btMultiBodyConstraintSolver.cpp

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/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2013 Erwin Coumans  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 "btMultiBodyConstraintSolver.h"
#include "BulletCollision/NarrowPhaseCollision/btPersistentManifold.h"
#include "btMultiBodyLinkCollider.h"

#include "BulletDynamics/ConstraintSolver/btSolverBody.h"
#include "btMultiBodyConstraint.h"
#include "BulletDynamics/ConstraintSolver/btContactSolverInfo.h"

#include "LinearMath/btQuickprof.h"

btScalar btMultiBodyConstraintSolver::solveSingleIteration(int iteration, btCollisionObject** bodies ,int numBodies,btPersistentManifold** manifoldPtr, int numManifolds,btTypedConstraint** constraints,int numConstraints,const btContactSolverInfo& infoGlobal,btIDebugDraw* debugDrawer)
{
        btScalar leastSquaredResidual  = btSequentialImpulseConstraintSolver::solveSingleIteration(iteration, bodies ,numBodies,manifoldPtr, numManifolds,constraints,numConstraints,infoGlobal,debugDrawer);
        
        //solve featherstone non-contact constraints

        //printf("m_multiBodyNonContactConstraints = %d\n",m_multiBodyNonContactConstraints.size());

        for (int j=0;j<m_multiBodyNonContactConstraints.size();j++)
        {
                int index = iteration&1? j : m_multiBodyNonContactConstraints.size()-1-j;

                btMultiBodySolverConstraint& constraint = m_multiBodyNonContactConstraints[index];
                
                btScalar residual = resolveSingleConstraintRowGeneric(constraint);
                leastSquaredResidual = btMax(leastSquaredResidual,residual*residual);

                if(constraint.m_multiBodyA) 
                        constraint.m_multiBodyA->setPosUpdated(false);
                if(constraint.m_multiBodyB) 
                        constraint.m_multiBodyB->setPosUpdated(false);
        }

        //solve featherstone normal contact
        for (int j0=0;j0<m_multiBodyNormalContactConstraints.size();j0++)
        {
                int index = j0;//iteration&1? j0 : m_multiBodyNormalContactConstraints.size()-1-j0;

                btMultiBodySolverConstraint& constraint = m_multiBodyNormalContactConstraints[index];
                btScalar residual = 0.f;

                if (iteration < infoGlobal.m_numIterations)
                {
                        residual = resolveSingleConstraintRowGeneric(constraint);
                }

                leastSquaredResidual = btMax(leastSquaredResidual,residual*residual);
 
                if(constraint.m_multiBodyA) 
                        constraint.m_multiBodyA->setPosUpdated(false);
                if(constraint.m_multiBodyB) 
                        constraint.m_multiBodyB->setPosUpdated(false);
        }

        //solve featherstone frictional contact
        if (infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS && ((infoGlobal.m_solverMode&SOLVER_DISABLE_IMPLICIT_CONE_FRICTION) == 0))
        {
                for (int j1 = 0; j1<this->m_multiBodyTorsionalFrictionContactConstraints.size(); j1++)
                {
                        if (iteration < infoGlobal.m_numIterations)
                        {
                                int index = j1;//iteration&1? j1 : m_multiBodyTorsionalFrictionContactConstraints.size()-1-j1;

                                btMultiBodySolverConstraint& frictionConstraint = m_multiBodyTorsionalFrictionContactConstraints[index];
                                btScalar totalImpulse = m_multiBodyNormalContactConstraints[frictionConstraint.m_frictionIndex].m_appliedImpulse;
                                //adjust friction limits here
                                if (totalImpulse>btScalar(0))
                                {
                                        frictionConstraint.m_lowerLimit = -(frictionConstraint.m_friction*totalImpulse);
                                        frictionConstraint.m_upperLimit = frictionConstraint.m_friction*totalImpulse;
                                        btScalar residual = resolveSingleConstraintRowGeneric(frictionConstraint);
                                        leastSquaredResidual = btMax(leastSquaredResidual , residual*residual);

                                        if (frictionConstraint.m_multiBodyA)
                                                frictionConstraint.m_multiBodyA->setPosUpdated(false);
                                        if (frictionConstraint.m_multiBodyB)
                                                frictionConstraint.m_multiBodyB->setPosUpdated(false);
                                }
                        }
                }

                for (int j1 = 0; j1 < this->m_multiBodyFrictionContactConstraints.size(); j1++)
                {
                        if (iteration < infoGlobal.m_numIterations)
                        {
                                int index = j1;//iteration&1? j1 : m_multiBodyFrictionContactConstraints.size()-1-j1;
                                btMultiBodySolverConstraint& frictionConstraint = m_multiBodyFrictionContactConstraints[index];

                                btScalar totalImpulse = m_multiBodyNormalContactConstraints[frictionConstraint.m_frictionIndex].m_appliedImpulse;
                                j1++;
                                int index2 = j1;//iteration&1? j1 : m_multiBodyFrictionContactConstraints.size()-1-j1;
                                btMultiBodySolverConstraint& frictionConstraintB = m_multiBodyFrictionContactConstraints[index2];
                                btAssert(frictionConstraint.m_frictionIndex == frictionConstraintB.m_frictionIndex);

                                if (frictionConstraint.m_frictionIndex == frictionConstraintB.m_frictionIndex)
                                {
                                        frictionConstraint.m_lowerLimit = -(frictionConstraint.m_friction*totalImpulse);
                                        frictionConstraint.m_upperLimit = frictionConstraint.m_friction*totalImpulse;
                                        frictionConstraintB.m_lowerLimit = -(frictionConstraintB.m_friction*totalImpulse);
                                        frictionConstraintB.m_upperLimit = frictionConstraintB.m_friction*totalImpulse;
                                        btScalar residual = resolveConeFrictionConstraintRows(frictionConstraint, frictionConstraintB);
                                        leastSquaredResidual = btMax(leastSquaredResidual, residual*residual);
                                        
                                        if (frictionConstraintB.m_multiBodyA)
                                                frictionConstraintB.m_multiBodyA->setPosUpdated(false);
                                        if (frictionConstraintB.m_multiBodyB)
                                                frictionConstraintB.m_multiBodyB->setPosUpdated(false);
                                
                                        if (frictionConstraint.m_multiBodyA)
                                                frictionConstraint.m_multiBodyA->setPosUpdated(false);
                                        if (frictionConstraint.m_multiBodyB)
                                                frictionConstraint.m_multiBodyB->setPosUpdated(false);
                                }
                        }
                }

                
        }
        else
        {
                for (int j1 = 0; j1<this->m_multiBodyFrictionContactConstraints.size(); j1++)
                {
                        if (iteration < infoGlobal.m_numIterations)
                        {
                                int index = j1;//iteration&1? j1 : m_multiBodyFrictionContactConstraints.size()-1-j1;

                                btMultiBodySolverConstraint& frictionConstraint = m_multiBodyFrictionContactConstraints[index];
                                btScalar totalImpulse = m_multiBodyNormalContactConstraints[frictionConstraint.m_frictionIndex].m_appliedImpulse;
                                //adjust friction limits here
                                if (totalImpulse>btScalar(0))
                                {
                                        frictionConstraint.m_lowerLimit = -(frictionConstraint.m_friction*totalImpulse);
                                        frictionConstraint.m_upperLimit = frictionConstraint.m_friction*totalImpulse;
                                        btScalar residual = resolveSingleConstraintRowGeneric(frictionConstraint);
                                        leastSquaredResidual = btMax(leastSquaredResidual, residual*residual);

                                        if (frictionConstraint.m_multiBodyA)
                                                frictionConstraint.m_multiBodyA->setPosUpdated(false);
                                        if (frictionConstraint.m_multiBodyB)
                                                frictionConstraint.m_multiBodyB->setPosUpdated(false);
                                }
                        }
                }
        }
        return leastSquaredResidual;
}

btScalar btMultiBodyConstraintSolver::solveGroupCacheFriendlySetup(btCollisionObject** bodies,int numBodies,btPersistentManifold** manifoldPtr, int numManifolds,btTypedConstraint** constraints,int numConstraints,const btContactSolverInfo& infoGlobal,btIDebugDraw* debugDrawer)
{
        m_multiBodyNonContactConstraints.resize(0);
        m_multiBodyNormalContactConstraints.resize(0);
        m_multiBodyFrictionContactConstraints.resize(0);
        m_multiBodyTorsionalFrictionContactConstraints.resize(0);
        
        m_data.m_jacobians.resize(0);
        m_data.m_deltaVelocitiesUnitImpulse.resize(0);
        m_data.m_deltaVelocities.resize(0);

        for (int i=0;i<numBodies;i++)
        {
                const btMultiBodyLinkCollider* fcA = btMultiBodyLinkCollider::upcast(bodies[i]);
                if (fcA)
                {
                        fcA->m_multiBody->setCompanionId(-1);
                }
        }

        btScalar val = btSequentialImpulseConstraintSolver::solveGroupCacheFriendlySetup( bodies,numBodies,manifoldPtr, numManifolds, constraints,numConstraints,infoGlobal,debugDrawer);

        return val;
}

void    btMultiBodyConstraintSolver::applyDeltaVee(btScalar* delta_vee, btScalar impulse, int velocityIndex, int ndof)
{
    for (int i = 0; i < ndof; ++i) 
                m_data.m_deltaVelocities[velocityIndex+i] += delta_vee[i] * impulse;
}

