btDeformableMultiBodyConstraintSolver.cpp

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/*
 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 "btDeformableMultiBodyConstraintSolver.h"
#include "BulletReducedDeformableBody/btReducedDeformableBodySolver.h"
#include <iostream>
 
// override the iterations method to include deformable/multibody contact
btScalar btDeformableMultiBodyConstraintSolver::solveDeformableGroupIterations(btCollisionObject** bodies, int numBodies, btCollisionObject** deformableBodies, int numDeformableBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer)
{
        {
                // pair deformable body with solver body
                pairDeformableAndSolverBody(bodies, numBodies, numDeformableBodies, infoGlobal);
 
                solveGroupCacheFriendlySplitImpulseIterations(bodies, numBodies, deformableBodies, numDeformableBodies, manifoldPtr, numManifolds, constraints, numConstraints, infoGlobal, debugDrawer);
 
                int maxIterations = m_maxOverrideNumSolverIterations > infoGlobal.m_numIterations ? m_maxOverrideNumSolverIterations : infoGlobal.m_numIterations;
                for (int iteration = 0; iteration < maxIterations; iteration++)
                {
                        // rigid bodies are solved using solver body velocity, but rigid/deformable contact directly uses the velocity of the actual rigid body. So we have to do the following: Solve one iteration of the rigid/rigid contact, get the updated velocity in the solver body and update the velocity of the underlying rigid body. Then solve the rigid/deformable contact. Finally, grab the (once again) updated rigid velocity and update the velocity of the wrapping solver body
 
                        // solve rigid/rigid in solver body
                        m_leastSquaresResidual = solveSingleIteration(iteration, bodies, numBodies, manifoldPtr, numManifolds, constraints, numConstraints, infoGlobal, debugDrawer);
                        // solver body velocity -> rigid body velocity
                        solverBodyWriteBack(infoGlobal);
                        btScalar deformableResidual = m_deformableSolver->solveContactConstraints(deformableBodies, numDeformableBodies, infoGlobal);
                        // update rigid body velocity in rigid/deformable contact
                        m_leastSquaresResidual = btMax(m_leastSquaresResidual, deformableResidual);
                        // solver body velocity <- rigid body velocity
                        writeToSolverBody(bodies, numBodies, infoGlobal);
 
 
                        // std::cout << "------------Iteration " << iteration << "------------\n";
                        // std::cout << "m_leastSquaresResidual: " << m_leastSquaresResidual << "\n";
 
                        if (m_leastSquaresResidual <= infoGlobal.m_leastSquaresResidualThreshold || (iteration >= (maxIterations - 1)))
                        {
#ifdef VERBOSE_RESIDUAL_PRINTF
                                if (iteration >= (maxIterations - 1))
                                        printf("residual = %f at iteration #%d\n", m_leastSquaresResidual, iteration);
#endif
                                m_analyticsData.m_numSolverCalls++;
                                m_analyticsData.m_numIterationsUsed = iteration + 1;
                                m_analyticsData.m_islandId = -2;
                                if (numBodies > 0)
                                        m_analyticsData.m_islandId = bodies[0]->getCompanionId();
                                m_analyticsData.m_numBodies = numBodies;
                                m_analyticsData.m_numContactManifolds = numManifolds;
                                m_analyticsData.m_remainingLeastSquaresResidual = m_leastSquaresResidual;
                                
                                m_deformableSolver->deformableBodyInternalWriteBack();
                                // std::cout << "[===================Next Step===================]\n";
                                break;
                        }
                }
        }
        return 0.f;
}
 
void btDeformableMultiBodyConstraintSolver::solveDeformableBodyGroup(btCollisionObject** bodies, int numBodies, btCollisionObject** deformableBodies, int numDeformableBodies, btPersistentManifold** manifold, int numManifolds, btTypedConstraint** constraints, int numConstraints, btMultiBodyConstraint** multiBodyConstraints, int numMultiBodyConstraints, const btContactSolverInfo& info, btIDebugDraw* debugDrawer, btDispatcher* dispatcher)
{
        m_tmpMultiBodyConstraints = multiBodyConstraints;
        m_tmpNumMultiBodyConstraints = numMultiBodyConstraints;
 
        // inherited from MultiBodyConstraintSolver
        solveGroupCacheFriendlySetup(bodies, numBodies, manifold, numManifolds, constraints, numConstraints, info, debugDrawer);
 
        // overriden
        solveDeformableGroupIterations(bodies, numBodies, deformableBodies, numDeformableBodies, manifold, numManifolds, constraints, numConstraints, info, debugDrawer);
 
        // inherited from MultiBodyConstraintSolver
        solveGroupCacheFriendlyFinish(bodies, numBodies, info);
 
        m_tmpMultiBodyConstraints = 0;
        m_tmpNumMultiBodyConstraints = 0;
}
 
void btDeformableMultiBodyConstraintSolver::writeToSolverBody(btCollisionObject** bodies, int numBodies, const btContactSolverInfo& infoGlobal)
{
        // reduced soft body solver directly modifies the solver body
        if (m_deformableSolver->isReducedSolver())
        {
                return;
        }
 
        for (int i = 0; i < numBodies; i++)
        {
                int bodyId = getOrInitSolverBody(*bodies[i], infoGlobal.m_timeStep);
 
