I have spent about a week cleaning up this model and also layouted its lightmaps by hand to get the best possible result. However, after building lighting in production quality, out comes this:
And here are the lightmap UVs I created for the castle and for the floor visible in the above screenshot
I have different charts (islands? chunks?) for the sides of the bridge and for its top to prevent shadow smear across hard edges. But somehow there’s a large patch of light on the bridge and a large patch of shadow on the ground that do not belong there.
What could be the problem here?