The ever-increasing power of computers and hardware rendering systems has, to date, primarily motivated the creation of visually rich and perceptually realistic virtual environment (VE) applications. Comparatively very little effort has been expended on the user interaction components of VEs. As a result, VE user interfaces are often poorly designed and are rarely evaluated with users. Although usability engineering is a newly emerging facet of VE development, user-centered design and usability evaluation in VEs as a practice still lags far behind what is needed. This paper presents a structured, iterative approach for the user-centered design and evaluation of VE user interaction. This approach consists of the iterative use of expert heuristic evaluation, followed by formative usability evaluation, followed by summative evaluation. We describe our application of this approach to a real-world VE for battlefield visualization, describe the resulting series of design iterations, and present evidence that this approach provides a cost-effective strategy for assessing and iteratively improving user interaction design in VEs. This paper is among the first to report applying an iterative, structured, user-centered design and evaluation approach to VE user interaction design.

This paper describes the software architecture of Dragon, a real-time situational awareness virtual environment for battlefield visualization. Dragon receives data from a number of different sources and creates a single, coherent, and consistent three-dimensional display. We describe the problem of Battlefield Visualization and the challenges it imposes. We discuss the Dragon architecture, the rational for its design, and its performance in an actual application. The battlefield VR system is also suitable for similar civilian domains such as large-scale disaster relief and hostage rescue.

In this paper we describe a battlefield visualization system, called Dragon, which we have implemented on a virtual reality responsive workbench. The Dragon system has been successfully deployed as part of two large military exercises: the Hunter Warrior advanced warfighting experiment, in March 1997, and the Joint Counter Mine advanced concept tactical demonstration, in August and September 1997. We describe battlefield visualization, the Dragon system, and the workbench, and we describe our experiences as part of these two real-world deployments, with an emphasis on lessons learned and needed future work.

The Virtual Workbench (VW) is a non-immersive virtual environment that allows users to view and interact with stereoscopic objects displayed on a workspace similar to a tabletop workspace used in day-to-day life. A VW is an ideal environment for collaborative work where several colleagues can gather around the table to study 3D virtual objects. The Virtual Reality laboratory at the Naval Research Laboratory has implemented the VW using a concept similar to (Froehlich et al., 1994). This paper investigates how the VW can be used as a non-immersive display device for understanding and interpreting complex objects encountered in the scientific visualization field. Different techniques for interacting with 3D visualization objects on the table and using VW as a display device for visualization are evaluated using several cases.

This paper describes a mechanism for improving rendering rates dynamically during runtime in an interactive three-dimensional graphics application. Well-known techniques such as transforming hierarchical geometry into a flat list and removing redundant graphics primitives are often performed off-line on static databases, or continuously every rendering frame. In addition, these optimizations are usually performed over the whole database. We observe that much of the database remains static for a fixed period of time, while other portions are modified continuously (e.g. the camera position), or are repeatedly modified during some finite interval (e.g. during user interaction). We have implemented a runtime optimization mechanism which is sensitive to repeated, local database changes. This mechanism employs timing strategies which optimize only when the cost of optimization will be amortized over a sufficient number of frames. Using this optimization scheme, we observe a rendering speedup of roughly 2.5 in existing applications. We discuss our initial implementation of this mechanism, the improved timing measurements, the issues and assumptions we made, and future improvements.