btMultiBodyConstraint.cpp

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#include "btMultiBodyConstraint.h"
#include "BulletDynamics/Dynamics/btRigidBody.h"
#include "btMultiBodyPoint2Point.h"  //for testing (BTMBP2PCONSTRAINT_BLOCK_ANGULAR_MOTION_TEST macro)
 
btMultiBodyConstraint::btMultiBodyConstraint(btMultiBody* bodyA, btMultiBody* bodyB, int linkA, int linkB, int numRows, bool isUnilateral, int type)
        : m_bodyA(bodyA),
          m_bodyB(bodyB),
          m_linkA(linkA),
          m_linkB(linkB),
          m_type(type),
          m_numRows(numRows),
          m_jacSizeA(0),
          m_jacSizeBoth(0),
          m_isUnilateral(isUnilateral),
          m_numDofsFinalized(-1),
          m_maxAppliedImpulse(100)
{
}
 
void btMultiBodyConstraint::updateJacobianSizes()
{
        if (m_bodyA)
        {
                m_jacSizeA = (6 + m_bodyA->getNumDofs());
        }
 
        if (m_bodyB)
        {
                m_jacSizeBoth = m_jacSizeA + 6 + m_bodyB->getNumDofs();
        }
        else
                m_jacSizeBoth = m_jacSizeA;
}
 
void btMultiBodyConstraint::allocateJacobiansMultiDof()
{
        updateJacobianSizes();
 
        m_posOffset = ((1 + m_jacSizeBoth) * m_numRows);
        m_data.resize((2 + m_jacSizeBoth) * m_numRows);
}
 
btMultiBodyConstraint::~btMultiBodyConstraint()
{
}
 
void btMultiBodyConstraint::applyDeltaVee(btMultiBodyJacobianData& data, btScalar* delta_vee, btScalar impulse, int velocityIndex, int ndof)
{
        for (int i = 0; i < ndof; ++i)
                data.m_deltaVelocities[velocityIndex + i] += delta_vee[i] * impulse;
}
 
btScalar btMultiBodyConstraint::fillMultiBodyConstraint(btMultiBodySolverConstraint& solverConstraint,
                                                                                                                btMultiBodyJacobianData& data,
                                                                                                                btScalar* jacOrgA, btScalar* jacOrgB,
                                                                                                                const btVector3& constraintNormalAng,
                                                                                                                const btVector3& constraintNormalLin,
                                                                                                                const btVector3& posAworld, const btVector3& posBworld,
                                                                                                                btScalar posError,
                                                                                                                const btContactSolverInfo& infoGlobal,
                                                                                                                btScalar lowerLimit, btScalar upperLimit,
                                                                                                                bool angConstraint,
                                                                                                                btScalar relaxation,
                                                                                                                bool isFriction, btScalar desiredVelocity, btScalar cfmSlip,
                                                                                                                btScalar damping)
{
        solverConstraint.m_multiBodyA = m_bodyA;
        solverConstraint.m_multiBodyB = m_bodyB;
        solverConstraint.m_linkA = m_linkA;
        solverConstraint.m_linkB = m_linkB;
 
        btMultiBody* multiBodyA = solverConstraint.m_multiBodyA;
        btMultiBody* multiBodyB = solverConstraint.m_multiBodyB;
 
        btSolverBody* bodyA = multiBodyA ? 0 : &data.m_solverBodyPool->at(solverConstraint.m_solverBodyIdA);
        btSolverBody* bodyB = multiBodyB ? 0 : &data.m_solverBodyPool->at(solverConstraint.m_solverBodyIdB);
 
        btRigidBody* rb0 = multiBodyA ? 0 : bodyA->m_originalBody;
        btRigidBody* rb1 = multiBodyB ? 0 : bodyB->m_originalBody;
 
        btVector3 rel_pos1, rel_pos2;  //these two used to be inited to posAworld and posBworld (respectively) but it does not seem necessary
        if (bodyA)
                rel_pos1 = posAworld - bodyA->getWorldTransform().getOrigin();
        if (bodyB)
                rel_pos2 = posBworld - bodyB->getWorldTransform().getOrigin();
 
