Lighting not building

Hi there, I’m sure I’m missing something really simple here but I can’t seem to build the lighting at all. I click ‘build lighting only’ and then when I click play there is an error message saying lighting needs to be rebuilt.

I have noticed that the Build Status dialogue box appears only for a split second. I’m assuming this is causing the problem as I have enough lighting and assets in my scene to keep the light build busy for more than a split second.

Thank you for reading


Try disabling static lighting in World Settings by hitting “No Pre-Computed Lighting” then rebuild.

Edit: Just so you know this will remove static lighting, but /should/ allow you to build

Also, have you tried building all levels? Do you still get the error?

Hey Selwyn!
Probably there is some error preventing light from Building. Navigate to Top bar -> Window -> Developer tools -> Message log and see if there is something off. If it is - please post it here so we can help you to solve this issue :slight_smile:

Hey guys thanks for responding. I will try your suggestions when I get home later and will post my results.

@Lindsay Aries: In regards to removing all static lighting when I go into play mode everything will run very slowly. For taking a screenshot of my scene however this will probably work.

Hey zeORB, when I build geometry it only tells me I need to rebuild lighting. When I then click Build Lighting Only this message then disappears but when I click play I still have the error message i the top left saying lighting needs to be built 22 unbuilt objects

Ok so it seems to only be an issue with the latest build (4.7.3). I installed 4.6.1 and the light build worked exactly as it was supposed to

Update: I installed UE4 (build 4.7.3) onto my work computer and it worked just fine. The first time I ran the lighting build it told me a firewall was blocking swarm and if I wanted to allow it through the firewall. After allowing it through it built the lighting and didn’t prompt me again after that.

Previously, I had temporarily disabled my firewall on my home computer to see if it that would fix the problem but it didn’t work. However, I’m pretty sure this is a firewall problem and I probably missed something last time.

I’ll have another look at it tonight and post my results.

Thanks for reading


I have done everything I can regarding the firewall but no success.

This is what I get in the log for Swarm Agent

21:06:49: Starting up SwarmAgent …
21:06:49: … registering SwarmAgent with remoting service
21:06:49: … registering SwarmAgent network channels
21:06:49: … initializing SwarmAgent
21:06:49: … certificate check has failed
21:06:49: … initializing cache
21:06:49: … using cache folder ‘C:/Users/selwyn369/AppData/Local/UnrealEngine/4.7/Saved/Swarm\SwarmCache’
21:06:49: … recreating SwarmAgent cache staging area
21:06:49: … initializing connection to SwarmCoordinator
21:06:49: … using SwarmCoordinator on RENDER-01
21:06:51: … SwarmCoordinator failed to be initialized
21:06:51: … initializing local performance monitoring subsystem
21:06:53: … initialization successful, SwarmAgent now running
21:06:58: [Interface:TryOpenConnection] Local connection established
21:06:58: [Interface:OpenJob] Error: Invalid namespace

Any ideas what these errors are about?

Selwyn, try to delete SwarmCache in C:\Users\YourUsername\AppData\Local\UnrealEngine\4.1\Saved\Swarm\SwarmCache
If it does not help - create post on Answerhub

This didn’t work. Everytime I deletedthe folder it would reappear when I attempted to build the lighting.

I have now posted on Answerhub

Thanks anyway