The user stands in front of the camera with a tag in their hand (printed image that can be tracked) and they are replaced with a virtual object that interacts with them, identifying their position and orientation.

It can also be implemented in a helmet with a camera. The tags are placed on the walls or on signage, for each user to have their own experience, creating different scenarios.

Augmented Reality Demo:
http://ar.siainteractive.com/