Navigation is the most common interactive task performed in three-dimensional virtual environments (VEs), but it is also a task that users often find difficult. We investigated how body-based information about the translational and rotational components of movement helped participants to perform a navigational search task (finding targets hidden inside boxes in a room-sized space). When participants physically walked around the VE while viewing it on a head-mounted display (HMD), they then performed 90% of trials perfectly, comparable to participants who had performed an equivalent task in the real world during a previous study. By contrast, participants performed less than 50% of trials perfectly if they used a tethered HMD (move by physically turning but pressing a button to translate) or a desktop display (no body-based information). This is the most complex navigational task in which a real-world level of performance has been achieved in a VE. Behavioral data indicates that both translational and rotational body-based information are required to accurately update one's position during navigation, and participants who walked tended to avoid obstacles, even though collision detection was not implemented and feedback not provided. A walking interface would bring immediate benefits to a number of VE applications.

During navigation, humans combine visual information from their surroundings with body-based information from the translational and rotational components of their movement. Theories of navigation focus on the role of visual and rotational body-based information, even though experimental evidence shows they are not sufficient for complex spatial tasks. To investigate the contribution of all three sources of information, we asked participants to search a computer-generated virtual room for targets. Participants were provided with only visual information or with visual information supplemented with body-based information for all movement (walk group) or rotational movement (rotate group). The walk group performed the task with near-perfect efficiency, irrespective of whether a rich or impoverished visual scene was provided. The visual-only and rotate groups were significantly less efficient and frequently searched parts of the room at least twice. These results suggest that full physical movement plays a critical role in navigational search, but only moderate visual detail is required.

Three levels of virtual environment (VE) metric are proposed, based on: (1) users' task performance (time taken, distance traveled, and number of errors made), (2) physical behavior (locomotion, looking around, and time and error classification), and (3) decision making (i.e., cognitive) rationale (think aloud, interview, and questionnaire). Examples of the use of these metrics are drawn from a detailed review of research into VE wayfinding. A case study from research into the fidelity that is required for efficient VE wayfinding is presented, showing the unsuitability in some circumstances of common metrics of task performance such as time and distance, and the benefits to be gained by making fine-grained analyses of users' behavior. Taken as a whole, the paper highlights the range of techniques that have been successfully used to evaluate wayfinding and explains in detail how some of these techniques may be applied.

Two experiments investigated participants' ability to search for targets in a cluttered small-scale space. The first experiment was conducted in the real world with two field of view conditions (full vs. restricted), and participants found the task trivial to perform in both. The second experiment used the same search task but was conducted in a desktop virtual environment (VE), and investigated two movement interfaces and two visual scene conditions. Participants restricted to forward only movement performed the search task quicker and more efficiently (visiting fewer targets) than those who used an interface that allowed more flexible movement (forward, backward, left, right, and diagonal). Also, participants using a high fidelity visual scene performed the task significantly quicker and more efficiently than those who used a low fidelity scene. The performance differences among all the conditions decreased with practice, but the performance of the best VE group approached that of the real-world participants. These results indicate the importance of using high fidelity scenes in VEs, and suggest that the use of a simple control system is sufficient for maintaining one's spatial orientation during searching.

Virtual environments (VEs) offer huge potential for a wide range of applications including the transfer of spatial knowledge from virtual spaces to real world places; beneficial in situations where it would be impractical, too expensive or dangerous, to acquire that knowledge from the real environment. Research has shown that people can acquire near perfect spatial knowledge about real world environments from threedimensional (3D) VEs. However, the rate of learning is substantially slower, and the information less accurate, than that acquired from the real world. It is often assumed that poor navigational ability in VEs is due to the reduced fidelity of the VE system, fidelity is defined as how closely the various components of the VE system resemble those of the real world. This thesis attempts to better understand the effects of, and the relationship between, three aspects of VE fidelity, field of view, visual scene characteristics and the movement interface. Four experimental studies showed that a wide FOV, a high fidelity visual scene, and a simple movement interface, modestly increased participants' ability to navigate effciently in a desktop VE. However, a study that required participants to physically walk around a VE, displayed via a tracked head mounted display (HMD), showed dramatic performance benefits over the use of stationary desktop displays, and a rotationally tracked HMD that required abstract input for translational movement. Proprioceptive and vestibular feedback allowed participants to navigate a VE as efficiently as they did in a real world study. The potential of VEs for spatial applications, such as learning real world spaces, will not be realised without understanding the effects of the VE system on participants' performance and behaviour. The studies reported in this thesis not only provide much needed empirical results that could be of great benefit to VE application designers, but will also be of interest to researchers investigating human navigation.

The difficulties people frequently have navigating in virtual environments (VEs) are well known. Usually these difficulties are quantified in terms of performance (e.g., time taken or number of errors made in following a path), with these data used to compare navigation in VEs to equivalent real-world settings. However, an important cause of any performance differences is changes in people's navigational behaviour. This paper reports a study that investigated the effect of visual scene fidelity and field of view (FOV) on participants' behaviour in a navigational search task, to help identify the thresholds of fidelity that are required for efficient VE navigation. With a wide FOV (144 degrees), participants spent significantly larger proportion of their time travelling through the VE, whereas participants who used a normal FOV (48 degrees) spent significantly longer standing in one place planning where to travel. Also, participants who used a wide FOV and a high fidelity scene came significantly closer to conducting the search "perfectly" (visiting each place once). In an earlier real-world study, participants completed 93% of their searches perfectly and planned where to travel while they moved. Thus, navigating a high fidelity VE with a wide FOV increased the similarity between VE and real-world navigational behaviour, which has important implications for both VE design and understanding human navigation. Detailed analysis of the errors that participants made during their non-perfect searches highlighted a dramatic difference between the two FOVs. With a narrow FOV participants often travelled right past a target without it appearing on the display, whereas with the wide FOV targets that were displayed towards the sides of participants overall FOV were often not searched, indicating a problem with the demands made by such a wide FOV display on human visual attention.