Uwe Kloos

Egocentric distance perception in large screen immersive displays

Abstract Many scientists have demonstrated that compared to the real world egocentric distances in head-mounted display virtual environments are underestimated. However, distance perception in large screen immersive displays has received less attention. We investigate egocentric distance perception in a virtual office room projected using a semi-spherical, a Max Planck Institute CyberMotion Simulator cabin and a flat large screen immersive display. The goal of our research is to systematically investigate distance perception in large screen immersive displays with commonly used technical specifications. We specifically investigate the role of distance to the target, stereoscopic projection and motion parallax on distance perception. We use verbal reports and blind walking as response measures for the real world experiment. Due to the limited space in the three large screen immersive displays we use only verbal reports as the response measure for the experiments in the virtual environment. Our results show an overall underestimation of distance perception in the large screen immersive displays, while verbal estimates of distances are nearly veridical in the real world. We find that even when providing motion parallax and stereoscopic depth cues to the observer in the flat large screen immersive display, participants estimate the distances to be smaller than intended. Although stereo cues in the flat large screen immersive display do increase distance estimates for the nearest distance, the impact of the stereoscopic depth cues is not enough to result in veridical distance perception. Further, we demonstrate that the distance to the target significantly influences the percent error of verbal estimates in both the real and virtual world. The impact of the distance to the target on the distance judgments is the same in the real world and in two of the used large screen displays, namely, the MPI CyberMotion Simulator cabin and the flat displays. However, in the semi-spherical display we observe a significantly different influence of distance to the target on verbal estimates of egocentric distances. Finally, we discuss potential reasons for our results. Based on the findings from our research we give general suggestions that could serve as methods for improving the LSIDs in terms of the accuracy of depth perception and suggest methods to compensate for the underestimation of verbal distance estimates in large screen immersive displays.

Velocity-dependent dynamic curvature gain for redirected walking

The aim of Redirected Walking (RDW) is to redirect a person along their path of travel in a Virtual Environment (VE) in order to increase the virtual space that can be explored in a given tracked area. Among other techniques, the user is redirected on a curved real-world path while visually walking straight in the VE (curvature gain). In this paper, we describe two experiments we conducted to test and extend RDW techniques. In Experiment 1, we measured the effect of walking speed on the detection threshold for curvature of the walking path. In a head-mounted display (HMD) VE, we found a decreased sensitivity for curvature for the slowest walking speed. When participants walked at 0.75 m/s, their detection threshold was approximately 0.1m−1 (radius of approximately 10m). In contrast, for faster walking speeds (>1.0m/s), we found a significantly lower detection threshold of approximately 0.036m−1 (radius of approximately 27m). In Experiment 2, we implemented many well known redirection techniques into one dynamic RDW application. We integrated a large virtual city model and investigated RDW for free exploration. Further, we implemented a dynamic RDW controller which made use of the results from Experiment 1 by dynamically adjusting the applied curvature gain depending on the actual walking velocity of the user. In addition, we investigated the possible role of avatars to slow the users down or make them rotate their heads while exploring. Both the dynamic curvature gain controller and the avatar controller were evaluated in Experiment 2. We measured the average distance that was walked before reaching the boundaries of the tracked area. The mean walked distance was significantly larger in the condition where the dynamic gain controller was applied. This distance increased from approximately 15m for static gains to approximately 22m for dynamic gains. This did not come at the cost of an increase in simulator sickness. Applying the avatar controller did reveal an effect on walking distance or simulator sickness.

The influence of eye height and avatars on egocentric distance estimates in immersive virtual environments

It is well known that eye height is an important visual cue in the perception of apparent sizes and affordances in virtual environments. However, the influence of visual eye height on egocentric distances in virtual environments has received less attention. To explore this influence, we conducted an experiment where we manipulated the virtual eye height of the user in a head-mounted display virtual environment. As a measurement we asked the participants to verbally judge egocentric distances and to give verbal estimates of the dimensions of the virtual room. In addition, we provided the participants a self-animated avatar to investigate if this virtual self-representation has an impact on the accuracy of verbal distance judgments, as recently evidenced for distance judgments accessed with an action-based measure. When controlled for ownership, the avatar had a significant influence on the verbal estimates of egocentric distances as found in previous research. Interestingly, we found that the manipulation of eye height has a significant influence on the verbal estimates of both egocentric distances and the dimensions of the room. We discuss the implications which these research results have on those interested in space perception in both immersive virtual environments and the real world.

Egocentric distance judgments in a large screen display immersive virtual environment

People underestimate egocentric distances in head-mounted display virtual environments, as compared to estimates done in the real world. Our work investigates whether distances are still compressed in a large screen display immersive virtual environment, where participants are able to see their own body surrounded by the virtual environment. We conducted our experiment in both the real world using a real room and the large screen display immersive virtual environment using a 3D model of the real room. Our results showed a significant underestimation of verbal reports of egocentric distances in the large screen display immersive virtual environment, while the distance judgments of the real world were closer to veridical. Moreover, we observed a significant effect of distances in both environments. In the real world closer distances were slightly underestimated, while further distances were slightly overestimated. In contrast to the real world in the virtual environment participants overestimated closer distances (up to 2.5m) and underestimated distances that were further than 3m. A possible reason for this effect of distances in the virtual environment may be that participants perceived stereo cues differently when the target was projected on the floor versus on the front of the large screen.

