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Lightning Build Failed. Swarm Failed to Kick off

The racing car game is not a big level and lightening was stuck at 0%. It is running differently in 4.7.

It seems that my swarm agent is not frozen. I’ll leave my level to build for like an hour or so and check back to see if there is progress.

EDIT: So after about 30 minutes of building, the ‘Distributed Progress’ bar in Swarm Agent is at 0.06%. ****…

EDIT 2: Alright so after getting past the first 1%, it speeded up quite a bit. Now it’s at around 26%. I suppose that on a large map like mine (8200 unbuilt objects), you just have to wait.

Thanks for everyone’s help in getting my problem solved

Hope it works out!

I had the same Problem in 4.21 . Solution: I deleted assets from Level and tryed rebuilding again until it builds lighting. Then I reload level withought saving and rebuild. Error gone:) hope it helps:)

Had the same problem today, was a single mesh too ^^"

None of those solutions helped me. The solution was this:

rmb the swarm agent (in the system tray) > exit > rebuild lighting

This seems to be related to swarm being linked to the last-used engine version. When its closed it resets the config to the current Unreal Engine version in-use.

Hi @GuaiamuStudio, @Valachio how did you find the wrong mesh? i have about 250 meshes in the problematic level and when I start to separate in small groups it seems that it stop having problems so I can’t find wich mesh is making all this trouble.

but I’m sure that is the problem, since the materials are all right and used in other levels with no problem, and the swarm agent wok fine with other levels, and just something in this level, that is part of it, so when i copy the geometry to a new level stay there is giving me the same problem.

This has been an issue for us when we import meshes from Revit via Datasmith that have overly-long filenames. Changing the **display name in the World Outliner **to something shorter often fixes this. We found this out the hard way by going through and deleting meshes until we found the culprit mesh. Best practice is to rename things before bringing them in via Datasmith but sometimes we don’t have the luxury of that.

TLDR: Move Unreal Engine folder from C drive to desktop / some other file

I had the same issue recently with version 4.25. When you try to build UnrealLightmass, visual studio tries to access a few files located in Engine\Binaries\Win64. One of these files is tbbmalloc. Visual Studio did not have access to this file because my Unreal Engine Source file was in my C drive (C:). As a consequence, Visual Studio couldn’t build some of the UE4 Modules and so when I launched the editor, I couldn’t build the lighting.

I have the same problem right now and it’s so annoying. I tried all possible solutions I found at google, but nothing helps… I build engine from sources, rebuild lightmass, cleared lightmass cache - nothing works out for me.

And it’s second time I have that problem. First time it was single mesh. I found it by deleting half of meshes in the scene - tried build the lighting - if it works then delete half from it and so on… until I found single mesh.

But not it’s again… And I don’t want to do it AGAIN. And I just want to know what actions drive to this problem otherwise I will need do it over and over again.