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/******************************************************************************
* SOFA, Simulation Open-Framework Architecture, version 1.0 beta 4 *
* (c) 2006-2009 MGH, INRIA, USTL, UJF, CNRS *
* *
* This library is free software; you can redistribute it and/or modify it *
* under the terms of the GNU Lesser General Public License as published by *
* the Free Software Foundation; either version 2.1 of the License, or (at *
* your option) any later version. *
* *
* This library is distributed in the hope that it will be useful, but WITHOUT *
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or *
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License *
* for more details. *
* *
* You should have received a copy of the GNU Lesser General Public License *
* along with this library; if not, write to the Free Software Foundation, *
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. *
*******************************************************************************
* SOFA :: Modules *
* *
* Authors: The SOFA Team and external contributors (see Authors.txt) *
* *
* Contact information: contact@sofa-framework.org *
******************************************************************************/
// Author: François Faure, INRIA-UJF, (C) 2006
//
// Copyright: See COPYING file that comes with this distribution
#ifndef SOFA_COMPONENT_FORCEFIELD_STIFFSPRINGFORCEFIELD_INL
#define SOFA_COMPONENT_FORCEFIELD_STIFFSPRINGFORCEFIELD_INL
#include <sofa/component/forcefield/StiffSpringForceField.h>
#include <sofa/component/forcefield/SpringForceField.inl>
#include <assert.h>
namespace sofa
{
namespace component
{
namespace forcefield
{
template<class DataTypes>
void StiffSpringForceField<DataTypes>::init()
{
this->SpringForceField<DataTypes>::init();
}
template<class DataTypes>
void StiffSpringForceField<DataTypes>::addSpringForce( double& potentialEnergy, VecDeriv& f1, const VecCoord& p1, const VecDeriv& v1, VecDeriv& f2, const VecCoord& p2, const VecDeriv& v2, int i, const Spring& spring)
{
int a = spring.m1;
int b = spring.m2;
Coord u = p2[b]-p1[a];
Real d = u.norm();
if( d>1.0e-4 )
{
Real inverseLength = 1.0f/d;
u *= inverseLength;
Real elongation = (Real)(d - spring.initpos);
potentialEnergy += elongation * elongation * spring.ks / 2;
/* serr<<"StiffSpringForceField<DataTypes>::addSpringForce, p1 = "<<p1<<sendl;
serr<<"StiffSpringForceField<DataTypes>::addSpringForce, p2 = "<<p2<<sendl;
serr<<"StiffSpringForceField<DataTypes>::addSpringForce, new potential energy = "<<potentialEnergy<<sendl;*/
Deriv relativeVelocity = v2[b]-v1[a];
Real elongationVelocity = dot(u,relativeVelocity);
Real forceIntensity = (Real)(spring.ks*elongation+spring.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)spring.ks-tgt) * u[j] * u[k];
}
m[j][j] += tgt;
}
}
else // null length, no force and no stiffness
{
Mat& m = this->dfdx[i];
for( int j=0; j<N; ++j )
{
for( int k=0; k<N; ++k )
{
m[j][k] = 0;
}
}
}
}
template<class DataTypes>
void StiffSpringForceField<DataTypes>::addSpringDForce(VecDeriv& f1, const VecDeriv& dx1, VecDeriv& f2, const VecDeriv& dx2, int i, const Spring& spring, double kFactor, double /*bFactor*/)
{
const int a = spring.m1;
const int b = spring.m2;
const Coord d = dx2[b]-dx1[a];
Deriv dforce = this->dfdx[i]*d;
dforce *= kFactor;
f1[a]+=dforce;
f2[b]-=dforce;
//serr<<"StiffSpringForceField<DataTypes>::addSpringDForce, a="<<a<<", b="<<b<<", dforce ="<<dforce<<sendl;
}
template<class DataTypes>
void StiffSpringForceField<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());
m_potentialEnergy = 0;
//serr<<"StiffSpringForceField<DataTypes>::addForce()"<<sendl;
for (unsigned int i=0; i<springs.size(); i++)
{
//serr<<"StiffSpringForceField<DataTypes>::addForce() between "<<springs[i].m1<<" and "<<springs[i].m2<<sendl;
this->addSpringForce(m_potentialEnergy,f1,x1,v1,f2,x2,v2, i, springs[i]);
}
}
template<class DataTypes>
void StiffSpringForceField<DataTypes>::addDForce(VecDeriv& df1, VecDeriv& df2, const VecDeriv& dx1, const VecDeriv& dx2, double kFactor, double bFactor)
{
df1.resize(dx1.size());
df2.resize(dx2.size());
//serr<<"StiffSpringForceField<DataTypes>::addDForce, dx1 = "<<dx1<<sendl;
//serr<<"StiffSpringForceField<DataTypes>::addDForce, df1 before = "<<f1<<sendl;
const helper::vector<Spring>& springs = this->springs.getValue();
for (unsigned int i=0; i<springs.size(); i++)
{
this->addSpringDForce(df1,dx1,df2,dx2, i, springs[i], kFactor, bFactor);
}
//serr<<"StiffSpringForceField<DataTypes>::addDForce, df1 = "<<f1<<sendl;
//serr<<"StiffSpringForceField<DataTypes>::addDForce, df2 = "<<f2<<sendl;
}
template<class DataTypes>
void StiffSpringForceField<DataTypes>::addKToMatrix(sofa::defaulttype::BaseMatrix * mat, double kFact, unsigned int &offset)
{
const sofa::helper::vector<Spring >& ss = this->springs.getValue();
for (unsigned int e=0; e<ss.size(); e++)
{
const Spring& s = ss[e];
unsigned p1 = offset+N*s.m1;
unsigned p2 = offset+N*s.m2;
for(int i=0; i<N; i++)
for (int j=0; j<N; j++)
{
Real k = (Real)(this->dfdx[e][i][j]*kFact);
mat->add(p1+i,p1+j, -k);
mat->add(p1+i,p2+j, k);
mat->add(p2+i,p1+j, k);//or mat->add(p1+j,p2+i, k);
mat->add(p2+i,p2+j, -k);
}
}
}
} // namespace forcefield
} // namespace component
} // namespace sofa
#endif
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