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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 "Wm5MassSpringSurface.h"
#include "Wm5Memory.h"
namespace Wm5
{
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
MassSpringSurface<Real,TVector>::MassSpringSurface (int numRows, int numCols,
Real step)
:
ParticleSystem<Real,TVector>(numRows*numCols, step)
{
mNumRows = numRows;
mNumCols = numCols;
mNumRowsM1 = mNumRows - 1;
mNumColsM1 = mNumCols - 1;
mPositionGrid = new1<TVector*>(mNumRows);
mVelocityGrid = new1<TVector*>(mNumRows);
for (int row = 0; row < mNumRows; ++row)
{
mPositionGrid[row] = &mPositions[mNumCols*row];
mVelocityGrid[row] = &mVelocities[mNumCols*row];
}
mConstantsR = new2<Real>(mNumCols, mNumRowsM1);
mLengthsR = new2<Real>(mNumCols, mNumRowsM1);
mConstantsC = new2<Real>(mNumColsM1, mNumRows);
mLengthsC = new2<Real>(mNumColsM1, mNumRows);
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
MassSpringSurface<Real,TVector>::~MassSpringSurface ()
{
delete1(mPositionGrid);
delete1(mVelocityGrid);
delete2(mConstantsR);
delete2(mLengthsR);
delete2(mConstantsC);
delete2(mLengthsC);
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
int MassSpringSurface<Real,TVector>::GetNumRows () const
{
return mNumRows;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
int MassSpringSurface<Real,TVector>::GetNumCols () const
{
return mNumCols;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
void MassSpringSurface<Real,TVector>::SetMass (int row, int col, Real mass)
{
ParticleSystem<Real,TVector>::SetMass(GetIndex(row, col), mass);
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
Real MassSpringSurface<Real,TVector>::GetMass (int row, int col) const
{
return ParticleSystem<Real,TVector>::GetMass(GetIndex(row, col));
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector** MassSpringSurface<Real,TVector>::Positions2D () const
{
return mPositionGrid;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector& MassSpringSurface<Real,TVector>::Position (int row, int col)
{
return ParticleSystem<Real,TVector>::Position(GetIndex(row, col));
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector** MassSpringSurface<Real,TVector>::Velocities2D () const
{
return mVelocityGrid;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector& MassSpringSurface<Real,TVector>::Velocity (int row, int col)
{
return ParticleSystem<Real,TVector>::Velocity(GetIndex(row, col));
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
Real& MassSpringSurface<Real,TVector>::ConstantR (int row, int col)
{
return mConstantsR[row][col];
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
Real& MassSpringSurface<Real,TVector>::LengthR (int row, int col)
{
return mLengthsR[row][col];
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
Real& MassSpringSurface<Real,TVector>::ConstantC (int row, int col)
{
return mConstantsC[row][col];
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
Real& MassSpringSurface<Real,TVector>::LengthC (int row, int col)
{
return mLengthsC[row][col];
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector MassSpringSurface<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 mPositions since the RK4 solver in ParticleSystem
// evaluates the acceleration function at intermediate positions. The
// edge and corner points of the surface of masses must be handled
// separately since each has fewer than four springs attached to it.
TVector acceleration = ExternalAcceleration(i,time,positions,
velocities);
TVector diff, force;
Real ratio;
int row, col, prev, next;
GetCoordinates(i, row, col);
if (row > 0)
{
prev = i - mNumCols; // index to previous row-neighbor
diff = positions[prev] - positions[i];
ratio = LengthR(row - 1, col)/diff.Length();
force = ConstantR(row - 1, col)*((Real)1 - ratio)*diff;
acceleration += mInvMasses[i]*force;
}
if (row < mNumRowsM1)
{
next = i + mNumCols; // index to next row-neighbor
diff = positions[next] - positions[i];
ratio = LengthR(row, col)/diff.Length();
force = ConstantR(row, col)*((Real)1 - ratio)*diff;
acceleration += mInvMasses[i]*force;
}
if (col > 0)
{
prev = i - 1; // index to previous col-neighbor
diff = positions[prev] - positions[i];
ratio = LengthC(row, col - 1)/diff.Length();
force = ConstantC(row, col - 1)*((Real)1 - ratio)*diff;
acceleration += mInvMasses[i]*force;
}
if (col < mNumColsM1)
{
next = i + 1; // index to next col-neighbor
diff = positions[next] - positions[i];
ratio = LengthC(row, col)/diff.Length();
force = ConstantC(row, col)*((Real)1 - ratio)*diff;
acceleration += mInvMasses[i]*force;
}
return acceleration;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
TVector MassSpringSurface<Real,TVector>::ExternalAcceleration (int, Real,
const TVector*, const TVector*)
{
return TVector::ZERO;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
int MassSpringSurface<Real,TVector>::GetIndex (int row, int col) const
{
return col + mNumCols*row;
}
//----------------------------------------------------------------------------
template <typename Real, typename TVector>
void MassSpringSurface<Real,TVector>::GetCoordinates (int i, int& row,
int& col) const
{
col = i % mNumCols;
row = i / mNumCols;
}
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
// Explicit instantiation.
//----------------------------------------------------------------------------
template WM5_PHYSICS_ITEM
class MassSpringSurface<float,Vector2f>;
template WM5_PHYSICS_ITEM
class MassSpringSurface<float,Vector3f>;
template WM5_PHYSICS_ITEM
class MassSpringSurface<double,Vector2d>;
template WM5_PHYSICS_ITEM
class MassSpringSurface<double,Vector3d>;
//----------------------------------------------------------------------------
}
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