how to make the viz.connect avater invisible?

[shashkes]

Hi, for an experiment I'm running I want the avatar that is created using viz.connect and optotrak sensors and representing the subjects movements to become invisible for some of the trials and visible again for others.
I don't want to remove the avatar because I still want to register the location of the sensors I just want the avatar not to appear on the screen so on some trials the subject gets visual feedback of their movements while on others not.
what is the best way to do that?
Thanks!