        if (multiBodyA)
        {
                if (solverConstraint.m_linkA < 0)
                {
                        rel_pos1 = posAworld - multiBodyA->getBasePos();
                }
                else
                {
                        rel_pos1 = posAworld - multiBodyA->getLink(solverConstraint.m_linkA).m_cachedWorldTransform.getOrigin();
                }
 
                const int ndofA = multiBodyA->getNumDofs() + 6;
 
                solverConstraint.m_deltaVelAindex = multiBodyA->getCompanionId();
 
                if (solverConstraint.m_deltaVelAindex < 0)
                {
                        solverConstraint.m_deltaVelAindex = data.m_deltaVelocities.size();
                        multiBodyA->setCompanionId(solverConstraint.m_deltaVelAindex);
                        data.m_deltaVelocities.resize(data.m_deltaVelocities.size() + ndofA);
                }
                else
                {
                        btAssert(data.m_deltaVelocities.size() >= solverConstraint.m_deltaVelAindex + ndofA);
                }
 
                //determine jacobian of this 1D constraint in terms of multibodyA's degrees of freedom
                //resize..
                solverConstraint.m_jacAindex = data.m_jacobians.size();
                data.m_jacobians.resize(data.m_jacobians.size() + ndofA);
                //copy/determine
                if (jacOrgA)
                {
                        for (int i = 0; i < ndofA; i++)
                                data.m_jacobians[solverConstraint.m_jacAindex + i] = jacOrgA[i];
                }
                else
                {
                        btScalar* jac1 = &data.m_jacobians[solverConstraint.m_jacAindex];
                        //multiBodyA->fillContactJacobianMultiDof(solverConstraint.m_linkA, posAworld, constraintNormalLin, jac1, data.scratch_r, data.scratch_v, data.scratch_m);
                        multiBodyA->fillConstraintJacobianMultiDof(solverConstraint.m_linkA, posAworld, constraintNormalAng, constraintNormalLin, jac1, data.scratch_r, data.scratch_v, data.scratch_m);
                }
 
                //determine the velocity response of multibodyA to reaction impulses of this constraint (i.e. A[i,i] for i=1,...n_con: multibody's inverse inertia with respect to this 1D constraint)
                //resize..
                data.m_deltaVelocitiesUnitImpulse.resize(data.m_deltaVelocitiesUnitImpulse.size() + ndofA);  //=> each constraint row has the constrained tree dofs allocated in m_deltaVelocitiesUnitImpulse
                btAssert(data.m_jacobians.size() == data.m_deltaVelocitiesUnitImpulse.size());
                btScalar* delta = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
                //determine..
                multiBodyA->calcAccelerationDeltasMultiDof(&data.m_jacobians[solverConstraint.m_jacAindex], delta, data.scratch_r, data.scratch_v);
 
                btVector3 torqueAxis0;
                if (angConstraint)
                {
                        torqueAxis0 = constraintNormalAng;
                }
                else
                {
                        torqueAxis0 = rel_pos1.cross(constraintNormalLin);
                }
                solverConstraint.m_relpos1CrossNormal = torqueAxis0;
                solverConstraint.m_contactNormal1 = constraintNormalLin;
        }
        else  //if(rb0)
        {
                btVector3 torqueAxis0;
                if (angConstraint)
                {
                        torqueAxis0 = constraintNormalAng;
                }
                else
                {
                        torqueAxis0 = rel_pos1.cross(constraintNormalLin);
                }
                solverConstraint.m_angularComponentA = rb0 ? rb0->getInvInertiaTensorWorld() * torqueAxis0 * rb0->getAngularFactor() : btVector3(0, 0, 0);
                solverConstraint.m_relpos1CrossNormal = torqueAxis0;
                solverConstraint.m_contactNormal1 = constraintNormalLin;
        }
 
        if (multiBodyB)
        {
                if (solverConstraint.m_linkB < 0)
                {
                        rel_pos2 = posBworld - multiBodyB->getBasePos();
                }
                else
                {
                        rel_pos2 = posBworld - multiBodyB->getLink(solverConstraint.m_linkB).m_cachedWorldTransform.getOrigin();
                }
 
                const int ndofB = multiBodyB->getNumDofs() + 6;
 
                solverConstraint.m_deltaVelBindex = multiBodyB->getCompanionId();
                if (solverConstraint.m_deltaVelBindex < 0)
                {
                        solverConstraint.m_deltaVelBindex = data.m_deltaVelocities.size();
                        multiBodyB->setCompanionId(solverConstraint.m_deltaVelBindex);
                        data.m_deltaVelocities.resize(data.m_deltaVelocities.size() + ndofB);
                }
 
