Pathfinding Service Navmesh never properly clears

[sicknoobie (Marioman73)]

I’ve noticed in my experience that after a while, PathfindingService calls just fail and barely even try computing for longer than like 0.1 seconds.

I believe this is due to the Navigation Mesh never clearing, so it just builds up as various different maps/areas are loaded and eventually the service just gives up trying to pathfind.

I will be working on a reproduction for this, but this issue is currently seen in

NVZ:RR Testing Place

and

Noobs vs Zombies: Realish Reborn

Expected behavior

I expect PathfindingService to consistently find paths within basic and advanced geometry without arbitrarily failing.

Here’s a video of npcs failing to pathfind in basic geometry
Server uptime about 10ish hours (pretty standard)

Watch Recording (366) | Streamable

Here’s a video of the same npcs successfully pathfinding in the same basic gemetry
server uptime < 1 hour (just started it)

External Media

Evidently there is a problem here because there should be ZERO reason they can’t navigate the same space just because the server is old

[Sylmat]

Hello there!

Not sure if those applies to your issue, but it seems like it might give you some clarity on your problem?

Roblox's core scripts are memory leaking on the server

The navmesh manages the world by dividing it into 64x64 tiles on the XZ plane. When parts or terrain within a tile change, the corresponding navmesh for that tile is deleted and a new one is generated. This process involves releasing the old memory and allocating new memory. We plan to add a feature in the future to remove navmeshes from tiles that haven’t been used for a long time. However, for now, once a tile’s navmesh is generated, the memory remains allocated as long as the parts and terrai…

(This message comes from a private message related to another bug)

@oldmannt

We’ve confirmed the bug you reported: Pathfinding is incorrectly returning NoPath because the agent’s position is exactly in an area without a navmesh. This is a known issue caused by our navmesh generation process. A part that is not an integer multiple of 1 stud in length can cause small gaps in the navmesh, as the system’s voxel size is 1 stud. Parts that are not aligned to the stud grid may cause the same problem.

[sicknoobie (Marioman73)]

Does add some context for sure but unfortunately doesn’t address the issue. NPCs in each map are able to pathfind perfectly fine when the map is played first/second in the server (or within the first 10ish matches) but after a while they simply cant pathfind anymore despite the map geometry being the same. I do think its related to the fact the navmesh never properly fully clears up, and the new Timeout system bugging out somehow.

[TechyPlains (Techy)]

This is an ongoing issue I’ve experienced as well. The Navigation Mesh doesn’t get destroyed, meaning if you load maps in the same position, the Navigation Mesh will stack on top of the previous NavMesh, causing confusion with Pathfinding.

I’m unsure if any engineers at Roblox are even aware of this issue, since I’ve made a post about this issue a couple months ago and it’s never been addressed.

Really hoping this gets resolved, as it’s a pretty big issue for games with continuous map loading.
Unless there’s a workaround for the time being (I don’t know of any), there’s really not much we can do considering there’s no API or control over the NavMesh we can use as developers.

[sicknoobie (Marioman73)]

Yeah, really frustrating at the moment as my game’s main appeal (the NPCs you fight alongside and against) are entirely reliant on the feature.

It’s also especially bad as the new time-out based approach to calculations seems to just crap out way faster than before. Prior to PathfindingUseImprovedSearch, paths would fail if they explored like some crazy high number of possibilities and still found no solution. While this did result in sometimes paths taking a while, it at least meant they actually got calculated.

In situations like this one, I think the service now just straight up almost immediately times out paths so they literally can’t find a path at all.

I REALLY wish we could get a PathSettings that would let us use the old behavior of paths failing to compute after exploring all/most possibilities as opposed to an arbitrary calculation time. That’s more of a feature request though than a solution to this bug. (Though it could help being a solution I suppose)

[TechyPlains (Techy)]

I went ahead and did some digging to try and pinpoint the issue and see if anyone else was experiencing this issue.

I did end up finding this exact issue, however the post was made 8 years ago. Apparently it was “resolved”, however this doesn’t seem to be the case as of today.

The Pathfinding NavMesh doesn't update when models are removed/destroyed

In Resurrection we have the typical COD doors/debris that you spend your points to clear a pathway. Only problem is, when the debris get cleared, the NavMesh doesn’t update. So zombies think they can’t go up the stairs. To trick it into updating, we had spawn an invisible unanchored part after deleted the debris. [Whyitnoupdate] Is there some method I am unaware of to force it to update certain areas? Is this actually a bug or just a lack of feature? Or am I crazy?