//----------------------------------------------------------------------------------------------------------------------
//----------------------------------------------------------------------------------------------------------------------
/// Calculates the forces for a particle using leap frog method of integration
/// _currentParticle - The particle we are going to calculate the forces for
/// _particleIndex - Vector of all our particles if we want to brut force or the neighbour particles for SPH
/// _timeStep - the time step between updates
public void calcForces(particle _currentParticle, List<particle> _particleIndex, float _timeStep)
{
float densityCurrent = 0;
var gravitiy = new Vector3 (0f,-9.8f,0f);
var pressureGrad = Vector3.zero;
var viscosity = Vector3.zero;
var viscosityVector = Vector3.zero;
var Acceleration = Vector3.zero;
for(int i = 0; i<_particleIndex.Count;i++){
// Calculate desity of all particles
if(_currentParticle!=_particleIndex[i]){
densityCurrent += _particleIndex[i].getMass()*calcDensityKern(_currentParticle, _particleIndex[i]);
}
}
_currentParticle.setDensity(densityCurrent);
var pressTemp = Vector3.zero;
var visTemp = Vector3.zero;
float pressureCurrent, pressureNeighbour, pressure;
for(int i=0; i<_particleIndex.Count;i++)
{
// Calcualate pressure
pressureCurrent = m_gasConstant * (_currentParticle.getDensity() - _currentParticle.getRestDensity());
pressureNeighbour = m_gasConstant * (_particleIndex[i].getDensity() - _particleIndex[i].getRestDensity());
pressure = ((pressureCurrent /(pressureCurrent*pressureCurrent)) + (pressureNeighbour /(pressureNeighbour*pressureNeighbour)))*(_particleIndex[i].getMass());
pressTemp = calcPressureKern(_currentParticle,_particleIndex[i]);
//pressTemp*= pressure; //!omfg not an assignment
pressureGrad +=(pressTemp);
// Calculate viscosiy vector
viscosityVector = _particleIndex[i].getVel() - _currentParticle.getVel();
viscosityVector *=(_particleIndex[i].getMass());
viscosityVector /=(_particleIndex[i].getDensity());
// Calculate viscosiy
visTemp = calcViscosityKern(_currentParticle,_particleIndex[i]);
//visTemp = visTemp.cross(viscosityVector); //!omfg not an assignment
viscosity +=(visTemp);
}
viscosity *=m_viscosityCoefficient;
//Calcualate external force if the is one
var Forces = Vector3.zero;
if(m_externalForceStrenth != 0 && m_externalForceRadius != 0)
{
Forces = _currentParticle.getPos() - m_externalForcePos;
if (Forces.length()<=m_externalForceRadius && Forces.length() > 0)
{
//find the direction the force is in
Forces.Normalize();
//Forces *=((m_externalForceRadius-Forces.length())/m_externalForceRadius);
Forces *=(m_externalForceStrenth);
if(m_externalForcePush == false)
{
Forces =-Forces;
}
}
else
{
Forces.set(0f,0f,0f);
}
}
// Calculate our acceleration
Acceleration = gravitiy - pressureGrad + viscosity + Forces; //tweak center
//---------------leap frog integration------------------------
//Calculate velocity
var VelHalfBack = _currentParticle.getVel() - _currentParticle.getAcc() * _timeStep/2;
var VelHalfForward = VelHalfBack + Acceleration * _timeStep;
var Velocity = (VelHalfBack + VelHalfForward) * 0.5f;
//Calculate our new position
var Position = _currentParticle.getPos() + VelHalfForward *(_timeStep);
_currentParticle.setVel(Velocity);
_currentParticle.setPos(Position);
//---------------Debuging----------------
// Debug.Log("the viscosity is "+"["<<viscosity.m_x+","<<viscosity.m_y+","<<viscosity.m_z+"]");
// Debug.Log("the pressure grad is "+"["<<pressureGrad.m_x<<","<<pressureGrad.m_y<<","<<pressureGrad.m_z<<"]");
// Debug.Log("the accelleration is "+"["<<Acceleration.m_x<<","<<Acceleration.m_y<<","<<Acceleration.m_z<<"]");
// Debug.Log("the velocity is "+"["<<Velocity.m_x+","<<Velocity.m_y<<","<<Velocity.m_z<<"]");
}