                //determine jacobian of this 1D constraint in terms of multibodyB's degrees of freedom
                //resize..
                solverConstraint.m_jacBindex = data.m_jacobians.size();
                data.m_jacobians.resize(data.m_jacobians.size() + ndofB);
                //copy/determine..
                if (jacOrgB)
                {
                        for (int i = 0; i < ndofB; i++)
                                data.m_jacobians[solverConstraint.m_jacBindex + i] = jacOrgB[i];
                }
                else
                {
                        //multiBodyB->fillContactJacobianMultiDof(solverConstraint.m_linkB, posBworld, -constraintNormalLin, &data.m_jacobians[solverConstraint.m_jacBindex], data.scratch_r, data.scratch_v, data.scratch_m);
                        multiBodyB->fillConstraintJacobianMultiDof(solverConstraint.m_linkB, posBworld, -constraintNormalAng, -constraintNormalLin, &data.m_jacobians[solverConstraint.m_jacBindex], data.scratch_r, data.scratch_v, data.scratch_m);
                }
 
                //determine velocity response of multibodyB to reaction impulses of this constraint (i.e. A[i,i] for i=1,...n_con: multibody's inverse inertia with respect to this 1D constraint)
                //resize..
                data.m_deltaVelocitiesUnitImpulse.resize(data.m_deltaVelocitiesUnitImpulse.size() + ndofB);
                btAssert(data.m_jacobians.size() == data.m_deltaVelocitiesUnitImpulse.size());
                btScalar* delta = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
                //determine..
                multiBodyB->calcAccelerationDeltasMultiDof(&data.m_jacobians[solverConstraint.m_jacBindex], delta, data.scratch_r, data.scratch_v);
 
                btVector3 torqueAxis1;
                if (angConstraint)
                {
                        torqueAxis1 = constraintNormalAng;
                }
                else
                {
                        torqueAxis1 = rel_pos2.cross(constraintNormalLin);
                }
                solverConstraint.m_relpos2CrossNormal = -torqueAxis1;
                solverConstraint.m_contactNormal2 = -constraintNormalLin;
        }
        else  //if(rb1)
        {
                btVector3 torqueAxis1;
                if (angConstraint)
                {
                        torqueAxis1 = constraintNormalAng;
                }
                else
                {
                        torqueAxis1 = rel_pos2.cross(constraintNormalLin);
                }
                solverConstraint.m_angularComponentB = rb1 ? rb1->getInvInertiaTensorWorld() * -torqueAxis1 * rb1->getAngularFactor() : btVector3(0, 0, 0);
                solverConstraint.m_relpos2CrossNormal = -torqueAxis1;
                solverConstraint.m_contactNormal2 = -constraintNormalLin;
        }
        {
                btVector3 vec;
                btScalar denom0 = 0.f;
                btScalar denom1 = 0.f;
                btScalar* jacB = 0;
                btScalar* jacA = 0;
                btScalar* deltaVelA = 0;
                btScalar* deltaVelB = 0;
                int ndofA = 0;
                //determine the "effective mass" of the constrained multibodyA with respect to this 1D constraint (i.e. 1/A[i,i])
                if (multiBodyA)
                {
                        ndofA = multiBodyA->getNumDofs() + 6;
                        jacA = &data.m_jacobians[solverConstraint.m_jacAindex];
                        deltaVelA = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
                        for (int i = 0; i < ndofA; ++i)
                        {
                                btScalar j = jacA[i];
                                btScalar l = deltaVelA[i];
                                denom0 += j * l;
                        }
                }
                else if (rb0)
                {
                        vec = (solverConstraint.m_angularComponentA).cross(rel_pos1);
                        if (angConstraint)
                        {
                                denom0 = constraintNormalAng.dot(solverConstraint.m_angularComponentA);
                        }
                        else
                        {
                                denom0 = rb0->getInvMass() + constraintNormalLin.dot(vec);
                        }
                }
                //
                if (multiBodyB)
                {
                        const int ndofB = multiBodyB->getNumDofs() + 6;
                        jacB = &data.m_jacobians[solverConstraint.m_jacBindex];
                        deltaVelB = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
                        for (int i = 0; i < ndofB; ++i)
                        {
                                btScalar j = jacB[i];
                                btScalar l = deltaVelB[i];
                                denom1 += j * l;
                        }
                }
                else if (rb1)
                {
                        vec = (-solverConstraint.m_angularComponentB).cross(rel_pos2);
                        if (angConstraint)
                        {
                                denom1 = constraintNormalAng.dot(-solverConstraint.m_angularComponentB);
                        }
                        else
                        {
                                denom1 = rb1->getInvMass() + constraintNormalLin.dot(vec);
                        }
                }
 
                //
                btScalar d = denom0 + denom1;
                if (d > SIMD_EPSILON)
                {
                        solverConstraint.m_jacDiagABInv = relaxation / (d);
                }
                else
                {
                        //disable the constraint row to handle singularity/redundant constraint
                        solverConstraint.m_jacDiagABInv = 0.f;
                }
        }
 
        //compute rhs and remaining solverConstraint fields
        btScalar penetration = isFriction ? 0 : posError;
 
        btScalar rel_vel = 0.f;
        int ndofA = 0;
        int ndofB = 0;
        {
                btVector3 vel1, vel2;
                if (multiBodyA)
                {
                        ndofA = multiBodyA->getNumDofs() + 6;
                        btScalar* jacA = &data.m_jacobians[solverConstraint.m_jacAindex];
                        for (int i = 0; i < ndofA; ++i)
                                rel_vel += multiBodyA->getVelocityVector()[i] * jacA[i];
                }
                else if (rb0)
                {
                        rel_vel += rb0->getLinearVelocity().dot(solverConstraint.m_contactNormal1);
                        rel_vel += rb0->getAngularVelocity().dot(solverConstraint.m_relpos1CrossNormal);
                }
                if (multiBodyB)
                {
                        ndofB = multiBodyB->getNumDofs() + 6;
                        btScalar* jacB = &data.m_jacobians[solverConstraint.m_jacBindex];
                        for (int i = 0; i < ndofB; ++i)
                                rel_vel += multiBodyB->getVelocityVector()[i] * jacB[i];
                }
                else if (rb1)
                {
                        rel_vel += rb1->getLinearVelocity().dot(solverConstraint.m_contactNormal2);
                        rel_vel += rb1->getAngularVelocity().dot(solverConstraint.m_relpos2CrossNormal);
                }
 
                solverConstraint.m_friction = 0.f;  //cp.m_combinedFriction;
        }
 
        solverConstraint.m_appliedImpulse = 0.f;
        solverConstraint.m_appliedPushImpulse = 0.f;
 
        {
                btScalar positionalError = 0.f;
                btScalar velocityError = (desiredVelocity - rel_vel) * damping;
 
                btScalar erp = infoGlobal.m_erp2;
 
                //split impulse is not implemented yet for btMultiBody*
                //if (!infoGlobal.m_splitImpulse || (penetration > infoGlobal.m_splitImpulsePenetrationThreshold))
                {
                        erp = infoGlobal.m_erp;
                }
 
                positionalError = -penetration * erp / infoGlobal.m_timeStep;
 
                btScalar penetrationImpulse = positionalError * solverConstraint.m_jacDiagABInv;
                btScalar velocityImpulse = velocityError * solverConstraint.m_jacDiagABInv;
 
                //split impulse is not implemented yet for btMultiBody*
 
                //  if (!infoGlobal.m_splitImpulse || (penetration > infoGlobal.m_splitImpulsePenetrationThreshold))
                {
                        //combine position and velocity into rhs
                        solverConstraint.m_rhs = penetrationImpulse + velocityImpulse;
                        solverConstraint.m_rhsPenetration = 0.f;
                }
                /*else
        {
            //split position and velocity into rhs and m_rhsPenetration
            solverConstraint.m_rhs = velocityImpulse;
            solverConstraint.m_rhsPenetration = penetrationImpulse;
        }
        */
 
                solverConstraint.m_cfm = 0.f;
                solverConstraint.m_lowerLimit = lowerLimit;
                solverConstraint.m_upperLimit = upperLimit;
        }
 
        return rel_vel;
}