public DEMParticles simulate(DEMParticles particles, float t)
{
Vector2[] forces = particles.forces;
List<Vector2> positions = particles.positions;
List<Vector2> velocities = particles.velocities;
List<float> massesInv = particles.massesInv;
for (int iTarget = 0; iTarget < particles.length; iTarget++) {
AABB boundingBox = particles.buildAABB(iTarget);
int[] neighborIndices = spacePartitioner.search(boundingBox);
forces[iTarget] = estimateForce(particles, iTarget, neighborIndices, t);
}
for (int iTarget = 0; iTarget < particles.length; iTarget++) {
forces[iTarget] += boundaryForce.calcForce(particles, iTarget, t);
}
for (int iTarget = 0; iTarget < particles.length; iTarget++) {
Vector2 accel = forces[iTarget] * massesInv[iTarget];
Vector2 velocity = velocities[iTarget];
positions[iTarget] += t * velocity;
velocities[iTarget] += t * accel;
}
return particles;
}
public Vector2 estimateForce(DEMParticles particles,
int iTarget, int[] neighbors, float t)
{
Vector2 resForce = externalForce.calcForce(particles, iTarget, t);
Vector2 targetPosition = particles.positions[iTarget];
Vector2 targetVelocity = particles.velocities[iTarget];
float targetRadius = particles.radii[iTarget];
for (int i = 0; i < neighbors.Length; i++) {
int iNeighbor = neighbors[i];
if (iTarget == iNeighbor)
continue;
Vector2 pos = targetPosition - particles.positions[iNeighbor];
Vector2 v = targetVelocity - particles.velocities[iNeighbor];
float r12 = particles.radii[iNeighbor] + targetRadius;
float dist2 = Vector2.SqrMagnitude(pos);
if (dist2 >= (r12 * r12) || dist2 <= Mathf.Epsilon)
continue;
float dist = Mathf.Sqrt((float)dist2);
float dxCoeff = ((r12 - dist) / dist);
resForce += (kn * dxCoeff * pos - cn * v);
}
return resForce;
}
public Vector2 calcForce(DEMParticles particles, int iParticle, float dt)
{
Vector2 position = particles.positions[iParticle];
Vector2 velocity = particles.velocities[iParticle];
Vector2 dx = new Vector2(
Mathf.Min(0, position.x - boundary[0]) + Mathf.Max(0, position.x - boundary[2]),
Mathf.Min(0, position.y - boundary[1]) + Mathf.Max(0, position.y - boundary[3]));
Vector2 dv = new Vector2((dx.x == 0 ? 0 : velocity.x), (dx.y == 0 ? 0 : velocity.y));
return - kn * dx - cn * dv;
}
// Use this for initialization
void Start()
{
this.particles = new DEMParticles();
this.spacePartitioner = new GridSP<int>(
boundBL, boundTR, 20, 20, new IntEqualityComparer());
this.gravitationalForce = new GravitationalForce(new Vector2(0, -9.8f));
this.boundaryForce = new BoundaryForce(
kn, cn, boundBL.x, boundBL.y, boundTR.x, boundTR.y);
this.dem = new DEM(spacePartitioner, gravitationalForce, boundaryForce);
spheres = new GameObject[nParticles];
for (int i = 0; i < nParticles; i++) {
GameObject s = GameObject.CreatePrimitive(PrimitiveType.Sphere);
s.transform.localScale = new Vector3(diameter, diameter, diameter);
s.transform.position = new Vector3(
Random.Range(boundBL.x, boundTR.x),
Random.Range(boundBL.y, boundTR.y),
0);
Destroy(s.collider);
spheres[i] = s;
}
int length = spheres.Length;
float[] radii = new float[length];
float[] masses = new float[length];
Vector2[] positions = new Vector2[length];
Vector2[] velocities = new Vector2[length];
for (int i = 0; i < length; i++) {
GameObject sphere = spheres[i];
float radius = 0.5f * sphere.transform.localScale.x;
radii[i] = radius;
masses[i] = mass; //(rho * Mathf.PI * radius);
positions[i] = new Vector2(
sphere.transform.position.x, sphere.transform.position.y);
velocities[i] = Vector2.zero;
}
particles.addParticle(masses, radii, positions, velocities);
for (int i = 0; i < length; i++) {
spacePartitioner.add(particles.buildAABB(i), i);
}
}
public Vector2 calcForce(DEMParticles particles, int iParticle, float dt)
{
return Vector2.zero;
}
public Vector2 calcForce(DEMParticles particles, int iParticle, float dt)
{
return particles.masses[iParticle] * gravity;
}
