putting objects on the screen

[jargon]

dear Farshizzo,
I was wondering if there's a way to place an object at the display screen- I specifically have a ball that I want create the illusion of distance with by scaling it manually- thus overriding Vizard's ball scaling. I tried to use

object= viz.add('object.wrl', viz.SCREEN)

but to no avail (I couldn't see the object- it dissappeared).
Maybe you have some ideas?

My other question is assuming that there is a way to place the object at the screen-- is there a way to have other objects that are behind it in the Vizard world occlude it as to make it seem like those objects are in front of my original object. THis would allow me to put this object on the screen, scale it my own way and yet have it seem like it's z position is greater than other object's (ie: it's further away from the user).

If these questions make no sense to you I'll attempt to clarify. Thanks,
Jargon