Hi Killer Ferret,
I’ve been playing around with some settings and seeing if I could give you some clear pointers on what to try out. In the attached images I’ve got two things for you to try.
In the first image I set up a basic Landscape with three trees of different sizes to clearly see the difference in shadow information.
In the landscape setting for “Static lighting resolution” I changed it from the default 1.0 to 4.0. You can choose to do this higher but I would not recommend raising this number too high as this would lead to long light build times.
In the second image I’ve opened up the static mesh for the tree (from the Mobile Temple example). I upped the lightmap resolution from 64 to 2048.
Also make sure to include a “Lightmass Importance Volume” surrounding your playable area as this will help reduce light build times. Playaround with these settings and you’ll get some better shadows from your meshes.
As for the the seam and the pre-shadows. I was able to reproduce the seam but when I upped the lightmap and rebuilt lighting it was no longer present. Not sure on the pre-shadows as I was not able to get that particular issue.
Let me know if anything else pops up or you have any questions. I’ll definitely do what I can do help you!