This study explores how VR controller interfaces affect how participants hold a virtual push broom in VR. We aim to understand how the affordances available with current VR controllers and a custom broom VR controller impact user hand placement in a visual VR broom task. We compare hand placement in two VR conditions against hand placement holding a real push broom. Our goal is to understand the roles that controllers have on recreating physically accurate actions in VR training scenarios. The results from this initial pilot show an effect of the broom controller condition but also that the order in which some of the conditions were presented to subjects affected the way subjects held the VR and real push brooms in subsequent actions. Future work will continue to explore how controller affordance may impact the role of training in VR.

As commodity virtual reality and augmented reality hardware becomes more accessible, the opportunity to use these systems for learning and training will increase. This study provides an exploratory look at performance differences for a simple memory matching task across four different technologies that could easily be used for learning and training. We compare time and number of attempts to successfully complete a memory matching game across virtual reality, augmented reality, a large touchscreen table-top display and a real environment. The results indicate that participants took more time to complete the task in both the augmented reality and real conditions. Augmented reality and real environments were statistically different than the fastest two conditions, which occurred in the virtual reality and table-top touch display conditions.

This article presents an analysis of using multiple Microsoft Kinects to track users in a VR system. More specifically, we analyse the capability of Kinects to track infrared points for use in VR applications. Multiple Kinect sensors may serve as a low cost and affordable means to track position information across a large lab space in applications where precise location tracking is not necessary. We present our findings and analysis of the tracking range of a Kinect sensor in situations in which multiple Kinects are present. Overall, the Kinect sensor works well for this application and in lieu of more expensive options, the Kinect sensors may be a viable option for very low-cost tracking in VR applications.

In visual perception, change blindness describes the phenomenon that persons viewing a visual scene may apparently fail to detect significant changes in that scene. These phenomena have been observed in both computer-generated imagery and real-world scenes. Several studies have demonstrated that change blindness effects occur primarily during visual disruptions such as blinks or saccadic eye movements. However, until now the influence of stereoscopic vision on change blindness has not been studied thoroughly in the context of visual perception research. In this paper, we introduce change blindness techniques for stereoscopic virtual reality (VR) systems, providing the ability to substantially modify a virtual scene in a manner that is difficult for observers to perceive. We evaluate techniques for semiimmersive VR systems, i.e., a passive and active stereoscopic projection system as well as an immersive VR system, i.e., a head-mounted display, and compare the results to those of monoscopic viewing conditions. For stereoscopic viewing conditions, we found that change blindness phenomena occur with the same magnitude as in monoscopic viewing conditions. Furthermore, we have evaluated the potential of the presented techniques for allowing abrupt, and yet significant, changes of a stereoscopically displayed virtual reality environment.

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.

In visual perception, change blindness describes the phenomenon that persons viewing a visual scene may apparently fail to detect significant changes in that scene. These phenomena have been observed in both computer generated imagery and real-world scenes. Several studies have demonstrated that change blindness effects occur primarily during visual disruptions such as blinks or saccadic eye movements. However, until now the influence of stereoscopic vision on change blindness has not been studied thoroughly in the context of visual perception research. In this paper we introduce change blindness techniques for stereoscopic projection systems, providing the ability to substantially modify a virtual scene in a manner that is difficult for observers to perceive. We evaluate techniques for passive and active stereoscopic viewing and compare the results to those of monoscopic viewing conditions. For stereoscopic viewing conditions, we found that change blindness phenomena occur with the same magnitude as in monoscopic viewing conditions. Furthermore, we have evaluated the potential of the presented techniques for allowing abrupt, and yet significant, changes of a stereoscopically displayed virtual reality environment.

The display units integrated in todays head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display's field of view. A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. Discrepancies between the geometric and physical FOV causes the imagery to be minified or magnified. This distortion has the potential to negatively or positively affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks.

Abstract This work introduces a technique for interactive walk‐throughs of non‐photorealistically rendered (NPR) scenes using three‐dimensional (3D) line primitives to define architectural features of the model, as well as indicate textural qualities. Line primitives are not typically used in this manner in favour of texture mapping techniques which can encapsulate a great deal of information in a single texture map, and take advantage of GPU optimizations for accelerated rendering. However, texture mapped images may not maintain the visual quality or aesthetic appeal that is possible when using 3D lines to simulate NPR scenes such as hand‐drawn illustrations or architectural renderings. In addition, line textures can be modified interactively, for instance changing the sketchy quality of the lines. The technique introduced here extracts feature edges from a model, and using these edges, generates a reduced set of line textures which indicate material properties while maintaining interactive frame rates. A clipping algorithm is presented to enable 3D lines to reside only in the interior of the 3D model without exposing the underlying triangulated mesh. The resulting system produces interactive illustrations with high visual quality that are free from animation artifacts.

Research has shown that people are able to judge distances accurately in full-cue, real-world environments using visually directed actions. However, in virtual environments viewed with head-mounted display (HMD) systems, there is evidence that people act as though the virtual space is smaller than intended. This is a surprising result given how well people act in real environments. The behavior in the virtual setting may be linked to distortions in the available visual cues or to a person's ability to locomote without vision. Either could result from issues related to added mass, moments of inertia, and restricted field of view in HMDs. This article describes an experiment in which distance judgments based on normal real-world and HMD viewing are compared with judgments based on real-world viewing while wearing two specialized devices. One is a mock HMD, which replicated the mass, moments of inertia, and field of view of the HMD and the other an inertial headband designed to replicate the mass and moments of inertia of the HMD, but constructed to not restrict the field of view of the observer or otherwise feel like wearing a helmet. Distance judgments using the mock HMD showed a statistically significant underestimation relative to the no restriction condition but not of a magnitude sufficient to account for all the distance compression seen in the HMD. Indicated distances with the inertial headband were not significantly smaller than those made with no restrictions.

