Appeared in Computational Geometry -- Theory and Applications 13, 1999, 65-90. Software design solutions are presented for combinatorial data structures, such as polyhedral surfaces and planar maps, tailored for program libraries in computational geometry. Design issues considered are flexibility, time and space efficiency, and ease-of-use. We focus on topological aspects of polyhedral surfaces and evaluate edge-based representations with respect to our design goals. A design for polyhedral surfaces in a halfedge data structure is developed following the generic programming paradigm known from the Standard Template Library STL for C++. Connections are shown to planar maps and face-based structures. Key words: Library design; Generic programming; Combinatorial data structure; Polyhedral surface; Halfedge data structure 1 Introduction Combinatorial structures, such as planar maps, are fundamental in computational geometry. In order to be useful in practice, a solid library for compu...

Reearch into virtual environments on the one hand and artificial intelligence and artificial life on the other has largely been carried out by two different groups of people with different preoccupations and interests, but some convergence is now apparent between the two fields. Applications in which activity independent of the user takes place --- involving crowds or other agents --- are beginning to be tackled, while synthetic agents, virtual humans and computer pets are all areas in which techniqes from the two fields require strong integration. The two communities have much to learn from each other if wheels are not to be reinvented on both sides. This paper reviews the issues arising from combining artificial intelligence and artificial life techniques with those of virtual environments to produce just such intelligent virtual environments. The discussion is illustrated with examples that include environments providing knowledge to direct or assist the user rather than r...

VRML ---the Virtual Reality Modeling Language--- has established as the standard description language for 3D worlds on the Internet. Although it recently has been extended by features in order to support behaviors and user interactions, enabling authors to realize interactive virtual worlds, there is still a lack of support to share such worlds with other users. In this paper we will present our approach on supporting large-scaled shared virtual worlds based on VRML by an appropriate network infrastructure as well as mechanisms to partition these worlds. We will show how virtual worlds can be populated by world-wide distributed users and applications, and the requirements to share behaviors and interactions between those. CR Categories and Subject Descriptors: C.2.2 [Computer Communication Networks]: Network Protocols; C.2.4 [Com- puter Communication Networks]: Distributed Systems - Distributed applications; H.5.1 [Information Interfaces and Presentation ] Multimedia Information Sy...

This paper discusses photogrammetric measurements of a 5m-diameter inflatable space antenna using four Kodak DC290 (2.1 megapixel) digital cameras. The study had two objectives: 1) Determine the photogrammetric measurement precision obtained using multiple consumergrade digital cameras and 2) Gain experience with new commercial photogrammetry software packages, specifically PhotoModeler Pro from Eos Systems, Inc. The paper covers the eight steps required using this hardware/software combination. The baseline data set contained four images of the structure taken from various viewing directions. Each image came from a separate camera. This approach simulated the situation of using multiple time-synchronized cameras, which will be required in future tests of vibrating or deploying ultralightweight space structures. With four images, the average measurement precision for more than 500 points on the antenna surface was less than 0.020 inches in-plane and approximately 0.050 inches out-of-plane.

Introduction The Einstein Tower World is part of the official web site of Palazzo Grassi in Venice [5], the world-wide known cultural institution promoting exhibitions ranging from Archaeology to Modern Arts. Starting from 1995, the web site of Palazzo Grassi hosts detailed information about its current exhibition, about all the exhibitions held starting from 1986 and the history of the palace itself, a Venetian 18th century building conceived by Giorgio Massari. The last exhibition held in 1997 was about German Expressionism, the artistic movement that developed in Germany early in this century, promoting a synesthetic union of all arts; thus, the main themes of this exhibition suggested to compose a full multimodal representation of what expressionism really meant: fusion of visual art, music and architecture. A selection of the expressionist works of the real exhibition are displayed in the frame of the Einstein Tower, an expressionist work itself conceived by Erich Mende

This paper describes some of the practical considerations in integrating three classes of geographic data into VRML models: topography, satellite and aerial imagery, and GPS data. In 1997, we constructed what may be the world's first VRML model of a relay racecourse integrating these classes of information. We summarize the lessons learned from building the models, and from presenting the models to users (in this case the runners). The evidence is that VRML[1] is a potentially excellent (probably the best) medium in which to convey this information, and we present some ideas on how VRML may fulfill its geographic potential. KEYWORDS CR Catagories and Subject Descriptors: I.6.5 [Computer Graphics]: Simulation - Model Development; I.3.5[Computer Graphics]: Computational Geometry and Object Modeling; Additional Keywords: Virtual Worlds, Virtual Environments, Virtual Geography, Interface Paradigms, VRML. INTRODUCTION "The Relay" is a long relay race through the hills and valleys of t...

In this paper we discuss how VRML can be extended by one-way equational constraints. We give the syntax of our extension, discuss what constraints can be used for in VRML and by means of example show how constraints can be translated into VRML using scripts and routes. 1 Introduction VRML has become the standard for providing 3D content on the internet. VRML has evolved from a description language of a static scene graph to a modeling language for 3D worlds including behavior, animations, and user interaction. A revised specification of VRML 2.0 [VAG96, HW96] is currently undergoing the ISO voting procedure and will certainly become the offical ISO Standard VRML'97. In the rest of this paper we use the term VRML as a synonym for both VRML 2.0 and VRML'97. From a programming language designer's point of view VRML lacks many features which have proven useful for specifying algorithms. As VRML was primarily designed with the intention to specify 3D objects and their behavior, we have to ...

3D visualizations of software can be used to highlight relationships between system compo-nents, and also allow focussing on the internals of software, particularly when applied to object oriented software. Such visualizations allow software engineers to comprehend larger software systems, due to more information being available through the use of a third dimen-sion. An architecture has been designed to carry out such visualizations. Major features of this architecture are a meta language to describe object oriented systems, a description language to generate generic visualizations, and an automated pipeline for generating visual-izations. Using this architecture, several visualizations have been generated and analysed, to

We present a new object-oriented language called VRML++ which extends the Virtual Reality Modeling Language (VRML 2.0), a specification language for interactive three-dimensional scenes on the internet. The new features of VRML++ are classes and inheritance, an improved type system, and dynamic routing. As a net result we get type-safe inclusion polymorphism and dynamic binding. We argue, that these features are essentials of object-oriented programming languages. Furthermore using these new features it is possible to define abstractions of routing structures which we call connection classes. VRML++ increases reuseability, readability, and extensibility of specifications while reducing run-time errors. Finally we discuss our implementation of VRML++. 1 Introduction The Virtual Reality Modeling Language (VRML) is a data format to describe interactive, threedimensional objects and scenes which are interconnected via the world wide web. Like the HyperText Markup Language(HTML), VRML is ...

We describe the introduction of a new interaction paradigm to 3D-applications. The everyday tool handling experience of working with pen and notebooks is extended to create a three dimensional two-handed interface, that supports easy-to-understand manipulation tasks in augmented and virtual environments. Our pair of magnetic tracked pen and pad gives sufficient tactile feedback and is familiar to inexperienced individuals, enabling them concentration on the tasks to be performed. We augment form and functionality to our device by displaying spatially aligned computer generated images to the user with see-trough head-mounted displays. On the basis of examples from object manipulation, navigation and system control we show the generality of applicability.