BK and I found this when screwing around on my map a while back. Those are all the same piece, of structure, but rotated at different angles and merged with certain other objects. I think this phenomenon occurs based on the lighting on the center of mass of the object. So if the center of mass is located inside of a large rock, like the ones on the right, then the game thinks the object is shrouded in darkness, so the object is black. The light grey objects might protrude into the light area of the cave that runs through the middle, so it appears very bright. The reddish/brown piece is influenced by the light sphere surrounding the brown tree, so it takes on the lighting traits of the tree. The same goes for the green piece.
