Good afternoon,
We would like to request the ability to have some physics objects prevent nav generation on top of them. Right now the only way to achieve this is to add null nav modifier volumes on top of each crate, rock, and other object that we want NPCs to never spawn or path on top of.
Unfortunately, this is inadequate for an open world game, as this would add tens of thousands of extra actors and components to the world, especially as we lean more into fast geo.
Cheers,
-Ian Stitzlein
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We added a feature that I think may work well for you. It is in CL 52186630 in UE5 Main. Here is a quick overview that the dev who added it wrote for our FN team:
"I added support for applying custom navigation areas to walkable surfaces during navmesh generation (see bUseSurfaceArea)
This allows to have a static mesh use a specific nav area. A typical example is to use a “FurnitureArea” on tables, couch etc., allowing navmesh queries to be aware of the environment.
How to Set It Up?
1. Select your Static Mesh in the Content Browser
2. Open Static Mesh Editor → Details panel → Navigation section
3. Enable bUseSurfaceArea checkbox
4. Set AreaClass to your custom nav area (e.g., NavArea_Obstacle)
5. The area will be applied when individual tile or navmesh is rebuilt
What Happens Behind the Scenes
- All walkable triangles from your mesh are marked with your custom area during voxelization (unwalkables remains unwalkable)
- This happens at rasterization time (not as a post-process modifier)
- The custom area replaces the default walkable area only for that mesh’s triangles"
One application of this is setting areas to null to prevent generation on top such as buildings, but not marking all the navmesh inside of the bounds as that nav area. This should only apply to the walkable area of the mesh, but if you notice there are places that are not respecting this or other oddities, please let us know! I would say this is experimental-ish as I don’t know FN’s usage of it, but we will support it. It should be in 5.8 as well if you are upgrading and don’t want to cherrypick CLs.
-James
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