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Item WebTalk: a 3D collaborative environment to access the Web(Eurographics Association, 1999) Paolini, P.; Barbieri, T.; Loiudice, P.; Alonzo, F.; Arru, M.; Zanti, M.; Gaia, G.The notion of cooperative visit and interaction within a web site, both at 2D and 3D level, could add decisive motivation to pursue exploitation of the third dimension in networked environments. A prototype developed at the HOC laboratory in Politecnico of Milan, WEBTALK, allows development of custom 3D environments in which actions and situations can be shared throughout a network. The current prototype makes use of standard web-based Internet/Intranet technology: it is composed of a VRML (Virtual Reality Modeling Language) graphical engine and a Java-based TCP/IP (the Internet Protocol) communication layer. The technique has proven itself successful and has given rise to several interesting applications, such as the creation of Virtual 3D Museum Spaces at the National Science Museum (www.museoscienza.org), in which visitors can visit the museum interacting with the exhibits themselves and sharing their experiences with other visitors - even joining a guided tour with the virtual museum guide. A new prototype will make use of a completely Java-based environment, using Sun’s Java 2 and Java 3D. The new WEBTALK will stress even further the issues of third party external authoring of virtual worlds and of cooperation patterns within the shared environments, with a distinction between shared object geometries, shared object behaviors, shared object data (stored in an on-line DBMS), and cooperation metaphors within the virtual world. Linking to 2D-based web sites resources will lead cooperation patterns to be extended also to regular web-space.Item Visual Learning with Computer Art Graphics Artwork Description(Eurographics Association, 1999) Ursyn, AnnaIn my work, I use the computer on different levels. For my two-dimensional works, I have been programing in Fortran IV then Fortran 77 using Cyber, then VAX mainframes and Interactive Graphic Library (IGL). I have been setting color combinations, transforming light intensity, applying grid patterns and moir effects in order to gain composition. The two-dimensional programs serve as a point of departure for photolithographs after computer programs and photo silkscreened prints on canvas and paper; they are included both into my two-dimensional and three-dimensional works. Scanners, digital camera and PC/PPCs serve for further image manipulation. All of these approaches are combined for image creation with the use of painterly markings. Printouts have been obtained in several ways: first, black-and white plots from the Versatec plotter and color slides via the Computer Output Microfilmer (COM) recorder, then the Apple, Hewlett-Packard, and Novajet printers/plotters.Item Graph Visualisation and Navigation in Information Visualisation(Eurographics Association, 1999) Herman, I.; Melancon, G.; Marshall, M.S.This is a survey on graph visualisation and navigation techniques, as used in information visualisation. Graphs appear in numerous applications, like web browsing, state–transition diagrams, computer data structures, etc. The ability to visualise and to navigate in these potentially very large, abstract graphs is often a crucial part of an application. Information visualisation has specific requirements, which means that this survey approaches the results of traditional graph drawing from a different perspective than the traditional surveys; as such it is a useful complementary survey to thoseItem Creating light-weight virtual humans for Virtual Environments(Eurographics Association, 1999) Oliveira, Joao; Buxton, BernardWith the advent of whole body, 3D electro-optical scanners, a new range of applications are emerging that exploit the availability of personalised, realistic human models. However, realistic rendering of such models usually entails a large number of polygons which can be unacceptable in many applications. We present a framework that exploits the approximate cylindrical and spherical symmetry of human body parts to create light-weight representations that retain the overall dimension of body parts, even at very low polygon counts.Item Graphics, Vision, and Visualization in Medical Imaging: A State of the Art Report(Eurographics Association, 1999) Ezquerra, Norberto; Navazo, Isabel; Morris, Tahia Infantes; Monclus, EvaThe field of medical imaging has significantly changed over the years, becoming both an integral part of health care and an increasingly important area of research spanning many disciplines. As the title of this paper suggests, one interesting result of this evolutionary process has been the fusion of traditionally disjointed yet highly interrelated areas: from computer vision and image processing, through graphics and visualization, to the integration of creative immersion and robotics-based mechanisms for interactively manipulating the information. As a result of these innovations, medical imaging has continued to re-invent itself, fundamentally changing the ways in which we see, communicate about, learn from, and interact with, medical information. With this in mind, the purpose of this state-of-the-art (STAR) report is two-fold. On one hand, the aim is to provide a brief summary of some of the salient methods, results, and potentially powerful trends that currently describe the field. On the other hand, the goal is to outline some of the remaining challenges as well as the possible opportunities. Clearly, the field is far too broad and complex for a single article to adequately reflect