Navmesh generator + pathfinding under MIT License

Recast
code.google.com/p/recastnavigation/
coded by memononen


Recast is state of the art navigation mesh construction toolset for games.

• It is automatic, which means that you can throw any level geometry at it and you will get robust mesh out
• It is fast which means swift turnaround times for level designers
• It is open source so it comes with full source and you can customize it to your hearts content.

The Recast process starts with constructing a voxel mold from a level geometry and then casting a navigation mesh over it. The process consists of three steps, building the voxel mold, partitioning the mold into simple regions, peeling off the regions as simple polygons.

• The voxel mold is build from the input triangle mesh by rasterizing the triangles into a multi-layer heightfield. Some simple filters are then applied to the mold to prune out locations where the character would not be able to move.
• The walkable areas described by the mold are divided into simple overlayed 2D regions. The resulting regions have only one non-overlapping contour, which simplifies the final step of the process tremendously.
• The navigation polygons are peeled off from the regions by first tracing the boundaries and then simplifying them. The resulting polygons are finally converted to convex polygons which makes them perfect for pathfinding and spatial reasoning about the level.