A Navigation Mesh (NavMesh) is the standard pathfinding system in most game engines, including Unreal Engine. It works by generating a 2D polygonal mesh over walkable surfaces — floors, ramps, stairs — that AI agents use to find paths from point A to point B.
The key limitation: NavMesh is inherently 2D. It projects the world onto flat walkable surfaces, which works great for ground-based characters but is useless for agents that need to move freely in 3D space (flying enemies, swimming creatures, zero-gravity scenarios).
In Unreal Engine, the NavMesh is managed by ARecastNavMesh (based on the open-source Recast/Detour library). It supports:
- Automatic generation from level geometry
- Dynamic updates when obstacles move
- Navigation modifiers (areas with different costs)
- Crowd avoidance via Detour Crowd
For 3D pathfinding, alternatives like DonAI Navigation use a Voxel-based approach instead.