ACM SIGGRAPH: Proceedings Web3D 2011 : 16th International Conference on 3D Web Technology. New York: ACM Press, 2011, pp. 81-88

The previous publications on X3DOM focused on the general integration model [Behr et al. 2009] and implementation strategies [Behr et al. 2010]. The aspects of dynamic and interactive worlds were an essential part, but not specifically addressed as such. The recent major additions to the system are CSS Animations and CSS 3D-Transforms as well as various forms of events for user interaction and system monitoring, which complement the existing design to support a large number of interactive and dynamic use cases. This overall design, including scene update mechanisms, animations, and a large number of DOM-based events are thus presented in this paper as part of a single overall system design.

Remondino, Fabio (Ed.) et al.: Proceedings of the 4th ISPRS International Workshop 3D-ARCH 2011 : 3D Virtual Reconstruction and Visualization of Complex Architectures [CD-ROM]. (The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XXXVIII-5/W16), 8 p.

Virtual Museums (VM) are a new model of communication that aims at creating a personalized, immersive, and interactive way to enhance our understanding of the world around us. The term "VM" is a short-cut that comprehends various types of digital creations. One of the carriers for the communication of the virtual heritage at future internet level as de-facto standard is browser front-ends presenting the content and assets of museums. A major driving technology for the documentation and presentation of heritage driven media is real-time 3D content, thus imposing new strategies for a web inclusion. 3D content must become a first class web media that can be created, modified, and shared in the same way as text, images, audio and video are handled on the web right now. A new integration model based on a DOM integration into the web browsers? architecture opens up new possibilities for declarative 3D content on the web and paves the way for new application scenarios for the virtual heritage at future internet level. With special regards to the X3DOM project as enabling technology for declarative 3D in HTML, this paper describes application scenarios and analyses its technological requirements for an efficient presentation and manipulation of virtual heritage assets on the web.

Shumaker, Randall (Ed.): Virtual and Mixed Reality - Systems and Applications: Part II : International Conference, Virtual and Mixed Reality 2011. Berlin, Heidelberg, New York: Springer, 2011. (Lecture Notes in Computer Science (LNCS) 6774), pp. 343-351

In this paper we present a GPU-accelerated implementation of the well-known freeform deformation algorithm to allow for deformable objects within fully interactive virtual environments. We furthermore outline how our real-time deformation approach can be integrated into the X3D standard for more accessibility of the proposed methods. The presented technique can be used to deform complex detailed geometries without pre-processing the mesh by simply generating a lattice around the model. The local deformation is then computed for this lattice instead of the complex geometry, which efficiently can be carried out on the GPU using CUDA.

Avis, Nick (Ed.) et al.: Eurographics 2011. Short Papers. Eurographics Association, 2011, pp. 25-28

Monte Carlo estimation of direct lighting is often dominated by visibility queries. If an error is tolerable, the calculations can be sped up by using a simple scalar occlusion factor per light source to attenuate radiance, thus decoupling the expensive estimation of visibility from the comparatively cheap sampling of unshadowed radiance and BRDF. In this paper we analyze the error associated with this approximation and derive an upper bound. We demonstrate in a simple relighting application how our result can be used to reduce noise by introducing a controlled error if a reliable estimate of the visibility is already available.

ACM SIGGRAPH: Proceedings Web3D 2011 : 16th International Conference on 3D Web Technology. New York: ACM Press, 2011, pp. 39-44

Rendering volumetric phenomena with believable appearance can add tremendous realism to virtual scenes. We introduce the CommonVolumeShader node, an extension of the X3D standard which has been specifically designed for physically-based rendering of participating media. CommonVolumeShader allows content authors to specify optical properties in a concise and purely declarative way and can accurately capture the appearance of many volumetric phenomena. We demonstrate results with implementations for an interactive ray tracer and a rasterization-based pipeline.

ACM SIGGRAPH: Proceedings Web3D 2010 : 15th International Conference on 3D Web Technology. New York: ACM Press, 2010, pp. 185-193

We present a scalable architecture, which implements and further evolve the HTML/X3D integration model X3DOM introduced in [Behr et al. 2009]. The goal of this model is to integrate and update declarative X3D content directly in the HTML DOM tree. The model was previously presented in a very abstract and generic way by only suggesting implementation strategies. The available opensource x3dom.js architecture provides concrete solutions to the previously open points and extents the generic model if necessary. The outstanding feature of the architecture is to provide a single declarative interface to application developers and at the same time support of various backends through a powerful fallback-model. This fallback-model does not provide a single implementation strategy for the runtime and rendering module but supports different methods transparently. This includes native browser implementations and X3D-plugins as well as a WebGL-based scene-graph, which allows running the content without the need for installing additional plugins on all browsers that support WebGL. The paper furthermore discusses generic aspects of the architecture like encoding and introspection, but also provides details concerning two backends. It shows how the system interfaces with X3D-plugins and WebGL and also discusses implementation specific features and limitations.

