You can't change the shape but here's two possibilities. 1.) You could move the light source slightly inside the projector and project it through a square opening (just like the real thing). The opening would cast the square shadow and give you a square result. Turn on the soft shadows if you have the rendering time too. 2.) You can also have an object cast a shadow without it being visible. A square opening would again do the trick. Just two thoughts. -Kix

-Kix