The documentation for rviz states that you can display "Markers" topics, 
of either type visualization_msgs/Marker or type 
visualization_msgs/MarkerArray.  However, when I try to display a topic 
containing the latter, I get an error that suggests that rviz only 
supports the former:

[ERROR] [1294492486.023123523]: Client [/rviz_1294492459278907231] wants topic /podMarkers to have datatype/md5sum [visualization_msgs/Marker/228d1b04f55d36e1f26bac3cbb43a616], but our version has [visualization_msgs/MarkerArray/97a0324c833ce13a630cfa35b6bbe3b1]. Dropping connection.

I tried rebuilding everything in case there was a versioning problem, but 
the error persists.  Any idea what I can do to make it work besides 
sending out a whole bunch of separate Marker messages?

Thanks ...

  -ross