Andrea Bönsch

Collision avoidance in the presence of a virtual agent in small-scale virtual environments

Computer-controlled, human-like virtual agents (VAs), are often embedded into immersive virtual environments (IVEs) in order to enliven a scene or to assist users. Certain constraints need to be fulfilled, e.g., a collision avoidance strategy allowing users to maintain their personal space. Violating this flexible protective zone causes discomfort in real-world situations and in IVEs. However, no studies on collision avoidance for small-scale IVEs have been conducted yet. Our goal is to close this gap by presenting the results of a controlled user study in a CAVE. 27 participants were immersed in a small-scale office with the task of reaching the office door. Their way was blocked either by a male or female VA, representing their co-worker. The VA showed different behavioral patterns regarding gaze and locomotion. Our results indicate that participants preferred collaborative collision avoidance: they expect the VA to step aside in order to get more space to pass while being willing to adapt their own walking paths.

Comparison and evaluation of viewpoint quality estimation algorithms for immersive virtual environments

The knowledge of which places in a virtual environment are interesting or informative can be used to improve user interfaces and to create virtual tours. Viewpoint Quality Estimation algorithms approximate this information by calculating quality scores for viewpoints. However, even though several such algorithms exist and have also been used, e.g., in virtual tour generation, they have never been comparatively evaluated on virtual scenes. In this work, we introduce three new Viewpoint Quality Estimation algorithms, and compare them against each other and six existing metrics, by applying them to two different virtual scenes. Furthermore, we conducted a user study to obtain a quantitative evaluation of viewpoint quality. The results reveal strengths and limitations of the metrics on actual scenes, and provide recommendations on which algorithms to use for real applications.

MRI visualisation by digitally reconstructed radiographs

Visualising volumetric medical images such as computed tomography and magnetic resonance imaging (MRI) on picture archiving and communication systems (PACS) clients is often achieved by image browsing in sagittal, coronal or axial views or three-dimensional (3D) rendering. This latter technique requires fine thresholding for MRI. On the other hand, computing virtual radiograph images, also referred to as digitally reconstructed radiographs (DRR), provides in a single two-dimensional (2D) image a complete overview of the 3D data. It appears therefore as a powerful alternative for MRI visualisation and preview in PACS. This study describes a method to compute DRR from T1-weighted MRI. After segmentation of the background, a histogram distribution analysis is performed and each foreground MRI voxel is labeled as one of three tissues: cortical bone, also known as principal absorber of the X-rays, muscle and fat. An intensity level is attributed to each voxel according to the Hounsfield scale, linearly related to the X-ray attenuation coefficient. Each DRR pixel is computed as the accumulation of the new intensities of the MRI dataset along the corresponding X-ray. The method has been tested on 16 T1-weighted MRI sets. Anterior-posterior and lateral DRR have been computed with reasonable qualities and avoiding any manual tissue segmentations. This proof-of-concept holds for research application for use in clinical PACS.

Peers at work: Economic real-effort experiments in the presence of virtual co-workers

Traditionally, experimental economics uses controlled and incentivized field and lab experiments to analyze economic behavior. However, investigating peer effects in the classic settings is challenging due to the reflection problem: Who is influencing whom? To overcome this, we enlarge the methodological toolbox of these experiments by means of Virtual Reality. After introducing and validating a real-effort sorting task, we embed a virtual agent as peer of a human subject, who independently performs an identical sorting task. We conducted two experiments investigating (a) the subjects productivity adjustment due to peer effects and (b) the incentive effects on competition. Our results indicate a great potential for Virtual-Reality-based economic experiments.

Turning anonymous members of a multiagent system into individuals

It is increasingly common to embed embodied, human-like, virtual agents into immersive virtual environments for either of the two use cases: (1) populating architectural scenes as anonymous members of a crowd and (2) meeting or supporting users as individual, intelligent and conversational agents. However, the new trend towards intelligent cyber physical systems inherently combines both use cases. Thus, we argue for the necessity of multiagent systems consisting of anonymous and autonomous agents, who temporarily turn into intelligent individuals. Besides purely enlivening the scene, each agent can thus be engaged into a situation-dependent interaction by the user, e.g., into a conversation or a joint task. To this end, we devise components for an agents behavioral design modeling the transition between an anonymous and an individual agent when a user approaches.

