Navmesh not generating on generated terrain

[blutreefrog (blue)]

After generating terrain using our game’s terrain generator, a NavMesh is expected to be generated so that pathfinding can work on the terrain. However, a navmesh does not generate. If parts are placed on the terrain, a navmesh generates around the parts, but the terrain itself is ignored by pathfinding service.

Expected behavior

A navmesh should be generated around our generated terrain. This issue can be fixed by lowering the terrain thickness in our terrain generator.

in ServerScriptService.Modules.TerrainGenerator.GenUtil, 596

changing (groundLayer <= 1000) to (groundLayer <= 2)

However, this is not ideal as we need the terrain thickness for various gameplay reasons.

A private message is associated with this bug report

[Bitsfps]

Terrain originally created using heightmap won't generate a Navigation mesh?

Just noticed my Mobs weren’t using at all the VoxelTerrain for pathfinding in one of my maps, turned on “Show Navmesh” and Navlinks in Studio and… no Navmesh on terrain, only in very specific places at the edge of the map. modifying the Navmesh will sometimes work, but as soon as you refresh the Terrain (closing and opening it again, pressing Play, etc.) the Navmesh is again, gone. The image bellow shows the only place where a Navmesh exists in the entire Terrain, which varies a lot in form, he…

My post about the same bug, but from my perspective and testing, it’s related to the Cracked Lava layer, as you can force the navmesh to generate/update automatically on Studio by removing some of it, but when you Play it’ll regenerate but it’ll bug out if you didn’t get rid of everything.

Terrain Thickness is just how Lava gets automatically generated, but seems to have nothing to do with it based on tests on lower-height imports from heightmaps.

I’ve explored this bug for a long time now, and my fix seems to work for every single person who talked about it until now.

[blutreefrog (blue)]

We use a custom terrain generator which as far as I know doesn’t use the cracked lava material, but I think it’s probably the same engine bug manifesting in a different way

[thirdtakeonit]

Thanks for the report! Just to confirm, we have a ticket filed in our internal database for this issue.

[hyperhumanist]

Hi @blutreefrog . Can you please provide a simplified example that reproduces this problem? Ideally attach a small .rbxl file that, when started, generates the broken terrain. Thanks!

[blutreefrog (blue)]

this is (as far as i am aware) being covered in a different bug report which was submitted privately, this one contains a repro place

https://devforum.roblox.com/t/private-information-bug-report-from-blutreefrog/2490828?u=blutreefrog

[portenio]

Apologies for the late reply.

A fix for this problem will go out with this week’s release.
I will keep you posted so you can confirm it’s been solved for your use case.

[blutreefrog (blue)]

thank you so much for the fix! out of curiosity what was the issue?

[portenio]

The issue to how we generate and process the terrain mesh within the pathfinding service. This led to certain scenarios where a step in the navmesh creation entirely ignored the terrain data. But these implementation details are internal and not accessible via the API.
The problem was not linked to the input you provided, so unfortunately there was no action you could have taken to prevent it.

The change is now fully deployed. Please let me know if you are still experiencing issues.