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Diffstat (limited to 'extern/bullet2/src/BulletSoftBody/btDeformableBodySolver.cpp')
| -rw-r--r-- | extern/bullet2/src/BulletSoftBody/btDeformableBodySolver.cpp | 506 |
1 files changed, 506 insertions, 0 deletions
diff --git a/extern/bullet2/src/BulletSoftBody/btDeformableBodySolver.cpp b/extern/bullet2/src/BulletSoftBody/btDeformableBodySolver.cpp new file mode 100644 index 00000000000..4b11fccecba --- /dev/null +++ b/extern/bullet2/src/BulletSoftBody/btDeformableBodySolver.cpp @@ -0,0 +1,506 @@ +/* + Written by Xuchen Han <xuchenhan2015@u.northwestern.edu> + + Bullet Continuous Collision Detection and Physics Library + Copyright (c) 2019 Google Inc. http://bulletphysics.org + This software is provided 'as-is', without any express or implied warranty. + In no event will the authors be held liable for any damages arising from the use of this software. + Permission is granted to anyone to use this software for any purpose, + including commercial applications, and to alter it and redistribute it freely, + subject to the following restrictions: + 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. + 2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. + 3. This notice may not be removed or altered from any source distribution. + */ + +#include <stdio.h> +#include <limits> +#include "btDeformableBodySolver.h" +#include "btSoftBodyInternals.h" +#include "LinearMath/btQuickprof.h" +static const int kMaxConjugateGradientIterations = 300; +btDeformableBodySolver::btDeformableBodySolver() + : m_numNodes(0), m_cg(kMaxConjugateGradientIterations), m_cr(kMaxConjugateGradientIterations), m_maxNewtonIterations(1), m_newtonTolerance(1e-4), m_lineSearch(false), m_useProjection(false) +{ + m_objective = new btDeformableBackwardEulerObjective(m_softBodies, m_backupVelocity); +} + +btDeformableBodySolver::~btDeformableBodySolver() +{ + delete m_objective; +} + +void btDeformableBodySolver::solveDeformableConstraints(btScalar solverdt) +{ + BT_PROFILE("solveDeformableConstraints"); + if (!m_implicit) + { + m_objective->computeResidual(solverdt, m_residual); + m_objective->applyDynamicFriction(m_residual); + if (m_useProjection) + { + computeStep(m_dv, m_residual); + } + else + { + TVStack rhs, x; + m_objective->addLagrangeMultiplierRHS(m_residual, m_dv, rhs); + m_objective->addLagrangeMultiplier(m_dv, x); + m_objective->m_preconditioner->reinitialize(true); + computeStep(x, rhs); + for (int i = 0; i < m_dv.size(); ++i) + { + m_dv[i] = x[i]; + } + } + updateVelocity(); + } + else + { + for (int i = 0; i < m_maxNewtonIterations; ++i) + { + updateState(); + // add the inertia term in the residual + int counter = 0; + for (int k = 0; k < m_softBodies.size(); ++k) + { + btSoftBody* psb = m_softBodies[k]; + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + if (psb->m_nodes[j].m_im > 0) + { + m_residual[counter] = (-1. / psb->m_nodes[j].m_im) * m_dv[counter]; + } + ++counter; + } + } + + m_objective->computeResidual(solverdt, m_residual); + if (m_objective->computeNorm(m_residual) < m_newtonTolerance && i > 0) + { + break; + } + // todo xuchenhan@: this really only needs to be calculated once + m_objective->applyDynamicFriction(m_residual); + if (m_lineSearch) + { + btScalar inner_product = computeDescentStep(m_ddv, m_residual); + btScalar alpha = 0.01, beta = 0.5; // Boyd & Vandenberghe suggested alpha between 0.01 and 0.3, beta between 0.1 to 0.8 + btScalar scale = 2; + btScalar f0 = m_objective->totalEnergy(solverdt) + kineticEnergy(), f1, f2; + backupDv(); + do + { + scale *= beta; + if (scale < 1e-8) + { + return; + } + updateEnergy(scale); + f1 = m_objective->totalEnergy(solverdt) + kineticEnergy(); + f2 = f0 - alpha * scale * inner_product; + } while (!