How can I prevent two Rectangle2D from overlapping?

Question

I am trying to create a Vampire survivor type game, and I am currently creating the logic of the enemies, but I have found a problem, and that is that they are able to overlap each other, to a point where you don't even notice that there are 2, which is uncomfortable because I need them to be able to collide and maybe be one on top of the other slightly, but not to that extreme.

I have tried to use a code to solve the collisions, but when I try to do it these two just move one after the other pushing each other, even so I feel that my code is not done in the best way.

Enemy Movement:

public void move(double playerX, double playerY, double fps, List<Enemies> enemiesList){
        double angle = Math.atan2(playerY - y, playerX - x);
        x += Math.cos(angle) * speed / fps;
        y += Math.sin(angle) * speed / fps;
        hitbox.setFrame(x, y, 40, 40);
        for (int i = 0; i < enemiesList.size(); i++) {
            if (this == enemiesList.get(i)) {

                continue;
            }
            if (hitbox.intersects(enemiesList.get(i).getHitbox())) {

                resolveCollition(enemiesList.get(i).getHitbox());
            }
        }

    }

the attempt to solve it

private void resolveCollition(Rectangle2D.Double otherHitbox) {
        double overX;
        double overY;
        if (this.hitbox.getCenterX() < hitbox.getCenterX()) {
            overX = hitbox.getMaxX() - this.hitbox.getMinX();
        } else {
            overX = hitbox.getMinX() - this.hitbox.getMaxX();
        }

        if (this.hitbox.getCenterY() < hitbox.getCenterY()) {
            overY = hitbox.getMaxY() - this.hitbox.getMinY();
        } else {
            overY = hitbox.getMinY() - this.hitbox.getMaxY();
        }
    
        x -= overX;
        y -= overY;
    }

I would like to know if there is a better way to solve the overlap issue without the enemies continuously pushing each other.

If it's always going to be just 2 enemies, stop one enemy and let the other move until they are no longer colliding. — Gilbert Le Blanc
– Gilbert Le Blanc, Commented Jan 14 at 17:44
As I said, it's a vampire survivor style game, so there will be... a lot of enemies on screen at the same time. — Mesa
– Mesa, Commented Jan 14 at 19:41

Marce Puente · Accepted Answer · 2025-01-15 13:58:41Z

0

You could implement something like:

public void move( object, direction, others ) {
   if( direction == LEFT ) {

        // empty object
      virtualObject.setLocation( object.getLocation() );
      virtualObject.incrementX();

        // method that verifies that in the current position 
        // there is no collision with other objects
      if( no collisions( virtualObject ) ) {
         object.incrementX();
      }
   }
   ...
   ...
   ...
}


enum Direction { LEFT, RIGHT, UP, DOWN }

edited Jan 15 at 13:58

answered Jan 15 at 1:50

Marce Puente

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2 Comments

Gilbert Le Blanc Jan 15 at 13:54

Shouldn't it be direction == LEFT? And why just LEFT?

Marce Puente Jan 15 at 14:02

Thanks, I correct this, ... I didn't think it was necessary to show all the options, it's just an example.

Mesa · Accepted Answer · 2025-01-15 19:45:09Z

Welp, I ended up with this:

double angle = Math.atan2(playerY - y, playerX - x);
    double deltaX = Math.cos(angle) * speed/fps;
    double deltaY = Math.sin(angle) * speed/fps;
    Rectangle2D deltaHitbox = new Rectangle2D.Double(x+deltaX, y+deltaY, 40, 40);
    Iterator<Enemies> iterator = enemiesList.iterator();
    while (iterator.hasNext()) {
        Enemies enemy = iterator.next();
        if (enemy == this)continue;
        if (enemy.hitbox.intersects(deltaHitbox)) {
            double deltaXCenter = -deltaHitbox.getCenterX() + enemy.hitbox.getCenterX();
            double deltaYCenter = -deltaHitbox.getCenterY() + enemy.hitbox.getCenterY();
            int separation = 40;
            if (Math.abs(deltaXCenter) > Math.abs(deltaYCenter)) {
                if (deltaXCenter > 0) {
                    x += (deltaXCenter - separation);
                } else {
                    x -= (Math.abs(deltaXCenter) - separation);
                }
            } else {
                if (deltaYCenter > 0) {
                    y += (deltaYCenter - separation);
                } else {
                    y -= (Math.abs(deltaYCenter) - separation);
                }
            }
        }
    }
    x += deltaX;
    y += deltaY;
    hitbox.setFrame(x, y, 40, 40);

so I simply calculate the difference between the centers when moving it hypothetically, and subtract the difference between them, so when it is added, it will always be at a distance which when adding the normal movement, it will not reach the other, and that works even when there is more than one (I do not know if I could explain the idea well).

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