Nick,
I had the same issue a while back and never found a really good solution. I believe that building shades are only defined by rectangles. I used 2 crossed rectangles (as shown below) and then assigned shading schedules based on the types of trees they were. If you figure out a better way, PLEASE SHARE!
[cid:697164417 at 02042010-3408]
Heather Hardie-Hill
