TAPsSpring.cpp

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/******************************************************************************
TAPsSpring.cpp

Spring class is a class for a spring connecting between two particles in 3D.

SUKITTI PUNAK   (09/15/2004)
UPDATE          (09/15/2004)
******************************************************************************/
#include "TAPsSpring.hpp"
// Using Inclusion Model (i.e. definitions are included in declarations)
//                       (this name.cpp is included in name.hpp)
// Each friend is defined directly inside its declaration.

BEGIN_NAMESPACE_TAPs
//=============================================================================
// Constructors and Destructor
//-----------------------------------------------------------------------------
// Spring Constructor
template <typename T>
Spring<T>::Spring
(
    Particle<T> &P1, 
    Particle<T> &P2, 
    T k, T d, T l 
)   : 
    m_rcP1( P1 ), 
    m_rcP2( P2 ), 
    m_tK( k ), 
    m_tD( d ), 
    m_tL( l )
{}
//-----------------------------------------------------------------------------
// Spring Constructor
template <typename T>
Spring<T>::Spring
(
    Particle<T> &P1, 
    Particle<T> &P2, 
    T k, T d
)   : 
    m_rcP1( P1 ), 
    m_rcP2( P2 ), 
    m_tK( k ), 
    m_tD( d )
{
    T x = P2.GetPosition().GetX() - P1.GetPosition().GetX();
    T y = P2.GetPosition().GetY() - P1.GetPosition().GetY();
    T z = P2.GetPosition().GetZ() - P1.GetPosition().GetZ();
    m_tL = sqrt( x*x + y*y + z*z );
}
//-----------------------------------------------------------------------------
// Spring Destructor
template <typename T>
Spring<T>::~Spring()
{}
//-----------------------------------------------------------------------------
//=============================================================================
// Calculate and Return the (Internal) Force of a Spring
//-----------------------------------------------------------------------------
template <typename T>
Vector3<T> Spring<T>::GetForce() const
{
    // Local Variables ---------------------------------------------------------
    // spring current length vector
    Vector3<T> cL = ( m_rcP1.GetPosition() - m_rcP2.GetPosition() );
    // spring current length scalar
    T scl = cL.Length();
    // velocity difference of the two particles linked by the spring
    Vector3<T> V = ( m_rcP1.GetVelocity() - m_rcP2.GetVelocity() );

    // F1 = -{Ks(l - r) + Kd[(V1-V2)*L]/l}*L/l
    // F2 = -F1
    //   where Ks = spring stiffness, Kd = spring damping,
    //     V1 and V2 are velocity of particles linked by the spring
    //     r = spring rest length
    //     L = vector of difference of positions of particle#1 and #2
    //     l = magnitude of L
    return -( (m_tK * (scl - m_tL)) +  (m_tD * ((V*cL) / scl)) ) * (cL / scl);
}
//-----------------------------------------------------------------------------
//=============================================================================
// Get/Set Functions
//-----------------------------------------------------------------------------
// Get Particle #1
template <typename T>
inline Particle<T> & Spring<T>::GetParticleOne ()
{   return m_rcP1;  }
//-----------------------------------------------------------------------------
// Get Particle #2
template <typename T>
inline Particle<T> & Spring<T>::GetParticleTwo ()
{   return m_rcP2;  }
//-----------------------------------------------------------------------------
// Get Constant K
template <typename T>
inline T Spring<T>::GetConstantK () const
{   return m_tK;    }
//-----------------------------------------------------------------------------
// Get Damping D
template <typename T>
inline T Spring<T>::GetDampingD () const
{   return m_tD;    }
//-----------------------------------------------------------------------------
// Get Rest Length L
template <typename T>
inline T Spring<T>::GetRestLengthL() const
{   return m_tL;    }
//-----------------------------------------------------------------------------
// Get Current Length
template <typename T>
inline T Spring<T>::GetCurrentLength() const
{   return ( m_rcP1.GetPosition() - m_rcP2.GetPosition() ).Length();    }
//-----------------------------------------------------------------------------
//=============================================================================
END_NAMESPACE_TAPs
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