Getcontacts() layermask not working

Unity Engine
1

Hey, I’m trying to use a layermask to filter results with getcontacts but it’s not working.

//reads all overlapping labels, saves them in the array and returns the amount in the array
Collider2D[] contactList = new Collider2D[5];
ContactFilter2D overlapFilter;

        public int GetOverlapContacts() {
            //int overlapAmount = GetComponent<Rigidbody2D>().OverlapCollider(overlapFilter,contactList);
            //overlapCount = GetComponent<BoxCollider2D>().OverlapCollider(overlapFilter, contactList);
            overlapFilter.useTriggers = true;
            overlapFilter.useLayerMask = true;
            overlapFilter.layerMask = LayerMask.NameToLayer("OverlapLabel");
            //overlapFilter.NoFilter();

            overlapCount = GetComponent<Rigidbody2D>().GetContacts(overlapFilter, contactList);
            Debug.Log("overlapCount " + overlapCount + " overlapFilter "+ overlapFilter.isFiltering);
            return overlapCount;
        }

The debug just returns 0, both the rigidbodies are overlapping and they are both on the overlapLabel layer.
Something I’m missing?

2

Ok so the solution is that you still need to bitshift the layermask.
So use

overlapFilter.layerMask = LayerMask.GetMask("OverlapLabel");
//or
overlapFilter.layerMask = 1 << LayerMask.NameToLayer("OverlapLabel");
3

Thanks for the help!

Bitshifting worked.

Just an additional question, why does bitshifting that work?

4

You revived a dead thread from 6 years ago.

A Layer Number (also called a Layer Index) is an integer in the range 0 to 31. (In the Inspector, they only show 0 to 30.) The LayerMask.NameToLayer() function returns a Layer Number, not a LayerMask value.

A LayerMask itself is a packed set of 32 bits, each bit representing one of the 32 possible layers. This lets you combine any possible combination of all 32 layers in a single value.

To convert from a Layer Number to a LayerMask value, you need to do some bit shifting.

Some quick shortcuts converting Layer Numbers to LayerMask Values and other operations.

LayerMask mask = (1 << layerNumber);

LayerMask mask = (1 << layerNumberA) | (1 << layerNumberB) | (1 << layerNumberC);

LayerMask mask = (1 << layerNumber) | ((int)(layerMaskToInclude));

LayerMask mask = ((int)(layerMaskToInclude)) & ~((int)(layerMaskToExclude));

LayerMask mask = 0; // no layers

LayerMask mask = ~0; // all layers

bool isObjectOnALayerInLayerMask = ((1 << gameObject.layer) & layerMaskToInclude) != 0;