Immersive Virtual Environments Allowing Optimal Free Walking Experience in a Limited Physical Space

Immersive virtual environments (VEs) aim at producing a sense of physical presence in a computergenerated world. This sense of presence or “being” in a place different from the one a user is physically situated is mediated with the help of immersive virtual reality (VR). VR uses technologies that address different perceptual cues to replace real-world sensory information with simulated input. Hence, VR gives a user the possibility to not just look at a computer-generated world but to actually be in this world and experience it as if it would be real. This makes VR a useful tool for various application areas such as industrial or architectural design, training, medical or psychiatric treatment, and entertainment. As most VR applications involve navigation tasks, numerous navigation methods for VEs were proposed in the past. Many of these methods use different gestures – e.g. joystick based interactions or foot gestures like stepping in-place – to achieve some movement in the VE. Such navigation metaphors may be well suited for very specific tasks, but they often lack naturalness and necessitate preliminary training. In the real world, the most intuitive way of navigation is walking. Thus, enabling real walking to navigate in VEs provides several benefits: It is more natural, more presence-enhancing, applicable to a broad range of applications, does not require prior training, and improves the spatial understanding of the environment. VR systems provide real walking in VEs by tracking a user’s viewpoint and mapping movements in the real world to movements in the VE in real time. In this setup, a user typically wears a head-mounted display to see the VE. This approach has the disadvantage that both the range of the tracking system and the size of the available real room restrict the user’s movements. To allow for unlimited walking in VEs, different mechanical locomotion devices – e.g. omni-directional treadmills – were proposed that keep a user in a small physical space in the real room. But theses devices are costly or often fail to preserve a fully natural sensation of walking. Hence, redirected walking (RDW) was proposed in the past as a cost-efficient alternative. RDW allows free walking in VEs without locomotion devices even when the VE is larger than the physical room. It employs different so-called redirection techniques to manipulate the user’s walking path such that the path in the VE and the path in the real room differ. Several redirection techniques were suggested and evaluated in the past. Depending on the technique, the redirection can be imperceptible, perceptible, or disturbing and cause breaks in presence. Generally, redirection techniques which allow for stronger redirection are more likely to be noticed by the user or cause breaks in presence. This introduces a trade-off between effectively redirecting a user in the real room and not disturbing the user with the redirection. In addition, methods were proposed in the past that apply a redirection technique such that the user remains within the boundaries of the real room. However, these methods are tailored to only one or a very limited set of redirection techniques and can