MetaSpace II (MS2) is a social Virtual Reality (VR) system where multiple users can not only see and hear but also interact with each other, grasp and manipulate objects, walk around in space, and get tactile feedback. MS2 allows walking in physical space by tracking each user’s skeleton in realtime and allows users to feel by employing passive haptics i.e., when users touch or manipulate an object in the virtual world, they simultaneously also touch or manipulate a corresponding object in the physical world. To enable these elements in VR, MS2 creates a correspondence in spatial layout and object placement by building the virtual world on top of a 3D scan of the real world. Through the association between the real and virtual world, users are able to walk freely while wearing a head-mounted device, avoid obstacles like walls and furniture, and interact with people and objects. Most current virtual reality (VR) environments are designed for a single user experience where interactions with virtual objects are mediated by hand-held input devices or hand gestures. Additionally, users are only shown a representation of their hands in VR floating in front of the camera as seen from a first person perspective. We believe, representing each user as a fullbody avatar that is controlled by natural movements of the person in the real world (see Figure 1d), can greatly enhance believability and a user’s sense immersion in VR.
We build upon the idea of natural locomotion in space allowing users to explore the virtual world by walking in the physical world. Not only do we track the user's position, we also track their full body as represented by 25 joints. This allows us to transfer the user's bodily motions to the onscreen avatar where a step taken forward in the real world is visible as an animation of a step taken forward by their avatar in the virtual world. A common limitation of a room-scale walking system is the difference in size of the physical and virtual worlds. A few mechanisms to overcome that difference have been explored. For example, a system that can imperceptibly rotate the virtual scene about the user @cite_41 @cite_42 , and a system that can apply redirection to steer users away from physical boundaries as they explore virtual environments @cite_18 . We are currently working on our own solution to allow exploration of large virtual spaces while walking in cluttered physical environments though that is not the focus of this paper.
@cite_41 @cite_18 @cite_42
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Over the past few years, virtual reality has experienced a resurgence. Fueled by a proliferation of consumer-level head-mounted display and motion tracking devices, an unprecedented quantity of immersive experiences and content are available for both desktop and mobile platforms. However, natural locomotion in immersive virtual environments remains a significant challenge. Many of the VR applications available to date require seated use or limit body movement within a small area, instead relying a gamepad or mouse keyboard for movement within the virtual world. Lacking support for natural walking, these virtual reality experiences do not fully replicate the physical and perceptual cues from the real world, and often fall short in maintaining the illusion that the user has been transported to another place. We present a virtual reality demonstration that supports infinite walking within a confined physical space. This is achieved using redirected walking, a class of techniques that introduce subtle discrepancies between physical and virtual motions [ 2001]. When employed properly, redirected walking can be stunningly effective. Previous research has made users believe that they walked in a straight line when they actually traveled in a wide circle, or that they walked between waypoints in a long virtual hallway when in fact they went back and forth between the same two points in the real world. While perceptually compelling, redirected walking is challenging to employ effectively in an unconstrained scenario because users' movements may often be unpredictable. Therefore, our recent research has focused on dynamic planning and optimization of redirected walking techniques, enabling the system to intelligently apply redirection as users explore virtual environments of arbitrary size and shape [ 2014b] [ 2014a]. In this Emerging Technologies exhibit, attendees will explore a large-scale, outdoor immersive virtual environment in a head-mounted display (see Figure 1). The demonstration will support natural walking within a physical area of at least 6x6m, using a wide-area motion tracking system provided by PhaseSpace Inc. The virtual reality scenario will instruct users to scout the environment while stopping to take panoramic photos at various locations in the virtual world. As users explore the environment, our automated planning algorithm will dynamically apply redirection to optimally steer them away from the physical boundaries of the exhibit, thus enabling the experience of limitless walking in a potentially infinite virtual world (see Figure 2). When an immersive virtual environment represents a space that is larger than the available space within which a user can travel by directly walking, it becomes necessary to consider alternative methods for traveling through that space. The traditional solution is to require the user to travel 'indirectly', using a device that changes his viewpoint in the environment without actually requiring him to move - for example, a joystick. However, other solutions involving variations on direct walking are also possible. In this paper, we present a new metaphor for natural, augmented direct locomotion through moderately large-scale immersive virtual environments (IVEs) presented via head mounted display systems, which we call seven league boots. The key characteristic of this method is that it involves determining a user's intended direction of travel and then augmenting only the component of his or her motion that is aligned with that direction. After reviewing previously proposed methods for enabling intuitive locomotion through large IVEs, we begin by describing the technical implementation details of our novel method, discussing the various alternative options that we explored and parameters that we varied in an attempt to attain optimal performance. We then present the results of a pilot observer experiment that we conducted in an attempt to obtain objective, qualitative insight into the relative strengths and weaknesses of our new method, in comparison to the three most commonly used alternative locomotion methods: flying, via use of a wand; normal walking, with a uniform gain applied to the output of the tracker; and normal walking without gain, but with the location and orientation of the larger virtual environment periodically adjusted relative to position of the participant in the real environment. In this study we found, among other things, that for travel down a long, straight virtual hallway, participants overwhelmingly preferred the seven league boots method to the other methods, overall Traveling through immersive virtual environments (IVEs) by means of real walking is an important activity to increase naturalness of VR-based interaction. However, the size of the virtual world often exceeds the size of the tracked space so that a straightforward implementation of omni-directional and unlimited walking is not possible. Redirected walking is one concept to solve this problem of walking in IVEs by inconspicuously guiding the user on a physical path that may differ from the path the user visually perceives. When the user approaches a virtual object she can be redirected to a real proxy object that is registered to the virtual counterpart and provides passive haptic feedback. In such passive haptic environments, any number of virtual objects can be mapped to proxy objects having similar haptic properties, e.g., size, shape and texture. The user can sense a virtual object by touching its real world counterpart. Redirecting a user to a registered proxy object makes it necessary to predict the user's intended position in the IVE. Based on this target position we determine a path through the physical space such that the user is guided to the registered proxy object. We present a taxonomy of possible redirection techniques that enable user guidance such that inconsistencies between visual and proprioceptive stimuli are imperceptible. We describe how a user's target in the virtual world can be predicted reliably and how a corresponding real-world path to the registered proxy object can be derived. Virtual Environments presented through head-mounted displays (HMDs) are often explored on foot. Exploration on foot is useful since the afferent and efferent cues of physical locomotion aid spatial awareness. However, the size of the virtual environment that can be explored on foot is limited to the dimensions of the tracking space of the HMD unless other strategies are used. This paper presents a system for exploring a large virtual environment on foot when the size of the physical surroundings is small by leveraging people's natural ability to spatially update. This paper presents three methods of "resetting" users when they reach the physical limits of the HMD tracking system. Resetting involves manipulating the users' location in physical space to move them out of the path of the physical obstruction while maintaining their spatial awareness of the virtual space.