Collider2D.GetContacts always returns empty.

Hey there,

I'm building a tool where I place a bunch of objects on a grid and then remove some if they're colliding with other types of objects. It seems like Collider2D.GetContacts would be ideal for what I'm trying to do, but it's not detecting any Contacts. I'm working with a bunch of overlapping Polygon & BoxCollider2Ds, none of which are triggers or rigidbodies.

Here's the code I'm working with:

Code (CSharp):

1.  
2. Collider2D[] hits = new Collider2D[100];
3. for (int i = 0; i < _plants.GetLength(0); i++)
4. {
5.    for (int j = 0; j < _plants.GetLength(1); j++)
6.    {
7.       ActivePlant plant = _plants[i, j];
8.       if(plant == null)
9.          continue;
10.      
11.       Collider2D collider = plant.GetComponent<Collider2D>();
12.       int hitCount = collider.GetContacts(hits);
13.      
14.       // if hitting Rocks or Water, destroy
15.    }
16. }
17.  

I've also tried Collider2D.Cast with no direction/distance, and that also didn't work. Collider2D.Raycast works, on the other hand, but it's not accurate enough; it's just casting a point. It does tell me, though, that *some* 2D physics are working.

I've been off of 2D development & Unity's Physics systems for a while, and I'm digging back into them now, so I expect that I'm just making a dumb mistake or forgot a setup step. Any help is appreciated!

 

I've figured it out. It was a misunderstanding of what 'GetContacts' was referring to. 'OverlapCollider' is what I was looking for, as that returns all of the other colliders that overlap an object. GetContacts must refer more to contact points in simulation, rather than overlaps.