Navigation

Recast for navmesh generation, Detour for pathfinding. The engine owns one NavigationSystem at engine.nav.

Pipeline

1. Gather geometry. Either bake from the scene graph (mjolnir.setup_navmesh with tag filters) or feed an explicit NavigationGeometry{vertices, indices, area_types} via NavGeometryBuilder.
2. Voxelize → contours → polygons. Recast voxelizes the input into a heightfield, erodes by agent radius, traces contours, triangulates, and produces a polygon mesh.
3. Bind query context. A Detour query object is attached so find_path / find_nearest_point work against the engine.

Quality knobs

NavMeshConfig.quality ∈ {LOW, MEDIUM, HIGH, ULTRA} selects the voxel cell size and contour simplification thresholds. Lower quality = faster bake + coarser mesh; useful for big open areas. Higher quality = small intricate spaces. MEDIUM is the recommended default. For full control, hand a recast.Config to build_navmesh directly.

Area costs

area_types[i] = 0 is walkable; nonzero indexes NavMesh.area_costs[] to weight terrain (sand slower than asphalt, swamp slower than dirt) without making it impassable. Path search follows the cost-weighted shortest path.

Pathfinding

find_path returns [][3]f32 (an empty slice if no path). find_nearest_point projects an off-mesh position onto the navmesh — the usual idiom is to combine it with a mouse-pick raycast to convert a click into a valid goal before pathing.

Walking the path is the caller’s job: the engine does not own agent movement. See the navigation example for the canonical lerp-toward- next-waypoint loop.