Hello , Please i need to know , after building light , i found that there are a lot of stains on the walls and so weird shadows in the color , or even the light has a very strange shape , why ? and how i avoid my mistake ? Thank you
Hi!
Could you upload a screenshot?
Hi!
Your lightmap resolution for the wall is way too low!! The wall should have at least 128 (preferable 256 and higher)!
i’m sorry i can’t understand very well cause i’m n’t very professional in UE4 actually , can u explain with simpler way please ?
how can i increase that resolution ?!
Sure no worries! 
You select your wall object, on the detail panel at the lighting part put a check mark into override lightmap resolution and set it to 256 or 512… then rebuild your light and should look better! 
i did that and i changed the resolution to 512 and i rebuilt the light , but the result is that the spot light doesn’t work until i try to move it !!!
i mean , i have the spot light shining incorrect on the low resolution wall , then i changed that resolution and rebuild , i got the spot light like switched off , and it switched on Only when i try to move it forward or backward ! , except that it’s off
Well when you move something in the scene that is Static or Stationary it “breaks up” the baked lighting!! /this is why your light changes when you move it after build)…
…to be honest I think you should collect more information about Unreal and lighting… there are really good tutorials about the subject!!
Good luck!