Unity3D Physics2D.OverlapAreaNonAlloc strange (bug?) behaviours with layers

Question

I have encountered a strange bug with Physics2D.OverlapAreaNonAlloc and created a test project to confirm it.

Scene : two cube on top of each other, with rigidbody2d and box collider, bottom one kinematic. The top one is the "Player".

I wanted to use Physics2D.OverlapAreaNonAlloc to do some enemy detection so I used a code that looks like this, that I attached to the player :

using UnityEngine;
using System.Collections;

public class Test : MonoBehaviour {

    Vector2 pointA;
    Vector2 pointB;
    Collider2D[] enemies = new Collider2D[2];

    void Update () {

        //Enemy detection
        pointA = (Vector2)gameObject.transform.position - new Vector2(0.1f, 0f);
        pointB = (Vector2)gameObject.transform.position + new Vector2(0.1f, 0.1f);

        if (Physics2D.OverlapAreaNonAlloc(pointA, pointB, enemies, 9) > 0)
        {
            Debug.Log("first enemy :" + enemies[0].name);
        }
    }
}

9 is the layer number of the enemies layer. There is no enemies in the scene so the previous code should never display something in my console. Sadly...

When I run the code, here is what happens : - if the "Player" layer is default, it is somehow detected by my Physics2D.OverlapAreaNonAlloc - If the "Player" layer is another layer, it is not detected.

I don't understand this behaviour, is "default" supposed to be a "super" layer that contains all layers ?

What does your collision matrix look like? See this help page if you don't know what that is. It could be that your layers are indeed set up as you think. — 31eee384

user3071284 user3071284 · Accepted Answer · 2015-10-22T18:43:36

Use LayerMask.GetMask() in the call to Physics2D.OverlapAreaNonAlloc().

// "Enemy" represents the layer assigned to your enemies
Physics2D.OverlapAreaNonAlloc(pointA, pointB, enemies, LayerMask.GetMask("Enemy"))

Unity3D Physics2D.OverlapAreaNonAlloc strange (bug?) behaviours with layers

1 Answers