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// Geometric Tools, LLC
// Copyright (c) 1998-2014
// Distributed under the Boost Software License, Version 1.0.
// http://www.boost.org/LICENSE_1_0.txt
// http://www.geometrictools.com/License/Boost/LICENSE_1_0.txt
//
// File Version: 5.0.1 (2010/10/01)
#include "Wm5PhysicsPCH.h"
#include "Wm5MassSpringCurve.h"
#include "Wm5Memory.h"
namespace Wm5
{
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
MassSpringCurve<Real,TVector>::MassSpringCurve (int numParticles, Real step)
:
ParticleSystem<Real,TVector>(numParticles, step)
{
mNumSprings = mNumParticles - 1;
mConstants = new1<Real>(mNumSprings);
mLengths = new1<Real>(mNumSprings);
memset(mConstants, 0, mNumSprings*sizeof(Real));
memset(mLengths, 0, mNumSprings*sizeof(Real));
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
MassSpringCurve<Real,TVector>::~MassSpringCurve ()
{
delete1(mConstants);
delete1(mLengths);
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
int MassSpringCurve<Real,TVector>::GetNumSprings () const
{
return mNumSprings;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
Real& MassSpringCurve<Real,TVector>::Constant (int i)
{
return mConstants[i];
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
Real& MassSpringCurve<Real,TVector>::Length (int i)
{
return mLengths[i];
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector MassSpringCurve<Real,TVector>::Acceleration (int i, Real time,
const TVector* positions, const TVector* velocities)
{
// Compute spring forces on position X[i]. The positions are not
// necessarily m_akPosition since the RK4 solver in ParticleSystem
// evaluates the acceleration function at intermediate positions. The end
// points of the curve of masses must be handled separately since each
// has only one spring attached to it.
TVector acceleration = ExternalAcceleration(i, time, positions,
velocities);
TVector diff, force;
Real ratio;
if (i > 0)
{
int iM1 = i-1;
diff = positions[iM1] - positions[i];
ratio = mLengths[iM1]/diff.Length();
force = mConstants[iM1]*((Real)1 - ratio)*diff;
acceleration += mInvMasses[i]*force;
}
int iP1 = i+1;
if (iP1 < mNumParticles)
{
diff = positions[iP1] - positions[i];
ratio = mLengths[i]/diff.Length();
force = mConstants[i]*((Real)1 - ratio)*diff;
acceleration += mInvMasses[i]*force;
}
return acceleration;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector MassSpringCurve<Real,TVector>::ExternalAcceleration (int, Real,
const TVector*, const TVector*)
{
return TVector::ZERO;
}
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
// Explicit instantiation.
//----------------------------------------------------------------------------
template WM5_PHYSICS_ITEM
class MassSpringCurve<float,Vector2f>;
template WM5_PHYSICS_ITEM
class MassSpringCurve<float,Vector3f>;
template WM5_PHYSICS_ITEM
class MassSpringCurve<double,Vector2d>;
template WM5_PHYSICS_ITEM
class MassSpringCurve<double,Vector3d>;
//----------------------------------------------------------------------------
}
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