A basic implementation of the Walk Manifold algorithm used in The Witness, written in JAI. The algorithm takes in a list of triangles representing the "walkable" surface, as well as some primitives representing "blockers" and return a connected manifold corresponding to valid positions for a specific "mover."
The algorithm itself generalizes to arbitrary functions for the surfaces and blockers. If for example you wanted to feed in a heightmap instead of triangles, that could be done with minimal code changes.
An explanation of the algorithm by it's inventor Casey Muratori can be found here https://www.youtube.com/watch?v=YE8MVNMzpbo
At the moment I am providing this without changes from my engine, just as a reference for other people looking to implement the algorithm. If you would find it useful as a module then shoot me a message, and if I get a few of those, I'll pull it out into a standalone thing.
The performance is pretty decent enough for my purposes for now, but there is still some low-hanging fruit performance wise. Some of these are marked with //@Speed comments, others are not.