Comparison and Evaluation of Viewpoint Quality Estimation Algorithms for Immersive Virtual Environments : Additional Material

The knowledge of which places in a virtual environment are interesting or informative can be used to improve user interfaces and to create virtual tours. Viewpoint Quality Estimation (VQE) algorithms approximate this information by calculating quality scores for viewpoints. In [FWBK15], we introduced three new VQE algorithms, and compared them against each other and six existing techniques, by applying them to two different virtual scenes. Furthermore, we conducted a user study to obtain a quantitative evaluation of viewpoint quality. This document describes the additional material provided for [FWBK15], which includes additional scene information, and raw data from algorithm outputs and the user study.

Score-based recommendation for efficiently selecting individual virtual agents in multi-agent systems

Controlling user-agent-interactions by means of an external operator includes selecting the virtual interaction partners fast and faultlessly. However, especially in immersive scenes with a large number of potential partners, this task is non-trivial. Thus, we present a score-based recommendation system supporting an operator in the selection task. Agents are recommended as potential partners based on two parameters: the users distance to the agents and the users gazing direction. An additional graphical user interface (GUI) provides elements for configuring the system and for applying actions to those agents which the operator has confirmed as interaction partners.

Evaluating Presence Strategies of Temporarily Required Virtual Assistants

Computer-controlled virtual humans can serve as assistants in virtual scenes. Here, they are usually in an almost constant contact with the user. Nonetheless, in some applications assistants are required only temporarily. Consequently, presenting them only when needed, i.e., minimizing their presence time, might be advisable.

Avatars as Peers at Work: An Experimental Study in Virtual Reality

Identification of peer effects is often complicated by the reflection problem: Does agent i influence agent j, or vice versa? To be able to identify a clear causality, we embed a virtual human (avatar) as co-worker of a human subject into an immersive virtual environment. We observe that low productive human subjects increase their work performance more when they observe a low productive avatar – compared to a high productive avatar. This result is in line with the predictions of the social comparison theory, in as much as we observe stronger peer effects when the perceived similarity in abilities between the peers is high.Abstract We introduce a novel methodology to study peer effects. Using virtual reality technology, we create a naturalistic work setting in an immersive virtual environment where we embed a computer-generated virtual human as the co-worker of a human subject, both performing a sorting task at a conveyor belt. In our setup, subjects observe the virtual peer, while the virtual human is not observing them. In two treatments, human subjects observe either a low productive or a highly productive virtual peer. We find that human subjects rate their presence feeling of “being there” in the immersive virtual environment as natural. Subjects also recognize that virtual peers in our two treatments showed different productivities. We do not find a general treatment effect on productivity. However, we find that competitive subjects display higher performance when they are in the presence of a highly productive peer - compared to when they observe a low productive peer. We use tracking data to learn about the subjects’ body movements. Analyzing hand and head data, we show that competitive subjects are more careful in the sorting task than non-competitive subjects. We also discuss some VR related methodological issues.

Poster: Guided tour creation in immersive virtual environments

Guided tours have been found to be a good approach to introducing users to previously unknown virtual environments and to allowing them access to relevant points of interest. Two important tasks during the creation of guided tours are the definition of views onto relevant information and their arrangement into an order in which they are to be visited. To allow a maximum of flexibility an interactive approach to these tasks is desirable. To this end, we present and evaluate two approaches to the mentioned interaction tasks in this paper. The first approach is a hybrid 2D/3D interaction metaphor in which a tracked tablet PC is used as a virtual digital camera that allows to specify and order views onto the scene. The second one is a purely 3D version of the first one, which does not require a tablet PC. Both approaches were compared in an initial user study, whose results indicate a superiority of the 3D over the hybrid approach.