[TruePath]

I don't get the worry about the NP complete problem of tiling a finite area.

Yes, of course, if you allow arbitrary adjacency rules then tiling is going to be NP complete but the goal here is to generate realistic tilings then it's reasonable to assume that if you have a compact connected region that obeys the tiling rules and any square there is some tile that is allowed to be placed in that square.

I mean this is how the real world works. You don't have holes in reality so if it's possible to have a part of the world that looks like such-and-such there must be a valid description of the stuff next to it.

[ijdykeman]

I think it’s important to point out that it’s NP hard, because if you don’t know that, who’s to say that some efficient, exact algorithm does not exist? Given that because the problem is NP hard, no fast and exact algorithm exists, so we can try to explore possible tradeoffs.

This post explores one point in the design space where you trade away exactness for speed. You’re suggesting trading away generality for exactness and speed by restricting the classes of possible inputs and putting in extra work to make the classes you do support very fast to process. A totally valid option.

[TruePath]

Damn't I didn't mean compact connected. I meant that if you have a convex region you can extend it. Obviously, non-convex regions can raise problems (e.g. maybe tropical rainforest can't transition to tundra in the space of a single tile). But it should work with convex regions.