just got the DVD out and watched that sequence Jay, its great to see exactly how they went about it to get the different results that were needed. I wonder how long it took to get to the final scene

Cheers for the extra tips Steve, it sounds like you've done a fair bit of rendering separate layers in the past

I've just had a quick play and got these layers from the settings. It kind of makes more sense then when you take it into photoshop and start playing with the layer settings.
Dont know if they are right though or if I need to play about with excluding things like reflective/refractive things?

shadow (with backdrop left in):


diffuse:


color:


specular: