Hi, I’m an Italian architect and I use Unreal Engine exclusively for architectural visualization for clients.
Today I am writing to ask you kindly what causes the annoying light trails that you can see in the two videos that I attach to the post.
Thank you!
does anyone know how to help me? 
When viewing the post for this topic, I get the message:
This video cannot be rendered because your browser does not support the codec. Perhaps others are too.
Maybe you could try putting a video up on youtube?
Thanks for the reply. I’ll try with google drive, if that doesn’t work too, I’ll try with youtube. here is the link:
https://drive.google.com/drive/folders/1-HoTkyKFn15k0Li-noU_-gS_8P3iiITP
Thank you!
Good morning. Does anybody know how to help me? Are the videos now able to see them from drive?
I am waiting for feedback, I have the presentation to clients soon and I hope I can be able to present the projects without those light errors.
Thank you!
It looks to me like that’s Lumen having issues, are you using Hardware Ray Tracing or Software? Also, go into Lit (View Mode) then Lumen and click Overview. Looking at the viewport you’re looking for Pink, pink is bad, it means the mesh is too “detailed” if you will. It needs to be broken down into smaller pieces (walls, floors, ceilings, doors, windows, etc should all be separate meshes, modular). This will cause light leak in some scenarios. Also really thin meshes will cause issues too.
Also, in your Post Process Volume, check under the Lumen settings>advanced and see if changing Lumen Scene Lighting Update Speed and Final Gather Lighting Update Speed help at all.
Thank you for your reply. I am using hardware ray tracing. As for the mesh, the model is already divided by walls, floors, doors…etc.
I tried changing the advanced options of Lumen but it didn’t improve the situation.
I attach an image of the lumen overview in the message. And this also relates to another problem: those black spots I also see in the reflections of mirrored surfaces.
5.2
Do the streaks happen in the upper left, lower right or lower left of the screen? Or just upper right?
Mainly in the upper right and only when I move. Sometimes also in the lower part of sofas and beds, in the most shaded areas.