This is really annoying me now. I know that I’m not the only one with this problem. I started building my project, but soon after the “Lightmass crashed” error has appeared. I did anything I know to fix this (clean and validate SwarmAgent cache, deleting its logs, lower lightmaps settings), but nothing worked. Mybe that it’s somehow connected with the size of my map, which is really big (260x260x100), or maybe it’s something with foliage (I have here lots of trees). Please help me, I don’t know what to do 
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Hi Hobrux,
Please try the steps listed on this page and let me know if they end up addressing your specific concerns:
Edit: Originally linked incorrect troubleshooting guide, please use the new link above!
Somehow it worked, but now it’s here again and I can’t fix it. Maybe it’s connected with trees in my scene, there is 3.88k trees, but I need at least 50k trees to fill my map (which is really big). I saw many games where was over 100k trees, but I don’t know how to do that. Lightmap resolution is 64 on all meshes, virtual memory is over 100gb, swarm was cleaned and validated, my computer’s performance is good. Please, do you have any ideas how to solve this?
Are you using LODs to reduce the amount of polys being rendered at the same time or are you using any form of instancing for optimization? If you have a lot of assets, especially high poly assets, it can put too much strain on the pc to be able to keep up.
Can you post your dxdiag here so I may take a look? Additionally, did you try the steps listed in the wiki page above?
I’m sorry, but I’m new to the engine and I dont know exactly what do you want. Can you please describe it?
And yes, I have tried all of 'em.
Is DxDiad a log?
Here is swarm log (uploaded in parts cause its size):
13:31:50: Starting up SwarmAgent …
13:31:50: … registering SwarmAgent with remoting service
13:31:50: … registering SwarmAgent network channels
13:31:50: … initializing SwarmAgent
13:31:50: … certificate check has failed
13:31:50: … initializing cache
13:31:50: … using cache folder ‘C:/Users/PC/AppData/Local/UnrealEngine/4.9/Saved/Swarm\SwarmCache’
13:31:50: … recreating SwarmAgent cache staging area
13:31:50: … initializing connection to SwarmCoordinator
13:31:50: … using SwarmCoordinator on RENDER-01
13:31:53: … SwarmCoordinator failed to be initialized
13:31:53: … initializing local performance monitoring subsystem
13:31:57: … local performance monitoring subsystem initialization failed
13:31:57: … initialization successful, SwarmAgent now running
13:32:03: [Interface:TryOpenConnection] Local connection established
13:32:04: [Job] Accepted Job E6369D01-483ED2CD-03581F97-78678846
13:32:06: [Job] Launched Job UnrealLightmass_2015-09-30_14-30-01_1325512-64bit.exe
13:32:06: [Job] PID is 5152
13:32:06: [Job] GUID is “E6369D01-483ED2CD-03581F97-78678846”
13:32:09: LogLightmass:Display: Lightmass Win64 started on: PC-PC. Command-line: E6369D01483ED2CD03581F9778678846
13:32:09: Lightmass Win64 started on: PC-PC. Command-line: E6369D01483ED2CD03581F9778678846
13:32:09: LogLightmass:Display: Processing scene GUID: E6369D01483ED2CD03581F9778678846 with 1 threads
13:32:09: Processing scene GUID: E6369D01483ED2CD03581F9778678846 with 1 threads
13:32:09: Building static lighting…
13:32:09: LogGenericPlatformMisc:Warning: Failed to determine engine directory: Defaulting to …/…/…/Engine/
13:32:09: Failed to determine engine directory: Defaulting to …/…/…/Engine/
13:32:09: [Job] Found a parent connection for PID 5152
13:32:09: [Job] 07E3C306 → 32F00D2C
13:32:09: [Interface:TryOpenConnection] Local connection established
the dxdiag can be found by going to your windows start menu and typing in dxdiag, then open the dxdiag.exe that appears. Save that to a .txt document and upload the .txt here so I can take a look.
Additionally, are you using any form of cull distance for your trees?
What steps are you taking to minimize the amount of impact your assets are having on performance?
Hi Hobrux,
We have not heard from you in several days. I am marking this thread as answered for tracking purposes. If you are still experiencing this error, please comment with the requested information.