the technical depth and extraordinary diversity of even a small portion of these topics. Thus, without any claim at completeness, the emphasis will be placed on highlighting selected frontier research activities and applications, focussing on aspects related to vision, graphics and visualization from an interpretive (rather than tutorial) perspective. In addition to these discussions, a list of URLs of some of the groups actively engaged in medical imaging research is also included. The overall objective is therefore to provide a "snap shot" of the field through a brief summary that will hopefully serve as a useful source of information for those wanting to learn more about the field, and, for those actively engaged in the field, a timely -and possibly inspirational- reference.Item Modelling and Haptic Interaction with non-rigid materials(Eurographics Association, 1999) Cugini, U.; Bordegoni, M.; Rizzi, C.; De Angelis, F.; Prati, M.This report presents an overview of main modelling and simulation techniques for non–rigid objects discussing advantages and disadvantages. Related techniques to face several problems rising when dealing with deformable objects simulation are also discussed. They concern numerical solvers, constraints management and collision detection. In the simulation of non-rigid objects another relevant issue is the provision of operational modality at higher and higher level and more and more useroriented. The paradigm of haptic interaction recently developed seems promising to achieve this goal. Haptic interaction allows the users to feel several physical properties of the modelled objects through the manipulation of their virtual representation. Thus, second part of the report focuses on the state-of-theart of haptic devices, technologies and applications concerning interaction with non-rigid models. A classification from different point of views is proposed. The specific work our group is performing in the area of non-rigid objects modelling and simulation and haptic interaction with non-rigid models is also illustrated.Item A Rapid Clustering Algorithm for Efficient Rendering(Eurographics Association, 1999) Müller, Gordon; Schäfer, Stephan; Fellner, Dieter W.Hierarchical radiosity using object clusters greatly improves rendering times and reduces memory consumption of radiosity computations. The key feature of the algorithm is using a hierarchy of object clusters to approximate the energy exchange between surfaces. The cluster hierarchy used for this purpose however, must accurately reflect the actual scene geometry to justify this approach. Bad clusters easily lead to rendering artifacts. Inspired by the results of our hierarchical bounding volume optimization for ray tracing, we applied the same scheme to a clustering algorithm for hierarchical radiosity. Using an object-oriented framework, the extension of the implementation was straight forward and seems to be promising. Due to the good performance of our hierarchy regarding ray tracing, the same data structure could successfully be used for two things: visibility checks based on ray casting and energy exchange for the radiosity computation. In this short paper, first results regarding our new clustering scheme will be presented. The properties of the underlying bounding volume optimization give reason for interesting applications enhancing various rendering techniques. Some of these new ideas will be discussed here.Item Tutorial 9 - Visibility(Eurographics Association, 1999) Chrysanthou, Yiorgos L.; Cohen-Or, Daniel; Fibich, Gadi; Halperin, Dan; Zadicario, Eyal; Lev-Yehudi, Shuly; Bartz, Dirk; Meißner, Michael; Hüttner, Tobias; Hüttner, Tobias; Bittner, Jiri; Havran, Vlastimil; Slavik, Pavel; Klosowski, James T.; Silva, Claudio T.The focus of this tutorial is a study of the techniques for solving visibility problems in virtual walkthroughs. The term walkthrough is referring not only to models of architectural models but rather to any large complex model, where the focus is on viewing and rendering the model. The tutorial touches on several applications such as fast visible surface determination, selection of relevant model sections to be transmitted on a client-server system, as well as improving image quality by shading algorithms.Item Monitoring of the visual arts degrade by means of the active vision system “3EYES”(Eurographics Association, 1999) Cojoc, D.; Grattoni, P.; Nerino, R.; Pettiti, G.Monitoring of some physical characteristics (colour, geometry, size of fissures, ...) of object surfaces is of utmost importance in the field of conservation and restoration of work of arts. In order to get effective results a very high repeatability in the localization of the test points is required. At present, repositioning is a tricky task and is performed by means of manual empirical procedures which can be time consuming and expensive. In this short paper an application of the 3EYES active vision system to the automation of the monitoring is presented. An application of the system to object monitoring in laboratory environment is described.Item The atrium of St. Mary Abbey in Pomposa: a hypermedial 3-D network database(Eurographics Association, 1999) Alessandri, Claudio; Gaiani, MarcoThe analysis carried out on the atrium of the church of Pomposa is an example of a multidisciplinary experience which gathered historians, computer analysts, structural and computer graphics experts on the same project. A 3-D virtual model and the related data base can be considered a common basis for the different approaches attempted and tools indispensable to a correct representation of the complexities characterizing the atrium.