Walking on gravel

In a demo of the Redirected Walking technology, the wearer of the head-mounted display sees a virtual representation of a Humvee and a building, and must walk around two walls and down a gravel path. The clever part of the demo is that the wearer walks into a side room and looks for something, and when they do so, they don't realize they are returning to the physical point in the lab where they started. So when they emerge from the "room" they are back on the gravel path.

However, while they think they are outside the room they have just gone into, they have moved to where the real gravel starts. This means that as long as they keep sending the wearer into side rooms to check on things, the researchers can make it possible for the wearer to keep going down the path for hundreds of feet, always on gravel, even though the actual gravel only covers 30 feet in the lab.