I have been using Chimera to export .stl files of proteins and RNA for 3D printing. The surface models print OK, but sticks or ribbons choke the printer. I looked close at the output meshes, and they have many extra surfaces which should be removed to make "legal" .stl format. Is that portion of the code open source? I'd like to take a closer look and see if it's possible to fix. It would be much easier to rectify the bad surfaces upon creation, rather than trying to remove them by post-processing. Thanks, Dennis Kolva Cornell U.