ACM SIGGRAPH: Proceedings Web3D 2010 : 15th International Conference on 3D Web Technology. New York: ACM Press, 2010, pp. 73-81

This paper presents methods based on the open standard X3D to rapidly describe life-like characters and other scene elements in the context of storyboarding and pre-visualization. Current frameworks that employ virtual agents often rely on non-standardized pipelines and lack functionality to describe lighting, camera staging or character behavior in a descriptive and simple manner. Even though demand for such a system is high, ranging from edutainment to pre-visualization in the movie industry, few such systems exist. Thereto, we present the ANSWER framework, which provides a set of interconnected components that aid a film director in the process of film production from the planning stage to post-production. Rich and intuitive user interfaces are used for scene authoring and the underlying knowledge model is populated using semantic web technologies over which reasoning is applied. This transforms the user input into animated pre-visualizations that enable a director to experience and understand certain film making decisions before production begins. In this context we also propose some extensions to the current X3D standard for describing cinematic contents.

ACM SIGGRAPH: Proceedings Web3D 2010 : 15th International Conference on 3D Web Technology. New York: ACM Press, 2010, pp. 7-15

This paper introduces a modern, declarative surface shader for the X3D standard that allows for a compact, expressive, and implementation-independent specification of surface appearance. X3D's Material node is portable, but its feature set has become inadequate over the last years. Explicit shader programs, on the other hand, offer the expressive power to specify advanced shading techniques, but are highly implementation-dependent. The motivation for our proposal is to bridge the gap between these two worlds - to provide X3D with renderer-independent support for modern materials and to increase interoperability with DCC tools. At the core of our proposal is the CommonSurfaceShader node. This node provides no explicit shader code, only a slim declarative interface consisting of a set of parameters with clearly defined semantics. Implementation details are completely hidden and portability is maximized. It supports diffuse and glossy surface reflection, bump mapping, and perfect specular reflection and refraction. This feature set can capture the appearance of many common materials accurately and is easily mappable to the material descriptions of other software packages and file formats. To verify our claims, we have implemented and analyzed the proposed node in three different rendering pipelines: a renderer based on hardware accelerated rasterization, an interactive ray tracer, and a path tracer.

iX, (2010), 11, pp. 54-63

3D im Web hat Geschichte. Der Erfolg ist aber bisher ausgeblieben. Das kann sich schlagartig ändern, wenn die Browser 3D-Szenen ohne weitere Hilfsmittel darstellen können. Die Open-Source-Projekte X3DOM und XM L3Dstreben dieses Ziel an. Erste Beispiele zeigen, wie es geht.

iX, Vol.12 (2010), pp. 116-121

Interaktive 3D-Szenen im Web, in die der Benutzer in seinem Browser sofort eintauchen kann, sind das Ziel der Open-Source-Projekte X3DOM und XML3D. Transformationen und neue Interaktionskonzepte öffnen den Weg in digitale Welten.

Fellner, Dieter W. (General Co-Chair) et al.: Proceedings Web3D 2009 : 14th International Conference on 3D Web Technology. New York: ACM Press, 2009, pp. 127-135

We present a model that allows to directly integrate X3D nodes into HTML5 DOM content. This model tries to fulfill the promise of the HTML5 specification, which references X3D for declarative 3D scenes but does not define a specific integration mode. The goal of this model is to ease the integration of X3D in modern web applications by directly mapping and synchronizing live DOM elements to a X3D scene model. This is a very similar approach to the current SVG integration model for 2D graphics. Furthermore, we propose a framework that includes a new X3D Profile for the DOM integration. This profile should make implementation simple, but in addition we show that the current X3D runtime model still scales well. A detailed discussion includes DOM integration issues like events, namespaces and scripting. We finally propose an implementation framework that should work with multiple browser frontends (e.g. Firefox andWebKit) and different X3D runtime backends. We hope to connect the technologies and the X3D/ W3C communities with this proposal and outline a model, how an integration without plugins could work. Moreover, we hope to inspire further work, which could lead to a native X3D implementation in browsers similar to the SVG implementations today.

