Hi everyone, after 2 full-time-days of testing and more than 40 times, I still have some issues with the lighting of my environment.
The main issue is that I have the dark, blurry artifacts on my walls (not the white ceiling corner panels! That’s just UV problems that needs to be fixed:D).
I already imported the walls, floor and ceiling seperately and have the “Lightmass Resolution” on 1024 (each mesh).
My first and main issue was, in 4.10, as you can see in the corner and the wall:
I read a lot of excisting threads, lighting trouble shooting, and the “Lets make Lightmass EPIC (and understandable)” thread.
I Also tried and test out a lot of “Lightmass Setting” from several treads but didn’t really worked out, incl. the “Lightmass Portals” in 4.11.
Then I upgraded my 4.10 project to 4.11, I noticed my scene was a lot darker and was not the same as before (first picture).
So I removed the “Saved” and “Intermediate” folders and rebuild the light again.
Then I change the “Lightmass Setting” until it was the closest I could get back as the first picture + without the artifacts.
That look as follow in 4.11:
My question is, how can I get rid of the artifacts and get the sharpness back of the first picture in my current scene (second picture, 4.11)? (Without that the artifact get more worse on the wall).
If I try to scale down the “Static Lighting Level Scale” below 1, the artifacts starts to get worse and worse. Even if I try to smooth it with the “Lighting Smoothness”.
What I did notice is if I increase the “Directional Light - Intensity”, the artifacts also get more worse.
Another question is, should I choose to go back and continue in 4.10, or 4.11?
Since my scene looks better and sharper in 4.10 but I can’t get rid of the artifacts in 4.10 and aswell as 4.11.
Maybe someone can give me good advice? 
**Small notes:
- I build on “Lighting Quality - Medium”.
- I DIDN’T change anything in the .ini files!
- As you can see in the pictures, I use for lighting: “Directional Light” and “Sky Light”.
- I already imported the walls, floor and ceiling seperately and have the “Lightmass Resolution” on 1024 each mesh. I also tried 256 and 512 on each mesh.
- The UV’s are good and the UV Channels 0 and 1 also look fine of each mesh (wall).**
An example of one of the testing results in 4.11:
Static Lighting Level Scale: 0.4
Lighting Smoothness: 0.8
Directional Light Intensity: 8 (I changed it from 6 to 8 based on the current scene).
I hope someone can help me and thanks a lot already!