5.5 baked lightmaps error

Development Rendering
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1

When building lighting on a converted 5.4 project to 5.5 i get

LightingResults: Error: Import Volumetric Lightmap failed: Expected 64 tasks, only 0 were reported as completed from Swarm

No other errors are listed. Same project static lighting builds fine in 5.4.4

7900xtx
7950x
64gb ram

Tested with an empty Level with a single stationary light and singe static mesh as well with same result

Even get the message on a completely empty level

I figure it must be a bug as the baked lighting worked great in 5.4.4

2

further looking into the logs:

[2024.12.23-22.44.32:515][856]LogStaticLightingSystem: Warning: No importance volume found, so the scene bounding box was used.  You can optimize your scene's quality and lighting build times by adding importance volumes.
[2024.12.23-22.44.32:515][856]LogStaticLightingSystem: Running Lightmass w/ ImmediateImport mode ENABLED
[2024.12.23-22.44.32:515][856]LogStaticLightingSystem: Running Lightmass w/ ImmediateProcess mode ENABLED
[2024.12.23-22.44.32:515][856]LogStaticLightingSystem: Running Lightmass w/ Sorting mode ENABLED
[2024.12.23-22.44.32:515][856]LogStaticLightingSystem: Running Lightmass w/ Mapping paddings ENABLED
[2024.12.23-22.44.32:515][856]LogStaticLightingSystem: Running Lightmass w/ Mapping debug paddings DISABLED
[2024.12.23-22.44.32:533][856]LogEditorBuildUtils: Build time 0:00
[2024.12.23-22.44.32:623][858]LogUObjectHash: Compacting FUObjectHashTables data took   0.40ms
Failed to find game directory: /home/blackbeard/unreal/UnrealLightmass/Binaries
Assertion failed: Tag == ETaskTag::EGameThread [File:./Runtime/Core/Private/HAL/ThreadingBase.cpp] [Line: 88] 
The Gamethread can only be tagged on the inital thread of the application
appError called: Assertion failed: Tag == ETaskTag::EGameThread [File:./Runtime/Core/Private/HAL/ThreadingBase.cpp] [Line: 88] 
The Gamethread can only be tagged on the inital thread of the application

Signal 11 caught.
Malloc Size=262146 LargeMemoryPoolOffset=262162 
Malloc Size=262146 LargeMemoryPoolOffset=524338 

=== Lightmass crashed (Signal=11): ===
1001[2024.12.23-22.44.32:855][862]LightingResults: Error: Import Volumetric Lightmap failed: Expected 64 tasks, only 0 were reported as completed from Swarm
[2024.12.23-22.44.33:108][862]LogUObjectHash: Compacting FUObjectHashTables data took   0.23ms
[2024.12.23-22.44.33:143][862]LogStaticLightingSystem: Illumination: 575.677 ms (6 us encoding lightmaps, 6 us encoding shadowmaps)
[2024.12.23-22.44.33:143][862]LogStaticLightingSystem: Lightmap texture memory:  0.0 MB (0.0 MB streaming, 0.0 MB non-streaming), 0 textures
[2024.12.23-22.44.33:143][862]LogStaticLightingSystem: Shadowmap texture memory: 0.0 MB (0.0 MB streaming, 0.0 MB non-streaming), 0 textures
[2024.12.23-22.44.33:143][862]DumpUnbuiltLightIteractions
[2024.12.23-22.44.33:143][862]Lights with unbuilt interactions: 0
[2024.12.23-22.44.33:143][862]
[2024.12.23-22.44.33:143][862]Primitives with unbuilt interactions: 0
[2024.12.23-22.44.33:175][862]Cmd: MAP CHECK NOTIFYRESULTS
[2024.12.23-22.44.33:175][862]MapCheck: Map check complete: 0 Error(s), 0 Warning(s), took 0.118ms to complete.
[2024.12.23-22.44.34:587][934]LogSlate: Window 'Message Log' being destroyed
[2024.12.23-22.44.34:628][934]LogSlate: Window 'Message Log' being destroyed

this is the 5.5.1 from https://www.unrealengine.com/en-US/linux

When i switch back to 5.4.4 i no longer get the crash or the Failed to find game directory: /home/blackbeard/unreal/UnrealLightmass/Binaries

Looks like the Assertion around the gamethread is causing the UnrealLightmass crash

3

Attempted to file an issue at https://unrealbugsubmissions.epicgames.com but the captcha keeps saying invalid

4

@theblackbeard420 Just here to say I got the same error and my log says pretty much the same thing as yours and thus I cannot build lighting on Linux. I also obtained my Unreal 5.5.1 from https://www.unrealengine.com/en-US/linux though I upgraded my project from 5.3.

Have not yet found a solution.

A newly created project also fails to build lighting. The lighting build works fine on Windows, though.

5

Still got the error on 5.5.2 on linux unfortunately.

I did send a bug report to Epic with a link to this thread for further details, hopefully this gets resolved, while I know Linux isn’t a priority this has been a bug since 5.5.0 and didn’t exist on 5.4 and 5.3 but i’m unable to use either 5.3 or 5.4 due to the high amount of crashes, i’m stuck on 5.5.

6

Same here… Please Epic, this is a disaster !
I’m trying to build on GNU/Linux (Manjaro).

7

This is a problem. Please fix baking lightmap 5.5+ for linux.

8

Same here on 5.5.3

9

Hopefully there is a solution for this soon. Though in the meantime I don’t mind downgrading to 5.4.x until this issue is fixed.

10

Currently I am stuck on this error and nothing I have done (I have done a plethora of different things, both on Linux and Windows) has worked.

I do not know if it is a single setting we are all missing or a bug of 5.5 UE engine.

11

I got the same error (Manjaro) with UE 5.5 so I had a look at the 5.6 branch. Unfortunately it won’t work there either. When trying to start it throws the following error:
symbol lookup error: /projects/UnrealEngine-5.6/Engine/Binaries/Linux/libembree4.so.4: undefined symbol: _ZTVSt15basic_streambufIcSt11char_traitsIcEE

12

Ran into the same problem. Any information would be great, because I can’t manage to bake lighting in an Unreal 5.5 project on Ubuntu.

13

Same here for a source compiled UE:

Version: 5.4.4-0+UE5
Platform: Ubuntu 24.04.2 LTS (x86_64)

But it works on a Windows machine with the non-source version.

14

Just test 5.6.1 compiled from source on Archlinux and the error is still there unfortunately, I have made a report to epic games but i’m unsure why it’s not fixed yet and seems to have existed for multiple versions now

Import Volumetric Lightmap failed: Expected 384 tasks, only 0 were reported as completed from Swarm
15

very frustrating that this issue is still here in 5.6 and 5.7. Actually makes these versions of the editor unusable for game development

16

my project can’t be downgraded to a version that works which is very frustraiting, hope this will see a fix as having to boot into windows if I want to bake lighting is absurd.

17

I’m having this same problem baking lightmass in UE 5.5, 5.6, 5.7 on Linux Mint.

18

For what it’s worth, when I built the GPU lightmass branch from source, it also fixed this problem with CPU lightmass.

I don’t think Epic is ever going to fix it themselves.

19

I’m on 5.7 on Ubuntu and got the error. The editor has also hung with the “Message Log” up taunting with the error. Is that it? It fails then hangs for everyone else?