Mark Low Height Areas in Navigation Mesh

Development Programming & Scripting AI
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1

Hello,

I was looking trough the options for the Navigation Mesh and discovered the option “Mark Low Height Areas”. This seemed to be perfect as I my game will allow the AI agents to crouch.

However, when checking the box nothing changes, no NavArea_LowHeight is being generated under anything and I cannot seem to affect these area’s either by placing down Nav Modifier Volumes.

Are there additional things I have to set up in order to get this to work?

Thanks

2

Any progress on this?

3

For anyone who is trying to figure it out in 2026 this is my approach:

Part 1 — Create NavArea_Crouch

  1. Content Browser → pick a sensible folder.
  2. Right-click → Blueprint Class.
  3. Expand All Classes, search NavArea. Select NavArea as the parent (if it’s not selectable, pick NavArea_Default — both are walkable by default). :warning: Do not pick NavArea_LowHeight or NavArea_Null — those are non-traversable.
  4. Name it NavArea_Crouch.
  5. Open it → Class Defaults and set:
  • Default Cost = 2.0 — walkable but pricier than open ground, so bots only duck through when it’s genuinely the better route.
  • Draw Color = something loud (e.g. bright orange or cyan) — this is what you’ll finally see in the nav overlay to confirm it worked.
  • Leave everything else (the walkable AreaFlags are inherited — you can’t/shouldn’t edit them).
  1. Save.

Part 2 — Enable Mark Low Height Areas project-wide (covers all maps)

Edit → Project Settings → Navigation Mesh.

  1. Under Generation, expand the Advanced rollout (the little arrow at the bottom of the section).
  2. Tick Mark Low Height Areas = True.
  3. This writes to DefaultEngine.ini, so all maps’ RecastNavMesh pick it up.

Part 3 — Place a NavModifierVolume over a passage (per passage, per map)

  1. Place Actors panel → search Nav Modifier Volume → drag it into the level near your passage.
  2. Position and scale it so it fully encloses the crouch gap — from at/below the floor up past the low ceiling, covering the whole passage footprint. It must overlap the low-clearance region (err on the side of slightly larger).
  3. In its Details → Nav Modification:
  • Area Class = NavArea_Crouch
  • Area Class To Replace = NavArea_LowHeight ← this is the magic; it auto-switches the volume into the “low pass” mode that keeps the low voxels.