btScalar btMultiBodyConstraintSolver::resolveSingleConstraintRowGeneric(const btMultiBodySolverConstraint& c)
{

        btScalar deltaImpulse = c.m_rhs - btScalar(c.m_appliedImpulse)*c.m_cfm;
        btScalar deltaVelADotn = 0;
        btScalar deltaVelBDotn = 0;
        btSolverBody* bodyA = 0;
        btSolverBody* bodyB = 0;
        int ndofA = 0;
        int ndofB = 0;

        if (c.m_multiBodyA)
        {
                ndofA = c.m_multiBodyA->getNumDofs() + 6;
                for (int i = 0; i < ndofA; ++i)
                        deltaVelADotn += m_data.m_jacobians[c.m_jacAindex + i] * m_data.m_deltaVelocities[c.m_deltaVelAindex + i];
        }
        else if (c.m_solverBodyIdA >= 0)
        {
                bodyA = &m_tmpSolverBodyPool[c.m_solverBodyIdA];
                deltaVelADotn += c.m_contactNormal1.dot(bodyA->internalGetDeltaLinearVelocity()) + c.m_relpos1CrossNormal.dot(bodyA->internalGetDeltaAngularVelocity());
        }

        if (c.m_multiBodyB)
        {
                ndofB = c.m_multiBodyB->getNumDofs() + 6;
                for (int i = 0; i < ndofB; ++i)
                        deltaVelBDotn += m_data.m_jacobians[c.m_jacBindex + i] * m_data.m_deltaVelocities[c.m_deltaVelBindex + i];
        }
        else if (c.m_solverBodyIdB >= 0)
        {
                bodyB = &m_tmpSolverBodyPool[c.m_solverBodyIdB];
                deltaVelBDotn += c.m_contactNormal2.dot(bodyB->internalGetDeltaLinearVelocity()) + c.m_relpos2CrossNormal.dot(bodyB->internalGetDeltaAngularVelocity());
        }


        deltaImpulse -= deltaVelADotn*c.m_jacDiagABInv;//m_jacDiagABInv = 1./denom
        deltaImpulse -= deltaVelBDotn*c.m_jacDiagABInv;
        const btScalar sum = btScalar(c.m_appliedImpulse) + deltaImpulse;

        if (sum < c.m_lowerLimit)
        {
                deltaImpulse = c.m_lowerLimit - c.m_appliedImpulse;
                c.m_appliedImpulse = c.m_lowerLimit;
        }
        else if (sum > c.m_upperLimit)
        {
                deltaImpulse = c.m_upperLimit - c.m_appliedImpulse;
                c.m_appliedImpulse = c.m_upperLimit;
        }
        else
        {
                c.m_appliedImpulse = sum;
        }
        
        if (c.m_multiBodyA)
        {
                applyDeltaVee(&m_data.m_deltaVelocitiesUnitImpulse[c.m_jacAindex], deltaImpulse, c.m_deltaVelAindex, ndofA);
#ifdef DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
                //note: update of the actual velocities (below) in the multibody does not have to happen now since m_deltaVelocities can be applied after all iterations
                //it would make the multibody solver more like the regular one with m_deltaVelocities being equivalent to btSolverBody::m_deltaLinearVelocity/m_deltaAngularVelocity
                c.m_multiBodyA->applyDeltaVeeMultiDof2(&m_data.m_deltaVelocitiesUnitImpulse[c.m_jacAindex], deltaImpulse);
#endif //DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
        }
        else if (c.m_solverBodyIdA >= 0)
        {
                bodyA->internalApplyImpulse(c.m_contactNormal1*bodyA->internalGetInvMass(), c.m_angularComponentA, deltaImpulse);

        }
        if (c.m_multiBodyB)
        {
                applyDeltaVee(&m_data.m_deltaVelocitiesUnitImpulse[c.m_jacBindex], deltaImpulse, c.m_deltaVelBindex, ndofB);
#ifdef DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
                //note: update of the actual velocities (below) in the multibody does not have to happen now since m_deltaVelocities can be applied after all iterations
                //it would make the multibody solver more like the regular one with m_deltaVelocities being equivalent to btSolverBody::m_deltaLinearVelocity/m_deltaAngularVelocity
                c.m_multiBodyB->applyDeltaVeeMultiDof2(&m_data.m_deltaVelocitiesUnitImpulse[c.m_jacBindex], deltaImpulse);
#endif //DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
        }
        else if (c.m_solverBodyIdB >= 0)
        {
                bodyB->internalApplyImpulse(c.m_contactNormal2*bodyB->internalGetInvMass(), c.m_angularComponentB, deltaImpulse);
        }
    btScalar deltaVel =deltaImpulse/c.m_jacDiagABInv;
        return deltaVel;
}


btScalar btMultiBodyConstraintSolver::resolveConeFrictionConstraintRows(const btMultiBodySolverConstraint& cA1,const btMultiBodySolverConstraint& cB)
{
        int ndofA=0;
        int ndofB=0;
        btSolverBody* bodyA = 0;
        btSolverBody* bodyB = 0;
        btScalar deltaImpulseB = 0.f;
        btScalar sumB = 0.f;
        {
                deltaImpulseB = cB.m_rhs-btScalar(cB.m_appliedImpulse)*cB.m_cfm;
                btScalar deltaVelADotn=0;
                btScalar deltaVelBDotn=0;
                if (cB.m_multiBodyA)
                {
                        ndofA  = cB.m_multiBodyA->getNumDofs() + 6;
                        for (int i = 0; i < ndofA; ++i) 
                                deltaVelADotn += m_data.m_jacobians[cB.m_jacAindex+i] * m_data.m_deltaVelocities[cB.m_deltaVelAindex+i];
                } else if(cB.m_solverBodyIdA >= 0)
                {
                        bodyA = &m_tmpSolverBodyPool[cB.m_solverBodyIdA];
                        deltaVelADotn += cB.m_contactNormal1.dot(bodyA->internalGetDeltaLinearVelocity())       + cB.m_relpos1CrossNormal.dot(bodyA->internalGetDeltaAngularVelocity());
                }

                if (cB.m_multiBodyB)
                {
                        ndofB  = cB.m_multiBodyB->getNumDofs() + 6;
                        for (int i = 0; i < ndofB; ++i) 
                                deltaVelBDotn += m_data.m_jacobians[cB.m_jacBindex+i] * m_data.m_deltaVelocities[cB.m_deltaVelBindex+i];
                } else if(cB.m_solverBodyIdB >= 0)
                {
                        bodyB = &m_tmpSolverBodyPool[cB.m_solverBodyIdB];
                        deltaVelBDotn += cB.m_contactNormal2.dot(bodyB->internalGetDeltaLinearVelocity())  + cB.m_relpos2CrossNormal.dot(bodyB->internalGetDeltaAngularVelocity());
                }

        
                deltaImpulseB   -=      deltaVelADotn*cB.m_jacDiagABInv;//m_jacDiagABInv = 1./denom
                deltaImpulseB   -=      deltaVelBDotn*cB.m_jacDiagABInv;
                sumB = btScalar(cB.m_appliedImpulse) + deltaImpulseB;
        }

        btScalar deltaImpulseA = 0.f;
        btScalar sumA = 0.f;
        const btMultiBodySolverConstraint& cA = cA1;
        {
                {
                        deltaImpulseA = cA.m_rhs-btScalar(cA.m_appliedImpulse)*cA.m_cfm;
                        btScalar deltaVelADotn=0;
                        btScalar deltaVelBDotn=0;
                        if (cA.m_multiBodyA)
                        {
                                ndofA  = cA.m_multiBodyA->getNumDofs() + 6;
                                for (int i = 0; i < ndofA; ++i) 
                                        deltaVelADotn += m_data.m_jacobians[cA.m_jacAindex+i] * m_data.m_deltaVelocities[cA.m_deltaVelAindex+i];
                        } else if(cA.m_solverBodyIdA >= 0)
                        {
                                bodyA = &m_tmpSolverBodyPool[cA.m_solverBodyIdA];
                                deltaVelADotn += cA.m_contactNormal1.dot(bodyA->internalGetDeltaLinearVelocity())       + cA.m_relpos1CrossNormal.dot(bodyA->internalGetDeltaAngularVelocity());
                        }

                        if (cA.m_multiBodyB)
                        {
                                ndofB  = cA.m_multiBodyB->getNumDofs() + 6;
                                for (int i = 0; i < ndofB; ++i) 
                                        deltaVelBDotn += m_data.m_jacobians[cA.m_jacBindex+i] * m_data.m_deltaVelocities[cA.m_deltaVelBindex+i];
                        } else if(cA.m_solverBodyIdB >= 0)
                        {
                                bodyB = &m_tmpSolverBodyPool[cA.m_solverBodyIdB];
                                deltaVelBDotn += cA.m_contactNormal2.dot(bodyB->internalGetDeltaLinearVelocity())  + cA.m_relpos2CrossNormal.dot(bodyB->internalGetDeltaAngularVelocity());
                        }

        
                        deltaImpulseA   -=      deltaVelADotn*cA.m_jacDiagABInv;//m_jacDiagABInv = 1./denom
                        deltaImpulseA   -=      deltaVelBDotn*cA.m_jacDiagABInv;
                        sumA = btScalar(cA.m_appliedImpulse) + deltaImpulseA;
                }
        }

        if (sumA*sumA+sumB*sumB>=cA.m_lowerLimit*cB.m_lowerLimit)
        {
                btScalar angle = btAtan2(sumA,sumB);
                btScalar sumAclipped = btFabs(cA.m_lowerLimit*btSin(angle));
                btScalar sumBclipped = btFabs(cB.m_lowerLimit*btCos(angle));

