/**
* @see net.phys2d.raw.collide.Collider#collide(net.phys2d.raw.Contact[], net.phys2d.raw.Body, net.phys2d.raw.Body)
*/
public int collide(Contact[] contacts, Body bodyA, Body bodyB) {
Line line = (Line) bodyA.getShape();
Circle circle = (Circle) bodyB.getShape();
Vector2f[] vertsA = line.getVertices(bodyA.getPosition(), bodyA.getRotation());
// compute intersection of the line A and a line parallel to
// the line A's normal passing through the origin of B
Vector2f startA = vertsA[0];
Vector2f endA = vertsA[1];
ROVector2f startB = bodyB.getPosition();
Vector2f endB = new Vector2f(endA);
endB.sub(startA);
endB.set(endB.y, -endB.x);
// endB.add(startB);// TODO: inline endB into equations below, this last operation will be useless..
//TODO: reuse mathutil.intersect
// float d = (endB.y - startB.getY()) * (endA.x - startA.x);
// d -= (endB.x - startB.getX()) * (endA.y - startA.y);
//
// float uA = (endB.x - startB.getX()) * (startA.y - startB.getY());
// uA -= (endB.y - startB.getY()) * (startA.x - startB.getX());
// uA /= d;
float d = endB.y * (endA.x - startA.x);
d -= endB.x * (endA.y - startA.y);
float uA = endB.x * (startA.y - startB.getY());
uA -= endB.y * (startA.x - startB.getX());
uA /= d;
Vector2f position = null;
if ( uA < 0 ) { // the intersection is somewhere before startA
position = startA;
} else if ( uA > 1 ) { // the intersection is somewhere after endA
position = endA;
} else {
position = new Vector2f(
startA.x + uA * (endA.x - startA.x),
startA.y + uA * (endA.y - startA.y));
}
Vector2f normal = endB; // reuse of vector object
normal.set(startB);
normal.sub(position);
float distSquared = normal.lengthSquared();
float radiusSquared = circle.getRadius() * circle.getRadius();
if ( distSquared < radiusSquared ) {
contacts[0].setPosition(position);
contacts[0].setFeature(new FeaturePair());
normal.normalise();
contacts[0].setNormal(normal);
float separation = (float) Math.sqrt(distSquared) - circle.getRadius();
contacts[0].setSeparation(separation);
return 1;
}