WorldPartition causes random, unrecoverable crashes

First time around I would have put this down to a random glitch, but this is the second time my project has been put in an unrecoverable state after switching to WorldPartition. It’s really concerning because while it’s okay to have buggy or incomplete features, any feature that can literally destroy your entire project needs immediate attention.

The first time, I had force-deleted an element from a WorldPartitioned level, against the warnings, so I thought maybe it was my fault.

The second time was just a random crash, the engine was just sitting there in the background while I was working on something else.

In both cases, on subsequent loads, the engine immediately crashes on startup and it is impossible to get it to finish loading.

Assertion failed: ActorPtr.IsValid() [File:D:/build/++UE5/Sync/Engine/Source/Runtime/Engine/Private/WorldPartition/WorldPartitionActorDesc.cpp] [Line: 279]

The only way to fix this, that I’ve found, is to systematically delete folders in YourProject\Content_ExternalActors_\Levels\AffectedLevelName until it decides it wants to load again, and when I say “fix”, this means “but losing potentially a lot of work”.

Obviously since there’s hundreds of directories in there, it’s a massively time-consuming process.

For a bigger-budget studio you would implement a Perforce or other VCS. For smalller or solo devs, we don’t really have the resources to be doing that.

Unfortunately I’ve no idea specifically what actions cause this, so can’t provide any steps to reliably reproduce it. I think someone would need to have a go at catching the failed assertion at WorldPartitionActorDesc.cpp:279 and handling it more gracefully.

I’m familiar enough with software development that I can theorise how I’d fix it, but not enough so with C++ that I could provide a patch. Perhaps someone on the UE5 team or someone who is familiar with the WorldPartition code would be able to take a look?

I know I’m not the only one to have suffered this issue, but it’s hard to gauge how widespread it is, so it might just be a very edge case. Hoping desperately it can be fixed, because days of my life are being consumed restoring folders one by one until I find the “problematic” one!

I woke up this morning unable to load my project because of the same crash.
I’ve been working on this project for a few weeks but now it looks like my day is ruined and I haven’t even had my coffee yet. :frowning:

Just bumping to see if anyone figured out any other type of fix before i go in and start deleting stuff oe by one.

Also to note that I did start off the project with world partition enabled, but after having some other issues with it, I disabled it in the Project Settings but it looks like that doesn’t get rid of it. :confused:

I have the same problem and trying to fix it now. I know the only thing I changed with regard to worlds partition was changing some blocking volumes to always loaded. Did anyone find a fix?

We’ve tracked down our problem. It was due to someone using the “Create blocking volume” function within the static mesh details panel. In some cases the volume being created extends to infinity and that’s probably the cause.

I have also had to deal with this, suffered from multiple weeks of work lost. Assumed the solution was failed, still suffered from the losses. Even copying the level directly seemed to induce the problem in the copied level. I found a ‘workaround’, but that’s a generous term: I discovered their packed level instances didn’t suffer from the crashes or corruptions, so I manually divided the world into PLIs and saved them as seperate folders. In the event of an engine crash, I would reconstruct the world using the PLIs.

Functionally, I was hacking together world composition, and it was a nightmare to use. World partition, when it works, is amazing. And I haven’t tested how well it works with any of the new engine versions, but I believe world partition needs to work well and consistantly, in order for UE5 to be shippable.

Hello. I had the absolutely same problem today. No idea what’s causing it.
I was able to fix that by deleting “Binary, Saved, and Intermediate” folders and then “generate visual studio project files”

Hope that helps!

EDIT: Do a regular backup using UE5. There are plenty of errors that can hard-crash your project

To everyone experiencing the editor freeizng when attempting to open the World Partition Window

I just found that if you have a Static Mesh Actor in your scene with no Static Mesh selected for it’s attribute it will cause that freezing. Delete the null Static Mesh Actor to fix it!

Out of curiosity, has Epic managed to officially fix this issue, or offer a patch/official reccomendation? Those folders are still lost, but I want to know if I’ll be running into those issues in the future.

I ran into the same issue (that Jason talked about, freezing / crash when opening World Partition Window).
Adding a dummy placeholder mesh into some blueprints i had (where a static mesh was set as an official variable), fixed the issue initially.

Then however, as i zoomed out, it froze.
My world is a prototype large open world map with enormous scales for a skybox and distant planet, so i figured those elements may have had something to do with it.

But even deleting EVERYTHING in the entire level, it still crashed.
Now, somehow, it’s fixed.
Here’s what i did.

  1. Rebuilt all levels with HLOD0’s
  2. Crashed the editor as it tried HLOD0’ing the millions of km of skybox / planet.
  3. Restarted editor, rebuilt all levels, deleted HLOD0’s
  4. Actually read up on data layers. Added a new datalayer in which i assigned the planet and skybox. Edited datalayer file to affect runtime. Set them to always loaded.
  5. Went into the individual skybox / planet blueprints / meshes, set everything related to collision or streaming to off (apart from virtual textures), or set relevant settings to always awake.
  6. Unchecked the new datalayer from editor and set it to unload in runtime.
  7. Played in editor. Stuff was correctly unloaded.
  8. Changed back to always loaded in runtime and editor. Saved All.
  9. Played again.

Saved All.
Moved random actor, ctrl z.
Saved All again.

Now, somehow, the world partition window works. No crash or freeze.
No clue which step did it.
From my guess, it was adding a datalayer so the engine had any clue how to deal with the enormous meshes surrounding the world.

I would suggest, adding a datalayer at all (instead of literally nothing), could solve it. But i dont wanna presume the others here are as incompetent as i was.
Just hope this helps someone.