camera mesh

This is a model of the Xtion I made when working with one on the Kuka arm...

We will need to have separate meshes for each non-fixed link in the chain. So a minimum:
(1) robot base up to and including lower pan-tilt motor
(2) upper pan tilt motor
(3) tilt bracket and camera plate and cameras

The pan-tilt inside the perspex sphere could also be separated as the joint states of that pan-tilt are published by scitos_mira. This would be mostly cosmetic as no sensors are in the head, with the only use I can think of being if we want to control the eye gaze to look at 3d world points...

@mudrole1, @kunzel ...