How to test for BoxCollider2D intersection in Unity?

Question

I have a Player object with a BoxCollider2D component and a Ladder object also with a BoxCollider2D component. Each object has a script, and in each script, I set up references to the box colliders in the normal way.

public BoxCollider2D box_collider;

void Start ()
{
    box_collider = GetComponent<BoxCollider2D>();   
}

My player script is called "PlayerController", so that's the class defined in the script.

In my Ladder's script I have the following:

void Update ()
{
    GameObject player = GameObject.Find("Player");
    PlayerController player_controller = player.GetComponent<PlayerController>();
    if (player_controller.box_collider.bounds.Intersects (box_collider.bounds))
        Debug.Log ("collision");
    else
        Debug.Log ("no collision");

}

This script invariably returns "no collision" and I'm not sure why.

Any ideas?

Answer 1

I believe what you want to achieve is to set a ladder to be a trigger on the box collider and set up a method on the ladder OnTriggerEnter2D. When player will collide/trigger entering into ladder, the ladder will be informed about that.

https://docs.unity3d.com/ScriptReference/MonoBehaviour.OnTriggerEnter2D.html

void OnTriggerEnter2D(Collider2D col)
{
     // check tag of col and process
}

Of course you can also check collison of objects, there are few other methods that might help (remmember to turn of isTrigger on collider in this case):

OnCollisionEnter2D - Sent when an incoming collider makes contact with this object's collider (2D physics only).

Answer 2

Another way, aside from using Ontrigger or OnCollision to find a intersection like ground, water, enemies ect.. Is to use layers and cast a check to see if you contacted one.

Physics2D.OverlapCircle(playerPosition, collisionRadius, ladderLayer)

here is a example of a bool returning true if I am touching the layer

[SerializeField]
private LayerMask groundLayer;
private float collisionRadius = .23f;
Transform playerFeet
public bool grounded = false;

groundLayer

 public bool GroundCheck()
{
    return grounded = Physics2D.OverlapCircle(playerFeet.position, collisionRadius, groundLayer);
}