i];
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for (int j = 0; j < psb->m_nodes.size(); ++j)
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{
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if (psb->m_nodes[j].m_im == 0)
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{
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btAlignedObjectArray<DeformableContactConstraint> c;
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c.push_back(DeformableContactConstraint(btVector3(1,0,0)));
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c.push_back(DeformableContactConstraint(btVector3(0,1,0)));
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c.push_back(DeformableContactConstraint(btVector3(0,0,1)));
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m_constraints[&(psb->m_nodes[j])] = c;
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btAlignedObjectArray<DeformableFrictionConstraint> f;
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f.push_back(DeformableFrictionConstraint());
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f.push_back(DeformableFrictionConstraint());
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f.push_back(DeformableFrictionConstraint());
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m_frictions[&(psb->m_nodes[j])] = f;
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}
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}
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}
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for (int i = 0; i < m_softBodies.size(); ++i)
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{
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btSoftBody* psb = m_softBodies[i];
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btMultiBodyJacobianData jacobianData_normal;
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btMultiBodyJacobianData jacobianData_complementary;
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for (int j = 0; j < psb->m_rcontacts.size(); ++j)
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{
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const btSoftBody::RContact& c = psb->m_rcontacts[j];
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// skip anchor points
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if (c.m_node->m_im == 0)
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{
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continue;
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}
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const btSoftBody::sCti& cti = c.m_cti;
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if (cti.m_colObj->hasContactResponse())
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{
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btVector3 va(0, 0, 0);
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btRigidBody* rigidCol = 0;
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btMultiBodyLinkCollider* multibodyLinkCol = 0;
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// grab the velocity of the rigid body
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if (cti.m_colObj->getInternalType() == btCollisionObject::CO_RIGID_BODY)
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{
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rigidCol = (btRigidBody*)btRigidBody::upcast(cti.m_colObj);
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va = rigidCol ? (rigidCol->getVelocityInLocalPoint(c.m_c1)) * m_dt : btVector3(0, 0, 0);
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}
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else if (cti.m_colObj->getInternalType() == btCollisionObject::CO_FEATHERSTONE_LINK)
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{
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multibodyLinkCol = (btMultiBodyLinkCollider*)btMultiBodyLinkCollider::upcast(cti.m_colObj);
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if (multibodyLinkCol)
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{
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findJacobian(multibodyLinkCol, jacobianData_normal, c.m_node->m_x, cti.m_normal);
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btScalar vel = 0.0;
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const btScalar* jac = &jacobianData_normal.m_jacobians[0];
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const int ndof = multibodyLinkCol->m_multiBody->getNumDofs() + 6;
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for (int j = 0; j < ndof; ++j)
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{
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vel += multibodyLinkCol->m_multiBody->getVelocityVector()[j] * jac[j];
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std::cout << multibodyLinkCol->m_multiBody->getVelocityVector()[j] << std::endl;
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std::cout << jac[j] << std::endl;
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}
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va = cti.m_normal * vel * m_dt;
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}
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}
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const btVector3 vb = c.m_node->m_v * m_dt;
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const btVector3 vr = vb - va;
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const btScalar dn = btDot(vr, cti.m_normal);
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if (dn < SIMD_EPSILON)
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{
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// find complementary jacobian
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btVector3 complementaryDirection;
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if (cti.m_colObj->getInternalType() == btCollisionObject::CO_FEATHERSTONE_LINK)
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{
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multibodyLinkCol = (btMultiBodyLinkCollider*)btMultiBodyLinkCollider::upcast(cti.m_colObj);
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if (multibodyLinkCol)
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{
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complementaryDirection = generateUnitOrthogonalVector(cti.m_normal);
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findJacobian(multibodyLinkCol, jacobianData_complementary, c.m_node->m_x, complementaryDirection);
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}
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}
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if (m_constraints.find(c.m_node) == m_constraints.end())
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{
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btAlignedObjectArray<DeformableContactConstraint> constraints;
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constraints.push_back(DeformableContactConstraint(c, jacobianData_normal));
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m_constraints[c.m_node] = constraints;
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btAlignedObjectArray<DeformableFrictionConstraint> frictions;
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frictions.push_back(DeformableFrictionConstraint(complementaryDirection, jacobianData_complementary));
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m_frictions[c.m_node] = frictions;
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}
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else
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{
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// group colinear constraints into one
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const btScalar angle_epsilon = 0.015192247; // less than 10 degree
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bool merged = false;
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btAlignedObjectArray<DeformableContactConstraint>& constraints = m_constraints[c.m_node];
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btAlignedObjectArray<DeformableFrictionConstraint>& frictions = m_frictions[c.m_node];
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for (int j = 0; j < constraints.size(); ++j)
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{
