public override void CalculateForceField(ParticleEnsemble ensemble)
{
// variable declarations
double posXi, posYi;
double posXj, posYj;
double ijSeparation = 0.0, LJforce = 0.0, PotentialEnergy = 0.0;
// variable initializations
int BoxHeight = ensemble.BoxHeight;
int BoxWidth = ensemble.BoxWidth;
double MaxForce = ensemble.MaxForceThreshold;
double MinForce = -1.0 * (ensemble.MaxForceThreshold);
DPVector zero = new DPVector(0, 0);
// initialize vectors holding forces
for (int i = 0; i < ensemble.NumberOfParticles; ++i)
{
LJforces[i] = zero;
}
ensemble.ResetAllParticlesNotWithinRange();
for (int i = 0; i < ensemble.NumberOfParticles; ++i)
{
Particle particlei = ensemble.GetParticle(i);
for (int j = (i + 1); j < ensemble.NumberOfParticles; ++j)
{
Particle particlej = ensemble.GetParticle(j);
// get the interparticle separation distances
ijSeparation = ensemble.GetInterParticleSeparation(i, j);
double LJgradientTermA = particlei.ParticleType.LJgradientTermA[particlej.TypeID];
double LJgradientTermB = particlei.ParticleType.LJgradientTermB[particlej.TypeID];
// update the radial distribution function
double cutoffDistance = particlei.ParticleType.MinimumDistance[particlej.TypeID]; // MinimumDistance[i, j];
if (ijSeparation < cutoffDistance)
{
// for each particle, change the appropriate element of the setWithinRangeOfAnotherParticle vector to true
posXi = particlei.Position.X;
posYi = particlei.Position.Y;
posXj = particlej.Position.X;
posYj = particlej.Position.Y;
LJforce = (posXj - posXi) * (LJgradientTermA / Math.Pow(ijSeparation, 13.0) + LJgradientTermB / Math.Pow(ijSeparation, 7.0)) / ijSeparation;
if (Math.Abs(LJforce) > MaxForce || Math.Abs(LJforce) < MinForce)
{
// error check for real-time stability...
LJforce = 0.0;
}
else if(double.IsNaN(LJforce) || double.IsInfinity(LJforce))
{
// error check for real-time stability...
LJforce = 0.0;
}
LJforces[i].X += LJforce;
LJforces[j].X += -1.0 * LJforce;
LJforce = (posYj - posYi) * (LJgradientTermA / Math.Pow(ijSeparation, 13.0) + LJgradientTermB / Math.Pow(ijSeparation, 7.0)) / ijSeparation;
if (Math.Abs(LJforce) > MaxForce || Math.Abs(LJforce) < MinForce)
{
// error check for real-time stability...
LJforce = 0.0;
}
else if (double.IsNaN(LJforce) || double.IsInfinity(LJforce))
{
// error check for real-time stability...
LJforce = 0.0;
}
LJforces[i].Y += LJforce;
LJforces[j].Y += -1.0 * LJforce;
ensemble.SetParticlesWithinRange(i, j);
ensemble.SetParticlesWithinRange(j, i);
}
//else
//{
// ensemble.SetParticlesNotWithinRange(i, j);
//ensemble.SetParticlesNotWithinRange(j, i);
//}
}
}
// set the forces in the Particle Ensemble Object
ensemble.AddForces(LJforces);
// set the potential energy
ensemble.AddPotentialEnergy(PotentialEnergy);
}
/// <summary>
/// function to calculate Soft Spheres forcefield
/// </summary>
/// <param name="ensemble"></param>
public override void CalculateForceField(ParticleEnsemble ensemble)
{
// variable declarations
int i;
double posXi, posYi, radius;
double PotentialEnergy = 0.0;
// variable initializations
int BoxHeight = ensemble.BoxHeight;
int BoxWidth = ensemble.BoxWidth;
DPVector zero = new DPVector(0, 0);
// #pragma omp parallel for
for (i = 0; i < ensemble.NumberOfParticles; ++i)
{
// initialize vectors holding forces
forces[i] = zero;
}
//#pragma omp parallel for
for (i = 0; i < ensemble.NumberOfParticles; ++i)
{
Particle particlei = ensemble.GetParticle(i);
posXi = particlei.Position.X;
posYi = particlei.Position.Y;
radius = particlei.Radius;
// get pixel vectors along the particle's X & Y axes for getting gradient of image field
// there are 2 steps to this process:
// (1) do some gaussian smoothing with a user defined width parameter (this determines how
// many pixels we need
// (2) determine the gradient from linear regression of the 3 surrounding points...
// cout << "particle " << i << " Xpos " << posXi << " Ypos " << posYi << endl;
// first get the vectors that we need - the length of the vectors depend on the width of the gaussian
// if the pixels are near the edge, the pixels beyond them (which arent in the image) are simply returned as zeros
if (m_CalculateForceField_TempArray.Length < RangeEitherSide + 1)
{
m_CalculateForceField_TempArray = new double[RangeEitherSide + 1];
}
int count;
GetSubsetOfPixelsAlongX(posYi, posXi, RangeEitherSide + 1, ref m_CalculateForceField_TempArray, out count);
forces[i].X = ensemble.GradientScaleFactor * GaussianSmoothedSlope(posXi, m_CalculateForceField_TempArray, count);
GetSubsetOfPixelsAlongY(posXi, posYi, RangeEitherSide + 1, ref m_CalculateForceField_TempArray, out count);
forces[i].Y = ensemble.GradientScaleFactor * GaussianSmoothedSlope(posYi, m_CalculateForceField_TempArray, count);
// get the gradient scale factor, depending on whether the particle is attractive or repulsive
ParticleInfo typeInfo = ParticleStaticObjects.AtomPropertiesDefinition.Lookup[(ensemble.Particles[i]).TypeID];
double attractiveOrRepulsiveFactor = typeInfo.AttractiveOrRepulsive;
forces[i].X *= attractiveOrRepulsiveFactor;
forces[i].Y *= attractiveOrRepulsiveFactor;
}
// set the forces in the Particle Ensemble Object
ensemble.AddForces(forces);
// add in the potential energy
ensemble.AddPotentialEnergy(PotentialEnergy);
}