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