You can turn off gravity on the viewpoint so that when collision detection is on the viewpoint won't drop back to the eyeheight you're using. Take a look at this page in the docs on viewpoint collision and gravity.
http://www.worldviz.com/vizhelp/View...nd_gravity.htm
You can also set the eyeheight of the viewpoint using
Code:
viz.eyeheight(height)