dynamic off mesh links about recastnavigation HOT 4 OPEN

One thing we did for Unitys heavily refactored version of Detour was to separate out the links and off-mesh connections from tiles. That also allowed us to make the navmesh data read only. Since the codebase is so heavily modified it is not feasible to bring the changes back to Detour.

The original idea of having links and off-mesh connections on the tiles was to avoid any runtime allocations. I think I might have gone a bit too far.

Anyways, in order to allow off-mesh connections (OMC) to be added at runtime, the way links are handled need to change too. We use one large pool per navmesh, plus indices as the size may vary. We also removed the restriction of OMC connecting to only neighbour tile. But it came with the penalty that we need to traverse all OMCs when adding or removing a tile.

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This is definitely a feature that would be nice to have. OMCs being allowed to neighbors only is not very flexible. It kind of puts an arbitrary limit of how small you can make tile sizes, which then again affects rebuilding the mesh at runtime.

We could avoid traversing all OMCs when adding/removing a tile by using a hashmap/LUT, similar to how tiles are stored. Or perhaps we could add a dynamic part to dtMeshTile that could store these things?

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I would imagine that you would need to maintain a global list of OMCs external to any tiles, as runtime data on the navmesh itself or whatever, perhaps dynamically allocated in a vector like array. Within those structs you could perhaps cache the tile indices for each endpoint so that if either tile endpoint changes it's easy to identify which of the connections are relevant to each tile to disconnect and reconnect afterwards.

from recastnavigation.

Ah yeah, of course, they need to be stored even if the mesh tiles they pertain have not been loaded yet. So storing the dynamic ones in dtMeshTile would not be feasible. OMCs to non-adjacent tiles could be stored there as far as I understand, though (ie. in the same way OMCs are stored when building the nav mesh at the moment).

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