This paper describes the use of a treadmill-based virtual environment (VE) to investigate the influence of visual motion on locomotion. First, we establish that a computer-controlled treadmill coupled with a wide field of view computer graphics display can be used to study interactions between perception and action. Previous work has demonstrated that humans recalibrate their visually directed actions to changing circumstances in their environment. Using a treadmill VE, we show that recalibration of action is reflected in the real world as a result of manipulating the relation between the visual indication of speed, presented using computer graphics, and the biomechanical speed of walking on a treadmill. We then extend this methodology to investigate whether the recalibration is based on perception of the speed of movement through the world or on the magnitude of optic flow itself. This was done by utilizing two different visual displays, which had essentially the same magnitude of optic flow, but which differed in the information present for the speed of forward motion. These results indicate that changes in optic flow are not necessary for recalibration to occur. The recalibration effect is dependent, at least in part, on visual perception of the speed of self-movement.

This paper presents the Environment Description Framework (EDF) for modeling complex networks of intersecting roads and pathways in virtual environments. EDF represents information about the layout of streets and sidewalks, the rules that govern behavior on roads and walkways, and the locations of agents with respect to navigable structures. The framework serves as the substrate on which behavior programs for autonomous vehicles and pedestrians are built. Pathways are modeled as ribbons in space. The ribbon structure provides a natural coordinate frame for defining the local geometry of navigable surfaces. EDF includes a powerful runtime interface supported by robust and efficient code for locating objects on the ribbon network, for mapping between Cartesian and ribbon coordinates, and for determining behavioral constraints imposed by the environment.

This paper presents steering behaviors that control autonomous vehicles populating roadways in virtual urban environments. Behavior programming is facilitated by a set of representations of the environment that use convenient frames of reference in natural coordinate systems. Roadway surfaces are modeled as three-dimensional ribbons that make the local orientation of the road explicit and allow relative distances on the road to be simply computed. Roads and intersections are connected to form a ribbon network. An egocentric representation called a path melds road and intersection segments into a single, continuous ribbon that captures the vehicle’s shortterm plan of navigation. A topological structure called a route supports wayfinding. We describe how the interrelated ribbon, path, and route representations are used to build multi-component behaviors that plan routes and safely navigate through traffic filled road networks – tracking lanes, shifting lanes to avoid congestion, anticipating lane changes needed to make turns dictated by the route, negotiating intersections, and respecting the rules of the road.

For humans to effectively interact with their environment, it is important for the visual system to determine the absolute size and distance of objects. Previous experiments performed in full-cue, real-world environments have demonstrated that blind walking to targets serves as an accurate indication of distance perception, up to about 25 m. In contrast, the same task performed in virtual environments (VEs) using head-mounted displays shows significant underestimation in walking. To date, blind walking is the only visually directed action task that has been used to evaluate distance perception in VEs beyond reaching distances. The possible influence of the response measure itself on absolute distance perception in virtual environments is currently an open question. Blind walking involves locomotion and the egocentric updating of the environment with one's own movement. We compared this measure to blind throwing, a task that involves the initiation of a movement directed by vision, but no further interaction within the environment. Both throwing and walking were compressed in the VE but accurate in the real world. We suggest that distance compression found in VEs may be a result of a general perceptual origin rather than specific to the response measure.

This paper describes a haptic rendering algorithm for arbitrary polygonal models using a six degree-of-freedom haptic interface. The algorithm supports activities such as virtual prototyping of complex polygonal models and adding haptic interaction to virtual environments. The underlying collision system computes local extrema in distance between the model controlled by the haptic device and the rest of the scene. The haptic rendering computes forces and torques on the moving model based on these local extrema. The system is demonstrated on models with tens of thousands of triangles and developed in an accessibility application for finding collision-free paths.

The paper presents a real-time database for modeling complex networks of intersecting roads and walkways in urban virtual environments. The database represents information about the layout of streets and sidewalks, the rules that govern behavior on roads and walkways, and the locations of agents with respect to road and sidewalk structures. This information is used by programs that control the behavior of autonomous vehicles and pedestrians populating the virtual urban environment. Roads and sidewalks are modeled as ribbons in space. The ribbon structure provides a natural coordinate frame for defining the local geometry of navigable surfaces. This geometry is important for way finding and also forms the geometric basis on which spatial relationships among agents are defined. The database includes a powerful run-time interface supported by robust and efficient code for locating objects on the ribbon network, for mapping between Cartesian and ribbon coordinates, and for determining behavioral constraints imposed by the environment.

In virtual environments, perceived egocentric distances are consistently underestimated when compared to the same distance judgments in the real world. The research presented in this paper explores two possible causes for the compressed distance perception in virtual environments: (1) real-time computer graphics rendering, and (2) immersive display technology. Our results show there is a significant difference in distance judgments between real and virtual environments. However, the differences between distance judgments in virtual photographic panorama environments and traditionally rendered virtual environments are small, suggesting that the display device is affecting distance judgments in virtual environments.