For Bugs Life, they created a full frame version by rendering the top and bottom that didn't exist in the theatrical version.
I didn't know that, but I did read that they also re-created some scenes completely to take better advantage of the full frame.
Back to the topic - I have a real love/hate relationship with 3D. The trouble is, it's not 3D. It's pseudo-3D as long as you keep your head perfectly still, and as long as you can stand the headaches, which for me is about 5 minutes.
DE