That is, upon detecting {HEAD ~ a change} in {TAIL ~ viewpoint} , the image of the person changes 
That is , upon detecting { HEAD ~ a change } in { TAIL ~ viewpoint } , the image of the person changes
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH