How to detect if a tilemap is overlapping another tilemap

I have multiple tilemaps instantiated next to each other. I want to check if a tilemap is overlapping a different tilemap. Specifically they're rooms, with wall tiles having collision enabled and floor tiles - disabled.

I want to check if one tilemaps wall-tiles are overlapping a different tilemaps floor-tiles...

So far I've gotten this to get collision:

Collider2D[] collidingObjects = new Collider2D[5];

ContactFilter2D contactFilter = new ContactFilter2D();

tilemap.GetComponent<TilemapCollider2D>().OverlapCollider(contactFilter, collidingObjects)

But with this I can only find out if Im colliding with a tilemap, but not necessarily overlapping. See, my rooms are touching each other...

 

You can query some information like .cellBounds or .localBounds, and there's probably other information you can get as well. Here are the docs:

https://docs.unity3d.com/ScriptReference/Tilemaps.Tilemap.html

If your tilemap shapes are not rectangular, at least you can use above for a gross check, then iterate down on individual tiles and see if they overlap. Keep in mind due to floating point imprecision, a tilemap that just barely "kisses" another tilemap (directly adjacent) may mathematically overlap with a simple rectangular check, so you might want to check if it overlaps by more than a certain amount, like more than half a tile.

 

How do I check overlapping of individual tiles? My rooms have different sizes and placement.

 

I would just iterate one tilemap and do per-tile rectangle-intersection checks against all the other tiles in the other tilemaps that intersect. You know how many tiles across and down and you know the size of the tiles, so producing the rects is just a little bit of math.

The good news is you only have to consider the case where the gross outer rectangles have intersected, otherwise by geometric definition, none of the inner rectangles could be intersecting.