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...

This paper presents a set of interaction techniques for hands-free multi-scale navigation through virtual environments. We believe that hands-free navigation, unlike the majority of navigation techniques based on hand motions, has the greatest potential for maximizing the interactivity of virtual environments since navigation modes are offloaded from modal hand gestures to more direct motions of the feet and torso. Not only are the users' hands freed to perform tasks such as modeling, notetaking and object manipulation, but we also believe that foot and torso movements may inherently be more natural for some navigation tasks. The particular interactions that we developed include a leaning technique for moving small and medium distances, a foot-gesture controlled Step WIM that acts as a floor map for moving larger distances, and a viewing technique that enables a user to view a full 360 degrees in only a three-walled semi-immersive environment by subtly amplifying the mapping between th...

This paper describes StyleCam, an approach for authoring 3D viewing experiences that incorporate stylistic elements that are not available in typical 3D viewers. A key aspect of StyleCam is that it allows the author to significantly tailor what the user sees and when they see it. The resulting viewing experience can approach the visual richness and pacing of highly authored visual content such as television commercials or feature films. At the same time, StyleCam allows for a satisfying level of interactivity while avoiding the problems inherent in using unconstrained camera models. The main components of StyleCam are camera surfaces which spatially constrain the viewing camera; animation clips that allow for visually appealing transitions between different camera surfaces; and a simple, unified, interaction technique that permits the user to seamlessly and continuously move between spatial-control of the camera and temporal-control of the animated transitions. Further, the user’s focus of attention is always kept on the content, and not on extraneous interface widgets. In addition to describing the conceptual model of StyleCam, its current implementation, and an example authored experience, we also present the results of an evaluation involving real users.

The navigation support provided by user interfaces of Virtual Environments (VEs) is often inadequate and tends to be overly complex, especially in the case of large-scale VEs. In this paper, we propose a novel navigation aid that aims at allowing users to easily locate objects and places inside large-scale VEs. The aid exploits 3D arrows to point towards the objects and places the user is interested in. We illustrate and discuss the experimental evaluation we carried out to assess the usefulness of the proposed solution, contrasting it with more traditional 2D navigation aids. In particular, we compared subjects ’ performance in 4 conditions which differ for the type of provided navigation aid: three conditions employed respectively the proposed “3D arrows ” aid, an aid based on 2D arrows, and a 2D aid based on a radar metaphor; the fourth condition was a control condition with no navigation aids available. Author Keywords Virtual environments, navigation aids, evaluation.

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Scrolling is used to navigate large information spaces on small screens, but is often too restrictive or cumbersome to use for particular types of content, such as multi-page, multi-column documents. To address this problem, we introduce content-aware scrolling (CAS), an approach that takes into account various characteristics of document content to determine scrolling direction, speed, and zoom. We also present the CAS widget, which supports scrolling through a content-aware path using traditional scrolling methods, demonstrating the advantages of making a traditional technique content-aware. ACM Classification: H.5.2 [Information interfaces and presentation]: User Interfaces—Graphical user interfaces

In this paper we propose a novel navigation metaphor for the exploration of 3D city models in virtual environments. The presented metaphor supports intuitive navigation without disorientation through 3D city models in a manner similar to travelling in the real world. Based on a graph representation of the road network of a 3D city model camera paths are calculated and used to enable smooth camera motion. We will explain how smooth camera motions are computed and describe a user interface usable in both desktop-based as well as projection-based environments to specify travel destinations.

In this article we present a novel approach, the 2-Layer Interface Paradigm (2LIP), for designing simple yet interactive 3D web applications, an attempt to marry advantages of 3D experience with the advantages of the narrative structure of hypertext. The hypertext information, together with graphics, and multimedia, is presented semi-transparently on the foreground layer. It overlays the 3D representation of the information displayed in the background of the interface. Hyperlinks are used for navigation in the 3D scenes (in both layers). We introduce a reference implementation of 2LIP: Copernicus-The Virtual 3D Encyclopedia, which can become a model for building 3D Wikipedia. Based on the evaluation of Copernicus we show that designing web interfaces according to 2LIP provides users with a better experience during browsing the Web, has a positive effect on the visual and associative memory, improves spatial cognition of presented information, and increases overall user’s satisfaction without harming the interaction. which might be hard to understand in the context of the Internet hypertext environment. We strongly believe that user interfaces should be as simple as possible. We have worked out a new way for designing interactive 3D web applications- 2-Layer Interface Paradigm (2LIP) [Jankowski and Kruk 2008]. 2LIP is an attempt to marry advantages of 3D experience with the advantages of the narrative structure of hypertext. It assumes that building graphical user interfaces involves the integration of two layers (see Figure 1): (1) the background layer is a 3D scene; (2) the foreground layer, above the 3D view is the hypertextual content, together with graphics, and multimedia (e.g., videos or other interactive 3D scenes). Hyperlinks are used for navigation in the 3D scenes (in both layers).

This paper introduces VirtualExplorer, a customizable plugin-based virtual reality framework for immersive scientific data visualization, exploration and geometric modeling. The framework is layered on top of a run-time plugin system and reconfigurable virtual user interface and provides a variety of plugin components. The system provides access to scene-graphbased APIs, including Performer and OpenInventor, direct OpenGL support for visualization of time-critical data as well as collision and generic device managers. Plugins can be loaded, disabled, enabled or unloaded at any time, triggered either through pre-defined events or through an external Python-based interface. The virtual user interface uses pre-defined geometric primitives that can be customized to meet application-specific needs. The entire widget set can be reconfigured dynamically on a per-widget basis or as a whole through a style manager. The system is being developed with a variety of application areas in mind, but its main emphasis is on user-guided data exploration and high-precision engineering design.

In this paper, we address the problem of historical data visualization. We describe the data acquisition, preparation, and visualization. Since the data contain four dimensions, the standard 3D exploration techniques have to be extended or appropriately adapted in order to enable interactive exploration. We discuss in detail two interaction concepts: (1) navigation with one fixed dimension, and (2) quasi 4D navigation allowing to simultaneously explore the four-dimensional space. In addition, we also present a picture-inpicture display mode, enabling the user to interactively view the data, while "flying with" a particular event, tracking its motion in time and space. Finally, we present a technique for guided exploration and animation generation, allowing for a vivid gain of insight into the historical data.