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Point2PointConstraint.cpp

/*
 * Copyright (c) 2005 Erwin Coumans http://continuousphysics.com/Bullet/
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies.
 * Erwin Coumans makes no representations about the suitability 
 * of this software for any purpose.  
 * It is provided "as is" without express or implied warranty.
*/
#include "Point2PointConstraint.h"
#include "Dynamics/RigidBody.h"
#include "Dynamics/MassProps.h"


static RigidBody s_fixed(MassProps(0,SimdVector3(0.f,0.f,0.f)),0.f,0.f,1.f,1.f);
static int gConstraintId = 1;

Point2PointConstraint::Point2PointConstraint():
m_rbA(s_fixed),m_rbB(s_fixed)
{
      m_constraintId = gConstraintId++;//just create some unique ID for now

      s_fixed.setMassProps(0.f,SimdVector3(0.f,0.f,0.f));
}

Point2PointConstraint::Point2PointConstraint(RigidBody& rbA,RigidBody& rbB, const SimdVector3& pivotInA,const SimdVector3& pivotInB)
:m_rbA(rbA),m_rbB(rbB),m_pivotInA(pivotInA),m_pivotInB(pivotInB)
{
      m_constraintId = gConstraintId++;//just create some unique ID for now
}


Point2PointConstraint::Point2PointConstraint(RigidBody& rbA,const SimdVector3& pivotInA)
:m_rbA(rbA),m_rbB(s_fixed),m_pivotInA(pivotInA),m_pivotInB(rbA.getCenterOfMassTransform()(pivotInA))
{
      s_fixed.setMassProps(0.f,SimdVector3(1e10f,1e10f,1e10f));
      m_constraintId = gConstraintId++;//just create some unique ID for now
}

void  Point2PointConstraint::BuildJacobian()
{
      SimdVector3 normal(0,0,0);

      for (int i=0;i<3;i++)
      {
            normal[i] = 1;
            new (&m_jac[i]) JacobianEntry(
                  m_rbA.getCenterOfMassTransform().getBasis().transpose(),
                  m_rbB.getCenterOfMassTransform().getBasis().transpose(),
                  m_rbA.getCenterOfMassTransform()*m_pivotInA - m_rbA.getCenterOfMassPosition(),
                  m_rbB.getCenterOfMassTransform()*m_pivotInB - m_rbB.getCenterOfMassPosition(),
                  normal,
                  m_rbA.getInvInertiaDiagLocal(),
                  m_rbA.getInvMass(),
                  m_rbB.getInvInertiaDiagLocal(),
                  m_rbB.getInvMass());
            normal[i] = 0;
      }

}

void  Point2PointConstraint::SolveConstraint(SimdScalar     timeStep)
{
      SimdVector3 pivotAInW = m_rbA.getCenterOfMassTransform()*m_pivotInA;
      SimdVector3 pivotBInW = m_rbB.getCenterOfMassTransform()*m_pivotInB;


      SimdVector3 normal(0,0,0);
      SimdScalar tau = 0.3f;
      SimdScalar damping = 1.f;

//    SimdVector3 angvelA = m_rbA.getCenterOfMassTransform().getBasis().transpose() * m_rbA.getAngularVelocity();
//    SimdVector3 angvelB = m_rbB.getCenterOfMassTransform().getBasis().transpose() * m_rbB.getAngularVelocity();

      for (int i=0;i<3;i++)
      {           
            normal[i] = 1;
            SimdScalar jacDiagABInv = 1.f / m_jac[i].getDiagonal();

            SimdVector3 rel_pos1 = pivotAInW - m_rbA.getCenterOfMassPosition(); 
            SimdVector3 rel_pos2 = pivotBInW - m_rbB.getCenterOfMassPosition();
            //this jacobian entry could be re-used for all iterations
            
            SimdVector3 vel1 = m_rbA.getVelocityInLocalPoint(rel_pos1);
            SimdVector3 vel2 = m_rbB.getVelocityInLocalPoint(rel_pos2);
            SimdVector3 vel = vel1 - vel2;
            
            SimdScalar rel_vel;
            rel_vel = normal.dot(vel);

      /*
            //velocity error (first order error)
            SimdScalar rel_vel = m_jac[i].getRelativeVelocity(m_rbA.getLinearVelocity(),angvelA,
                                                                                    m_rbB.getLinearVelocity(),angvelB);
      */
      
            //positional error (zeroth order error)
            SimdScalar depth = -(pivotAInW - pivotBInW).dot(normal); //this is the error projected on the normal
            
            SimdScalar impulse = depth*tau/timeStep  * jacDiagABInv -  damping * rel_vel * jacDiagABInv * damping;

            SimdVector3 impulse_vector = normal * impulse;
            m_rbA.applyImpulse(impulse_vector, pivotAInW - m_rbA.getCenterOfMassPosition());
            m_rbB.applyImpulse(-impulse_vector, pivotBInW - m_rbB.getCenterOfMassPosition());
            
            normal[i] = 0;
      }
}

void  Point2PointConstraint::UpdateRHS(SimdScalar     timeStep)
{

}


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