private void CreateSprings(FluidParticle p)
{
for (int i = 0; i < p.Neighbours.Count; ++i)
{
FluidParticle neighbour = p.Neighbours[i];
if (p.Index >= neighbour.Index)
{
continue;
}
float q;
Vector2.DistanceSquared(ref p.Position, ref neighbour.Position, out q);
if (q > _influenceRadiusSquared)
{
continue;
}
SpringHash hash = new SpringHash {
P0 = p, P1 = neighbour
};
if (!_springs.ContainsKey(hash))
{
//TODO: Use pool?
Spring spring = new Spring(p, neighbour)
{
RestLength = (float)Math.Sqrt(q)
};
_springs.Add(hash, spring);
}
}
}
public void Update(float deltaTime)
{
if (deltaTime == 0)
{
return;
}
float deltaTime2 = 0.5f * deltaTime * deltaTime;
ComputeNeighbours();
ApplyForces();
if (Definition.UseViscosity)
{
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
ApplyViscosity(p, deltaTime);
}
}
}
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
p.Update(deltaTime);
}
}
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
DoubleDensityRelaxation(p, deltaTime2);
}
}
if (Definition.UsePlasticity)
{
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
CreateSprings(p);
}
}
}
AdjustSprings(deltaTime);
UpdateVelocities(deltaTime);
}
public FluidParticle AddParticle(Vector2 position)
{
FluidParticle particle = new FluidParticle(position)
{
Index = Particles.Count
};
Particles.Add(particle);
return(particle);
}
public void Update(float timeStep)
{
_timeStep2 = 0.5f * timeStep * timeStep;
ComputeNeighbours();
ApplyForces();
if (Definition.UseViscosity)
{
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
ApplyViscosity(p, timeStep);
}
}
}
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
p.Update(timeStep);
}
}
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
DoubleDensityRelaxation(p);
}
}
if (Definition.UsePlasticity)
{
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
CreateSprings(p);
}
}
}
AdjustSprings(timeStep);
UpdateVelocities(timeStep);
}
private void ApplyViscosity(FluidParticle p, float timeStep)
{
for (int i = 0; i < p.Neighbours.Count; ++i)
{
FluidParticle neighbour = p.Neighbours[i];
if (p.Index >= neighbour.Index)
{
continue;
}
float q;
Vector2.DistanceSquared(ref p.Position, ref neighbour.Position, out q);
if (q > _influenceRadiusSquared)
{
continue;
}
Vector2 direction;
Vector2.Subtract(ref neighbour.Position, ref p.Position, out direction);
if (direction.LengthSquared() < float.Epsilon)
{
continue;
}
direction.Normalize();
Vector2 deltaVelocity;
Vector2.Subtract(ref p.Velocity, ref neighbour.Velocity, out deltaVelocity);
float u;
Vector2.Dot(ref deltaVelocity, ref direction, out u);
if (u > 0.0f)
{
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float impulseFactor = 0.5f * timeStep * q * (u * (Definition.ViscositySigma + Definition.ViscosityBeta * u));
Vector2 impulse;
Vector2.Multiply(ref direction, -impulseFactor, out impulse);
p.ApplyImpulse(ref impulse);
Vector2.Multiply(ref direction, impulseFactor, out impulse);
neighbour.ApplyImpulse(ref impulse);
}
}
}
private void ApplyViscosity(FluidParticle p, float timeStep)
{
for (int i = 0; i < p.Neighbours.Count; ++i)
{
FluidParticle neighbour = p.Neighbours[i];
if (p.Index >= neighbour.Index)
{
continue;
}
float q;
Vector2.DistanceSquared(ref p.Position, ref neighbour.Position, out q);
if (q > _influenceRadiusSquared)
{
continue;
}
Vector2 direction;
Vector2.Subtract(ref neighbour.Position, ref p.Position, out direction);