Gutiérrez, Teresa (Ed.) et al.: SKILLS 09 : Enaction on SKILLS. Donostia - San Sebastián: SKILLS Consortium, 2009, pp. 39-45

Within the European project SKILLS Virtual and Augmented Reality platforms have been developed that are used for the realization of different training simulators in the field of sports (training of rowing and juggling), surgery (training of maxillofacial and telerobotic surgery), rehabilitation (rehabilitation of upper limp), maintenance (training of assembly procedures) and robotics (training of robot programming). These platforms are integrating capturing and rendering technologies. The capturing technologies are used to register specific criteria of skills to be hold in a digital representation. Thus, parameters relevant for specific skills are qualified and used as evaluation factors within the training simulators. The training simulators not only can simulate the virtual environment of the training situation, but this environment can be enhanced via multimodal renderings, fostering the training process and accelerating the training effect. The integrative platforms from scalable and adaptable frameworks that can be used to realize different training protocols and that can be adapted to the trainee's degree of skill. Therefore the training protocol can be specified via standardized application scripts.

The 2nd Sino-German Workshop "Virtual Reality & Augmented Reality in Industry" : Invited Paper Proceedings. Participants Edition. Shanghai: Shanghai Jiao Tong University, 2009, pp. 78-83

Rapid development in processing power, graphic cards and mobile computers open up a wide domain for Mixed Reality applications. Thereby the Mixed Reality continuum covers the complete spectrum from Virtual Reality using immersive projection technology to Augmented Reality using mobile systems like Smartphones and UMPCs. At the Fraunhofer Institute for Computer Graphics (IGD) the Mixed Reality Framework instantreality (www.instantreality.org) has been developed as a single and consistent interface for AR/VR developers. This framework provides a comprehensive set of features to support classic Virtual Reality (VR) as well as mobile Augmented Reality (AR). The goal is to provide a very simple application interface which includes the latest research results in the fields of high-realistic rendering, 3D user interaction and total-immersive display technology. The system design is based on various industry standards to facilitate application development and deployment.

Fellner, Dieter W. (General Co-Chair) et al.: Proceedings Web3D 2009 : 14th International Conference on 3D Web Technology. New York: ACM Press, 2009, pp. 51-54

This paper presents a method for the GPU-based real-time simulation of droplet flows on 3D surfaces. It is also outlined, how this approach can be embedded into X3D. Therefore, a concept and its implementation is presented, which is able to simulate droplet flow on almost any surface of a given 3D model. The droplet flow is advanced in time according to the applied external forces, and leaves a trail of liquid behind. Different viscosities are considered as well as the contact angles of droplets that are placed on the surface. Because simulation and rendering of droplet flow is completely handled on the GPU, all fluid information is hold entirely in texture memory. Hence, real-time frame rates are achieved and moreover, the number of simulated drops does not influence performance.

Fellner, Dieter W. (General Co-Chair) et al.: Proceedings Web3D 2009 : 14th International Conference on 3D Web Technology. New York: ACM Press, 2009, pp. 79-82

Creating and setting the right parameters for the virtual camera is crucial for any content creation process. However, this is not easy since most current camera models, including the X3D Viewpoint, use a 3D position and orientation in 3D space to define the final visualized image. People use authoring tools or simple interactive navigation methods (e.g. "lookAt" or "showAll") to ease the process but at the end they still move a 6D (translation and rotation) camera beacon to get the final image. We thus propose a new X3D camera model, the CinematographicViewpoint node, which does not force the content creator to move the camera but allows the author to directly define what objects he would like to see on the screen. We borrow established techniques from the film area (e.g. rule of thirds and line of action) that allow defining objects and object-relations, which the camera model will use to automatically calculate the final transformation in space. The new camera model includes additionally a model for global visual effects (e.g. motion blur and depth of field), which allows incorporating classical film effects to real-time scenes. Both approaches combined allow content creators building visual results and camera movements that are closer to traditional filming much easier. The proposed approach also supports automatic camera movements that are bound to interactive content, which has not been possible before.

Latoschik, Marc Erich (Ed.) et al.: 2nd Workshop on Software Engineering and Architectures for Realtime Interactive Systems (SEARIS@VR2009) : IEEE Virtual Reality 2009 Workshop. Aachen: Shaker, 2009, pp. 41-50

In this paper we describe an X3D-based framework for simplifying the integration of virtual characters into dialog-based VR systems, by introducing another level of abstaction on top of X3D by means of a higher level language, which can be used for module communication and for coordinating the conversational behaviour of virtual humans. Therefore, we propose an self-contained and integrated system with matching techniques and building blocks that not only provides flexible control of the character, but also considers resultant dependencies, which need to be simulated during runtime. Furthermore, our system also takes physiological processes into account, which is essential for the correct perception of some emotions in the context of nonverbal communication. Thus, our proposed approach offers more efficiency by means of the integration into more abstact system architectures, into well established visualization techniques like the scene-graph, and into existing open standards.

