Alexander Kulik

Immersive Group-to-Group Telepresence

We present a novel immersive telepresence system that allows distributed groups of users to meet in a shared virtual 3D world. Our approach is based on two coupled projection-based multi-user setups, each providing multiple users with perspectively correct stereoscopic images. At each site the users and their local interaction space are continuously captured using a cluster of registered depth and color cameras. The captured 3D information is transferred to the respective other location, where the remote participants are virtually reconstructed. We explore the use of these virtual user representations in various interaction scenarios in which local and remote users are face-to-face, side-by-side or decoupled. Initial experiments with distributed user groups indicate the mutual understanding of pointing and tracing gestures independent of whether they were performed by local or remote participants. Our users were excited about the new possibilities of jointly exploring a virtual city, where they relied on a world-in-miniature metaphor for mutual awareness of their respective locations.

C1x6: a stereoscopic six-user display for co-located collaboration in shared virtual environments

Stereoscopic multi-user systems provide multiple users with individual views of a virtual environment. We developed a new projection-based stereoscopic display for six users, which employs six customized DLP projectors for fast time-sequential image display in combination with polarization. Our intelligent high-speed shutter glasses can be programmed from the application to adapt to the situation. For instance, it does this by staying open if users do not look at the projection screen or switch to a VIP high brightness mode if less than six users use the system. Each user is tracked and can move freely in front of the display while perceiving perspectively correct views of the virtual environment. Navigating a group of six users through a virtual world leads to situations in which the group will not fit through spatial constrictions. Our augmented group navigation techniques ameliorate this situation by fading out obstacles or by slightly redirecting individual users along a collision-free path. While redirection goes mostly unnoticed, both techniques temporarily give up the notion of a consistent shared space. Our user study confirms that users generally prefer this trade-off over naïve approaches.

Building on Realism and Magic for Designing 3D Interaction Techniques

Imagination-based interaction can complement reality-based interaction in the design of 3D user interfaces. This hybrid approach could lead to interface design guidelines that promote higher-level consistency, and thus usability, for a large range of diverse interfaces.

On 3D input devices

We provide an overview of some of our input device developments, which we designed in response to the need for more advanced 3D interfaces. Some of our devices are more task-specific and others are more general, but all of them support six or more degrees of freedom (DOF) and work in three dimensions. In our work, we try to understand the essential requirements of individual tasks and task combinations to develop corresponding devices and interaction techniques. This is our way of developing input devices for the 3D domain that work better for certain application areas than 2D mouses, gloves, and wands.

The influence of input device characteristics on spatial perception in desktop-based 3D applications

In desktop applications 3D input devices are mostly operated by the non-dominant hand to control 3D viewpoint navigation, while selection and geometry manipulations are handled by the dominant hand using the regular 2D mouse. This asymmetric bi-manual interface is an alternative to commonly used keyboard and mouse input, where the non-dominant hand assists the dominant hand with keystroke input to toggle modes. Our first study compared the keyboard and mouse interface to bi-manual interfaces using the 3D input devices SpaceTraveller and Globefish in a coarse spatial orientation task requiring egocentric and exocentric viewpoint navigation. The different interface configurations performed similarly with respect to task completion times, but the bi-manual techniques resulted in significantly less errors. This result is likely to be due to better workload balancing between the two hands allowing the user to focus on a single task for each hand. Our second study focused on a bi-manual 3D point selection task, which required the selection of small targets and good depth perception. The Globefish interface employing position control for rotations performed significantly better than the SpaceTraveller interface for this task.

Photoportals: shared references in space and time

Photoportals build on digital photography as a unifying metaphor for reference-based interaction in 3D virtual environments. Virtual photos and videos serve as threedimensional references to objects, places, moments in time and activities of users. Our Photoportals also provide access to intermediate or alternative versions of a scenario and allow the review of recorded task sequences that include life-size representations of the captured users. We propose to exploit such references to structure collaborative activities of collocated and remote users. Photoportals offer additional access points for multiple users and encourage mutual support through the preparation and provision of references for manipulation and navigation tasks. They support the pattern of territoriality with configurable space representations that can be used for private interaction, as well as be shared and exchanged with others.

two - 4 - six - A Handheld Device for 3D-Presentations

We introduce a novel one-handed input device for 3D interaction. Its functionality is based on a classification and valuation of used degrees of freedom in common VR applications like Architecture Review, Virtual Museums or Games, where navigation is the predominant interaction mode. The two - 4 - six device allows efficient and comfortable control of six degrees of freedom with the fingertips. The device contains an additional gyroscopic rotation tracking sensor to indicate directions for movement or selection.

A comparison of tracking- and controller-based input for complex bimanual interaction in virtual environments

We describe a user study comparing a two-handed controller-based input device to a two-handed tracking solution, both offering the control space of six degrees of freedom to each hand. For benchmarking the different input modalities we implemented a set of evaluation tasks requiring viewpoint navigation, selection and object manipulation in a maze-like virtual environment. The results of the study reveal similar overall performance for both input modalities for compound tasks. However significant differences with respect to the involved subtasks were found. Furthermore we can show that the integral attributes of a subtask do not necessarily need to be manipulated by a single hand. Instead, the simultaneously required degrees of freedom for operating integrally perceived subtasks may also be distributed to both hands for better control.

Facilitating system control in ray-based interaction tasks

This paper investigates the usability of tracked wands equipped with additional input sensors for system control tasks in 3D interaction scenarios. We integrated a thumb-operated circular touchpad into a hand-held wand and compared the performance of our input device to common ray-based interaction in a menu selection and parameter adjustment task. The results show that both interfaces can be highly efficient, but ray-based interaction is only competitive if large-sized graphical interface representations are provided. In contrast, touchpad input performs well independent of the size of the graphical elements due to proprioceptive and tactile feedback.

Elastic Control for Navigation Tasks on Pen-based Handheld Computers

Isotonic pen and finger interfaces for handheld devices are very suitable for many interaction tasks (eg. pointing, drawing). However, they are not appropriate for rate controlled techniques, as required for other tasks such as navigation in 3D environments. In this paper, we investigate the influence of elastic feedback to enhance user performance in rate controlled interaction tasks. We conducted an experiment, which proves evidence that elastic feedback, given to input movements with the pen, provides better control for 3D travel tasks. Based on these findings, we designed several prototypes that illustrate the ease of applying various elastic control conditions to contemporary handheld computers with finger- or pen-based input capabilities.