I'm currently trying to convert from grids to navigation meshes for pathfinding, since grids are either too coarse for accurate navigation, or too fine to be useful for object tracking.

While my map is fairly static, and the navigation mesh could be created in advance, this is somewhat of a tower defense game, where objects can be placed to block paths, so I need a way to recalculate portions of the navigation mesh to allow pathing around them.

Is there any existing documentation on good ways to do this? I'm still very new to navigation meshes, so the prospect of modifying them to cut or fill holes sounds daunting.