You often want tiles to overlap in order to make grid-based objects appear to be standing on the ground. An example of this can be seen in the image below.
Tiles of a tree overlapping ground tiles.
This effect can be achieved in multiple ways. One way is to create multiple Tilemaps and layer them, so that the ground Tilemap is in the back and the Tilemap with the tree is in the front. Another way of doing this is to use the Z position of the brush to paint in front of the ground tiles. But how does NavTiles determine the area type for one of these overlapping tiles?
NavTiles "compresses" all Tilemaps and Z positions into a single 2D grid — the NavTile grid. Overlapping tiles are treated as a single tile on this grid. In order to determine which tile's area should be used, the priority of the linked areas is used. These priorities can be found and changed in the Areas tab of the NavTile Settings Window.
In the example above, the tree tile is linked to the default "Non Walkable" area, and the ground tile is linked to the default "Walkable" area. Since the priority of the Non Walkable area is higher, NavTiles will mark this tile as Non Walkable, even though there is a Walkable tile below it.
An isometric Z as Y Tilemap where the walls are baked on top of the ground.
The same concept also applies to isometric Tilemaps. This allows agents to move around and behind walls that are placed "higher." Due to the fact that everything is baked onto the bottom tile, we do not currently support elevated floors (e.g. stairs to walk on). To find out more about the workflow for isometric Tilemaps, you can read this blogpost.