Institute for Systems and Technologies of Information, Control and Communication (INSTICC): VISIGRAPP 2009. Proceedings : International Joint Conference on Computer Vision and Computer Graphics Theory and Applications [CD-ROM]. INSTICC Press, 2009, GRAPP, pp. 387-392

This paper introduces novel techniques of interacting and controlling 3D content using multi-touch interaction principles for navigation and virtual camera control. Based on applications from GIS and for the architectural design review process, implementation and usage of these interaction techniques are illustrated. A comprehensive hardware and software setup is used, which not only includes tracking, but also an X3D based layer to simplify application development. Therefore it allows designers and other non-programmers to develop multi-touch applications very efficiently, while allowing to focus on user interaction and content.

Virtual and augmented reality have been around for a long time, but for most people they are movie fantasies. Very few people outside a few research labs have worked with or experienced these systems for themselves. On the other hand, interactive 3D graphics applications are ubiquitous, mostly in the form of games. More and more people are working in animation and games, creating models and programs for interactive 3D applications on standard monitors. The goal of this class is to demonstrate that the leap to actual immersive or augmented environments is not as big as you might think. It explains how high-powered 3D graphics cards, mainstream applications of stereoscopic displays in 3D TV and movies, and webcams that achieve TV-quality images have significantly lowered the barriers to entry. And how, in combination with those hardware advances, freely available software based on open standards like X3D provides all the tools you need to access the elusive world of virtual and augmented reality applications. Following a summary of the basic principles of stereo displays, tracking systems and post-WIMP interaction metaphors, the main part of the course is a practical introduction to creating and running your own interactive and immersive applications.

Spencer, Stephen N. (Ed.): Proceedings WEB3D 2008 : 13th International Symposium on 3D Web Technology. New York: ACM Press, 2008, pp. 57-65

In this paper we describe a layered approach to simplify character animation in X3D. Therefore, we present an interface and control language for specifying and synchronizing animations and similar actions at a higher level. Because this requires to have the accordant features on the lower X3D-based levels, we furthermore propose a set of nodes for realizing these demands. This includes for instance an audio node for text-to-speech that automatically calculates the actual phonemes and weighting factors for the corresponding visemes in order to achieve lip synchronization. To bridge the gap between these layers we also propose nodes for controlling animations, which are capable to convert the scripted schedules, and to mix an arbitrary number of interpolation based animations, whilst still being extensible to new concepts of on-line motion generation.

Spencer, Stephen N. (Ed.): Proceedings WEB3D 2008 : 13th International Symposium on 3D Web Technology. New York: ACM Press, 2008, pp. 27-30

Multi-touch interaction on tabletop displays is a very active field of todays HCI research. However, most publications still focus on tracking techniques or develop a gesture configuration for a specific application setup. Very few explore generic high level interfaces for multi-touch applications. In this paper we present a comprehensive hardware and software setup, which includes an X3D based layer to simplify the application development process. We present a robust FTIR based optical tracking system, examine in how far current sensor and navigation abstractions in the X3D standard are useful and finally present extensions to the standard, which enable designers and other non-programmers to develop multi-touch applications very efficiently.

Diese Masterarbeit befasst sich mit der hardwarebeschleunigten Echtzeitsimulation von Tropfenfluss auf 3D-Modellen. Nach Einführung in strömungsmechanische Grundlagen wird ein Konzept und dessen Implementierung als OpenSG-Anwendung vorgestellt, mit dem Tropfenfluss auf annähernd beliebigen Oberflächen von 3D-Modellen simuliert wird. Tropfen fließen darin entsprechend der wirkenden Kräfte und hinterlassen eine Flüssigkeitsspur. Ebenfalls werden unterschiedliche Viskositäten berücksichtigt und bei der Platzierung von Tropfen auf der Oberfläche werden deren Randwinkel berücksichtigt. Durch Nutzung von Grafikshadern läuft die Berechnung und Darstellung der Tropfensimulation in Echtzeit.

5th Intuition 2008. Proceedings : Virtual Reality in Industry and Society: From Research to Application. Turin, 2008, 7 p.

This paper describes the development of a virtual factory application based on multi-touch interaction, high resolution projection technology and industry standards like X3D. The application is a presentation tool to describe hidden complex physical processes inside a plant for bulk material handling. We are covering the project objectives, the scene architecture and the CAD and physical simulation production pipelines.

IEEE Computer Society: IEEE Virtual Reality 2007. VR Tutorial and Workshop Proceedings [CD-ROM] : IEEE Symposium on 3D User Interfaces. Piscataway, NJ: IEEE Service Center, 2007, 5 p.

