Eliminate Sideways Motion when colliding w/Objects

[Feuereissen]

Hi all,

I was wondering how to stop moving sideways when one backs up in a 3D environment and hits a wall. I am working with a VR environment in which users move about using a joystick or the PPT Tracking system. The World has been set up so that a transparent, circular wall has been set around the scene for users not to leave the bounds of the world we want to present. Every time the user backs up and hits the wall a slight sideways motion changes the position of the camera in the 3D world. Is there a elegant and quick way to detect the collision for that particular wall and inhibit this sidway motion?
Great, if anyone knows!

Cheers,

Dan