                
                if (sumA < -sumAclipped)
                {
                        deltaImpulseA = -sumAclipped - cA.m_appliedImpulse;
                        cA.m_appliedImpulse = -sumAclipped;
                }
                else if (sumA > sumAclipped)
                {
                        deltaImpulseA = sumAclipped - cA.m_appliedImpulse;
                        cA.m_appliedImpulse = sumAclipped;
                }
                else
                {
                        cA.m_appliedImpulse = sumA;
                }

                if (sumB < -sumBclipped)
                {
                        deltaImpulseB = -sumBclipped - cB.m_appliedImpulse;
                        cB.m_appliedImpulse = -sumBclipped;
                }
                else if (sumB > sumBclipped)
                {
                        deltaImpulseB = sumBclipped - cB.m_appliedImpulse;
                        cB.m_appliedImpulse = sumBclipped;
                }
                else
                {
                        cB.m_appliedImpulse = sumB;
                }
                //deltaImpulseA = sumAclipped-cA.m_appliedImpulse;
                //cA.m_appliedImpulse = sumAclipped;
                //deltaImpulseB = sumBclipped-cB.m_appliedImpulse;
                //cB.m_appliedImpulse = sumBclipped;
        } 
        else
        {
                cA.m_appliedImpulse = sumA;
                cB.m_appliedImpulse = sumB;
        }
        
        if (cA.m_multiBodyA)
        {
                applyDeltaVee(&m_data.m_deltaVelocitiesUnitImpulse[cA.m_jacAindex],deltaImpulseA,cA.m_deltaVelAindex,ndofA);
#ifdef DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
                //note: update of the actual velocities (below) in the multibody does not have to happen now since m_deltaVelocities can be applied after all iterations
                //it would make the multibody solver more like the regular one with m_deltaVelocities being equivalent to btSolverBody::m_deltaLinearVelocity/m_deltaAngularVelocity
                cA.m_multiBodyA->applyDeltaVeeMultiDof2(&m_data.m_deltaVelocitiesUnitImpulse[cA.m_jacAindex],deltaImpulseA);
#endif //DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
        } else if(cA.m_solverBodyIdA >= 0)
        {
                bodyA->internalApplyImpulse(cA.m_contactNormal1*bodyA->internalGetInvMass(),cA.m_angularComponentA,deltaImpulseA);

        }
        if (cA.m_multiBodyB)
        {
                applyDeltaVee(&m_data.m_deltaVelocitiesUnitImpulse[cA.m_jacBindex],deltaImpulseA,cA.m_deltaVelBindex,ndofB);
#ifdef DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
                //note: update of the actual velocities (below) in the multibody does not have to happen now since m_deltaVelocities can be applied after all iterations
                //it would make the multibody solver more like the regular one with m_deltaVelocities being equivalent to btSolverBody::m_deltaLinearVelocity/m_deltaAngularVelocity
                cA.m_multiBodyB->applyDeltaVeeMultiDof2(&m_data.m_deltaVelocitiesUnitImpulse[cA.m_jacBindex],deltaImpulseA);
#endif //DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
        } else if(cA.m_solverBodyIdB >= 0)
        {
                bodyB->internalApplyImpulse(cA.m_contactNormal2*bodyB->internalGetInvMass(),cA.m_angularComponentB,deltaImpulseA);
        }

        if (cB.m_multiBodyA)
        {
                applyDeltaVee(&m_data.m_deltaVelocitiesUnitImpulse[cB.m_jacAindex],deltaImpulseB,cB.m_deltaVelAindex,ndofA);
#ifdef DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
                //note: update of the actual velocities (below) in the multibody does not have to happen now since m_deltaVelocities can be applied after all iterations
                //it would make the multibody solver more like the regular one with m_deltaVelocities being equivalent to btSolverBody::m_deltaLinearVelocity/m_deltaAngularVelocity
                cB.m_multiBodyA->applyDeltaVeeMultiDof2(&m_data.m_deltaVelocitiesUnitImpulse[cB.m_jacAindex],deltaImpulseB);
#endif //DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
        } else if(cB.m_solverBodyIdA >= 0)
        {
                bodyA->internalApplyImpulse(cB.m_contactNormal1*bodyA->internalGetInvMass(),cB.m_angularComponentA,deltaImpulseB);
        }
        if (cB.m_multiBodyB)
        {
                applyDeltaVee(&m_data.m_deltaVelocitiesUnitImpulse[cB.m_jacBindex],deltaImpulseB,cB.m_deltaVelBindex,ndofB);
#ifdef DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
                //note: update of the actual velocities (below) in the multibody does not have to happen now since m_deltaVelocities can be applied after all iterations
                //it would make the multibody solver more like the regular one with m_deltaVelocities being equivalent to btSolverBody::m_deltaLinearVelocity/m_deltaAngularVelocity
                cB.m_multiBodyB->applyDeltaVeeMultiDof2(&m_data.m_deltaVelocitiesUnitImpulse[cB.m_jacBindex],deltaImpulseB);
#endif //DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS
        } else if(cB.m_solverBodyIdB >= 0)
        {
                bodyB->internalApplyImpulse(cB.m_contactNormal2*bodyB->internalGetInvMass(),cB.m_angularComponentB,deltaImpulseB);
        }

    btScalar deltaVel =deltaImpulseA/cA.m_jacDiagABInv+deltaImpulseB/cB.m_jacDiagABInv;
    return deltaVel;
}




void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySolverConstraint& solverConstraint, 
                                                                                                                                 const btVector3& contactNormal,
                                                                                                                                 btManifoldPoint& cp, const btContactSolverInfo& infoGlobal,
                                                                                                                                 btScalar& relaxation,
                                                                                                                                 bool isFriction, btScalar desiredVelocity, btScalar cfmSlip)
{
                        
        BT_PROFILE("setupMultiBodyContactConstraint");
        btVector3 rel_pos1;
        btVector3 rel_pos2;

        btMultiBody* multiBodyA = solverConstraint.m_multiBodyA;
        btMultiBody* multiBodyB = solverConstraint.m_multiBodyB;

        const btVector3& pos1 = cp.getPositionWorldOnA();
        const btVector3& pos2 = cp.getPositionWorldOnB();

        btSolverBody* bodyA = multiBodyA ? 0 : &m_tmpSolverBodyPool[solverConstraint.m_solverBodyIdA];
        btSolverBody* bodyB = multiBodyB ? 0 : &m_tmpSolverBodyPool[solverConstraint.m_solverBodyIdB];

        btRigidBody* rb0 = multiBodyA ? 0 : bodyA->m_originalBody;
        btRigidBody* rb1 = multiBodyB ? 0 : bodyB->m_originalBody;

        if (bodyA)
                rel_pos1 = pos1 - bodyA->getWorldTransform().getOrigin(); 
        if (bodyB)
                rel_pos2 = pos2 - bodyB->getWorldTransform().getOrigin();

        relaxation = infoGlobal.m_sor;
        
        btScalar invTimeStep = btScalar(1)/infoGlobal.m_timeStep;
        
         //cfm = 1 /       ( dt * kp + kd )
    //erp = dt * kp / ( dt * kp + kd )
    
    btScalar cfm;
        btScalar erp;
        if (isFriction)
        {
                cfm = infoGlobal.m_frictionCFM;
                erp = infoGlobal.m_frictionERP;
        } else
        {
                cfm = infoGlobal.m_globalCfm;
                erp = infoGlobal.m_erp2;

                if ((cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_CFM) || (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_ERP))
                {
                        if (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_CFM)
                                cfm  = cp.m_contactCFM;
                        if (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_ERP)
                                erp = cp.m_contactERP;                
                } else
                {
                        if (cp.m_contactPointFlags & BT_CONTACT_FLAG_CONTACT_STIFFNESS_DAMPING)
                        {
                                btScalar denom = ( infoGlobal.m_timeStep * cp.m_combinedContactStiffness1 + cp.m_combinedContactDamping1 );
                                if (denom < SIMD_EPSILON)
                                {
                                        denom = SIMD_EPSILON;
                                }
                                cfm = btScalar(1) / denom; 
                                erp = (infoGlobal.m_timeStep * cp.m_combinedContactStiffness1) / denom;
                        }
                }
        }

        cfm *= invTimeStep;

        if (multiBodyA)
        {
                if (solverConstraint.m_linkA<0)
                {
                        rel_pos1 = pos1 - multiBodyA->getBasePos();
                } else
                {
                        rel_pos1 = pos1 - 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 = m_data.m_deltaVelocities.size();
                        multiBodyA->setCompanionId(solverConstraint.m_deltaVelAindex);
                        m_data.m_deltaVelocities.resize(m_data.m_deltaVelocities.size()+ndofA);
                } else
                {
                        btAssert(m_data.m_deltaVelocities.size() >= solverConstraint.m_deltaVelAindex+ndofA);
                }

                solverConstraint.m_jacAindex = m_data.m_jacobians.size();
                m_data.m_jacobians.resize(m_data.m_jacobians.size()+ndofA);
                m_data.m_deltaVelocitiesUnitImpulse.resize(m_data.m_deltaVelocitiesUnitImpulse.size()+ndofA);
                btAssert(m_data.m_jacobians.size() == m_data.m_deltaVelocitiesUnitImpulse.size());

                btScalar* jac1=&m_data.m_jacobians[solverConstraint.m_jacAindex];
                multiBodyA->fillContactJacobianMultiDof(solverConstraint.m_linkA, cp.getPositionWorldOnA(), contactNormal, jac1, m_data.scratch_r, m_data.scratch_v, m_data.scratch_m);
                btScalar* delta = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
                multiBodyA->calcAccelerationDeltasMultiDof(&m_data.m_jacobians[solverConstraint.m_jacAindex],delta,m_data.scratch_r, m_data.scratch_v);

                btVector3 torqueAxis0 = rel_pos1.cross(contactNormal);
                solverConstraint.m_relpos1CrossNormal = torqueAxis0;
                solverConstraint.m_contactNormal1 = contactNormal;
        } else
        {
                btVector3 torqueAxis0 = rel_pos1.cross(contactNormal);
                solverConstraint.m_relpos1CrossNormal = torqueAxis0;
                solverConstraint.m_contactNormal1 = contactNormal;
                solverConstraint.m_angularComponentA = rb0 ? rb0->getInvInertiaTensorWorld()*torqueAxis0*rb0->getAngularFactor() : btVector3(0,0,0);
        }

