The OpenNI Viewer adds a coordinate axis represented by "cylinders of really low resolution" :) (hexagon in this case).
The viewer is a technology demonstrator and shouldn't be used for serious data I/O operations, as you can always
copy&paste some of the code and write your own.
We could optionally also add a command line parameter to disable it.
Wait - are you going to do screen captures, or how will you save the data to disk? Using PCL I/O functions the "hexagon"
will not be saved anyway. It's merely there for visualization purposes, and should be trivial to comment out that line
or write your own tool that does this. I don't recommend using openni_viewer for data capture by any means.