CentralDifferenceSolver.cpp

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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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*                               SOFA :: Modules                               *
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* Authors: The SOFA Team and external contributors (see Authors.txt)          *
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#include <sofa/component/odesolver/CentralDifferenceSolver.h>
#include <sofa/simulation/common/MechanicalVisitor.h>
#include <sofa/core/ObjectFactory.h>
#include <math.h>
#include <iostream>
#include "sofa/helper/system/thread/CTime.h"

using std::cerr;
using std::endl;

namespace sofa
{

namespace component
{

namespace odesolver
{

using namespace sofa::defaulttype;
using namespace core::componentmodel::behavior;

CentralDifferenceSolver::CentralDifferenceSolver()
: f_rayleighMass( initData(&f_rayleighMass,0.1,"rayleighMass","Rayleigh damping coefficient related to mass"))
{
}

void CentralDifferenceSolver::solve(double dt)
{
    MultiVector pos(this, VecId::position());
    MultiVector vel(this, VecId::velocity());
    MultiVector f(this, VecId::force());
    MultiVector dx(this, VecId::dx());
    const double r = f_rayleighMass.getValue();

    addSeparateGravity(dt);                // v += dt*g . Used if mass wants to added G separately from the other forces to v.

    //projectVelocity(vel);                  // initial velocities are projected to the constrained space

    // compute the current force
    computeForce(f);                       // f = P_n - K u_n

    accFromF(dx, f);                       // dx = M^{-1} ( P_n - K u_n )

    projectResponse(dx);                    // dx is projected to the constrained space

    // apply the solution
    if (r==0)
    {
#ifdef SOFA_NO_VMULTIOP // unoptimized version
        vel.peq( dx, dt );                  // vel = vel + dt M^{-1} ( P_n - K u_n )
    pos.peq( vel, dt );                    // pos = pos + h vel
#else // single-operation optimization
    simulation::MechanicalVMultiOpVisitor vmop;
    vmop.ops.resize(2);
    // vel += dx * dt
    vmop.ops[0].first = (VecId)vel;
    vmop.ops[0].second.push_back(std::make_pair((VecId)vel,1.0));
    vmop.ops[0].second.push_back(std::make_pair((VecId)dx,dt));
    // pos += vel * dt
    vmop.ops[1].first = (VecId)pos;
    vmop.ops[1].second.push_back(std::make_pair((VecId)pos,1.0));
    vmop.ops[1].second.push_back(std::make_pair((VecId)vel,dt));
    vmop.execute(getContext());
#endif
    }
    else
    {
#ifdef SOFA_NO_VMULTIOP // unoptimized version
        vel.teq( (1/dt - r/2)/(1/dt + r/2) );
        vel.peq( dx, 1/(1/dt + r/2) );     // vel = \frac{\frac{1}{dt} - \frac{r}{2}}{\frac{1}{dt} + \frac{r}{2}} vel + \frac{1}{\frac{1}{dt} + \frac{r}{2}} M^{-1} ( P_n - K u_n )
    pos.peq( vel, dt );                    // pos = pos + h vel
#else // single-operation optimization
    simulation::MechanicalVMultiOpVisitor vmop;
    vmop.ops.resize(2);
    vmop.ops[0].first = (VecId)vel;
    vmop.ops[0].second.push_back(std::make_pair((VecId)vel,(1/dt - r/2)/(1/dt + r/2)));
    vmop.ops[0].second.push_back(std::make_pair((VecId)dx,1/(1/dt + r/2)));
    vmop.ops[1].first = (VecId)pos;
    vmop.ops[1].second.push_back(std::make_pair((VecId)pos,1.0));
    vmop.ops[1].second.push_back(std::make_pair((VecId)vel,dt));
    vmop.execute(getContext());
#endif
    }
}

SOFA_DECL_CLASS(CentralDifferenceSolver)

int CentralDifferenceSolverClass = core::RegisterObject("Explicit time integrator using central difference (also known as Verlet of Leap-frop)")
.add< CentralDifferenceSolver >()
.addAlias("CentralDifference");
;

} // namespace odesolver

} // namespace component

} // namespace sofa