what I did for now is that I selected a subset of residues that sit around a cavity. Then I showed the surface of the original protein inside the selection to get only the inside surface of the cavity. Now it looks sort of like a hose with inside and outside just as I wanted.
Now I'd like to raytrace this and I find no texture on the outside surface, which is actually just the back of the inside. I put a picture on http://pwe.no-ip.org/other/Pymol.png to illustrate my problem. See how the inner surface has texture and its back doesn't!
How can I get this fixed? Any ideas?