I am doing a scene where I have a light fog going through a window and I want to define it to just the window part. Right now it is going through the geometry around the window also. Is there some kind of gobo I could set up so it only goes through the window. I also would like to put glass so fog goes through it, but it just blocks it from showing.If I make a transparency map on the glass will the light go through then?Need help please.

I posted here because more people look in here than lighting and rendering I think.