I was following the youtube level design tutorial, and I followed the same steps shown, however UE produced these odd wavy shadows which were quite different to the smooth shadows with slightly diffused edges like in the tutorial, so I am not sure why this has happened.
What is your build quality? And what are the lightmap resolutions you’re using for those BSP’s? Do you have a lightmass importance volume surrounding your scene?
I think in that picture the quality was preview, however I tried it with production quality and the same thing happened:
As for resolution it is 32 on all the BSPs, but I dont know what lightmass is, but I did include that bit of the details panel in this screenshot, if that is of any use.
EDIT: So I just looked up lightmass importance volume and tried one on this scene, however it had no effect (when the volume had default settings)
The answer is definitely the lightmap resolution but here’s a slide show that I made to demonstrate what is actually causing the problem and a solution:
Short answer is; BSP is meant to be used to block in a level but it’s not used for final scenes anymore. Increasing the light map resolution will fix the issue, but ultimately you should use Static Meshes instead. Also when you use meshes, always build your levels out of several smaller static meshes instead of scaling meshes to fill the entire scene. As you scale a mesh up, it requires a higher lightmap resolution to give you the same visual fidelity.