Damping in the magnetism plug-in

magnetism_plugin_test_code.cxx

/* start test code here */
/* Link 0 */
CDynamics3DMultiBodyObjectModel::CLink* pcLink0 = 
   dynamic_cast<CDynamics3DMultiBodyObjectModel::CLink*>(itDipole0->Body);

btMultiBodyLinkCollider& col0 = pcLink0->m_cMultiBodyLink;

btScalar* vel0 = col0.m_multiBody->getJointVelMultiDof(col0.m_link);

btVector3 cDampingTorque0(vel0[0],vel0[1],vel0[2]);
//btVector3 cDampingTorque0(vel0[0]*vel0[0]+vel0[0],
//                          vel0[1]*vel0[1]+vel0[1],
//                          vel0[2]*vel0[2]+vel0[2]);
//it is not right to use 2nd level as (vel0[0]*vel0[0]+vel0[0]), this changes the direction

//btScalar fConstant = 0.00;
// actually, I think there is no bad to remove the friction. The key problem is not lacking of friction, but the overreact within a timestep, which leads to the vibration.
btScalar fConstant = 0.000001;

cDampingTorque0 *= -fConstant;
itDipole0->Body->ApplyTorque(cDampingTorque0);

/* Link 1 */
CDynamics3DMultiBodyObjectModel::CLink* pcLink1 = 
   dynamic_cast<CDynamics3DMultiBodyObjectModel::CLink*>(itDipole1->Body);

btMultiBodyLinkCollider& col1 = pcLink1->m_cMultiBodyLink;

btScalar* vel1 = col1.m_multiBody->getJointVelMultiDof(col1.m_link);

btVector3 cDampingTorque1(vel1[0],vel1[1],vel1[2]);

cDampingTorque1 *= -fConstant;
itDipole1->Body->ApplyTorque(cDampingTorque1);