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const btAlignedObjectArray<btVector3>& dirs = constraints[j].m_direction;
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btScalar dot_prod = dirs[0].dot(cti.m_normal);
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if (std::abs(std::abs(dot_prod) - 1) < angle_epsilon)
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{
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// group the constraints
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constraints[j].append(c, jacobianData_normal);
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// push in an empty friction
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frictions[j].append();
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frictions[j].addJacobian(complementaryDirection, jacobianData_complementary);
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merged = true;
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break;
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}
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}
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const int dim = 3;
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// hard coded no more than 3 constraint directions
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if (!merged && constraints.size() < dim)
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{
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constraints.push_back(DeformableContactConstraint(c, jacobianData_normal));
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frictions.push_back(DeformableFrictionConstraint(complementaryDirection, jacobianData_complementary));
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}
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}
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}
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}
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}
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}
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}
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void btDeformableContactProjection::enforceConstraint(TVStack& x)
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{
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const int dim = 3;
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for (auto& it : m_constraints)
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{
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const btAlignedObjectArray<DeformableContactConstraint>& constraints = it.second;
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size_t i = m_indices[it.first];
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const btAlignedObjectArray<DeformableFrictionConstraint>& frictions = m_frictions[it.first];
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btAssert(constraints.size() <= dim);
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btAssert(constraints.size() > 0);
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if (constraints.size() == 1)
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{
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x[i] -= x[i].dot(constraints[0].m_direction[0]) * constraints[0].m_direction[0];
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for (int j = 0; j < constraints[0].m_direction.size(); ++j)
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x[i] += constraints[0].m_value[j] * constraints[0].m_direction[j];
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}
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else if (constraints.size() == 2)
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{
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btVector3 free_dir = btCross(constraints[0].m_direction[0], constraints[1].m_direction[0]);
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btAssert(free_dir.norm() > SIMD_EPSILON)
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free_dir.normalize();
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x[i] = x[i].dot(free_dir) * free_dir;
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for (int j = 0; j < constraints.size(); ++j)
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{
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for (int k = 0; k < constraints[j].m_direction.size(); ++k)
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{
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x[i] += constraints[j].m_value[k] * constraints[j].m_direction[k];
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}
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}
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}
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else
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{
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x[i].setZero();
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for (int j = 0; j < constraints.size(); ++j)
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{
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for (int k = 0; k < constraints[j].m_direction.size(); ++k)
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{
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x[i] += constraints[j].m_value[k] * constraints[j].m_direction[k];
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}
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}
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}
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// apply friction if the node is not constrained in all directions
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||||
if (constraints.size() < 3)
|
||||
{
|
||||
for (int f = 0; f < frictions.size(); ++f)
|
||||
{
|
||||
const DeformableFrictionConstraint& friction= frictions[f];
|
||||
for (int j = 0; j < friction.m_direction.size(); ++j)
|
||||
{
|
||||
// clear the old constraint
|
||||
if (friction.m_static_prev[j] == true)
|
||||
{
|
||||
x[i] -= friction.m_direction_prev[j] * friction.m_dv_prev[j];
|
||||
}
|
||||
// add the new constraint
|
||||
if (friction.m_static[j] == true)
|
||||
{
|
||||
x[i] += friction.m_direction[j] * friction.m_dv[j];
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
void btDeformableContactProjection::project(TVStack& x)
|
||||
{
|
||||
const int dim = 3;
|
||||
for (auto& it : m_constraints)
|
||||
{
|
||||
const btAlignedObjectArray<DeformableContactConstraint>& constraints = it.second;
|
||||
size_t i = m_indices[it.first];
|
||||
btAlignedObjectArray<DeformableFrictionConstraint>& frictions = m_frictions[it.first];
|
||||
btAssert(constraints.size() <= dim);
|
||||
btAssert(constraints.size() > 0);
|
||||
if (constraints.size() == 1)
|
||||
{
|
||||
x[i] -= x[i].dot(constraints[0].m_direction[0]) * constraints[0].m_direction[0];
|
||||
}
|
||||
else if (constraints.size() == 2)
|
||||
{
|
||||
btVector3 free_dir = btCross(constraints[0].m_direction[0], constraints[1].m_direction[0]);
|
||||
btAssert(free_dir.norm() > SIMD_EPSILON)
|
||||
free_dir.normalize();
|
||||
x[i] = x[i].dot(free_dir) * free_dir;
|
||||
}
|
||||
else
|
||||
x[i].setZero();
|
||||
|
||||
// apply friction if the node is not constrained in all directions
|
||||
if (constraints.size() < 3)
|
||||
{
|
||||
bool has_static_constraint = false;
|
||||
for (int f = 0; f < frictions.size(); ++f)
|
||||
{
|
||||
DeformableFrictionConstraint& friction= frictions[f];
|
||||
for (int j = 0; j < friction.m_static.size(); ++j)
|
||||
has_static_constraint = has_static_constraint || friction.m_static[j];
|
||||
}
|
||||
|
||||
for (int f = 0; f < frictions.size(); ++f)
|
||||
{
|
||||
DeformableFrictionConstraint& friction= frictions[f];
|
||||
for (int j = 0; j < friction.m_direction.size(); ++j)
|
||||
{
|
||||
// clear the old friction force
|
||||
if (friction.m_static_prev[j] == false)
|
||||
{
|
||||
x[i] -= friction.m_direction_prev[j] * friction.m_impulse_prev[j];
|
||||
}
|
||||
|
||||
// only add to the rhs if there is no static friction constraint on the node
|
||||
if (friction.m_static[j] == false && !has_static_constraint)
|
||||
{
|
||||
x[i] += friction.m_direction[j] * friction.m_impulse[j];
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
void btDeformableContactProjection::reinitialize(bool nodeUpdated)
|
||||
{
|
||||
btCGProjection::reinitialize(nodeUpdated);
|
||||
m_constraints.clear();
|
||||
m_frictions.clear();
|
||||
}
|
||||
|
||||
|
||||
|
||||
Reference in New Issue
Block a user