MidpointSolver.cpp

/***************************************************************************
 *   This file is part of OpenCAL: Open Computer Animation Library         *
 *   I created OpenCAL as my master's thesis Computer Science (multimedia) *
 *   at the tUL university in Diepenbeek, Belgium                          *
 *                                                                         *
 *   Copyright (C) 2003-2004 by Jeroen Dierckx                             *
 *   jeroen.dierckx@student.luc.ac.be                                      *
 *                                                                         *
 ***************************************************************************/

// Includes
#include "MidpointSolver.h"
#include <OpenCAL/ODESource.h>
using namespace OpenCAL;

using namespace std;


/******************************
* Constructors and destructor *
******************************/

MidpointSolver::MidpointSolver()
{
}

MidpointSolver::~MidpointSolver()
{
}


/******************
* Other functions *
******************/

void MidpointSolver::solve(float stepSize, ODESource *source)
{
    source->fillState();
    source->fillDerivative();

    PhaseSpace &state = *(source->getState());
    PhaseSpace &deriv = *(source->getDerivative());
    
    // Copy the original state
    PhaseSpace x0 = state;

    // First, evaluate an Euler step at half the stepSize
    state.add(deriv, stepSize * 0.5f);

    // Recalculate the derivative
    source->fromState();
    source->fillDerivative();

    // Then, take a step using these values
    state = x0;
    state.add(deriv, stepSize);
    
    source->fromState();
}

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