Integration of Recast & Detour into CEL and hierarchical pathfinding algorithm implementation

by leonardord for Crystal Space

This proposal revolves around two main goals. The first one is to integrate the Recast & Detour toolset into CEL, so navigation meshes can be generated automatically from maps. The second objective is to give CEL the ability to efficiently handle pathfinding in large maps, which are divided into smaller sectors connected by portals. This objective is to be achieved using a hierarchical pathfinding algorithm.