The orientations estimated with the Kinect camera can be
mapped to an avatar that can therefore be moved in real-time
replicating the patient's movements, as seen in figure 3a.
However, this mapping is not trivial. We first compute the
3D position of the 20 points identified on the body using the
Microsoft Kinect SDK API, we then link these points in pairs
according to their hierarchy inside the skeleton, creating a
skeleton with 19b ones. Each bone i has a starting point P