        

        if (multiBodyB)
        {
                if (solverConstraint.m_linkB<0)
                {
                        rel_pos2 = pos2 - multiBodyB->getBasePos();
                } else
                {
                        rel_pos2 = pos2 - 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 = m_data.m_deltaVelocities.size();
                        multiBodyB->setCompanionId(solverConstraint.m_deltaVelBindex);
                        m_data.m_deltaVelocities.resize(m_data.m_deltaVelocities.size()+ndofB);
                }

                solverConstraint.m_jacBindex = m_data.m_jacobians.size();

                m_data.m_jacobians.resize(m_data.m_jacobians.size()+ndofB);
                m_data.m_deltaVelocitiesUnitImpulse.resize(m_data.m_deltaVelocitiesUnitImpulse.size()+ndofB);
                btAssert(m_data.m_jacobians.size() == m_data.m_deltaVelocitiesUnitImpulse.size());

                multiBodyB->fillContactJacobianMultiDof(solverConstraint.m_linkB, cp.getPositionWorldOnB(), -contactNormal, &m_data.m_jacobians[solverConstraint.m_jacBindex], m_data.scratch_r, m_data.scratch_v, m_data.scratch_m);
                multiBodyB->calcAccelerationDeltasMultiDof(&m_data.m_jacobians[solverConstraint.m_jacBindex],&m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex],m_data.scratch_r, m_data.scratch_v);
                
                btVector3 torqueAxis1 = rel_pos2.cross(contactNormal);          
                solverConstraint.m_relpos2CrossNormal = -torqueAxis1;
                solverConstraint.m_contactNormal2 = -contactNormal;
        
        } else
        {
                btVector3 torqueAxis1 = rel_pos2.cross(contactNormal);          
                solverConstraint.m_relpos2CrossNormal = -torqueAxis1;
                solverConstraint.m_contactNormal2 = -contactNormal;
        
                solverConstraint.m_angularComponentB = rb1 ? rb1->getInvInertiaTensorWorld()*-torqueAxis1*rb1->getAngularFactor() : btVector3(0,0,0);
        }

        {
                                                
                btVector3 vec;
                btScalar denom0 = 0.f;
                btScalar denom1 = 0.f;
                btScalar* jacB = 0;
                btScalar* jacA = 0;
                btScalar* lambdaA =0;
                btScalar* lambdaB =0;
                int ndofA  = 0;
                if (multiBodyA)
                {
                        ndofA  = multiBodyA->getNumDofs() + 6;
                        jacA = &m_data.m_jacobians[solverConstraint.m_jacAindex];
                        lambdaA = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
                        for (int i = 0; i < ndofA; ++i)
                        {
                                btScalar j = jacA[i] ;
                                btScalar l =lambdaA[i];
                                denom0 += j*l;
                        }
                } else
                {
                        if (rb0)
                        {
                                vec = ( solverConstraint.m_angularComponentA).cross(rel_pos1);
                                denom0 = rb0->getInvMass() + contactNormal.dot(vec);
                        }
                }
                if (multiBodyB)
                {
                        const int ndofB  = multiBodyB->getNumDofs() + 6;
                        jacB = &m_data.m_jacobians[solverConstraint.m_jacBindex];
                        lambdaB = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
                        for (int i = 0; i < ndofB; ++i)
                        {
                                btScalar j = jacB[i] ;
                                btScalar l =lambdaB[i];
                                denom1 += j*l;
                        }

                } else
                {
                        if (rb1)
                        {
                                vec = ( -solverConstraint.m_angularComponentB).cross(rel_pos2);
                                denom1 = rb1->getInvMass() + contactNormal.dot(vec);
                        }
                }

                 

                 btScalar d = denom0+denom1+cfm;
                 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 restitution = 0.f;
    btScalar distance = 0;
    if (!isFriction)
    {
        distance = cp.getDistance()+infoGlobal.m_linearSlop;
    } else
    {
        if (cp.m_contactPointFlags & BT_CONTACT_FLAG_FRICTION_ANCHOR)
        {
          distance = (cp.getPositionWorldOnA() - cp.getPositionWorldOnB()).dot(contactNormal);
        }
    }
  
    
        btScalar rel_vel = 0.f;
        int ndofA  = 0;
        int ndofB  = 0;
        {

                btVector3 vel1,vel2;
                if (multiBodyA)
                {
                        ndofA  = multiBodyA->getNumDofs() + 6;
                        btScalar* jacA = &m_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->getVelocityInLocalPoint(rel_pos1) + 
                                                        (rb0->getTotalTorque()*rb0->getInvInertiaTensorWorld()*infoGlobal.m_timeStep).cross(rel_pos1)+
                                                        rb0->getTotalForce()*rb0->getInvMass()*infoGlobal.m_timeStep).dot(solverConstraint.m_contactNormal1);
                        }
                }
                if (multiBodyB)
                {
                        ndofB  = multiBodyB->getNumDofs() + 6;
                        btScalar* jacB = &m_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->getVelocityInLocalPoint(rel_pos2)+
                                        (rb1->getTotalTorque()*rb1->getInvInertiaTensorWorld()*infoGlobal.m_timeStep).cross(rel_pos2) +
                                        rb1->getTotalForce()*rb1->getInvMass()*infoGlobal.m_timeStep).dot(solverConstraint.m_contactNormal2);
                        }
                }

                solverConstraint.m_friction = cp.m_combinedFriction;

                if(!isFriction)
                {
                        restitution =  restitutionCurve(rel_vel, cp.m_combinedRestitution, infoGlobal.m_restitutionVelocityThreshold);  
                        if (restitution <= btScalar(0.))
                        {
                                restitution = 0.f;
                        }
                }
        }


        //disable warmstarting for btMultiBody, it has issues gaining energy (==explosion)
        if (0)//infoGlobal.m_solverMode & SOLVER_USE_WARMSTARTING)
        {
                solverConstraint.m_appliedImpulse = isFriction ? 0 : cp.m_appliedImpulse * infoGlobal.m_warmstartingFactor;

                if (solverConstraint.m_appliedImpulse)
                {
                        if (multiBodyA)
                        {
                                btScalar impulse = solverConstraint.m_appliedImpulse;
                                btScalar* deltaV = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
                                multiBodyA->applyDeltaVeeMultiDof(deltaV,impulse);
                                
                                applyDeltaVee(deltaV,impulse,solverConstraint.m_deltaVelAindex,ndofA);
                        } else
                        {
                                if (rb0)
                                        bodyA->internalApplyImpulse(solverConstraint.m_contactNormal1*bodyA->internalGetInvMass()*rb0->getLinearFactor(),solverConstraint.m_angularComponentA,solverConstraint.m_appliedImpulse);
                        }
                        if (multiBodyB)
                        {
                                btScalar impulse = solverConstraint.m_appliedImpulse;
                                btScalar* deltaV = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
                                multiBodyB->applyDeltaVeeMultiDof(deltaV,impulse);
                                applyDeltaVee(deltaV,impulse,solverConstraint.m_deltaVelBindex,ndofB);
                        } else
                        {
                                if (rb1)
                                        bodyB->internalApplyImpulse(-solverConstraint.m_contactNormal2*bodyB->internalGetInvMass()*rb1->getLinearFactor(),-solverConstraint.m_angularComponentB,-(btScalar)solverConstraint.m_appliedImpulse);
                        }
                }
        } else
        {
                solverConstraint.m_appliedImpulse = 0.f;
        }

        solverConstraint.m_appliedPushImpulse = 0.f;

        {

                btScalar positionalError = 0.f;
                btScalar velocityError = restitution - rel_vel;// * damping;    //note for friction restitution is always set to 0 (check above) so it is acutally velocityError = -rel_vel for friction
                if (isFriction)
                {
                        positionalError = -distance * erp/infoGlobal.m_timeStep;
                } else
                {
                        if (distance>0)
                        {
                                positionalError = 0;
                                velocityError -= distance / infoGlobal.m_timeStep;

                        } else
                        {
                                positionalError = -distance * erp/infoGlobal.m_timeStep;
                        }
                }

                btScalar  penetrationImpulse = positionalError*solverConstraint.m_jacDiagABInv;
                btScalar velocityImpulse = velocityError *solverConstraint.m_jacDiagABInv;

                if(!isFriction)
                {
                //      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_lowerLimit = 0;
                        solverConstraint.m_upperLimit = 1e10f;
                }
                else
                {
                        solverConstraint.m_rhs = penetrationImpulse+velocityImpulse;
                        solverConstraint.m_rhsPenetration = 0.f;
                        solverConstraint.m_lowerLimit = -solverConstraint.m_friction;
                        solverConstraint.m_upperLimit = solverConstraint.m_friction;
                }

                solverConstraint.m_cfm = cfm*solverConstraint.m_jacDiagABInv;
                


        }

}

void btMultiBodyConstraintSolver::setupMultiBodyTorsionalFrictionConstraint(btMultiBodySolverConstraint& solverConstraint,
                                                                  const btVector3& constraintNormal,
                                                                  btManifoldPoint& cp,
                                                                    btScalar combinedTorsionalFriction,
                                                                    const btContactSolverInfo& infoGlobal,
                                                                  btScalar& relaxation,
                                                                  bool isFriction, btScalar desiredVelocity, btScalar cfmSlip)
{
    
    BT_PROFILE("setupMultiBodyRollingFrictionConstraint");
    btVector3 rel_pos1;
    btVector3 rel_pos2;
    
    btMultiBody* multiBodyA = solverConstraint.m_multiBodyA;
    btMultiBody* multiBodyB = solverConstraint.m_multiBodyB;
    
    const btVector3& pos1 = cp.getPositionWorldOnA();
    const btVector3& pos2 = cp.getPositionWorldOnB();
    
    btSolverBody* bodyA = multiBodyA ? 0 : &m_tmpSolverBodyPool[solverConstraint.m_solverBodyIdA];
    btSolverBody* bodyB = multiBodyB ? 0 : &m_tmpSolverBodyPool[solverConstraint.m_solverBodyIdB];
    
    btRigidBody* rb0 = multiBodyA ? 0 : bodyA->m_originalBody;
    btRigidBody* rb1 = multiBodyB ? 0 : bodyB->m_originalBody;
    
    if (bodyA)
        rel_pos1 = pos1 - bodyA->getWorldTransform().getOrigin();
    if (bodyB)
        rel_pos2 = pos2 - bodyB->getWorldTransform().getOrigin();
    
    relaxation = infoGlobal.m_sor;
    
   // btScalar invTimeStep = btScalar(1)/infoGlobal.m_timeStep;
    
    
    if (multiBodyA)
    {
        if (solverConstraint.m_linkA<0)
        {
            rel_pos1 = pos1 - multiBodyA->getBasePos();
        } else
        {
            rel_pos1 = pos1 - 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 = m_data.m_deltaVelocities.size();
            multiBodyA->setCompanionId(solverConstraint.m_deltaVelAindex);
            m_data.m_deltaVelocities.resize(m_data.m_deltaVelocities.size()+ndofA);
        } else
        {
            btAssert(m_data.m_deltaVelocities.size() >= solverConstraint.m_deltaVelAindex+ndofA);
        }
        
        solverConstraint.m_jacAindex = m_data.m_jacobians.size();
        m_data.m_jacobians.resize(m_data.m_jacobians.size()+ndofA);
        m_data.m_deltaVelocitiesUnitImpulse.resize(m_data.m_deltaVelocitiesUnitImpulse.size()+ndofA);
        btAssert(m_data.m_jacobians.size() == m_data.m_deltaVelocitiesUnitImpulse.size());
        
        btScalar* jac1=&m_data.m_jacobians[solverConstraint.m_jacAindex];
        multiBodyA->fillConstraintJacobianMultiDof(solverConstraint.m_linkA, cp.getPositionWorldOnA(), constraintNormal, btVector3(0,0,0), jac1, m_data.scratch_r, m_data.scratch_v, m_data.scratch_m);
        btScalar* delta = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
        multiBodyA->calcAccelerationDeltasMultiDof(&m_data.m_jacobians[solverConstraint.m_jacAindex],delta,m_data.scratch_r, m_data.scratch_v);
        
        btVector3 torqueAxis0 = -constraintNormal;
        solverConstraint.m_relpos1CrossNormal = torqueAxis0;
        solverConstraint.m_contactNormal1 = btVector3(0,0,0);
    } else
    {
        btVector3 torqueAxis0 = -constraintNormal;
        solverConstraint.m_relpos1CrossNormal = torqueAxis0;
        solverConstraint.m_contactNormal1 = btVector3(0,0,0);
        solverConstraint.m_angularComponentA = rb0 ? rb0->getInvInertiaTensorWorld()*torqueAxis0*rb0->getAngularFactor() : btVector3(0,0,0);
    }
    
    
    
    if (multiBodyB)
    {
        if (solverConstraint.m_linkB<0)
        {
            rel_pos2 = pos2 - multiBodyB->getBasePos();
        } else
        {
            rel_pos2 = pos2 - 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 = m_data.m_deltaVelocities.size();
            multiBodyB->setCompanionId(solverConstraint.m_deltaVelBindex);
            m_data.m_deltaVelocities.resize(m_data.m_deltaVelocities.size()+ndofB);
        }
        
        solverConstraint.m_jacBindex = m_data.m_jacobians.size();
        
        m_data.m_jacobians.resize(m_data.m_jacobians.size()+ndofB);
        m_data.m_deltaVelocitiesUnitImpulse.resize(m_data.m_deltaVelocitiesUnitImpulse.size()+ndofB);
        btAssert(m_data.m_jacobians.size() == m_data.m_deltaVelocitiesUnitImpulse.size());
        
        multiBodyB->fillConstraintJacobianMultiDof(solverConstraint.m_linkB, cp.getPositionWorldOnB(), -constraintNormal, btVector3(0,0,0), &m_data.m_jacobians[solverConstraint.m_jacBindex], m_data.scratch_r, m_data.scratch_v, m_data.scratch_m);
        multiBodyB->calcAccelerationDeltasMultiDof(&m_data.m_jacobians[solverConstraint.m_jacBindex],&m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex],m_data.scratch_r, m_data.scratch_v);
        
        btVector3 torqueAxis1 = constraintNormal;
        solverConstraint.m_relpos2CrossNormal = torqueAxis1;
        solverConstraint.m_contactNormal2 = -btVector3(0,0,0);
        
    } else
    {
        btVector3 torqueAxis1 = constraintNormal;
        solverConstraint.m_relpos2CrossNormal = torqueAxis1;
        solverConstraint.m_contactNormal2 = -btVector3(0,0,0);
        
        solverConstraint.m_angularComponentB = rb1 ? rb1->getInvInertiaTensorWorld()*torqueAxis1*rb1->getAngularFactor() : btVector3(0,0,0);
    }
    
    {
        
        btScalar denom0 = 0.f;
        btScalar denom1 = 0.f;
        btScalar* jacB = 0;
        btScalar* jacA = 0;
        btScalar* lambdaA =0;
        btScalar* lambdaB =0;
        int ndofA  = 0;
        if (multiBodyA)
        {
            ndofA  = multiBodyA->getNumDofs() + 6;
            jacA = &m_data.m_jacobians[solverConstraint.m_jacAindex];
            lambdaA = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
            for (int i = 0; i < ndofA; ++i)
            {
                btScalar j = jacA[i] ;
                btScalar l =lambdaA[i];
                denom0 += j*l;
            }
        } else
        {
            if (rb0)
            {
                                btVector3 iMJaA = rb0?rb0->getInvInertiaTensorWorld()*solverConstraint.m_relpos1CrossNormal:btVector3(0,0,0);
                                denom0 = iMJaA.dot(solverConstraint.m_relpos1CrossNormal);
            }
        }
        if (multiBodyB)
        {
            const int ndofB  = multiBodyB->getNumDofs() + 6;
            jacB = &m_data.m_jacobians[solverConstraint.m_jacBindex];
            lambdaB = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
            for (int i = 0; i < ndofB; ++i)
            {
                btScalar j = jacB[i] ;
                btScalar l =lambdaB[i];
                denom1 += j*l;
            }
            
        } else
        {
            if (rb1)
            {
                                btVector3 iMJaB = rb1?rb1->getInvInertiaTensorWorld()*solverConstraint.m_relpos2CrossNormal:btVector3(0,0,0);
                                denom1 = iMJaB.dot(solverConstraint.m_relpos2CrossNormal);
            }
        }
        
        
        
        btScalar d = denom0+denom1+infoGlobal.m_globalCfm;
        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 restitution = 0.f;
    btScalar penetration = isFriction? 0 : cp.getDistance();
    
    btScalar rel_vel = 0.f;
    int ndofA  = 0;
    int ndofB  = 0;
    {
        
        btVector3 vel1,vel2;
        if (multiBodyA)
        {
            ndofA  = multiBodyA->getNumDofs() + 6;
            btScalar* jacA = &m_data.m_jacobians[solverConstraint.m_jacAindex];
            for (int i = 0; i < ndofA ; ++i)
                rel_vel += multiBodyA->getVelocityVector()[i] * jacA[i];
        } else
        {
            if (rb0)
            {
                                btSolverBody* solverBodyA = &m_tmpSolverBodyPool[solverConstraint.m_solverBodyIdA];
                                rel_vel += solverConstraint.m_contactNormal1.dot(rb0?solverBodyA->m_linearVelocity+solverBodyA->m_externalForceImpulse:btVector3(0,0,0))
                                + solverConstraint.m_relpos1CrossNormal.dot(rb0?solverBodyA->m_angularVelocity:btVector3(0,0,0));
        
