/// <summary>
/// Checks the distance between the particles and corrects it, if they are to near.
/// </summary>
/// <param name="particles">The particles.</param>
/// <param name="grid">The grid.</param>
private void CheckParticleDistance(FluidParticles particles, IndexGrid grid)
{
float minDist = 0.5f * CellSpace;
float minDistSq = minDist * minDist;
Vector2 dist;
for (int i = 0; i < particles.Count; i++)
{
foreach (var nIdx in grid.GetNeighbourIndex(particles[i]))
{
Vector2.Sub(ref particles[nIdx].Position, ref particles[i].Position, out dist);
float distLenSq = dist.LengthSquared;
if (distLenSq < minDistSq)
{
if (distLenSq > Constants.FLOAT_EPSILON)
{
float distLen = (float)Math.Sqrt((double)distLenSq);
Vector2.Mult(ref dist, 0.5f * (distLen - minDist) / distLen, out dist);
Vector2.Sub(ref particles[nIdx].Position, ref dist, out particles[nIdx].Position);
Vector2.Sub(ref particles[nIdx].PositionOld, ref dist, out particles[nIdx].PositionOld);
Vector2.Add(ref particles[i].Position, ref dist, out particles[i].Position);
Vector2.Add(ref particles[i].PositionOld, ref dist, out particles[i].PositionOld);
}
else
{
float diff = 0.5f * minDist;
particles[nIdx].Position.Y -= diff;
particles[nIdx].PositionOld.Y -= diff;
particles[i].Position.Y += diff;
particles[i].PositionOld.Y += diff;
}
}
}
}
}
public SPHSimulation(float cellSpace, RectangleF domain)
{
this.CellSpace = cellSpace;
this.Domain = domain;
this.Viscosity = Constants.VISC0SITY;
this.m_grid = new IndexGrid(cellSpace, domain);
this.SKGeneral = new SKPoly6(cellSpace);
this.SKPressure = new SKSpiky(cellSpace);
this.SKViscosity = new SKViscosity(cellSpace);
}
/// <summary>
/// Calculates the pressure and densities.
/// </summary>
/// <param name="particles">The particles.</param>
/// <param name="grid">The grid.</param>
private void CalculatePressureAndDensities(FluidParticles particles, IndexGrid grid)
{
Vector2 dist;
foreach (var particle in particles)
{
particle.Density = 0.0f;
foreach (var nIdx in grid.GetNeighbourIndex(particle))
{
Vector2.Sub(ref particle.Position, ref particles[nIdx].Position, out dist);
particle.Density += particle.Mass * this.SKGeneral.Calculate(ref dist);
}
particle.UpdatePressure();
}
}
/// <summary>
/// Calculates the pressure and viscosity forces.
/// </summary>
/// <param name="particles">The particles.</param>
/// <param name="grid">The grid.</param>
/// <param name="globalForce">The global force.</param>
private void CalculateForces(FluidParticles particles, IndexGrid grid, Vector2 globalForce)
{
Vector2 f, dist;
float scalar;
for (int i = 0; i < particles.Count; i++)
{
// Add global force to every particle
particles[i].Force += globalForce;
foreach (var nIdx in grid.GetNeighbourIndex(particles[i]))
{
// Prevent double tests
if (nIdx < i)
{
if (particles[nIdx].Density > Constants.FLOAT_EPSILON)
{
Vector2.Sub(ref particles[i].Position, ref particles[nIdx].Position, out dist);
// pressure
// f = particles[nIdx].Mass * ((particles[i].Pressure + particles[nIdx].Pressure) / (2.0f * particles[nIdx].Density)) * WSpikyGrad(ref dist);
scalar = particles[nIdx].Mass * (particles[i].Pressure + particles[nIdx].Pressure) / (2.0f * particles[nIdx].Density);
f = this.SKPressure.CalculateGradient(ref dist);
Vector2.Mult(ref f, scalar, out f);
particles[i].Force -= f;
particles[nIdx].Force += f;
// viscosity
// f = particles[nIdx].Mass * ((particles[nIdx].Velocity - particles[i].Velocity) / particles[nIdx].Density) * WViscosityLap(ref dist) * Constants.VISC0SITY;
scalar = particles[nIdx].Mass * this.SKViscosity.CalculateLaplacian(ref dist) * this.Viscosity * 1 / particles[nIdx].Density;
f = particles[nIdx].Velocity - particles[i].Velocity;
Vector2.Mult(ref f, scalar, out f);
particles[i].Force += f;
particles[nIdx].Force -= f;
}
}
}
}
}
