CollisionDetection.java

gehe zur Dokumentation dieser Datei

package de.lathanda.eos.game.geom;
 
import de.lathanda.eos.game.Game;
import de.lathanda.eos.game.Sprite;
import java.util.SortedSet;
import java.util.TreeSet;
 
public class CollisionDetection {
 
    private final SortedSet<Sprite> list = new TreeSet<>();
    private final Game game;
    public CollisionDetection(Game game) {
        this.game = game;
    }
 
    public void addObject(Sprite sprite) {
        list.add(sprite);
    }
 
    public void removeObject(Sprite sprite) {
        list.remove(sprite);
    }
 
    public void checkCollision() {
        /*
         * result is the only set that scales with O(n²), but we cannot avoid
         * that effect, as there can be so many collisions
         */
 
        SortedSet<ShapeOrder> xList = new TreeSet<>();
        SortedSet<Shape> open = new TreeSet<>();
        Collision col;
 
        // phase 1: sort objects
        Shape shape;
        for (Sprite w : list) {
            shape = w.getShape();
            if (shape != null) {
                shape.setSprite(w);
                xList.add(new ShapeOrder(ShapeOrder.OrderType.X0, shape));
                xList.add(new ShapeOrder(ShapeOrder.OrderType.X1, shape));
            } else {
                // this is legal
                // it can be used in order to temporary prevent collisions
            }
        }
 
        // phase 2: scan for potential collisions
        // we enter every potential x collision into a tree structure
        for (ShapeOrder shapeOrder : xList) {
            switch (shapeOrder.bracket) {
            case OPEN:
                open.add(shapeOrder.shape);
                break;
            case CLOSE:
                open.remove(shapeOrder.shape);
 
                // every id that is open collides with this id
                for (Shape id : open) {
                    if (id.getBottom() < shapeOrder.shape.getTop() && shapeOrder.shape.getBottom() < id.getTop()) {
                        col = new Collision(shapeOrder.shape, id);
                        // the rectangle bounds intersect, now we check if they
                        // really collide
                        // this avoids testing every pair with the really slow
                        // exact calculations
                        if (col.verifyCollision()) {
                            if (!col.a.getSprite().processCollision(col.b.getSprite(), game)) {
                                col.b.getSprite().processCollision(col.a.getSprite(), game);
                            }
                        }
                    }
                }
                break;
            }
        }
    }
}