            }
        }
        if (multiBodyB)
        {
            ndofB  = multiBodyB->getNumDofs() + 6;
            btScalar* jacB = &m_data.m_jacobians[solverConstraint.m_jacBindex];
            for (int i = 0; i < ndofB ; ++i)
                rel_vel += multiBodyB->getVelocityVector()[i] * jacB[i];
            
        } else
        {
            if (rb1)
            {
                                btSolverBody* solverBodyB = &m_tmpSolverBodyPool[solverConstraint.m_solverBodyIdB];
                                rel_vel += solverConstraint.m_contactNormal2.dot(rb1?solverBodyB->m_linearVelocity+solverBodyB->m_externalForceImpulse:btVector3(0,0,0))
                        + solverConstraint.m_relpos2CrossNormal.dot(rb1?solverBodyB->m_angularVelocity:btVector3(0,0,0));

            }
        }

        solverConstraint.m_friction =combinedTorsionalFriction;
        
        if(!isFriction)
        {
            restitution =  restitutionCurve(rel_vel, cp.m_combinedRestitution, infoGlobal.m_restitutionVelocityThreshold);
            if (restitution <= btScalar(0.))
            {
                restitution = 0.f;
            }
        }
    }
    
    
    solverConstraint.m_appliedImpulse = 0.f;
    solverConstraint.m_appliedPushImpulse = 0.f;
    
    {
        
        btScalar velocityError = 0 - rel_vel;// * damping;      //note for friction restitution is always set to 0 (check above) so it is acutally velocityError = -rel_vel for friction
        
       
        
        btScalar velocityImpulse = velocityError*solverConstraint.m_jacDiagABInv;
        
        solverConstraint.m_rhs = velocityImpulse;
        solverConstraint.m_rhsPenetration = 0.f;
        solverConstraint.m_lowerLimit = -solverConstraint.m_friction;
        solverConstraint.m_upperLimit = solverConstraint.m_friction;
        
        solverConstraint.m_cfm = infoGlobal.m_globalCfm*solverConstraint.m_jacDiagABInv;
        
        
        
    }
    
}

btMultiBodySolverConstraint&    btMultiBodyConstraintSolver::addMultiBodyFrictionConstraint(const btVector3& normalAxis,btPersistentManifold* manifold,int frictionIndex,btManifoldPoint& cp,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity, btScalar cfmSlip)
{
        BT_PROFILE("addMultiBodyFrictionConstraint");
        btMultiBodySolverConstraint& solverConstraint = m_multiBodyFrictionContactConstraints.expandNonInitializing();
    solverConstraint.m_orgConstraint = 0;
    solverConstraint.m_orgDofIndex = -1;
    
        solverConstraint.m_frictionIndex = frictionIndex;
        bool isFriction = true;

        const btMultiBodyLinkCollider* fcA = btMultiBodyLinkCollider::upcast(manifold->getBody0());
        const btMultiBodyLinkCollider* fcB = btMultiBodyLinkCollider::upcast(manifold->getBody1());
        
        btMultiBody* mbA = fcA? fcA->m_multiBody : 0;
        btMultiBody* mbB = fcB? fcB->m_multiBody : 0;

        int solverBodyIdA = mbA? -1 : getOrInitSolverBody(*colObj0,infoGlobal.m_timeStep);
        int solverBodyIdB = mbB ? -1 : getOrInitSolverBody(*colObj1,infoGlobal.m_timeStep);

        solverConstraint.m_solverBodyIdA = solverBodyIdA;
        solverConstraint.m_solverBodyIdB = solverBodyIdB;
        solverConstraint.m_multiBodyA = mbA;
        if (mbA)
                solverConstraint.m_linkA = fcA->m_link;

        solverConstraint.m_multiBodyB = mbB;
        if (mbB)
                solverConstraint.m_linkB = fcB->m_link;

        solverConstraint.m_originalContactPoint = &cp;

        setupMultiBodyContactConstraint(solverConstraint, normalAxis, cp, infoGlobal,relaxation,isFriction, desiredVelocity, cfmSlip);
        return solverConstraint;
}

btMultiBodySolverConstraint&    btMultiBodyConstraintSolver::addMultiBodyTorsionalFrictionConstraint(const btVector3& normalAxis,btPersistentManifold* manifold,int frictionIndex,btManifoldPoint& cp,
                                                                btScalar combinedTorsionalFriction,
                                                                                                     btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity, btScalar cfmSlip)
{
    BT_PROFILE("addMultiBodyRollingFrictionConstraint");

        bool useTorsionalAndConeFriction = (infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS && ((infoGlobal.m_solverMode&SOLVER_DISABLE_IMPLICIT_CONE_FRICTION) == 0));

    btMultiBodySolverConstraint& solverConstraint = useTorsionalAndConeFriction? m_multiBodyTorsionalFrictionContactConstraints.expandNonInitializing() : m_multiBodyFrictionContactConstraints.expandNonInitializing();
    solverConstraint.m_orgConstraint = 0;
    solverConstraint.m_orgDofIndex = -1;
    
    solverConstraint.m_frictionIndex = frictionIndex;
    bool isFriction = true;
    
    const btMultiBodyLinkCollider* fcA = btMultiBodyLinkCollider::upcast(manifold->getBody0());
    const btMultiBodyLinkCollider* fcB = btMultiBodyLinkCollider::upcast(manifold->getBody1());
    
    btMultiBody* mbA = fcA? fcA->m_multiBody : 0;
    btMultiBody* mbB = fcB? fcB->m_multiBody : 0;
    
    int solverBodyIdA = mbA? -1 : getOrInitSolverBody(*colObj0,infoGlobal.m_timeStep);
    int solverBodyIdB = mbB ? -1 : getOrInitSolverBody(*colObj1,infoGlobal.m_timeStep);
    
    solverConstraint.m_solverBodyIdA = solverBodyIdA;
    solverConstraint.m_solverBodyIdB = solverBodyIdB;
    solverConstraint.m_multiBodyA = mbA;
    if (mbA)
        solverConstraint.m_linkA = fcA->m_link;
    
    solverConstraint.m_multiBodyB = mbB;
    if (mbB)
        solverConstraint.m_linkB = fcB->m_link;
    
    solverConstraint.m_originalContactPoint = &cp;
    
    setupMultiBodyTorsionalFrictionConstraint(solverConstraint, normalAxis, cp, combinedTorsionalFriction,infoGlobal,relaxation,isFriction, desiredVelocity, cfmSlip);
    return solverConstraint;
}

void    btMultiBodyConstraintSolver::convertMultiBodyContact(btPersistentManifold* manifold,const btContactSolverInfo& infoGlobal)
{
        const btMultiBodyLinkCollider* fcA = btMultiBodyLinkCollider::upcast(manifold->getBody0());
        const btMultiBodyLinkCollider* fcB = btMultiBodyLinkCollider::upcast(manifold->getBody1());
        
        btMultiBody* mbA = fcA? fcA->m_multiBody : 0;
        btMultiBody* mbB = fcB? fcB->m_multiBody : 0;

        btCollisionObject* colObj0=0,*colObj1=0;

        colObj0 = (btCollisionObject*)manifold->getBody0();
        colObj1 = (btCollisionObject*)manifold->getBody1();

        int solverBodyIdA = mbA? -1 : getOrInitSolverBody(*colObj0,infoGlobal.m_timeStep);
        int solverBodyIdB = mbB ? -1 : getOrInitSolverBody(*colObj1,infoGlobal.m_timeStep);

//      btSolverBody* solverBodyA = mbA ? 0 : &m_tmpSolverBodyPool[solverBodyIdA];
//      btSolverBody* solverBodyB = mbB ? 0 : &m_tmpSolverBodyPool[solverBodyIdB];


//      if (!solverBodyA || (solverBodyA->m_invMass.isZero() && (!solverBodyB || solverBodyB->m_invMass.isZero())))
        //      return;

    //only a single rollingFriction per manifold
    int rollingFriction=1;
    
        for (int j=0;j<manifold->getNumContacts();j++)
        {

                btManifoldPoint& cp = manifold->getContactPoint(j);

                if (cp.getDistance() <= manifold->getContactProcessingThreshold())
                {
                
                        btScalar relaxation;

                        int frictionIndex = m_multiBodyNormalContactConstraints.size();

                        btMultiBodySolverConstraint& solverConstraint = m_multiBodyNormalContactConstraints.expandNonInitializing();

        //              btRigidBody* rb0 = btRigidBody::upcast(colObj0);
        //              btRigidBody* rb1 = btRigidBody::upcast(colObj1);
            solverConstraint.m_orgConstraint = 0;
            solverConstraint.m_orgDofIndex = -1;
                        solverConstraint.m_solverBodyIdA = solverBodyIdA;
                        solverConstraint.m_solverBodyIdB = solverBodyIdB;
                        solverConstraint.m_multiBodyA = mbA;
                        if (mbA)
                                solverConstraint.m_linkA = fcA->m_link;

                        solverConstraint.m_multiBodyB = mbB;
                        if (mbB)
                                solverConstraint.m_linkB = fcB->m_link;

                        solverConstraint.m_originalContactPoint = &cp;