The semantics of the X3D ISO standard describe an abstract functional behavior of time-based, interactive 3D, multimedia information. It is independent of any specific software or hardware setup. However, X3D clients and applications today are mainly built for desktop systems running a web-browser. During the last years we have build a VR environment which utilizes the VRML- and X3DISO standards as a basis for an application programming and description language. In this paper we discuss some of our results and experiences. We present necessary extensions to the ISO standard, e.g. to support different interaction and navigation tasks, and discuss how existing parts can be interpreted differently in a VR environment.

ACM SIGGRAPH: Proceedings WEB3D 2007 : 12th International Conference on 3D Web Technology. New York: ACM Press, 2007, pp. 27-36

In this paper, we explore and discuss X3D as an application description language for advanced mixed reality environments. X3D has been established as an important platform for today's web-based visualization and VR applications. Yet, there are very few examples for augmented reality systems utilizing X3D beyond a simple geometric description format. In order to fulfill the image compositing and synthesis requests of today's augmented reality applications, we propose extensions to X3D, especially with a focus on lighting and realistic rendering.

Diese Arbeit beschreibt ein Rahmensystem zur effektiven Visualisierung von sehr großen Landschaftsdaten in Clustersystemen. Die beiden wichtigsten Beiträge sind dabei die Vorstellung eines neuen Level-of-Detail Algorithmus, der für den Einsatz mit modernen Grafikkarten optimiert wurde und die Beschreibung eines Rahmensystems, zur Visualisierung von Landschaftsdaten in verteilten Systemen mittels OpenSG. Dieses Rahmensystem unterstützt sowohl den Einsatz von effizienten Kompressions- und Out-of-Core Mechanismen, als auch die Verwendung von verschiedenen Level-of-Detail Algorithmen. Die neue Level-of-Detail Methode ist eine blockbasierte Variante des Quadtree Algorithmus, die nicht auf einzelnen Dreiecken, sondern auf Blöcken von Dreiecken arbeitet, und dadurch besser für den Einsatz mit aktuellen Grafikkarten geeignet ist. Trotzdem ist die Methode relativ einfach zu verstehen und zu implementieren, und sehr gut für den Einsatz in Clustersystemen geeignet, da die Synchronisierung der Clusterknoten durch die Unabhängigkeit der Blöcke voneinander stark vereinfacht wird.

Schenk, Michael (Ed.): 8. IFF-Wissenschaftstage 2005. Tagungsband : Virtual Reality and Augmented Reality zum Planen, Testen und Betreiben technischer Systeme. Magdeburg: Fraunhofer IFF, 2005, pp. 121-130

HCI International 2005. [Proceedings CD-ROM]. Mahwah, New Jersey: Lawrence Erlbaum Associates, Inc., 2005, 10 p.

All modern VR and AR toolkits provide some kind of sensor abstraction for different types of input and output devices and user interaction. Almost all systems today define a single layer of abstraction. Most toolkits usually support only low level data streams leaving most of the user interface implementation work to the IT professional. Some provide only high level interaction responder (e.g. X3D) without the possibility to access low level I/O information and streams. No toolkit supports adoption of UI elements to the environment the user is working in, e.g. immersive or desktop. In our approach we build three level of abstraction for user interaction which leads to a more flexible and scalable result. Application programmers are free to use low level streams (e.g. tracker data) directly, high level responder (e.g. the user `touched' something) and even application requests (e.g. the systems needs a float input or a list of selected objects) which are automatically mapped to 2D UI elements or immersive responder, depending on the environment and used devices. Two examples illustrate the flexibility and efficiency of our approach.

