It is not hard to do them but they must follow some specific guidelines that will make them work correctly and you don't have to go figuring out how to do this properly (it can take several hours or more) cause I already did all that work for you.
Transparencies for example are a bit tricky and I will tell you how to correct problems with that completely and many other important things like how to deal with the problems that you will likely encounter with the textures and how to make the colors look correct in the screensaver cause if you don't set them in a specific way they will render very grayish and ugly.
The AC3D screensaver program is freely available at:
I also included this free tutorial with the 3D models mods package that I created for the screensaver (it includes 75 3D models for the screensaver) that is also available freely there in my Deviantart gallery.
The tutorial is freely available here at Deviantart:
And also here at Mediafire: