Traversal & navigation
Navmesh Agent, Doorway & Clearance Planner
Direct answer
A navigable opening must exceed the agent capsule, with extra width for voxelisation and reliable clearance. For a 34 cm agent radius and 19 cm navigation cell, a conservative doorway target is 106 cm: the 68 cm capsule diameter plus one horizontal cell of allowance on each side.
Result
- Doorway check
- —
- Conservative doorway target
- —cm
- Physical clearance per side
- —cm
- Vertical headroom
- —cm
- Agent radius in nav cells
- —
- Step-height check
- —
- Maximum slope as grade
- —%
Method & assumptions
How this is worked out
Physical passage width begins at twice the agent radius. The conservative target adds one horizontal voxel cell to each side, acknowledging that rasterisation and erosion reduce usable space near collision boundaries.
Side clearance is measured against the physical capsule diameter. Headroom subtracts agent height from the clear ceiling. Step walkability compares the tested obstacle with Agent Max Step Height.
This planner catches dimension conflicts before a navmesh build, but it cannot reproduce Recast rasterisation exactly. Collision shape, cell height, region filtering, ledges and tile boundaries still require an in-engine check.
Relevant Unreal navigation settings
| Setting | Controls | Failure symptom |
|---|---|---|
| Agent Radius | Horizontal capsule clearance | Doorways or corridors disappear |
| Agent Height | Required vertical clearance | Low spaces are not navigable |
| Agent Max Step Height | Climbable vertical discontinuity | Kerbs split the navmesh |
| Agent Max Slope | Walkable surface angle | Steep ramps are removed |
| Cell Size / Height | Voxelisation precision | Thin or small features vanish |
The smallest agent supported by a NavMesh determines what can traverse it. Projects with substantially different agent sizes may need separate supported-agent configurations.
Questions
Why does a doorway wider than the capsule still fail?
Navmesh generation voxelises and erodes walkable space around obstacles. A door that only equals capsule diameter has no tolerance for voxel cells, collision bevels or alignment, so the remaining polygon can disappear.
Is Agent Height the same as capsule half height?
No. Nav Agent Height is the total height used for pathfinding clearance. Compare it with the full clear opening, while checking the actual character capsule configuration separately.
Should every AI use the same navmesh?
Only when their radii, heights, steps and slopes are close enough. Very different agents can need separate supported-agent settings or dedicated navigation data so small agents do not define paths that large ones cannot use.
Sources and assumptions
Sources define the engine settings or mathematical model. Project-specific performance and final playability still need measurement in the target build.