Auf der Grundlage der Szenengraphenstruktur wurde in dieser Arbeit ein einheitliches Modell von Graphen entwickelt, das es erlaubt, alle dynamischen Aspekte einer Mixed Reality (MR) Applikation mit Hilfe von Komponenten und typisierten Kanten zu modellieren. Das Konzept abstrahiert die klassischen topologischen Beziehungen sowie statische und dynamische Nachrichtenkanäle als Kanten innerhalb unterschiedlich gerichteter Graphen. Es wurden daraus abgeleitete Anforderungen diskutiert und entsprechende Lösungen entwickelt. Dabei wurden in dieser Arbeit insbesondere Problemstellungen wie Erweiterbarkeit, die Verwaltung und Bereitstellung von Metabeschreibungen und die korrekte Verarbeitung von Nachrichten untersucht und neuartige Ansätze entwickelt. Aufbauend auf dem einheitlichen Graphenmodell wurden neue Interaktionsmechanismen entwickelt. Dabei wurde gezeigt, dass bisherige MR-Systeme sich meist auf eine statische Abstraktion von virtuellen Gerätegruppen beschränken und kaum darauf aufbauende Interaktionsmodelle anbieten. Aus diesem Grund wurde in dieser Arbeit ein neuartiges, mehrstufiges Sensorkonzept entwickelt und vorgestellt, das unabhängig von Geräteklassifikationen Interaktionsverfahren beinhaltet, welche abhängig von der Ausprägung der Laufzeitumgebung interaktive Elemente bereitstellt. Es wurden drei aufeinander aufbauende Sensorgruppen entwickelt, die als Komponenten der dynamischen und hierarchischen Graphen zum Einsatz kommen. Ein weiterer Schwerpunkt dieser Arbeit ist die Entwicklung von Verfahren zur Abbildung der Parallelverarbeitung von Prozessen und deren Skalierbarkeit. Hierbei wurden die typischen Abläufe in einem VR-System untersucht und eine Lösung entwickelt, die zwei unterschiedliche Ansätze der Parallelisierung beinhaltet. Einerseits wurde die klassische Trennung der Applikation und Darstellung verallgemeinert, andererseits wurde zusätzlich ein neuartiges Verfahren entwickelt und vorgestellt, welches die automatische Parallelisierung auf den Ereigniskanten der Applikationsgraphen bereitstellt. Um globale Applikationsvorgaben erfüllen zu können, wie zum Beispiel das Darstellen mit einer fixen Bildwiederholrate, ist eine globale Skalierbarkeit der Kosten gefordert. Zur Lösung dieses Problems wurde ein globales Modell einwickelt und eingeführt, das automatisch lokale Kosten der Prozesse zur Darstellung und Veränderung skaliert. Das in dieser Arbeit entwickelte Modell zur Parallelisierung und Skalierung von MR-Systemen ist eine wesentliche Verbesserung gegenüber den bisherigen Verfahren, da es auf der Grundlage der globalen Zielvorgaben und der Applikationsgraphen selbständig und automatisch den Ressourcenverbrauch regelt und verteilt.

Over the last fifteen years volume rendering have become an important part of examining, exploring and evaluating volume data. Huge medical datasets generated by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) have with volume rendering been made possible to explore in 3D. Even interaction with the data is today possible and it has been shown that this is of great value when diagnosing, practicing and/or learning. In order to make interactive volume rendering possible a range of sophisticated methods have been developed. Often high-end graphic hardware are applied when developing applications for 3D volume rendering. This is an obstacle when it comes to integrating the techniques into the normal hospital environment. It would be preferable if the applications are general enough to run on standard computers. In this thesis a volume renderer for standard computers with good visual result and a relatively high update rate, sufficient for interaction, is developed. The last years tremendous development of graphic hardware have made it possible to write programs, so called shaders, directly communicating with the graphic pipeline. The developed renderer employs the use of such shaders because of its superiority in speed to normal software rendering. One purpose for the renderer is that it will be used for exploring medical data as a part of a project between Fraunhofer Institut and the Hospital of Mainz.

Echtzeitgenerierte virtuelle Szenen, die nah an der Realität liegen sollen, sind ohne qualitativ hochwertige Schatten nicht vorstellbar. Schon seit längerem werden gerade für komplexe Szenen Shadow-Mapping-Verfahren eingesetzt, da diese weitgehend unabhängig von der Komplexität der Szene arbeiten. Dieses Verfahren hat jedoch einige Nachteile, wie die relativ schlechte Schattenqualität, auf die in dieser Arbeit eingegangen, und entsprechende Lösungen vorgestellt werden. Der Schwerpunkt lag dabei in der Implementation eines Shadow-Viewports in das Open Source Szenengraphensystem "OpenSG". Dabei ist der Shadow Viewport Modular aufgebaut und erweiterbar. Er bietet die Möglichkeit, aus verschiedenen Schattenverfahren zu wählen und diese auf eine gegebene Szene anzuwenden. Darunter befinden sich Verfahren zur Erzeugung von harten als auch weichen Schatten. Für harte Schatten wurden, neben dem Standard Shadow Mapping, verschiedene perspektivische Shadow-Mapping-Verfahren betrachtet. Für die Erzeugung weicher Schatten wird auf Verfahren auf Basis eines PCF-Filters eingegangen und eine Modifikation vorgestellt, mit der auch perspektivisch korrekte Soft-Shadows in Echtzeit berechnet werden können. Am Ende werden die gewonnenen Ergebnisse aufgezeigt und anhand von Screenshots in verschiedenen Situationen hinsichtlich der erreichten Schattenqualität miteinander verglichen, um die Stärken und Schwächen der gezeigten Verfahren aufzuzeigen.

