Texture a plane in the background will work if the cloud is sufficiently distant and/or the image/animation doesn't move around it's point of view to expose this cloud as a textured plane.

Another method, taken from the POVRAY folks, is to layer a few planes with similar noise pattern and the shader is semi transparent as well. This way we are sort of simulating the light through cloudy layers. Carrara doesn't do this all that well because of limited recursion depth. I.E. it stops at 25-28 levels. Not really enough to get realistic effects but with some playing you might get something usable. It will significantly slow down the rendering though.

Message edited on: 09/07/2004 12:43