void solveColorMixing()
{
float strength = fluidSystemDef.colorMixingStrength;
if (strength > 0)
{
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
if ((contact.a.flags & contact.b.flags & FluidParticleType.ColorMixingParticle) > 0)
{
Color a = contact.a.color;
Color b = contact.b.color;
float dr = (b.r - a.r) * strength;
float dg = (b.g - a.g) * strength;
float db = (b.b - a.b) * strength;
float da = (b.a - a.a) * strength;
a.r += dr;
a.g += dg;
a.b += db;
a.a += da;
b.r -= dr;
b.g -= dg;
b.b -= db;
b.a -= da;
contact.a.color = a;
contact.b.color = b;
float dm = (contact.b.mass - contact.a.mass) * strength;
contact.a.mass += dm;
contact.b.mass -= dm;
}
}
}
}
void solveViscous()
{
float viscousStrength = fluidSystemDef.viscousStrength;
for (int i = 0; i < bodyContactBuffer.Count; i++)
{
FluidParticleBodyContact contact = bodyContactBuffer [i];
if ((contact.fp.flags & FluidParticleType.ViscousParticle) > 0)
{
// b2Vec2 v = b->GetLinearVelocityFromWorldPoint(p) -
// m_velocityBuffer.data[a];
Vector2 v = contact.body.velocity - contact.fp.velocity;
Vector2 f = viscousStrength * contact.mass * contact.weight * v;
contact.fp.velocity += getParticleInvMass() * f;
// b->ApplyLinearImpulse(-f, p, true);
}
}
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
if ((contact.flags & FluidParticleType.ViscousParticle) > 0)
{
Vector2 v = contact.b.velocity - contact.a.velocity;
Vector2 f = viscousStrength * contact.weight * v;
contact.a.velocity += f;
contact.b.velocity -= f;
}
}
}
void solveDamping(float dt)
{
// reduces normal velocity of each contact
float linearDamping = fluidSystemDef.dampingStrength;
float quadraticDamping = 1 / getCriticalVelocity(dt);
for (int i = 0; i < bodyContactBuffer.Count; i++)
{
FluidParticleBodyContact contact = bodyContactBuffer [i];
FluidParticle a = contact.fp;
Vector2 p = a.position;
Vector2 v = contact.body.velocity - a.velocity;
float vn = Vector2.Dot(v, contact.normal);
if (vn < 0)
{
float damping = Mathf.Max(linearDamping * contact.weight, Mathf.Min(-quadraticDamping * vn, 0.5f));
Vector2 f = damping * contact.mass * vn * contact.normal;
a.velocity += getParticleInvMass() * f;
contact.body.AddForceAtPosition(-f / dt, p);
}
}
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
Vector2 v = contact.b.velocity - contact.a.velocity;
float vn = Vector2.Dot(v, contact.normal);
if (vn < 0)
{
float damping = Mathf.Max(linearDamping * contact.weight, Mathf.Min(-quadraticDamping * vn, 0.5f));
Vector2 f = damping * vn * contact.normal;
contact.a.velocity += f;
contact.b.velocity -= f;
}
}
}
void addContact(FluidParticle a, FluidParticle b)
{
Vector2 d = b.position - a.position;
float distBtParticlesSq = d.sqrMagnitude;
if (distBtParticlesSq < squaredDiameter)
{
float dist = Mathf.Sqrt(distBtParticlesSq);
FluidParticleContact contact = new FluidParticleContact();
contactBuffer.Add(contact);
contact.a = a;
contact.b = b;
contact.flags = a.flags | b.flags;
contact.weight = 1 - dist * inverseDiameter; // * (b.mass / a.mass);
contact.normal = d / dist;
}
}
void computeWeight()
{
for (int i = 0; i < count; i++)
{
particleBuffer [i].weight = 0;
}
for (int i = 0; i < bodyContactBuffer.Count; i++)
{
FluidParticleBodyContact contact = bodyContactBuffer [i];
contact.fp.weight += contact.weight;
}
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
contact.a.weight += contact.weight;
contact.b.weight += contact.weight;
}
}
void solvePowder(float dt)
{
float powderStrength = fluidSystemDef.powderStrength * getCriticalVelocity(dt);
float minWeight = 1.0f - particleStride;
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
if ((contact.flags & FluidParticleType.PowderParticle) > 0)
{
if (contact.weight > minWeight)
{
Vector2 f = powderStrength * (contact.weight - minWeight) * contact.normal;
contact.a.velocity -= f;
contact.b.velocity += f;
}
}
}
}
void solveTensile(float dt)
{
for (int i = 0; i < count; i++)
{
particleBuffer [i].accumulation2 = Vector2.zero;
}
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
if ((contact.flags & FluidParticleType.TensileParticle) > 0)
{
Vector2 weightedNormal = (1 - contact.weight) * contact.weight * contact.normal;
contact.a.accumulation2 -= weightedNormal;
contact.b.accumulation2 += weightedNormal;
}
}