                        bool isFriction = false;
                        setupMultiBodyContactConstraint(solverConstraint, cp.m_normalWorldOnB,cp, infoGlobal, relaxation, isFriction);

//                      const btVector3& pos1 = cp.getPositionWorldOnA();
//                      const btVector3& pos2 = cp.getPositionWorldOnB();

#define ENABLE_FRICTION
#ifdef ENABLE_FRICTION
                        solverConstraint.m_frictionIndex = frictionIndex;

                        

                        btPlaneSpace1(cp.m_normalWorldOnB,cp.m_lateralFrictionDir1,cp.m_lateralFrictionDir2);
                        cp.m_lateralFrictionDir1.normalize();
                        cp.m_lateralFrictionDir2.normalize();

            if (rollingFriction > 0 )
             {
                if (cp.m_combinedSpinningFriction>0)
                {
                    addMultiBodyTorsionalFrictionConstraint(cp.m_normalWorldOnB,manifold,frictionIndex,cp,cp.m_combinedSpinningFriction, colObj0,colObj1, relaxation,infoGlobal);
                }
                if (cp.m_combinedRollingFriction>0)
                {

                                        applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_ROLLING_FRICTION);
                                        applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_ROLLING_FRICTION);
                                        applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_ROLLING_FRICTION);
                                        applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_ROLLING_FRICTION);
                                        
                                        if (cp.m_lateralFrictionDir1.length()>0.001)
                            addMultiBodyTorsionalFrictionConstraint(cp.m_lateralFrictionDir1,manifold,frictionIndex,cp,cp.m_combinedRollingFriction, colObj0,colObj1, relaxation,infoGlobal);

                                        if (cp.m_lateralFrictionDir2.length()>0.001)
                    addMultiBodyTorsionalFrictionConstraint(cp.m_lateralFrictionDir2,manifold,frictionIndex,cp,cp.m_combinedRollingFriction, colObj0,colObj1, relaxation,infoGlobal);
                }
              rollingFriction--;
            }
                        if (!(infoGlobal.m_solverMode & SOLVER_ENABLE_FRICTION_DIRECTION_CACHING) || !(cp.m_contactPointFlags&BT_CONTACT_FLAG_LATERAL_FRICTION_INITIALIZED))
                        {/*
                                cp.m_lateralFrictionDir1 = vel - cp.m_normalWorldOnB * rel_vel;
                                btScalar lat_rel_vel = cp.m_lateralFrictionDir1.length2();
                                if (!(infoGlobal.m_solverMode & SOLVER_DISABLE_VELOCITY_DEPENDENT_FRICTION_DIRECTION) && lat_rel_vel > SIMD_EPSILON)
                                {
                                        cp.m_lateralFrictionDir1 *= 1.f/btSqrt(lat_rel_vel);
                                        if((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
                                        {
                                                cp.m_lateralFrictionDir2 = cp.m_lateralFrictionDir1.cross(cp.m_normalWorldOnB);
                                                cp.m_lateralFrictionDir2.normalize();//??
                                                applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                                applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                                addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir2,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation);

                                        }

                                        applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                        applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                        addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation);

                                } else
                                */
                                {
                                        

                                        applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                        applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                        addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1,manifold,frictionIndex,cp,colObj0,colObj1, relaxation,infoGlobal);
                    

                                        if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
                                        {
                                                applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                                applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
                                                addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir2,manifold,frictionIndex,cp,colObj0,colObj1, relaxation,infoGlobal);
                                        }

                                        if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS) && (infoGlobal.m_solverMode & SOLVER_DISABLE_VELOCITY_DEPENDENT_FRICTION_DIRECTION))
                                        {
                                                cp.m_contactPointFlags|=BT_CONTACT_FLAG_LATERAL_FRICTION_INITIALIZED;
                                        }
                                }

                        } else
                        {
                                addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1,manifold,frictionIndex,cp,colObj0,colObj1, relaxation,infoGlobal,cp.m_contactMotion1, cp.m_frictionCFM);

                                if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
                                        addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir2,manifold,frictionIndex,cp,colObj0,colObj1, relaxation, infoGlobal,cp.m_contactMotion2, cp.m_frictionCFM);

                                //setMultiBodyFrictionConstraintImpulse( solverConstraint, solverBodyIdA, solverBodyIdB, cp, infoGlobal);
                                //todo:
                                solverConstraint.m_appliedImpulse = 0.f;
                                solverConstraint.m_appliedPushImpulse = 0.f;
                        }
                

#endif //ENABLE_FRICTION

                }
        }
}

void btMultiBodyConstraintSolver::convertContacts(btPersistentManifold** manifoldPtr,int numManifolds, const btContactSolverInfo& infoGlobal)
{
        //btPersistentManifold* manifold = 0;

        for (int i=0;i<numManifolds;i++)
        {
                btPersistentManifold* manifold= manifoldPtr[i];
                const btMultiBodyLinkCollider* fcA = btMultiBodyLinkCollider::upcast(manifold->getBody0());
                const btMultiBodyLinkCollider* fcB = btMultiBodyLinkCollider::upcast(manifold->getBody1());
                if (!fcA && !fcB)
                {
                        //the contact doesn't involve any Featherstone btMultiBody, so deal with the regular btRigidBody/btCollisionObject case
                        convertContact(manifold,infoGlobal);
                } else
                {
                        convertMultiBodyContact(manifold,infoGlobal);
                }
        }

        //also convert the multibody constraints, if any

        
        for (int i=0;i<m_tmpNumMultiBodyConstraints;i++)
        {
                btMultiBodyConstraint* c = m_tmpMultiBodyConstraints[i];
                m_data.m_solverBodyPool = &m_tmpSolverBodyPool;
                m_data.m_fixedBodyId = m_fixedBodyId;
                
                c->createConstraintRows(m_multiBodyNonContactConstraints,m_data,        infoGlobal);
        }

}



btScalar btMultiBodyConstraintSolver::solveGroup(btCollisionObject** bodies,int numBodies,btPersistentManifold** manifold,int numManifolds,btTypedConstraint** constraints,int numConstraints,const btContactSolverInfo& info, btIDebugDraw* debugDrawer,btDispatcher* dispatcher)
{
        //printf("btMultiBodyConstraintSolver::solveGroup: numBodies=%d, numConstraints=%d\n", numBodies, numConstraints);
        return btSequentialImpulseConstraintSolver::solveGroup(bodies,numBodies,manifold,numManifolds,constraints,numConstraints,info,debugDrawer,dispatcher);
}

#if 0
static void applyJointFeedback(btMultiBodyJacobianData& data, const btMultiBodySolverConstraint& solverConstraint, int jacIndex, btMultiBody* mb, btScalar appliedImpulse)
{
        if (appliedImpulse!=0 && mb->internalNeedsJointFeedback())
        {
                //todo: get rid of those temporary memory allocations for the joint feedback
                btAlignedObjectArray<btScalar> forceVector;
                int numDofsPlusBase = 6+mb->getNumDofs();
                forceVector.resize(numDofsPlusBase);
                for (int i=0;i<numDofsPlusBase;i++)
                {
                        forceVector[i] = data.m_jacobians[jacIndex+i]*appliedImpulse;
                }
                btAlignedObjectArray<btScalar> output;
                output.resize(numDofsPlusBase);
                bool applyJointFeedback = true;
                mb->calcAccelerationDeltasMultiDof(&forceVector[0],&output[0],data.scratch_r,data.scratch_v,applyJointFeedback);
        }
}
#endif


void btMultiBodyConstraintSolver::writeBackSolverBodyToMultiBody(btMultiBodySolverConstraint& c, btScalar deltaTime)
{
#if 1 
        
        //bod->addBaseForce(m_gravity * bod->getBaseMass());
        //bod->addLinkForce(j, m_gravity * bod->getLinkMass(j));

        if (c.m_orgConstraint)
        {
                c.m_orgConstraint->internalSetAppliedImpulse(c.m_orgDofIndex,c.m_appliedImpulse);
        }
        

        if (c.m_multiBodyA)
        {
                
                c.m_multiBodyA->setCompanionId(-1);
                btVector3 force = c.m_contactNormal1*(c.m_appliedImpulse/deltaTime);
                btVector3 torque = c.m_relpos1CrossNormal*(c.m_appliedImpulse/deltaTime);
                if (c.m_linkA<0)
                {
                        c.m_multiBodyA->addBaseConstraintForce(force);
                        c.m_multiBodyA->addBaseConstraintTorque(torque);
                } else
                {
                        c.m_multiBodyA->addLinkConstraintForce(c.m_linkA,force);
                                //b3Printf("force = %f,%f,%f\n",force[0],force[1],force[2]);//[0],torque[1],torque[2]);
                        c.m_multiBodyA->addLinkConstraintTorque(c.m_linkA,torque);
                }
        }
        
        if (c.m_multiBodyB)
        {
                {
                        c.m_multiBodyB->setCompanionId(-1);
                        btVector3 force = c.m_contactNormal2*(c.m_appliedImpulse/deltaTime);
                        btVector3 torque = c.m_relpos2CrossNormal*(c.m_appliedImpulse/deltaTime);
                        if (c.m_linkB<0)
                        {
                                c.m_multiBodyB->addBaseConstraintForce(force);
                                c.m_multiBodyB->addBaseConstraintTorque(torque);
                        } else
                        {
                                {
                                        c.m_multiBodyB->addLinkConstraintForce(c.m_linkB,force);
                                        //b3Printf("t = %f,%f,%f\n",force[0],force[1],force[2]);//[0],torque[1],torque[2]);
                                        c.m_multiBodyB->addLinkConstraintTorque(c.m_linkB,torque);
                                }
                                        