                btRigidBody* body = btRigidBody::upcast(bodies[i]);
                if (body && body->getInvMass())
                {
                        btSolverBody& solverBody = m_tmpSolverBodyPool[bodyId];
                        solverBody.m_linearVelocity = body->getLinearVelocity() - solverBody.m_deltaLinearVelocity;
                        solverBody.m_angularVelocity = body->getAngularVelocity() - solverBody.m_deltaAngularVelocity;
                }
        }
}
 
void btDeformableMultiBodyConstraintSolver::solverBodyWriteBack(const btContactSolverInfo& infoGlobal)
{
        // reduced soft body solver directly modifies the solver body
        if (m_deformableSolver->isReducedSolver())
        {
                return;
        }
 
        for (int i = 0; i < m_tmpSolverBodyPool.size(); i++)
        {
                btRigidBody* body = m_tmpSolverBodyPool[i].m_originalBody;
                if (body)
                {
                        m_tmpSolverBodyPool[i].m_originalBody->setLinearVelocity(m_tmpSolverBodyPool[i].m_linearVelocity + m_tmpSolverBodyPool[i].m_deltaLinearVelocity);
                        m_tmpSolverBodyPool[i].m_originalBody->setAngularVelocity(m_tmpSolverBodyPool[i].m_angularVelocity + m_tmpSolverBodyPool[i].m_deltaAngularVelocity);
                }
        }
}
 
 
void btDeformableMultiBodyConstraintSolver::pairDeformableAndSolverBody(btCollisionObject** bodies, int numBodies, int numDeformableBodies, const btContactSolverInfo& infoGlobal)
{
        if (!m_deformableSolver->isReducedSolver())
        {
                return;
        }
 
        btReducedDeformableBodySolver* solver = static_cast<btReducedDeformableBodySolver*>(m_deformableSolver);
        
        for (int i = 0; i < numDeformableBodies; ++i)
        {
                for (int k = 0; k < solver->m_nodeRigidConstraints[i].size(); ++k)
    {
      btReducedDeformableNodeRigidContactConstraint& constraint = solver->m_nodeRigidConstraints[i][k];
 
                        if (!constraint.m_contact->m_cti.m_colObj->isStaticObject())
                        {
                                btCollisionObject& col_obj = const_cast<btCollisionObject&>(*constraint.m_contact->m_cti.m_colObj);
 
                                // object index in the solver body pool
                                int bodyId = getOrInitSolverBody(col_obj, infoGlobal.m_timeStep);
                                
                                const btRigidBody* body = btRigidBody::upcast(bodies[bodyId]);
                                if (body && body->getInvMass())
                                {
                                                // std::cout << "Node: " << constraint.m_node->index << ", body: " << bodyId << "\n";
                                        btSolverBody& solverBody = m_tmpSolverBodyPool[bodyId];
                                        constraint.setSolverBody(bodyId, solverBody);
                                }
                        }
    }
 
                // for (int j = 0; j < numBodies; j++)
                // {
                //      int bodyId = getOrInitSolverBody(*bodies[j], infoGlobal.m_timeStep);
 
                //      btRigidBody* body = btRigidBody::upcast(bodies[j]);
                //      if (body && body->getInvMass())
                //      {
                //              btSolverBody& solverBody = m_tmpSolverBodyPool[bodyId];
                //              m_deformableSolver->pairConstraintWithSolverBody(i, bodyId, solverBody);
                //      }
                // }    
        }
}
 
void btDeformableMultiBodyConstraintSolver::solveGroupCacheFriendlySplitImpulseIterations(btCollisionObject** bodies, int numBodies, btCollisionObject** deformableBodies, int numDeformableBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer)
{
        BT_PROFILE("solveGroupCacheFriendlySplitImpulseIterations");
        int iteration;
        if (infoGlobal.m_splitImpulse)
        {
                {
                        for (iteration = 0; iteration < infoGlobal.m_numIterations; iteration++)
                        {
                                btScalar leastSquaresResidual = 0.f;
                                {
                                        int numPoolConstraints = m_tmpSolverContactConstraintPool.size();
                                        int j;
                                        for (j = 0; j < numPoolConstraints; j++)
                                        {
                                                const btSolverConstraint& solveManifold = m_tmpSolverContactConstraintPool[m_orderTmpConstraintPool[j]];
 
                                                btScalar residual = resolveSplitPenetrationImpulse(m_tmpSolverBodyPool[solveManifold.m_solverBodyIdA], m_tmpSolverBodyPool[solveManifold.m_solverBodyIdB], solveManifold);
                                                leastSquaresResidual = btMax(leastSquaresResidual, residual * residual);
                                        }
                                        // solve the position correction between deformable and rigid/multibody
                                        //                    btScalar residual = m_deformableSolver->solveSplitImpulse(infoGlobal);
                                        btScalar residual = m_deformableSolver->m_objective->m_projection.solveSplitImpulse(deformableBodies, numDeformableBodies, infoGlobal);
                                        leastSquaresResidual = btMax(leastSquaresResidual, residual * residual);
                                }
                                if (leastSquaresResidual <= infoGlobal.m_leastSquaresResidualThreshold || iteration >= (infoGlobal.m_numIterations - 1))
                                {
#ifdef VERBOSE_RESIDUAL_PRINTF
                                        if (iteration >= (infoGlobal.m_numIterations - 1))
                                                printf("split impulse residual = %f at iteration #%d\n", leastSquaresResidual, iteration);
#endif
                                        break;
                                }
                        }
                }
        }
}