Minty - in the tutorial that JVRenderer pointed you to it actually says "Load a prop square and scale it to fill the background of your scene. (Or you could use the Nerd3D Backdrop Tool with no texture ;-) ) It also says "There must be something behind the figures for the volume to show up. A prop Square scaled to fill the window will work" I cant find any reference to Nerd3D Fog tool. It looks like a great Tutorial.