private double[] springPenalty(Vector3d xi, Vector3d xj, double dist) {
double[] F = new double[6];
// collision normal
Vector3d n = xi.minus(xj);
n = n.dot(1 / n.norm());
F[0] = -(k * (n.x()) * (-2 * proximity + dist));
F[1] = -(k * (n.y()) * (-2 * proximity + dist));
F[2] = -(k * (n.z()) * (-2 * proximity + dist));
F[3] = -F[0];
F[4] = -F[1];
F[5] = -F[2];
return F;
}
private double[] calculatePenaltyForces(double[] X, double[] V, HashSet<Collision> cSet) {
double[] penalty = new double[X.length];
// for each collision, apply the penalties
for (Collision col : cSet) {
// Collision col = col_rec[i];
// vertex-face collision
if (col.getType() == Collision.VERTEX_FACE) {
// System.out.println("VERTEX-FACE");
// get indicies
int[] parts = col.getParticles();
int p = parts[0];
int a = parts[1];
int b = parts[2];
int c = parts[3];
// get barycentric coords
double[] bc = col.getBaryCoords();
double u = bc[0];
double v = bc[1];
double w = bc[2];
// get collision point and collision velocities
Vector3d xa = new Vector3d(); // was Vector3d xa, xb, va, vb;
Vector3d xb = new Vector3d();
Vector3d va = new Vector3d();
Vector3d vb = new Vector3d();
xa.set(X[3 * p], X[3 * p + 1], X[3 * p + 2]);
xb.set(
u * X[3 * a] + v * X[3 * b] + w * X[3 * c],
u * X[3 * a + 1] + v * X[3 * b + 1] + w * X[3 * c + 1],
u * X[3 * a + 2] + v * X[3 * b + 2] + w * X[3 * c + 2]);
va.set(V[3 * p], V[3 * p + 1], V[3 * p + 2]);
vb.set(
u * V[3 * a] + v * V[3 * b] + w * V[3 * c],
u * V[3 * a + 1] + v * V[3 * b + 1] + w * V[3 * c + 1],
u * V[3 * a + 2] + v * V[3 * b + 2] + w * V[3 * c + 2]);
// System.out.println("REL VEL "+xa.minus(xb).dot(va.minus(vb))+" "+va+" "+vb+" "+xa+"
// "+xb);
// System.out.println("REL VEL2 "+xb.minus(xa).dot(vb.minus(va)));
/*if the objects have do not have
a seperating velocity, apply the
local spring penalty */
if (xa.minus(xb).dot(va.minus(vb)) < 0) {
double[] local_penalty = springPenalty(xa, xb, col.getDistance());
// apply to vertex
penalty[3 * p] += local_penalty[0];
penalty[3 * p + 1] += local_penalty[1];
penalty[3 * p + 2] += local_penalty[2];
// apply to triangle coordinates
penalty[3 * a] += bc[0] * local_penalty[3];
penalty[3 * a + 1] += bc[0] * local_penalty[4];
penalty[3 * a + 2] += bc[0] * local_penalty[5];
penalty[3 * b] += bc[1] * local_penalty[3];
penalty[3 * b + 1] += bc[1] * local_penalty[4];
penalty[3 * b + 2] += bc[1] * local_penalty[5];
penalty[3 * c] += bc[2] * local_penalty[3];
penalty[3 * c + 1] += bc[2] * local_penalty[4];
penalty[3 * c + 2] += bc[2] * local_penalty[5];
}
}
// edge-edge collision
if (col.getType() == Collision.EDGE_EDGE) {
// get indicies
int[] parts = col.getParticles();
int p1 = parts[0];
int q1 = parts[1];
int p2 = parts[2];
int q2 = parts[3];
// get barycentric coords
double[] coords = col.getBaryCoords();
double s = coords[0];
double t = coords[1];
Vector3d xa = new Vector3d(); // was Vector3d xa, xb, va, vb;
Vector3d xb = new Vector3d();
Vector3d va = new Vector3d();
Vector3d vb = new Vector3d();
// edge points
xa.set(
s * X[3 * p1] + (1 - s) * X[3 * q1],
s * X[3 * p1 + 1] + (1 - s) * X[3 * q1 + 1],
s * X[3 * p1 + 2] + (1 - s) * X[3 * q1 + 2]);
xb.set(
t * X[3 * p2] + (1 - t) * X[3 * q2],
t * X[3 * p2 + 1] + (1 - t) * X[3 * q2 + 1],
t * X[3 * p2 + 2] + (1 - t) * X[3 * q2 + 2]);
// velocities
va.set(
s * V[3 * p1] + (1 - s) * V[3 * q1],
s * V[3 * p1 + 1] + (1 - s) * V[3 * q1 + 1],
s * V[3 * p1 + 2] + (1 - s) * V[3 * q1 + 2]);
vb.set(
t * V[3 * p2] + (1 - t) * V[3 * q2],
t * V[3 * p2 + 1] + (1 - t) * V[3 * q2 + 1],
t * V[3 * p2 + 2] + (1 - t) * V[3 * q2 + 2]);
/*if the objects have do not have
a seperating velocity, apply the
local spring penalty */
if (xa.minus(xb).dot(va.minus(vb)) < 0) {
double[] local_penalty = springPenalty(xa, xb, col.getDistance());
// apply penalty to first edge
penalty[3 * p1] += s * local_penalty[0];
penalty[3 * p1 + 1] += s * local_penalty[1];
penalty[3 * p1 + 2] += s * local_penalty[2];
penalty[3 * q1] += (1 - s) * local_penalty[0];
penalty[3 * q1 + 1] += (1 - s) * local_penalty[1];
penalty[3 * q1 + 2] += (1 - s) * local_penalty[2];
// apply penalty to second edge
penalty[3 * p2] += t * local_penalty[3];
penalty[3 * p2 + 1] += t * local_penalty[4];
penalty[3 * p2 + 2] += t * local_penalty[5];
penalty[3 * q2] += (1 - t) * local_penalty[3];
penalty[3 * q2 + 1] += (1 - t) * local_penalty[4];
penalty[3 * q2 + 2] += (1 - t) * local_penalty[5];
}
}
}
return penalty;
}