Virtual environments (VEs) that use a real-walking locomotion interface have typically been restricted in size to the area of the tracked lab space. Techniques proposed to lift this size constraint, enabling real walking in VEs that are larger than the tracked lab space, all require reorientation techniques (ROTs) in the worst-case situation–when a user is close to walking out of the tracked space. We propose a new ROT using distractors–objects in the VE for the user to focus on while the VE rotates—and compare our method to current ROTs through two user studies. Our findings show ROTs using distractors were preferred and ranked more natural by users. Users were also less aware of the rotating VE when ROTs with distractors were used.

Navigating through large virtual environments using a headmounted display (HMD) is difficult due to the spatial limitations of the tracking system. We conducted two experiments to examine methods of exploring large virtual spaces with an HMD under translation conditions different than normal walking. Experiment 1 compares locomotion in the virtual environment using two different motor actions to translate the subject. The study contrasts user learning and orientation of two different translational gains of bipedal locomotion (not scaled and scaled by ten) with joystick locomotion, where rotation in both locomotion interfaces is accomplished by physically turning. Experiment 2 looks further at the effects of increasing the translational gain of bipedal locomotion in a virtual environment. A subject’s spatial learning and orientation were evaluated in three gain conditions where each physical step was: not scaled, scaled by two, or scaled by ten (1:1, 2:1, 10:1, respectively). A sub-study of this experiment compared the performance of people who played video games against people who did not.

Abstract. First person games are computer games, in which the user experiences the virtual game world from an avatar’s view. This avatar is the user’s alter ego in the game. In this paper, we present a telepresence interface for the first person game Quake III Arena, which gives the user the impression of presence in the game and thus leads to identification with his avatar. This is achieved by tracking the user’s motion and using this motion data as control input for the avatar. As the user is wearing a head-mounted display and he perceives his actions affecting the virtual environment, he fully immerses into the target environment. Without further processing of the user’s motion data, the virtual environment would be limited to the size of the user’s real environment, which is not desirable. The use of Motion Compression, however, allows exploring an arbitrarily large virtual environment while the user is actually moving in an environment of limited size. 1

Redirected walking allows users to walk through large-scale immersive virtual environments (IVEs) while physically remaining in a reasonably small workspace by intentionally injecting scene motion into the IVE. In a constant stimuli experiment with a twoalternative-forced-choice task we have quantified how much humans can unknowingly be redirected on virtual paths which are different from the paths they actually walk. 18 subjects have been tested in four different experiments: (E1a) discrimination between virtual and physical rotation, (E1b) discrimination between two successive rotations, (E2) discrimination between virtual and physical translation, and discrimination of walking direction (E3a) without and (E3b) with start-up. In experiment E1a subjects performed rotations to which different gains have been applied, and then had to choose whether or not the visually perceived rotation was greater than the physical rotation. In experiment E1b subjects discriminated between two successive rotations where different gains have been applied to the physical rotation. In experiment E2 subjects chose if they thought that the physical walk was longer than the visually perceived scaled travel distance. In experiment E3a subjects walked a straight path in the IVE which was physically bent to the left or to the right, and they estimate the direction of the curvature. In experiment E3a the gain was applied immediately, whereas the gain was applied after a start-up of two meters in experiment E3b. Our results show that users can be turned physically about 68% more or 10 % less than the perceived virtual rotation, distances can be up- or down-scaled by 22%, and users can be redirected on an circular arc with a radius greater than 24 meters while they believe they are walking straight.

Walking is the most natural way of moving within a virtual environment (VE). Mapping the user’s movement one-to-one to the real world clearly has the drawback that the limited range of the tracking sensors and a rather small working space in the real word restrict the users ’ interaction. In this paper we introduce concepts for virtual locomotion interfaces that support exploration of large-scale virtual environments by redirected walking. Based on the results of a user study we have quantified to which degree users can unknowingly be redirected in order to guide them through an arbitrarily sized VE in which virtual paths differ from the paths tracked in the real working space. We describe the concepts of generic redirected walking in detail and present implications that have been derived from the initially conducted user study. Furthermore we discuss example applications from different domains in order to point out the benefits of our approach.

In immersive virtual environments (IVEs) users can control their virtual viewpoint by moving their tracked head and by walking through the real world. Usually, movements in the real world are mapped one-to-one to virtual camera motions. With redirection techniques, the virtual camera is manipulated by applying gains to user motion so that the virtual world moves differently than the real world. Thus, users can walk through large-scale IVEs while physically remaining in a reasonably small workspace. In psychophysical experiments with a two-alternative-forced-choice tasks we have quantified how much humans can unknowingly be redirected on physical paths which are different from the visually perceived paths. We tested 12 subjects in three different experiments: (E1) discrimination between virtual and physical rotation, (E2) discrimination between virtual and physical straightforward movements, and (E3) discrimination of path curvature. In experiment E1, subjects performed rotations with different gains, and then had to choose whether the visually perceived rotation was smaller or greater than the physical rotation. In experiment E2, subjects chose whether the physical walk was shorter or longer than the visually perceived scaled travel distance. In experiment E3, subjects estimate the path curvature when walking a curved path in the real world while the visual display shows a straight path in the virtual world. Our results show that users can be turned physically about 49 % more or 20 % less than the perceived virtual rotation, distances can be downscaled by 14 % and up-scaled by 26%, and users can be redirected on a circular arc with a radius greater than 22m while they believe they are walking straight.

Abstract — Intention recognition is an important topic in human-robot cooperation that can be tackled using probabilistic model-based methods. A popular instance of such methods are Bayesian networks where the dependencies between random variables are modeled by means of a directed graph. Bayesian networks are very efficient for treating networks with conditionally independent parts. Unfortunately, such independence sometimes has to be constructed by introducing so called hidden variables with an intractably large state space. An example are human actions which depend on human intentions and on other human actions. Our goal in this paper is to find models for intention-action mapping with a reduced state space in order to allow for tractable on-line evaluation. We present a systematic derivation of the reduced model and experimental results of recognizing the intention of a real human in a virtual environment. I.

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.

This work presents an advanced dual-handed, mobile telerobotic system developed

In this paper we present a framework that provides a novel interface to avatar control in immersive computer games. The user’s motion is tracked and transferred to to the game environment. This motion data is used as control input for the avatar. The game graphics are rendered according to the avatar’s motion and presented to the user on a head-mounted display. As a result, the user immerses into the game environment and identifies with the avatar. However, without further processing of the motion data, the virtual environment would be limited to the size of the user’s real environment, which is not desirable. By using Motion Compression, the framework allows exploring an arbitrarily large virtual environment while the user is actually moving in an environment of limited size. Based on the proposed framework, two game applications were implemented, a modification of a commercially available game and a custom designed game. These two applications prove, that a telepresence system using Motion Compression is a highly intuitive interface to game control. 1