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); }
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); }
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); } }
public Spring(FluidParticle p0, FluidParticle p1) { Active = true; P0 = p0; P1 = p1; }
//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); }