/usr/include/sofa/component/odesolver/DampVelocitySolver.h is in libsofa1-dev 1.0~beta4-6.
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*       SOFA, Simulation Open-Framework Architecture, version 1.0 beta 4      *
*                (c) 2006-2009 MGH, INRIA, USTL, UJF, CNRS                    *
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* 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.                                             *
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License *
* for more details.                                                           *
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* You should have received a copy of the GNU Lesser General Public License    *
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* 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                             *
******************************************************************************/
#ifndef SOFA_COMPONENT_ODESOLVER_DampVelocitySolver_H
#define SOFA_COMPONENT_ODESOLVER_DampVelocitySolver_H
#include <sofa/core/componentmodel/behavior/OdeSolver.h>
#include <sofa/component/odesolver/OdeSolverImpl.h>
namespace sofa
{
namespace component
{
namespace odesolver
{
/** Velocity damping and thresholding.
This is not an ODE solver, but it can be used as a post-process after a real ODE solver.
*/
class SOFA_COMPONENT_ODESOLVER_API DampVelocitySolver : public sofa::component::odesolver::OdeSolverImpl
{
public:
    DampVelocitySolver();
    void solve (double dt);
    Data<double> rate;
    Data<double> threshold;
	/// Given an input derivative order (0 for position, 1 for velocity, 2 for acceleration),
	/// how much will it affect the output derivative of the given order.
	virtual double getIntegrationFactor(int inputDerivative, int outputDerivative) const
	{
		const double dt = getContext()->getDt();
		double matrix[3][3] = {
			{ 1, 0, 0},
			{ 0, exp(-rate.getValue()*dt), 0},
			{ 0, 0, 0}};
		if (inputDerivative >= 3 || outputDerivative >= 3)
			return 0;
		else
			return matrix[outputDerivative][inputDerivative];
	}
	/// Given a solution of the linear system,
	/// how much will it affect the output derivative of the given order.
	///
	virtual double getSolutionIntegrationFactor(int /*outputDerivative*/) const
	{
		return 0;
	}
};
} // namespace odesolver
} // namespace component
} // namespace sofa
#endif
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