(f1 < f2 + SIMD_EPSILON)); // if anything here is nan then the search continues + revertDv(); + updateDv(scale); + } + else + { + computeStep(m_ddv, m_residual); + updateDv(); + } + for (int j = 0; j < m_numNodes; ++j) + { + m_ddv[j].setZero(); + m_residual[j].setZero(); + } + } + updateVelocity(); + } +} + +btScalar btDeformableBodySolver::kineticEnergy() +{ + btScalar ke = 0; + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + btSoftBody::Node& node = psb->m_nodes[j]; + if (node.m_im > 0) + { + ke += m_dv[node.index].length2() * 0.5 / node.m_im; + } + } + } + return ke; +} + +void btDeformableBodySolver::backupDv() +{ + m_backup_dv.resize(m_dv.size()); + for (int i = 0; i < m_backup_dv.size(); ++i) + { + m_backup_dv[i] = m_dv[i]; + } +} + +void btDeformableBodySolver::revertDv() +{ + for (int i = 0; i < m_backup_dv.size(); ++i) + { + m_dv[i] = m_backup_dv[i]; + } +} + +void btDeformableBodySolver::updateEnergy(btScalar scale) +{ + for (int i = 0; i < m_dv.size(); ++i) + { + m_dv[i] = m_backup_dv[i] + scale * m_ddv[i]; + } + updateState(); +} + +btScalar btDeformableBodySolver::computeDescentStep(TVStack& ddv, const TVStack& residual, bool verbose) +{ + m_cg.solve(*m_objective, ddv, residual, false); + btScalar inner_product = m_cg.dot(residual, m_ddv); + btScalar res_norm = m_objective->computeNorm(residual); + btScalar tol = 1e-5 * res_norm * m_objective->computeNorm(m_ddv); + if (inner_product < -tol) + { + if (verbose) + { + std::cout << "Looking backwards!" << std::endl; + } + for (int i = 0; i < m_ddv.size(); ++i) + { + m_ddv[i] = -m_ddv[i]; + } + inner_product = -inner_product; + } + else if (std::abs(inner_product) < tol) + { + if (verbose) + { + std::cout << "Gradient Descent!" << std::endl; + } + btScalar scale = m_objective->computeNorm(m_ddv) / res_norm; + for (int i = 0; i < m_ddv.size(); ++i) + { + m_ddv[i] = scale * residual[i]; + } + inner_product = scale * res_norm * res_norm; + } + return inner_product; +} + +void btDeformableBodySolver::updateState() +{ + updateVelocity(); + updateTempPosition(); +} + +void btDeformableBodySolver::updateDv(btScalar scale) +{ + for (int i = 0; i < m_numNodes; ++i) + { + m_dv[i] += scale * m_ddv[i]; + } +} + +void btDeformableBodySolver::computeStep(TVStack& ddv, const TVStack& residual) +{ + if (m_useProjection) + m_cg.solve(*m_objective, ddv, residual, false); + else + m_cr.solve(*m_objective, ddv, residual, false); +} + +void btDeformableBodySolver::reinitialize(const btAlignedObjectArray<btSoftBody*>& softBodies, btScalar dt) +{ + m_softBodies.copyFromArray(softBodies); + bool nodeUpdated = updateNodes(); + + if (nodeUpdated) + { + m_dv.resize(m_numNodes, btVector3(0, 0, 0)); + m_ddv.resize(m_numNodes, btVector3(0, 0, 0)); + m_residual.resize(m_numNodes, btVector3(0, 0, 0)); + m_backupVelocity.resize(m_numNodes, btVector3(0, 0, 0)); + } + + // need to setZero here as resize only set value for newly allocated items + for (int i = 0; i < m_numNodes; ++i) + { + m_dv[i].setZero(); + m_ddv[i].setZero(); + m_residual[i].setZero(); + } + + if (dt > 0) + { + m_dt = dt; + } + m_objective->reinitialize(nodeUpdated, dt); + updateSoftBodies(); +} + +void btDeformableBodySolver::setConstraints(const btContactSolverInfo& infoGlobal) +{ + BT_PROFILE("setConstraint"); + m_objective->setConstraints(infoGlobal); +} + +btScalar btDeformableBodySolver::solveContactConstraints(btCollisionObject** deformableBodies, int numDeformableBodies, const btContactSolverInfo& infoGlobal) +{ + BT_PROFILE("solveContactConstraints"); + btScalar maxSquaredResidual = m_objective->m_projection.update(deformableBodies, numDeformableBodies, infoGlobal); + return maxSquaredResidual; +} + +void btDeformableBodySolver::updateVelocity() +{ + int counter = 0; + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + psb->m_maxSpeedSquared = 0; + if (!psb->isActive()) + { + counter += psb->m_nodes.size(); + continue; + } + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + // set NaN to zero; + if (m_dv[counter] != m_dv[counter]) + { + m_dv[counter].setZero(); + } + if (m_implicit) + { + psb->m_nodes[j].m_v = m_backupVelocity[counter] + m_dv[counter]; + } + else + { + psb->m_nodes[j].m_v = m_backupVelocity[counter] + m_dv[counter] - psb->m_nodes[j].m_splitv; + } + psb->m_maxSpeedSquared = btMax(psb->m_maxSpeedSquared, psb->m_nodes[j].m_v.length2()); + ++counter; + } + } +} + +void btDeformableBodySolver::updateTempPosition() +{ + int counter = 0; + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + if (!psb->isActive()) + { + counter += psb->m_nodes.size(); + continue; + } + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + psb->m_nodes[j].m_q = psb->m_nodes[j].m_x + m_dt * (psb->m_nodes[j].m_v + psb->m_nodes[j].m_splitv); + ++counter; + } + psb->updateDeformation(); + } +} + +void btDeformableBodySolver::backupVelocity() +{ + int counter = 0; + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + m_backupVelocity[counter++] = psb->m_nodes[j].m_v; + } + } +} + +void btDeformableBodySolver::setupDeformableSolve(bool implicit) +{ + int counter = 0; + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + if (!psb->isActive()) + { + counter += psb->m_nodes.size(); + continue; + } + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + if (implicit) + { + // setting the initial guess for newton, need m_dv = v_{n+1} - v_n for dofs that are in constraint. + if (psb->m_nodes[j].m_v == m_backupVelocity[counter]) + m_dv[counter].setZero(); + else + m_dv[counter] = psb->m_nodes[j].m_v - psb->m_nodes[j].m_vn; + m_backupVelocity[counter] = psb->m_nodes[j].m_vn; + } + else + { + m_dv[counter] = psb->m_nodes[j].m_v + psb->m_nodes[j].m_splitv - m_backupVelocity[counter]; + } + psb->m_nodes[j].m_v = m_backupVelocity[counter]; + ++counter; + } + } +} + +void btDeformableBodySolver::revertVelocity() +{ + int counter = 0; + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + psb->m_nodes[j].m_v = m_backupVelocity[counter++]; + } + } +} + +bool btDeformableBodySolver::updateNodes() +{ + int numNodes = 0; + for (int i = 0; i < m_softBodies.size(); ++i) + numNodes += m_softBodies[i]->m_nodes.size(); + if (numNodes != m_numNodes) + { + m_numNodes = numNodes; + return true; + } + return false; +} + +void btDeformableBodySolver::predictMotion(btScalar solverdt) +{ + // apply explicit forces to velocity + if (m_implicit) + { + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + if (psb->isActive()) + { + for (int j = 0; j < psb->m_nodes.size(); ++j) + { + psb->m_nodes[j].m_q = psb->m_nodes[j].m_x + psb->m_nodes[j].m_v * solverdt; + } + } + } + } + m_objective->applyExplicitForce(m_residual); + for (int i = 0; i < m_softBodies.size(); ++i) + { + btSoftBody* psb = m_softBodies[i]; + + if (psb->isActive()) + { + // predict motion for collision detection + predictDeformableMotion(psb, solverdt); + } + } +} + +void btDeformableBodySolver::predictDeformableMotion(btSoftBody* psb, btScalar dt) +{ + BT_PROFILE("btDeformableBodySolver::predictDeformableMotion"); + int i, ni; + + /* Update */ + if (psb->m_bUpdateRtCst) + { + psb->m_bUpdateRtCst = false; + psb->updateConstants(); + psb->m_fdbvt.clear(); + if (psb->m_cfg.collisions & btSoftBody::fCollision::SDF_RD) + { + psb->initializeFaceTree(); + } + } + + /* Prepare */ + psb->m_sst.sdt = dt * psb->m_cfg.timescale; + psb->m_sst.isdt = 1 / psb->m_sst.sdt; + psb->m_sst.velmrg = psb->m_sst.sdt * 3; + psb->m_sst.radmrg = psb->getCollisionShape()->getMargin(); + psb->m_sst.updmrg = psb->m_sst.radmrg * (btScalar)0.25; + /* Bounds */ + psb->updateBounds(); + + /* Integrate */ + // do not allow particles to move more than the bounding box size + btScalar max_v = (psb->m_bounds[1] - psb->m_bounds[0]).norm() / dt; + for (i = 0, ni = psb->m_nodes.size(); i < ni; ++i) + { + btSoftBody::Node& n = psb->m_nodes[i]; + // apply drag + n.m_v *= (1 - psb->m_cfg.drag); + // scale velocity back + if (m_implicit) + { + n.m_q = n.m_x; + } + else + { + if (n.m_v.norm() > max_v) + { + n.m_v.safeNormalize(); + n.m_v *= max_v; + } + n.m_q = n.m_x + n.m_v * dt; + } + n.m_splitv.setZero(); + n.m_constrained = false; + } + + /* Nodes */ + psb->updateNodeTree(true, true); + if (!psb->m_fdbvt.empty()) + { + psb->updateFaceTree(true, true); + } + /* Clear contacts */ + psb->m_nodeRigidContacts.resize(0); + psb->m_faceRigidContacts.resize(0); + psb->m_faceNodeContacts.resize(0); + /* Optimize dbvt's */ + // psb->m_ndbvt.optimizeIncremental(1); + // psb->m_fdbvt.optimizeIncremental(1); +} + +void btDeformableBodySolver::updateSoftBodies() +{ + BT_PROFILE("updateSoftBodies"); + for (int i = 0; i < m_softBodies.size(); i++) + { + btSoftBody* psb = (btSoftBody*)m_softBodies[i]; + if (psb->isActive()) + { + psb->updateNormals(); + } + } +} + +void btDeformableBodySolver::setImplicit(bool implicit) +{ + m_implicit = implicit; + m_objective->setImplicit(implicit); +} + +void btDeformableBodySolver::setLineSearch(bool lineSearch) +{ + m_lineSearch = lineSearch; +} |