Velocity-Dependent Dynamic Curvature Gain for Redirected Walking

The aim of Redirected Walking (RDW) is to redirect a person along their path of travel in a Virtual Environment (VE) in order to increase the virtual space that can be explored in a given tracked area. Among other techniques, the user is redirected on a curved real-world path while visually walking straight in the VE (curvature gain). In this paper, we describe two experiments we conducted to test and extend RDW techniques. In Experiment 1, we measured the effect of walking speed on the detection threshold for curvature of the walking path. In a head-mounted display (HMD) VE, we found a decreased sensitivity for curvature for the slowest walking speed. When participants walked at 0.75 m/s, their detection threshold was approximately 0.1m−1 (radius of approximately 10m). In contrast, for faster walking speeds (>1.0m/s), we found a significantly lower detection threshold of approximately 0.036m−1 (radius of approximately 27m). In Experiment 2, we implemented many well known redirection techniques into one dynamic RDW application. We integrated a large virtual city model and investigated RDW for free exploration. Further, we implemented a dynamic RDW controller which made use of the results from Experiment 1 by dynamically adjusting the applied curvature gain depending on the actual walking velocity of the user. In addition, we investigated the possible role of avatars to slow the users down or make them rotate their heads while exploring. Both the dynamic curvature gain controller and the avatar controller were evaluated in Experiment 2. We measured the average distance that was walked before reaching the boundaries of the tracked area. The mean walked distance was significantly larger in the condition where the dynamic gain controller was applied. This distance increased from approximately 15m for static gains to approximately 22m for dynamic gains. This did not come at the cost of an increase in simulator sickness. Applying the avatar controller did reveal an effect on walking distance or simulator sickness.

Perception of strength and power of realistic male characters

We investigated the influence of body shape and pose on the perception of physical strength and social power for male virtual characters. In the first experiment, participants judged the physical strength of varying body shapes, derived from a statistical 3D body model. Based on these ratings, we determined three body shapes (weak, average, and strong) and animated them with a set of power poses for the second experiment. Participants rated how strong or powerful they perceived virtual characters of varying body shapes that were displayed in different poses. Our results show that perception of physical strength was mainly driven by the shape of the body. However, the social attribute of power was influenced by an interaction between pose and shape. Specifically, the effect of pose on power ratings was greater for weak body shapes. These results demonstrate that a character with a weak shape can be perceived as more powerful when in a high-power pose.

Animations of Medical Training Scenarios in Immersive Virtual Environments

Medical training centers often provide various simulations for students and professionals. Their goal is not only to make trainees practice specific scenarios but also to help them effectively transfer the acquired skills to the real world. Having in mind that virtual environments have already been acknowledged for their potential to improve the medical training process, we propose an approach for rapid generation of animated medical scenarios, which can be used as an additional training tool that fits into the time frame of a semester training program.

Short paper: a video self-avatar influences the perception of heights in an augmented reality oculus rift

This paper compares the influence a video self-avatar and a lack of a visual representation of a body have on height estimation when standing at a virtual visual cliff. A height estimation experiment was conducted using a custom augmented reality Oculus Rift hardware and software prototype also described in this paper. The results show a consistency with previous research demonstrating that the presence of a visual body influences height estimates, just as it has been shown to influence distance estimates and affordance estimates.

Short paper: virtual storyteller in immersive virtual environments using fairy tales annotated for emotion states

This paper describes the implementation of an automatically generated virtual storyteller from fairy tale texts which were previously annotated for emotion. In order to gain insight into the effectiveness of our virtual storyteller we recorded face, body and voice of an amateur actor and created an actor animation video of one of the fairy tales. We also got the actors annotation of the fairy tale text and used this to create a virtual storyteller video. With these two videos, the virtual storyteller and the actor animation, we conducted a user study to determine the effectiveness of our virtual storyteller at conveying the intended emotions of the actor. Encouragingly, participants performed best (when compared to the intended emotions of the actor) when they marked the emotions of the virtual storyteller. Interestingly, the actor himself was not able to annotate the animated actor video with high accuracy as compared to his annotated text. This argues that for future work we must have our actors also annotate their body and facial expressions, not just the text, in order to further investigate the effectiveness of our virtual storyteller. This research is a first step towards using our virtual storyteller in real-time immersive virtual environments.

Multi-resolution-display system for virtual reality setups

Most large-area video projection systems offer only limited spacial resolution. Consequently, images of detailed scenery cannot be displayed at full fidelity. A possible but significantly more costly strategy is a tiled projection display. If this solution is not feasible then either aliasing occurs or some anti-aliasing method is used at the cost of reduced scene quality. In this paper we describe a novel cost effective multi-resolution display system. It allows users to select any part of a stereoscopic projection and view it in significantly higher resolution than possible with the standard projection alone. To achieve this, a pair of video projectors, which can be moved by stepper motors, project a high-resolution inset into a small portion of the low-resolution image. To avoid crosstalk between the low and high resolution projections, a mask is rendered into the low resolution scene to black out the area on the screen that is covered by the inlay. To demonstrate the effectiveness of our multi-resolution display setup it has been integrated into a number of real life scenarios: a virtual factory, an airplane cabin simulation, and a focus and context volume visualization application.