Spencer, Stephen N. (Ed.): Web3D 2004. Proceedings : Ninth International Conference on 3D Web Technology. New York: ACM, 2004, pp. 71-78, 182

Conceptually, the semantics of X3D describe an abstract functional behaviour of time-based, interactive 3D, multimedia information and do not all specify a specific software or hardware setup. However X3D clients and applications today are mainly built for desktop systems running a web browser. In this papr we explore how suitable X3D and W3C technologies can be utilized as an application and programming model for immersive virtual environments. We present a system implementation, necessary extensions to the X3D specification and discuss how standard nodes can be interpreted differently in an immersive setting.

IEEE Transactions on Visualization and Computer Graphics, Vol.9 (2003), 1, pp. 3-15

We advocate the use of point sets to represent shapes. We provide a definition of a smooth manifold surface from a set of points close to the original surface. The definition is based on local maps from differential geometry, which are approximated by the method of moving least squares (MLS). The computation of points on the surface is local, which results in an out-of-core technique that can handle any point set. We show that the approximation error is bounded and present tools to increase or decrease the density of the points, thus allowing an adjustment of the spacing among the points to control the error. To display the point set surface, we introduce a novel point rendering technique. The idea is to evaluate the local maps according to the image resolution. This results in high quality shading effects and smooth silhouettes at interactive frame rates.

Thema Forschung, (2003), 1, pp. 66-73

Hamza, M.H. (Ed.): Third IASTED International Conference on Visualization, Imaging, and Image Processing. Proceedings Vol. II. Anaheim: ACTA Press, 2003, pp. 944-949

This paper describes a Virtual Reality system in order to convey a vivid experience of the appearance, history and context of Cultural Heritage assets through Digital Storytelling, and to encourage the visitor to visit the real place he is virtually immersed in. The storytelling experience is implemented using Mixed Reality technologies and Digital Storytelling techniques, in order to "tell a story" with narrative and emotional characteristics. The storytelling technologies are a good mean to wake up the visitor´s interest, and to facilitate the understanding of the contextual information of the cultural asset.

Linear geometry interpolation (or morphing) is useful to display key frame animations. This work briefly explains prerequisites and useful properties for morphing and describes a prototype implementation within the geometry framework of OpenSG.

An algorithm for striping triangle meshes in the context of OpenSG is presented. The technique is similar to STRIPE, however, a careful yet simple implementation leads to significant faster execution. Furthermore, we propose to randomly sample several partitions and chose the one that minimizes a given cost function. More samples are expected to lead to better solutions, thus, introducing a parameter to scale between speed and quality.

Peng, Shietung (Ed.) et al.: First International Symposium on Cyber Worlds. Proceedings 2002. Los Alamitos, Calif.: IEEE Computer Society, 2002, pp. 553-560

Are Virtual and Augmented Reality (VR/AR) well suited for entertaining and educating a lay audience? In this paper we try to find an answer to this question and work out the conditions and requirements for successful installations. We will describe our testbed, the Cybernarium Days 2002, the world s first public exhibition exclusively dedicated to Virtual and Augmented Reality, which attracted more than 10.000 visitors in 6 days. We also present the results of the user questioning, which took place during the exhibition, and the lessons learnt . Furthermore we focus on software aspects, which enabled us to use low cost hardware and offered a way to build new exhibits in a short time. Since the raise or fall of a VR/AR installation is mainly influenced by its user interface, we present a classification scheme for devices and outline their advantages and disadvantages, offering other VR/AR-developers a guideline for their work on public VR/AR-exhibits.

One of the main shortcomings of current scenegraphs is the inability to support multi thread-safe data. Another area that leaves things to be desired is extensibility. This work describes a system that allows multiple asynchronous threads to independently manipulate the scenegraph without interfering. This demands replication of data. As scenegraph data can get very big, a distinction of structural and content data is introduced, and a method to replicate the latter only if necessary. To make the whole concept generic and easily extensible, Reflectivity is introduced to the system. Besides allowing to manage multiple independent threads the described approaches can also be used for generic scenegraph access ,e.g. for loader/writer and GUIs. An extension allows also to the use the developed methods for cluster support.

Bartz, Dirk (Ed.) et al.: Fourth Eurographics Workshop on Parallel Graphics and Visualisation 2002. Proceedings. New York: ACM Press, 2002, pp. 33-37

One of the main shortcomings of current scene graphs is their inability to support multi-thread safe data structures. This work describes the general framework used by the OpenSG scene graph system to enable multiple concurrent threads to independently manipulate the scene graph without interfering with each other. Furthermore the extensions of the presented mechanisms needed to support cluster systems are discussed.

