Cannot visualize markers in rviz!

edit

I use openni_kinect and openni_tracker to track with kinect. Then, when a user is detected I can see the /tf in Rviz and it works.

However, when I try to use markers (eg. hone_markers, pointing_markers, ...) I see nothing in rviz. Topics are ok I think, because if I look rxgraph everything seems ok (rviz subscribed to topic /hone_markers, for example).

What should I do in order to visualize the markers in rviz?

Thanks in advance