RepulsiveSpringForceField.inl

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/******************************************************************************
*       SOFA, Simulation Open-Framework Architecture, version 1.0 beta 3      *
*                (c) 2006-2008 MGH, INRIA, USTL, UJF, CNRS                    *
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* This library is free software; you can redistribute it and/or modify it     *
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* for more details.                                                           *
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*******************************************************************************
*                               SOFA :: Modules                               *
*                                                                             *
* Authors: The SOFA Team and external contributors (see Authors.txt)          *
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#ifndef SOFA_COMPONENT_INTERACTIONFORCEFIELD_REPULSIVESPRINGFORCEFIELD_INL
#define SOFA_COMPONENT_INTERACTIONFORCEFIELD_REPULSIVESPRINGFORCEFIELD_INL

#include <sofa/component/interactionforcefield/RepulsiveSpringForceField.h>
#include <sofa/component/forcefield/StiffSpringForceField.inl>

namespace sofa
{

namespace component
{

namespace interactionforcefield
{
using std::cerr;
using std::endl;

template<class DataTypes>
void RepulsiveSpringForceField<DataTypes>::addForce(VecDeriv& f1, VecDeriv& f2, const VecCoord& x1, const VecCoord& x2, const VecDeriv& v1, const VecDeriv& v2)
{
        const helper::vector<Spring>& springs= this->springs.getValue();
    this->dfdx.resize(springs.size());
    f1.resize(x1.size());
    f2.resize(x2.size());
    for (unsigned int i=0; i<springs.size(); i++)
    {
#if 1
        int a = springs[i].m1;
        int b = springs[i].m2;
        Coord u = x2[b]-x1[a];
        Real d = u.norm();
        if (d < springs[i].initpos)
        {
            Real inverseLength = 1.0f/d;
            u *= inverseLength;
            Real elongation = (Real)(d - springs[i].initpos);
            Deriv relativeVelocity = v2[b]-v1[a];
            Real elongationVelocity = dot(u,relativeVelocity);
            Real forceIntensity = (Real)(springs[i].ks*elongation+springs[i].kd*elongationVelocity);
            Deriv force = u*forceIntensity;
            f1[a]+=force;
            f2[b]-=force;
            
            Mat& m = this->dfdx[i];
            Real tgt = forceIntensity * inverseLength;
            for( int j=0; j<N; ++j )
            {
                for( int k=0; k<N; ++k )
                {
                    m[j][k] = ((Real)springs[i].ks-tgt) * u[j] * u[k];
                }
                m[j][j] += tgt;
            }
        }
        else
#endif
        {
            Mat& m = this->dfdx[i];
            for( int j=0; j<N; ++j )
                for( int k=0; k<N; ++k )
                    m[j][k] = 0.0;
        }
    }
}

template <class DataTypes> 
    double RepulsiveSpringForceField<DataTypes>::getPotentialEnergy()
{
    cerr<<"RepulsiveSpringForceField::getPotentialEnergy-not-implemented !!!"<<endl;
    return 0;
}


} // namespace interactionforcefield

} // namespace component

} // namespace sofa

#endif