Great library @mourner. I've been adapting this to simplify non-square meshes, by buffering the east and southern edges with filler values. This forms a bigger square, whatever the next larger 2^n +1 integer may be (a 225x500 mesh becomes 513x513).

To keep the algorithm from simplifying away vertices on the real edge, I fill the placeholder values with a constant, extremely low/high elevation, and then trim them away:

Two questions:

• is this worth adding into core functionality? I'm curious if we can further optimize by skipping simplification on values that are known to be placeholders.

• this strategy forms an interesting bandana pattern, where the eastern and southern edges keep a really fine detail (probably finer than necessary) where they were trimmed away. The savings might be minimal, but can we simplify those edges further?