Hello, there Unreal people!
I need some help with light. I have made these walls (Grid-base system) in blender. When I imported them, they looked fine (before I hit the “build light button”.) After that, they look like they are separated into pieces. I don’t know whats causing this and I would be more than happy if someone could help me! Thank you in advance!
I assume you’re using static light. The easiest solution is just switch to movable 
Alternative is set static lighting level scale to 0.1 and smoothness to 0.6 for a starter…
Won’t that affect the performance?
( see the above also ).
It really depends on a lot of things. I’d only use static lights if you are going for a specific arch viz look, or you really need to squeeze every ounce out of the system, mobile for instance.
Well, then I better make a map in Blender and import it as a whole, hopefully, I will get rid of the lighting problems…
No, that will make it worse.
Really, don’t bother with static unless you specifically need it. Try tweaking the params like I said above…
Ok, thanks a lot for now 
Ok, that fixed the main problem, but now there is this line between the white borders. I think it has to do something with the smoothing?
Have you tried increasing it?
Yep, and still, I have those lines there…
I have discovered that those lines are there only if I am going from a shadow to a light place. I covered it with the ceiling and its looking fine, But I still have some windows there so the problem is the same
No it doesn’t effect performance BUT building time!
Hi!
Could you show us the lightmap uv of this (or problematic mesh)?
What is the lightmap resolution of the mesh?
Ok, so I fixed it by some miracle. It was actually a problem in blender. I needed to apply the edge split modifier to the mesh… But thank you so much for helping me <3