Here, you can find more about it here, and I don't think you need to modify your assets too much, this allows Godot 4.x users to create terrains which is a super tool for us since allows us to create procedural stuff and more. Is there a best practice template for 2D top-down auto tiling? - Godot Forums
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Ah. Cool. I’ve worked on autotiles in the past, specifically for RPGmaker. I wonder how much overlap there is between Godot’s system and that one. Autotiles are interesting. When I started out, a lot of people were using custom maps made with placeable tiles and props and then importing them to engine. Autotiles just didn’t seem all that in demand but I imagine projects that use procedural generation (or folks who need to make a lot of maps quickly) could make great use of them.