                        }
                }
        }
#endif

#ifndef DIRECTLY_UPDATE_VELOCITY_DURING_SOLVER_ITERATIONS

        if (c.m_multiBodyA)
        {
                c.m_multiBodyA->applyDeltaVeeMultiDof(&m_data.m_deltaVelocitiesUnitImpulse[c.m_jacAindex],c.m_appliedImpulse);
        }
        
        if (c.m_multiBodyB)
        {
                c.m_multiBodyB->applyDeltaVeeMultiDof(&m_data.m_deltaVelocitiesUnitImpulse[c.m_jacBindex],c.m_appliedImpulse);
        }
#endif



}

btScalar btMultiBodyConstraintSolver::solveGroupCacheFriendlyFinish(btCollisionObject** bodies,int numBodies,const btContactSolverInfo& infoGlobal)
{
        BT_PROFILE("btMultiBodyConstraintSolver::solveGroupCacheFriendlyFinish");
        int numPoolConstraints = m_multiBodyNormalContactConstraints.size();
        

        //write back the delta v to the multi bodies, either as applied impulse (direct velocity change) 
        //or as applied force, so we can measure the joint reaction forces easier
        for (int i=0;i<numPoolConstraints;i++)
        {
                btMultiBodySolverConstraint& solverConstraint = m_multiBodyNormalContactConstraints[i];
                writeBackSolverBodyToMultiBody(solverConstraint,infoGlobal.m_timeStep);

                writeBackSolverBodyToMultiBody(m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex],infoGlobal.m_timeStep);

                if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
                {
                        writeBackSolverBodyToMultiBody(m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1],infoGlobal.m_timeStep);
                }
        }


        for (int i=0;i<m_multiBodyNonContactConstraints.size();i++)
        {
                btMultiBodySolverConstraint& solverConstraint = m_multiBodyNonContactConstraints[i];
                writeBackSolverBodyToMultiBody(solverConstraint,infoGlobal.m_timeStep);
        }

        
        if (infoGlobal.m_solverMode & SOLVER_USE_WARMSTARTING)
        {
                BT_PROFILE("warm starting write back");
                for (int j=0;j<numPoolConstraints;j++)
                {
                        const btMultiBodySolverConstraint& solverConstraint = m_multiBodyNormalContactConstraints[j];
                        btManifoldPoint* pt = (btManifoldPoint*) solverConstraint.m_originalContactPoint;
                        btAssert(pt);
                        pt->m_appliedImpulse = solverConstraint.m_appliedImpulse;
                        pt->m_appliedImpulseLateral1 = m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_appliedImpulse;
                        
                        //printf("pt->m_appliedImpulseLateral1 = %f\n", pt->m_appliedImpulseLateral1);
                        if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
                        {
                                pt->m_appliedImpulseLateral2 = m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_appliedImpulse;
                        }
                        //do a callback here?
                }
        }
#if 0
        //multibody joint feedback
        {
                BT_PROFILE("multi body joint feedback");
                for (int j=0;j<numPoolConstraints;j++)
                {
                        const btMultiBodySolverConstraint& solverConstraint = m_multiBodyNormalContactConstraints[j];
                
                        //apply the joint feedback into all links of the btMultiBody
                        //todo: double-check the signs of the applied impulse

                        if(solverConstraint.m_multiBodyA && solverConstraint.m_multiBodyA->isMultiDof())
                        {
                                applyJointFeedback(m_data,solverConstraint, solverConstraint.m_jacAindex,solverConstraint.m_multiBodyA, solverConstraint.m_appliedImpulse*btSimdScalar(1./infoGlobal.m_timeStep));
                        }
                        if(solverConstraint.m_multiBodyB && solverConstraint.m_multiBodyB->isMultiDof())
                        {
                                applyJointFeedback(m_data,solverConstraint, solverConstraint.m_jacBindex,solverConstraint.m_multiBodyB,solverConstraint.m_appliedImpulse*btSimdScalar(-1./infoGlobal.m_timeStep));
                        }
#if 0
                        if (m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_multiBodyA && m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_multiBodyA->isMultiDof())
                        {
                                applyJointFeedback(m_data,m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex],
                                        m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_jacAindex,
                                        m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_multiBodyA,
                                        m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_appliedImpulse*btSimdScalar(1./infoGlobal.m_timeStep));

                        }
                        if (m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_multiBodyB && m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_multiBodyB->isMultiDof())
                        {
                                applyJointFeedback(m_data,m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex],
                                        m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_jacBindex,
                                        m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_multiBodyB,
                                        m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_appliedImpulse*btSimdScalar(-1./infoGlobal.m_timeStep));
                        }
                
                        if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
                        {
                                if (m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_multiBodyA && m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_multiBodyA->isMultiDof())
                                {
                                        applyJointFeedback(m_data,m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1],
                                                m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_jacAindex,
                                                m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_multiBodyA,
                                                m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_appliedImpulse*btSimdScalar(1./infoGlobal.m_timeStep));
                                }

                                if (m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_multiBodyB && m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_multiBodyB->isMultiDof())
                                {
                                        applyJointFeedback(m_data,m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1],
                                                m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_jacBindex,
                                                m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_multiBodyB,
                                                m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex+1].m_appliedImpulse*btSimdScalar(-1./infoGlobal.m_timeStep));
                                }
                        }
#endif
                }
        
                for (int i=0;i<m_multiBodyNonContactConstraints.size();i++)
                {
                        const btMultiBodySolverConstraint& solverConstraint = m_multiBodyNonContactConstraints[i];
                        if(solverConstraint.m_multiBodyA && solverConstraint.m_multiBodyA->isMultiDof())
                        {
                                applyJointFeedback(m_data,solverConstraint, solverConstraint.m_jacAindex,solverConstraint.m_multiBodyA, solverConstraint.m_appliedImpulse*btSimdScalar(1./infoGlobal.m_timeStep));
                        }
                        if(solverConstraint.m_multiBodyB && solverConstraint.m_multiBodyB->isMultiDof())
                        {
                                applyJointFeedback(m_data,solverConstraint, solverConstraint.m_jacBindex,solverConstraint.m_multiBodyB,solverConstraint.m_appliedImpulse*btSimdScalar(1./infoGlobal.m_timeStep));
                        }
                }
        }

        numPoolConstraints = m_multiBodyNonContactConstraints.size();

#if 0
        //@todo: m_originalContactPoint is not initialized for btMultiBodySolverConstraint
        for (int i=0;i<numPoolConstraints;i++)
        {
                const btMultiBodySolverConstraint& c = m_multiBodyNonContactConstraints[i];

                btTypedConstraint* constr = (btTypedConstraint*)c.m_originalContactPoint;
                btJointFeedback* fb = constr->getJointFeedback();
                if (fb)
                {
                        fb->m_appliedForceBodyA += c.m_contactNormal1*c.m_appliedImpulse*constr->getRigidBodyA().getLinearFactor()/infoGlobal.m_timeStep;
                        fb->m_appliedForceBodyB += c.m_contactNormal2*c.m_appliedImpulse*constr->getRigidBodyB().getLinearFactor()/infoGlobal.m_timeStep;
                        fb->m_appliedTorqueBodyA += c.m_relpos1CrossNormal* constr->getRigidBodyA().getAngularFactor()*c.m_appliedImpulse/infoGlobal.m_timeStep;
                        fb->m_appliedTorqueBodyB += c.m_relpos2CrossNormal* constr->getRigidBodyB().getAngularFactor()*c.m_appliedImpulse/infoGlobal.m_timeStep; /*RGM ???? */
                        
                }

                constr->internalSetAppliedImpulse(c.m_appliedImpulse);
                if (btFabs(c.m_appliedImpulse)>=constr->getBreakingImpulseThreshold())
                {
                        constr->setEnabled(false);
                }

        }
#endif 
#endif

        return btSequentialImpulseConstraintSolver::solveGroupCacheFriendlyFinish(bodies,numBodies,infoGlobal);
}


void  btMultiBodyConstraintSolver::solveMultiBodyGroup(btCollisionObject** bodies,int numBodies,btPersistentManifold** manifold,int numManifolds,btTypedConstraint** constraints,int numConstraints,btMultiBodyConstraint** multiBodyConstraints, int numMultiBodyConstraints, const btContactSolverInfo& info, btIDebugDraw* debugDrawer,btDispatcher* dispatcher)
{
        //printf("solveMultiBodyGroup: numBodies=%d, numConstraints=%d, numManifolds=%d, numMultiBodyConstraints=%d\n", numBodies, numConstraints, numManifolds, numMultiBodyConstraints);

        //printf("solveMultiBodyGroup start\n");
        m_tmpMultiBodyConstraints = multiBodyConstraints;
        m_tmpNumMultiBodyConstraints = numMultiBodyConstraints;
        
        btSequentialImpulseConstraintSolver::solveGroup(bodies,numBodies,manifold,numManifolds,constraints,numConstraints,info,debugDrawer,dispatcher);

        m_tmpMultiBodyConstraints = 0;
        m_tmpNumMultiBodyConstraints = 0;
        

}