This paper explores a user interface technique which augments an immersive head tracked display with a hand-held miniature copy of the virtual environment. We call this interface technique the Worlds in Miniature (WIM) metaphor. In addition to the first-person perspective offered by a virtual reality system, a World in Miniature offers a second dynamic viewport onto the virtual environment. Objects may be directly manipulated either through the immersive viewport or through the three-dimensional viewport offered by the WIM. In addition to describing object manipulation, this paper explores ways in which Worlds in Miniature can act as a single unifying metaphor for such application independent interaction techniques as object selection, navigation, path planning, and visualization. The WIM metaphor offers multiple points of view and multiple scales at which the user can operate, without requiring explicit modes or commands. Informal user observation indicates that users adapt to the ...

In this paper we introduce through-the-lens camera control, a body of techniques that permit a user to manipulate a virtual camera by controlling and constraining features in the image seen through its lens. Rather than solving for camera parameters directly, constrained optimization is used to compute their time derivatives based on desired changes in user-defined controls. This effectively permits new controls to be defined independent of the underlying parameterization. The controls can also serve as constraints, maintaining their values as others are changed. We describe the techniques in general and work through a detailed example of a specific camera model. Our implementation demonstrates a gallery of useful controls and constraints and provides some examples of how these may be used in composing images and animations.

We present a categorization of techniques for firstperson motion control, or travel, through immersive virtual environments, as well as a framework for evaluating the quality of different techniques for specific virtual environment tasks. We conduct three quantitative experiments within this framework: a comparison of different techniques for moving directly to a target object varying in size and distance, a comparison of different techniques for moving relative to a reference object, and a comparison of different motion techniques and their resulting sense of “disorientation ” in the user. Results indicate that “pointing ” techniques are advantageous relative to “gaze-directed ” steering techniques for a relative motion task, and that motion techniques which instantly teleport users to new locations are correlated with increased user disorientation. 1.

We present a survey of design issues for developing effective free-space three-dimensional (3D) user interfaces. Our survey is based upon previous work in 3D interaction, our experience in developing free-space interfaces, and our informal observations of test users. We illustrate our design issues using examples drawn from instances of 3D interfaces. For example, our first issue suggests that users have difficulty understanding three-dimensional space. We offer a set of strategies which may help users to better perceive a 3D virtual environment, including the use of spatial references, relative gesture, two-handed interaction, multisensory feedback, physical constraints, and head tracking. We describe interfaces which employ these strategies. Our major contribution is the synthesis of many scattered results, observations, and examples into a common framework. This framework should serve as a guide to researchers or systems builders who may not be familiar with design issues in spatial input. Where appropriate, we also try to identify areas in free-space 3D interaction which we see as likely candidates for additional research. An extended and annotated version of the references list for this paper is available on-line through mosaic at address

We present a task-based taxonomy of navigation techniques for 3D virtual environments, used to categorize existing techniques, drive exploration of the design space, and inspire new techniques. We briefly discuss several new techniques, and describe in detail one new technique, Speed-coupled Flying with Orbiting. This technique couples control of movement speed to camera height and tilt, allowing users to seamlessly transition between local environment-views and global overviews. Users can also orbit specific objects for inspection. Results from two competitive user studies suggest users performed better with Speed-coupled Flying with Orbiting over alternatives, with performance also enhanced by a large display.

Virtual colonoscopy is a non-invasive computerized medical procedure for examining the entire colon to detect polyps. We present an interactive virtual colonoscopy method, which uses a physicallybased camera control model and a hardware-assisted visibility algorithm. By employing a potential field and rigid body dynamics, our camera control supplies a convenient and intuitive mechanism for examining the colonic surface while avoiding collisions. Our Zbuffer -assisted visibility algorithm culls invisible regions based on their visibility through a chain of portals, thus providing interactive rendering speed. We demonstrate our method with experimental results on a plastic pipe phantom, the Visible Human, and several patients. CR Categories: I.3.3 [Picture/Image Generation]: Display Algorithms; I.3.5 [Computational Geometry and Object Modeling]: Physically Based Modeling; I.3.6 [Methodologies and Techniques]: Interaction Techniques; I.3.7 [Three-Dimensional Graphics and Realism ]: Hidde...

"Fish tank virtual reality" refers to the use of a standard graphics workstation to achieve real-time display of three-dimensional scenes using stereopsis and dynamic head-coupled perspective. Fish tank VR has a number of advantages over head-mounted immersion VR which make it more practical for many applications. After discussing the characteristics of fish tank VR, we describe a set of three experiments conducted to study the benefits of fish tank VR over a traditional workstation graphics display. These experiments tested user performance under two conditions: (a) whether or not stereoscopic display was used and (b) whether or not the perspective display was coupled dynamically to the positions of a user's eyes. Subjects using a comparison protocol consistently preferred headcoupling without stereo over stereo without head-coupling. Error rates in a tree tracing task similar to one used by Sollenberger and Milgram showed an order of magnitude improvement for headcoupled stereo over ...

In this paper, a method of encapsulating camera tasks into well defined units called “camera modules ” is described. Through this encapsulation, camera modules can be programmed and sequenced, and thus can be used as the underlying framework for controlling the virtual camera in widely disparate types of graphi-cal environments. Two examples of the camera framework are shown: an agent which can film a conversation between two virtual actors and a visual programming language for filming a virtual football game.

Despite intense and wide-spread research in both virtual environments (VEs) and usability, the exciting new technology of VEs has not yet been closely coupled with the important characteristic of usability -- a necessary coupling if VEs are to reach their full potential. Although numerous methods exist for usability evaluation of interactive computer applications, these methods have well-known limitations, especially for evaluating VEs. Thus, there is a great need to develop usability evaluation methods and criteria specifically for VEs. Our goal is to increase awareness of the need for usability engineering of VEs and to lay a scientific foundation for developing high-impact methods for usability engineering of VEs. The first step in our multi-year research plan has been accomplished, yielding a comprehensive multi-dimensional taxonomy of usability characteristics specifically for VEs. This taxonomy was developed by collecting and synthesizing information from literature, conferences, World Wide Web (WWW) searches, investigative research visits to top VE facilities, and interviews of VE researchers and developers. The taxonomy consists of four main areas of usability issues: Users and User Tasks in VEs, general user and task characteristics and types of tasks in VEs

problematic and forces the human VE participant to attend to the interface and its control knobs in addition to or instead of the goals and constraints of the task at hand. If the intention of the human VE participant is, e.g., to observe some object X, then allowing him or her to simply tell the system, Show me object X is a more direct and productive interface. This is an instance of task level interaction. In earlier work we characterized the levels of abstraction at which one can interact with virtual objects and processes, and we described the varying access panels one obtains (5). Here we will describe a system for specifying behaviors for virtual cameras in terms of task level goals and constraints. As in our earlier work on camera control (6, 7), we make task level control available as well as enabling various direct manipulation metaphors. This paper describes a framework for exploring intelligent camera controls in a 3D virtual environment. It presents a methodology for ...