VistaGlide was a robotic, motion-control camera dolly system that allowed an actor to play two or more parts in a single scene, with a computer controlling the pan, tilt, focus, zoom and the split line during each pass. It was developed for use in Back to the Future Part II and Back to the Future Part III where several instances of multiple characters or other selves are shown side by side – thus enabling the actors to seemingly interact with themselves, walk around themselves, and even pass objects between themselves.