Hi. I’m facing a hair pulling issue. I’m working on a level that is so far only made of trees and a couple of vehicles. The map isn’t that big, it’s a 1km heightmap I scaled down by 55%. The lightmap value of every mesh is set to 128. I can’t build the lighting because it takes WAY too long. In fact I don’t even build the lighting because it would take days. I don’t think my specs are causing this, I have a quadcore i5 with 16 gigs of ram and a GTX 1050ti. Nothing fancy but I don’t have any performance issues. What could be causing this problem?
Hi,
Unfortunately. building the lighting for an open world map is expected to take a very long time, especially, if all of your lightmaps are at 128x. You are also in the risk of running out of RAM in the building process, at which point the Editor will crash. Also, your game could become very taxing on the GPU if there are a lot of lightmaps around.
What setting are you building on (however on large maps it will still take several hours even on Preview)? Also look around in the Project or Editor (can’t remember) settings, you will see some additional options to optimize the process, but I wouldn’t have high hopes. I would consider dynamic lighting anyway for such a huge map. Imagine moving a single object, and having to rebuild the lighting for the whole map. Of course, you can make ‘sectors’ but then you will introduce seam problems where those ‘sectors’ meet.
haha I wasn’t even aware of dynamic lighting in UE4. I enabled it in the project settings and now everything is fine. 
Thank you for your help, much appreciated.
Hi,
No problem, I’m glad that I could help!
Take a look at this page, it has a lot of useful info about lighting in Unreal 
https://docs.unrealengine.com/latest/INT/Engine/Rendering/LightingAndShadows/