Hi Parisa,
You may use the "node3d.getPosition()" inside the Update(): fuction called every 0 seconds using the timer function:
Code:
def myPostion():
mynode.getPostion("co-ordinate system") #you may use ur viewpoint as mynode to get ur position.
vizact.timer(0,myPosition)
and to draw you may use pls c to the link:
http://docs.worldviz.com/vizard/Changing_on-the-fly.htm
Regards
Mr.Rajnish Vishwakarma