float criticalVelocity = getCriticalVelocity(dt);
float pressureStrength = fluidSystemDef.surfaceTensionPressureStrength * criticalVelocity;
float normalStrength = fluidSystemDef.surfaceTensionNormalStrength * criticalVelocity;
float maxVelocityVariation = maxParticleForce * criticalVelocity;
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
if ((contact.flags & FluidParticleType.TensileParticle) > 0)
{
float h = contact.a.weight + contact.b.weight;
Vector2 s = contact.b.accumulation2 - contact.a.accumulation2;
float fn = Mathf.Min(
pressureStrength * (h - 2) + normalStrength * Vector2.Dot(s, contact.normal),
maxVelocityVariation
) * contact.weight;
Vector2 f = fn * contact.normal;
contact.a.velocity -= f;
contact.b.velocity += f;
}
}
}
void solveStaticPressure(float dt)
{
float criticalPressure = getCriticalPressure(dt);
float pressurePerWeight = fluidSystemDef.staticPressureStrength * criticalPressure;
float maxPressure = maxParticlePressure * criticalPressure;
float relaxation = fluidSystemDef.staticPressureRelaxation;
for (int t = 0; t < fluidSystemDef.staticPressureIterations; t++)
{
for (int i = 0; i < count; i++)
{
particleBuffer [i].accumulation = 0;
}
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
if ((contact.flags & FluidParticleType.StaticPressureParticle) > 0)
{
contact.a.accumulation += contact.weight * contact.b.staticPressure;
contact.b.accumulation += contact.weight * contact.a.staticPressure;
}
}
for (int i = 0; i < count; i++)
{
FluidParticle fp = particleBuffer [i];
if ((fp.flags & FluidParticleType.StaticPressureParticle) > 0)
{
float h = (fp.accumulation + pressurePerWeight * (fp.weight - minParticleWeight)) / (fp.weight + relaxation);
fp.staticPressure = Mathf.Clamp(h, 0.0f, maxPressure);
}
else
{
fp.staticPressure = 0;
}
}
}
}
void solvePressure(float dt)
{
// calculates pressure as a linear function of density
float criticalPressure = getCriticalPressure(dt);
float pressurePerWeight = fluidSystemDef.pressureStrength * criticalPressure;
float maxPressure = maxParticlePressure * criticalPressure;
for (int i = 0; i < count; i++)
{
FluidParticle fp = particleBuffer [i];
float h = pressurePerWeight * Mathf.Max(0f, fp.weight - minParticleWeight);
fp.accumulation = Mathf.Min(h, maxPressure);
}
// // ignores particles which have their own repulsive force
// if (m_allParticleFlags & k_noPressureFlags)
// {
// for (int32 i = 0; i < m_count; i++)
// {
// if (m_flagsBuffer.data[i] & k_noPressureFlags)
// {
// m_accumulationBuffer[i] = 0;
// }
// }
// }
// static pressure
if ((allParticleFlags & FluidParticleType.StaticPressureParticle) > 0)
{
for (int i = 0; i < count; i++)
{
FluidParticle fp = particleBuffer [i];
if ((fp.flags & FluidParticleType.StaticPressureParticle) > 0)
{
fp.accumulation += fp.staticPressure;
}
}
}
// applies pressure between each particles in contact
float velocityPerPressure = dt / (fluidSystemDef.density * particleDiameter);
for (int i = 0; i < bodyContactBuffer.Count; i++)
{
FluidParticleBodyContact contact = bodyContactBuffer [i];
FluidParticle a = contact.fp;
Rigidbody2D b = contact.body;
Vector2 p = a.position;
float h = a.accumulation + pressurePerWeight * contact.weight;
Vector2 f = velocityPerPressure * contact.weight * contact.mass * h * contact.normal;
a.velocity -= getParticleInvMass() * f;
b.AddForceAtPosition(f / dt, p);
}
float strength = fluidSystemDef.temperaturMixingStrength;
for (int i = 0; i < contactBuffer.Count; i++)
{
FluidParticleContact contact = contactBuffer [i];
FluidParticle a = contact.a;
FluidParticle b = contact.b;
float h = a.accumulation + b.accumulation;
Vector2 f = velocityPerPressure * contact.weight * h * contact.normal;
a.velocity -= f;
b.velocity += f;
float t = (b.temperature - a.temperature) * strength;
a.temperature += t;
b.temperature -= t;
if (Mathf.Abs(a.mass - b.mass) >= 0.01f)
{
if (b.mass < a.mass)
{
a = contact.b;
b = contact.a;
}
a.velocity.y += fluidSystemDef.densityStrength;
b.velocity.y -= fluidSystemDef.densityStrength;
}
else if (Mathf.Abs(a.temperature - b.temperature) >= 0.1f)
{
if (b.temperature > a.temperature)
{
a = contact.b;
b = contact.a;
}
a.velocity.y += fluidSystemDef.temperatureStrength;
b.velocity.y -= fluidSystemDef.temperatureStrength;
}
}
}
