After attaching a TileSet to a TileMap, you can do the following steps:
- Select the TileMap
- Open the TileSet from the inspector
- Expand the child you wish to use as the autotile
a) You should create the TileSet using a single Sprite node that holds the entire sprite sheet, rather than making a separate Sprite node for each tile.
- In the expanded view, check the "Is Autotile" box.
- Below the output box (at the bottom of the editor), you should see several tabs, one of which is called Autotiles. Select that tab to enter the Autotile view.
- You will now see several tabs: Icon, Bitmask, Collision, Occlusion, Navigation and Priority.
To setup autotiling, use the icon tab to select which tile is displayed in the tile sidebar, the bitmasking tab to draw the manner in which the tiles interact, the collision tab to create the tile's collision shape(s) and the priority tab to select what tile should be drawn by default. I haven't used the occlusion or navigation tabs yet, so I'm not certain how they work, but they are similar to the other tabs in implementation. In order to get the autotiling to work, the most important tab is the bitmask tab. I was unable to find an actual tutorial on this subject yet, but I found this demonstration which should give you a better idea of what is happening: autotile demonstration.
Anyway, hope that helps. Let me know if it does/n't!