if (direction.LengthSquared() < float.Epsilon)
{
continue;
}
direction.Normalize();
Vector2 deltaVelocity;
Vector2.Subtract(ref p.Velocity, ref neighbour.Velocity, out deltaVelocity);
float u;
Vector2.Dot(ref deltaVelocity, ref direction, out u);
if (u > 0.0f)
{
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float impulseFactor = 0.5f * timeStep * q * (u * (Definition.ViscositySigma + Definition.ViscosityBeta * u));
Vector2 impulse;
Vector2.Multiply(ref direction, -impulseFactor, out impulse);
p.ApplyImpulse(ref impulse);
Vector2.Multiply(ref direction, impulseFactor, out impulse);
neighbour.ApplyImpulse(ref impulse);
}
}
}
public void Add(FluidParticle particle)
{
ulong key = HashKey(particle.Position);
List<FluidParticle> bucket;
if (!_hash.TryGetValue(key, out bucket))
{
if (_bucketPool.Count > 0)
{
bucket = _bucketPool.Pop();
}
else
{
bucket = new List<FluidParticle>();
}
_hash.Add(key, bucket);
}
bucket.Add(particle);
}
public void Add(FluidParticle particle)
{
ulong key = HashKey(particle.Position);
List<FluidParticle> bucket;
if (!_hash.TryGetValue(key, out bucket))
{
if (_bucketPool.Count > 0)
{
bucket = _bucketPool.Pop();
}
else
{
bucket = new List<FluidParticle>();
}
_hash.Add(key, bucket);
}
bucket.Add(particle);
}
private void ComputeNeighbours()
{
_hashGrid.GridSize = Definition.InfluenceRadius;
_hashGrid.Clear();
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
if (p.IsActive)
{
_hashGrid.Add(p);
}
}
for (int i = 0; i < Particles.Count; ++i)
{
FluidParticle p = Particles[i];
p.Neighbours.Clear();
_hashGrid.Find(ref p.Position, p.Neighbours);
}
}
//private void DoubleDensityRelaxation1(FluidParticle p, float timeStep)
//{
// _density = 0;
// _densityNear = 0;
// _len2 = p.Neighbours.Count;
// if (_len2 > MaxNeighbors)
// _len2 = MaxNeighbors;
// for (_j = 0; _j < _len2; _j++)
// {
// _q = Vector2.DistanceSquared(p.Position, p.Neighbours[_j].Position);
// _distanceCache[_j] = _q;
// if (_q < _influenceRadiusSquared && _q != 0)
// {
// _q = (float)Math.Sqrt(_q);
// _q /= Definition.InfluenceRadius;
// _qq = ((1 - _q) * (1 - _q));
// _density += _qq;
// _densityNear += _qq * (1 - _q);
// }
// }
// _pressure = Definition.Stiffness * (_density - Definition.DensityRest);
// _pressureNear = Definition.StiffnessNear * _densityNear;
// _dx = Vector2.Zero;
// for (_j = 0; _j < _len2; _j++)
// {
// _q = _distanceCache[_j];
// if (_q < _influenceRadiusSquared && _q != 0)
// {
// _q = (float)Math.Sqrt(_q);
// _rij = p.Neighbours[_j].Position;
// _rij -= p.Position;
// _rij *= 1 / _q;
// _q /= _influenceRadiusSquared;
// _d = ((timeStep * timeStep) * (_pressure * (1 - _q) + _pressureNear * (1 - _q) * (1 - _q)));
// _rij *= _d * 0.5f;
// p.Neighbours[_j].Position += _rij;
// _dx -= _rij;
// }
// }
// p.Position += _dx;
//}
private void DoubleDensityRelaxation(FluidParticle particle, float deltaTime2)
{
_density = 0.0f;
_densityNear = 0.0f;
int neightborCount = particle.Neighbours.Count;
if (neightborCount > MaxNeighbors)
{
neightborCount = MaxNeighbors;
}
for (int i = 0; i < neightborCount; ++i)
{
FluidParticle neighbour = particle.Neighbours[i];
if (particle.Index == neighbour.Index)
{
continue;
}
float q;
Vector2.DistanceSquared(ref particle.Position, ref neighbour.Position, out q);
_distanceCache[i] = q;
if (q > _influenceRadiusSquared)
{
continue;
}
