How to access and use skeleton joint coordinates using OpenNI, ASUS Xtion, and ROS?

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The information you are interested in that is contained in the /tf data will be transformations from some frame on the Kinect to some frame on the user (e.g. right_hand). What you need to do is write a node that creates a tf listener that periodically looks up this transform data. Here are the tutorials on tf listeners in Python and C++. Once you have that transformation information, it's up to you to decide what to do with it. For example, you could publish the relevant geometric information on a new topic that a robot control node subscribes to. Or you could directly control the robot in the node with the tf listener.

EDIT

The above links aren't working (seems like a bug in Askbot or Askbot config)... they work in my preview window. Here are the links:

Python: http://wiki.ros.org/tf/Tutorials/Writ...

C++: http://wiki.ros.org/tf/Tutorials/Writ...

EDIT 2

Fixed links using answer from @joq here.