To make virtual environment experiences more engaging, we propose to use multiple interaction devices and to support collaborative travel for co-located groups of users. Results of a preliminary pilot study of a collaborative travel task for pairs of users in a projection-based display system suggest that the use of multiple controllers is much more effective and satisfying than swapping and sharing a single device. The study also highlights functional differences between coordination policies for collaborative travel.

Users of virtual environments regularly have problems using 3D motion interfaces and exhibit a disturbing tendency to become disoriented and get quickly in large virtual worlds. We introduce the active guideline, a novel auxiliary motion technique and navigation aid for virtual environments. Similar to the ubiquitous Back-button interface for web navigation, the active guideline implicitly records a history of the user's motion and allows immediate and convenient travel back (and forth) along a trace of the previously traveled path. This lets users revisit previous viewpoints, allowing them to recover from being lost in space by enabling easy, continuous backtracking all the way up to the home position. In contrast to bookmarking of viewpoints, the active guideline is always-on and requires no active user intervention or strategic planning to successfully function as a navigation aid. This paper discusses the behavior and implementation of the active guideline and presents results of an initial study exploring the usability of the technique.

Ideally, virtual worlds should be dynamic, mutable, and complex in order to be attractive for immersed users. As such worlds can be designed easily by rewriting techniques, we propose a distributed Virtual Reality (VR) system that is based on an interactive animation system using a rewriting technique for geometric and behavioral modeling. The emphasis is on concepts and extensions for the integration of user immersion, user interaction, and networking into a rewriting-based animation system, Finally, the modeling of a ball game with two immersed users, as well as a virtual park, serve as case studies to illustrate the proposed concepts and extensions.