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float densityDelta = q * q;
_density += densityDelta;
_densityNear += densityDelta * q;
}
_pressure = Definition.Stiffness * (_density - Definition.DensityRest);
_pressureNear = Definition.StiffnessNear * _densityNear;
// For gameplay purposes
particle.Density = _density + _densityNear;
particle.Pressure = _pressure + _pressureNear;
Vector2 delta = Vector2.Zero;
for (int i = 0; i < neightborCount; ++i)
{
FluidParticle neighbour = particle.Neighbours[i];
if (particle.Index == neighbour.Index)
{
continue;
}
float q = _distanceCache[i];
if (q > _influenceRadiusSquared)
{
continue;
}
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float dispFactor = deltaTime2 * (q * (_pressure + _pressureNear * q));
Vector2 direction;
Vector2.Subtract(ref neighbour.Position, ref particle.Position, out direction);
if (direction.LengthSquared() < float.Epsilon)
{
continue;
}
direction.Normalize();
Vector2 disp;
Vector2.Multiply(ref direction, dispFactor, out disp);
Vector2.Add(ref neighbour.Position, ref disp, out neighbour.Position);
Vector2.Multiply(ref direction, -dispFactor, out disp);
Vector2.Add(ref delta, ref disp, out delta);
}
Vector2.Add(ref particle.Position, ref delta, out particle.Position);
}
public Spring(FluidParticle p0, FluidParticle p1)
{
Active = true;
P0 = p0;
P1 = p1;
}
public Spring(FluidParticle p0, FluidParticle p1)
{
Active = true;
P0 = p0;
P1 = p1;
}
public FluidParticle AddParticle(Vector2 p)
{
FluidParticle particle = new FluidParticle(p) { Index = Particles.Count };
Particles.Add(particle);
return particle;
}
private void CreateSprings(FluidParticle p)
{
for (int i = 0; i < p.Neighbours.Count; ++i)
{
FluidParticle neighbour = p.Neighbours[i];
if (p.Index >= neighbour.Index)
continue;
float q;
Vector2.DistanceSquared(ref p.Position, ref neighbour.Position, out q);
if (q > _influenceRadiusSquared)
continue;
SpringHash hash = new SpringHash { P0 = p, P1 = neighbour };
if (!_springs.ContainsKey(hash))
{
//TODO: Use pool?
Spring spring = new Spring(p, neighbour) { RestLength = (float)Math.Sqrt(q) };
_springs.Add(hash, spring);
}
}
}
//private void DoubleDensityRelaxation1(FluidParticle p, float timeStep)
//{
// _density = 0;
// _densityNear = 0;
// _len2 = p.Neighbours.Count;
// if (_len2 > MaxNeighbors)
// _len2 = MaxNeighbors;
// for (_j = 0; _j < _len2; _j++)
// {
// _q = Vector2.DistanceSquared(p.Position, p.Neighbours[_j].Position);
// _distanceCache[_j] = _q;
// if (_q < _influenceRadiusSquared && _q != 0)
// {
// _q = (float)Math.Sqrt(_q);
// _q /= Definition.InfluenceRadius;
// _qq = ((1 - _q) * (1 - _q));
// _density += _qq;
// _densityNear += _qq * (1 - _q);
// }
// }
// _pressure = Definition.Stiffness * (_density - Definition.DensityRest);
// _pressureNear = Definition.StiffnessNear * _densityNear;
// _dx = Vector2.Zero;
// for (_j = 0; _j < _len2; _j++)
// {
// _q = _distanceCache[_j];
// if (_q < _influenceRadiusSquared && _q != 0)
// {
// _q = (float)Math.Sqrt(_q);
// _rij = p.Neighbours[_j].Position;
// _rij -= p.Position;
// _rij *= 1 / _q;
// _q /= _influenceRadiusSquared;
// _d = ((timeStep * timeStep) * (_pressure * (1 - _q) + _pressureNear * (1 - _q) * (1 - _q)));
// _rij *= _d * 0.5f;
// p.Neighbours[_j].Position += _rij;
// _dx -= _rij;
// }
// }
// p.Position += _dx;
//}
private void DoubleDensityRelaxation(FluidParticle particle)
{
_density = 0.0f;
_densityNear = 0.0f;
int neightborCount = particle.Neighbours.Count;
if (neightborCount > MaxNeighbors)
neightborCount = MaxNeighbors;
for (int i = 0; i < neightborCount; ++i)
{
FluidParticle neighbour = particle.Neighbours[i];
if (particle.Index == neighbour.Index)
continue;
float q;
Vector2.DistanceSquared(ref particle.Position, ref neighbour.Position, out q);
_distanceCache[i] = q;
if (q > _influenceRadiusSquared)
continue;
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float densityDelta = q * q;
_density += densityDelta;
_densityNear += densityDelta * q;
}
_pressure = Definition.Stiffness * (_density - Definition.DensityRest);
_pressureNear = Definition.StiffnessNear * _densityNear;
// For gameplay purposes
particle.Density = _density + _densityNear;
particle.Pressure = _pressure + _pressureNear;
Vector2 delta = Vector2.Zero;
for (int i = 0; i < neightborCount; ++i)
{
FluidParticle neighbour = particle.Neighbours[i];
if (particle.Index == neighbour.Index)
continue;
float q = _distanceCache[i];
if (q > _influenceRadiusSquared)
continue;
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float dispFactor = _timeStep2 * (q * (_pressure + _pressureNear * q));
Vector2 direction;
Vector2.Subtract(ref neighbour.Position, ref particle.Position, out direction);
if (direction.LengthSquared() < float.Epsilon)
continue;
direction.Normalize();
Vector2 disp;
Vector2.Multiply(ref direction, dispFactor, out disp);
Vector2.Add(ref neighbour.Position, ref disp, out neighbour.Position);
Vector2.Multiply(ref direction, -dispFactor, out disp);
Vector2.Add(ref delta, ref disp, out delta);
}
Vector2.Add(ref particle.Position, ref delta, out particle.Position);
}
private void DoubleDensityRelaxation(FluidParticle p, float timeStep)
{
float density = 0.0f;
float densityNear = 0.0f;
for (int i = 0; i < p.Neighbours.Count; ++i)
{
FluidParticle neighbour = p.Neighbours[i];
if (p.Index == neighbour.Index)
{
continue;
}
float q;
Vector2.DistanceSquared(ref p.Position, ref neighbour.Position, out q);
if (q > _influenceRadiusSquared)
{
continue;
}
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float densityDelta = q * q;
density += densityDelta;
densityNear += densityDelta * q;
}
float pressure = Definition.Stiffness * (density - Definition.DensityRest);
float pressureNear = Definition.StiffnessNear * densityNear;
// For gameplay purposes
p.Density = density + densityNear;
p.Pressure = pressure + pressureNear;
Vector2 delta = Vector2.Zero;
for (int i = 0; i < p.Neighbours.Count; ++i)
{
FluidParticle neighbour = p.Neighbours[i];
if (p.Index == neighbour.Index)
{
continue;
}
float q;
Vector2.DistanceSquared(ref p.Position, ref neighbour.Position, out q);
if (q > _influenceRadiusSquared)
{
continue;
}
q = 1.0f - (float)Math.Sqrt(q) / Definition.InfluenceRadius;
float dispFactor = 0.5f * timeStep * timeStep * (q * (pressure + pressureNear * q));
Vector2 direction;
Vector2.Subtract(ref neighbour.Position, ref p.Position, out direction);
if (direction.LengthSquared() < float.Epsilon)
{
continue;
}
direction.Normalize();
Vector2 disp;
Vector2.Multiply(ref direction, dispFactor, out disp);
Vector2.Add(ref neighbour.Position, ref disp, out neighbour.Position);
Vector2.Multiply(ref direction, -dispFactor, out disp);
Vector2.Add(ref delta, ref disp, out delta);
}
Vector2.Add(ref p.Position, ref delta, out p.Position);
}