Its been a while since I've been mapping, but I'm coming back to it.
A while ago I remember someone posting how to edit a light so it creates more complex shadows. You just enter a key/value combination and the shadows are more detailed. I remember the post had all sorts of pictures explaining how to do it. Sorry that I can't give any more details of what I'm trying to figure out, but hopefully some of you will remember that post and be able to clue me in.
I used the search function but I couldn't find it.
Its faster to compile if you just select the surfaces you want nice shadows on and open the surface inspeactor and put in the value you want in the 'density' box