package org.openpixi.pixi.physics.collision.algorithms;
import java.util.ArrayList;
import org.openpixi.pixi.physics.collision.util.Pair;
import org.openpixi.pixi.physics.force.Force;
import org.openpixi.pixi.physics.particles.Particle;
import org.openpixi.pixi.physics.solver.Solver;
public class VectorTransformation extends CollisionAlgorithm{
public VectorTransformation() {
super();
}
private void doCollision(Particle p1, Particle p2) {
//distance between the particles
double distance = Math.sqrt((p1.getX() - p2.getX()) * (p1.getX() - p2.getX()) + (p1.getY() - p2.getY()) * (p1.getY() - p2.getY()));
//finding the unit distance vector
double dnX = (p1.getX() - p2.getX()) / distance;
double dnY = (p1.getY() - p2.getY()) / distance;
//finding the tangential vector;
double dtX = dnY;
double dtY = - dnX;
//finding the minimal distance if the particles are overlapping
double minDistanceX = dnX * (p1.getRadius() + p2.getRadius() - distance);
double minDistanceY = dnY * (p1.getRadius() + p2.getRadius() - distance);
//moving the particles if they are overlapping (if not, the minimal distance is equal to zero)
p1.setX(p1.getX() + minDistanceX * p2.getMass() / (p1.getMass() + p2.getMass()));
p1.setY(p1.getY() + minDistanceY * p2.getMass() / (p1.getMass() + p2.getMass()));
p2.setX(p2.getX() - minDistanceX * p1.getMass() / (p1.getMass() + p2.getMass()));
p2.setY(p2.getY() - minDistanceY * p1.getMass() / (p1.getMass() + p2.getMass()));
//finding the normal and the tangential vectors of the particles corresponding with the collision plane
double v1NX = dnX * (p1.getVx() * dnX + p1.getVy() * dnY);
double v1NY = dnY * (p1.getVx() * dnX + p1.getVy() * dnY);
double v1TX = dtX * (p1.getVx() * dtX + p1.getVy() * dtY);
double v1TY = dtY * (p1.getVx() * dtX + p1.getVy() * dtY);
double v2NX = dnX * (p2.getVx() * dnX + p2.getVy() * dnY);
double v2NY = dnY * (p2.getVx() * dnX + p2.getVy() * dnY);
double v2TX = dtX * (p2.getVx() * dtX + p2.getVy() * dtY);
double v2TY = dtY * (p2.getVx() * dtX + p2.getVy() * dtY);
//calculating the new velocities
p1.setVx(v1TX + dnX * ((p1.getMass() - p2.getMass()) * Math.sqrt(v1NX * v1NX + v1NY * v1NY) + 2 * p2.getMass() * Math.sqrt(v2NX * v2NX + v2NY * v2NY)) / (p1.getMass() + p2.getMass()));
p1.setVy(v1TY + dnY * ((p1.getMass() - p2.getMass()) * Math.sqrt(v1NX * v1NX + v1NY * v1NY) + 2 * p2.getMass() * Math.sqrt(v2NX * v2NX + v2NY * v2NY)) / (p1.getMass() + p2.getMass()));
p2.setVx(v2TX - dnX * ((p2.getMass() - p1.getMass()) * Math.sqrt(v2NX * v2NX + v2NY * v2NY) + 2 * p1.getMass() * Math.sqrt(v1NX * v1NX + v1NY * v1NY)) / (p1.getMass() + p2.getMass()));
p2.setVy(v2TY - dnY * ((p2.getMass() - p1.getMass()) * Math.sqrt(v2NX * v2NX + v2NY * v2NY) + 2 * p1.getMass() * Math.sqrt(v1NX * v1NX + v1NY * v1NY)) / (p1.getMass() + p2.getMass()));
}
public void collide(ArrayList<Pair<Particle, Particle>> pairs, Force f, Solver s, double step) {
for(int i = 0; i < pairs.size(); i++) {
Particle p1 = (Particle) pairs.get(i).getFirst();
Particle p2 = (Particle) pairs.get(i).getSecond();
double distanceSquare = ((p1.getX() - p2.getX()) * (p1.getX() - p2.getX()) + (p1.getY() - p2.getY()) * (p1.getY() - p2.getY()));
if(distanceSquare <= ((p1.getRadius() + p2.getRadius()) * (p1.getRadius() + p2.getRadius()))) {
s.complete(p1, f, step);
s.complete(p2, f, step);
doCollision(p1, p2);
s.prepare(p1, f, step);
s.prepare(p2, f, step);
}
}
}
}