How to Time Travel in Highly Immersive Virtual Reality

What would it be like to be able to time travel to the past, meet your previous self, and override your previous actions in order to achieve a better outcome? While we cannot (yet?) achieve physical time travel, digital technologies now allow us to experience virtual time travel. We have developed a method for implementing time travel in highly immersive virtual reality (VR) and here we describe the underlying technology in the context of a scenario that involves a shooting event in a virtual gallery. Our method includes two layers of abstraction: i) a narrative layer that represents scenarios as a set of events and state transitions, and uses preconditions to enforce consistency, and ii) a VR layer that includes low level controllers for low level synchronization and animation. The narrative layer is designed to ensure that following time travel the events would unfold exactly as they did in the previous time around, except for the specific changes resulting from the actions of the time traveling participant. The VR layer controls the fine details, including recording and replaying motion capture data and audio, which allows the participants to experience their own previous selves as animated avatars. The system was used for a psychological experiment, and in this paper we focus on the technical method and on the lessons learned from implementing VR time travel.