Ertl, Thomas (Ed.) et al.: IEEE Visualization 2001. Proceedings. Los Alamitos, Calif.: IEEE Computer Society Press, 2001, pp. 21-28

We advocate the use of point sets to represent shapes. We provide a definition of a smooth manifold surface from a set of points close to the original surface. The definition is based on local maps from differential geometry, which are approximated by the method of moving least squares (MLS). We present tools to increase or decrease the density of the points, thus, allowing an adjustment of the spacing among the points to control the fidelity of the representation. To display the point set surface, we introduce a novel point rendering technique. The idea is to evaluate the local maps according to the image resolution. This results in high quality shading effects and smooth silhouettes at interactive frame rates.

Spencer, Stephen N.: Virtual Reality Modeling Language Symposium on 3D Technologies for the World Wide Web. Proceedings. New York: ACM Press, 2001, pp. 23-27

Volume visualization has become an invaluable visualization tool. A wide variety of data sets coming from medical applications (e.g. MRI, CT or 3D ultrasound) or geological sensory information are represented as structured volume grids. In many application it is fa-vorable to access the data sets from the net and explore the volume on a typical PC. Modern graphics hardware makes volume render-ing at interactive rates possible. However, protocols for exchange of 3D graphics content such as VRML97 are not equipped to process volume data. This paper presents an approach using 2D/3D textures and standard rendering hardware, which allows real-time rendering of volume and polygonal data in VRML applications. The proposed environment enables the user to navigate through - and interact with - the VRML scene, combining volume and surface model data sets.

Bearman, David (Ed.) et al.: International Cultural Heritage Informatics Meeting. Proceedings : Cultural Heritage and Technologies in the Third Millennium. Mailand, 2001, pp. 57-71

In this paper, innovative technologies for the presentation of complex cultural heritage sites with immersive 3D computer graphics are introduced, wich are based on new concepts, partly having been adopted from other computer graphics areas to the specific needs for cultural heritage presentations, partly having been developed especially for this purpose. The main focus of this project was to develop new concepts for the integration of historical, architectural and cultural data related to a cultural heritage site, into an immersive Virtual REality (VR) Environment suited for presentation of the digital model. These concepts include digital storytelling, virtual 3D avatars and 3D agents. The 3D avatar was implemented as a virtual tourist guide, who accompanies the visitors on their tour and shows them the places of interest. Futhermore, specifics of the very detailed and complex digital models of cultural heritage sites are adressed, in order to meet the high quality requirements of an interactive 3D visualization. Special focus has been put on both the frame rate and the visual quality. Beside Level-of-detail mechanisms, texture-paging techniques have been developed to allow the use of very high resolution textures. Lighting simulation based on radiosity simulation, which ensure a high visual quality, have been extended for the efficient simulation of global illumination effects within very complex models- These new concepts and techniques have been successfully applied in the immersive VR presentation of a digital model of the cathedral of Siena, which has been shown to the public during the EXPO 2000 in Hannover.

Die meisten VR-Systeme unterstützen applikationsabhängige Modellveränderungen, indem sie es den Entwicklern erlauben, ein zentrales Animationsmodul zu integrieren, welches die Geometrie- und Transformationsbeschreibungen zwischen den einzelnen Frames manipuliert. Im Gegensatz zu diesem traditionellen Ansatz übertragen neuere Systeme (z.B. das Avalon System) die Verantwortung für die Verhaltensbeschreibungen direkt an die Knoten im Szenengraphen. Somit beinhaltet der Szenengraph nicht nur die statischen Geometrien und Beziehungen, sondern auch die Beschreibungen für die dynamischen Verhaltens- und Interaktionselemente. Für den Ereignisaustausch stellen diese Elemente Ein- und Ausgänge bereit. Dynamische Applikationen für ein solches System werden entwickelt, indem ein Entwickler die im System vorhandenen Knoten verwendet und miteinander verknüpft und damit die Beziehungen zwischen den einzelnen Objekten spezifiziert. Verfügbare graphisch interaktive Modellierungssysteme unterstützen diese dynamischen Elemente und deren Verknüpfungen nur unzureichend. Sie erlauben im allgemeinen nur Geometrien und Hierarchien, aber nicht die dynamischen Beziehungen zu editieren. In der Diplomarbeit wurden verschiedene freie und kommerzielle VR-Systeme hinsichtlicht ihrer Fähigkeiten, den Entwickler bei der Erstellung dynamischer VR-Applikationen zu unterstützen, untersucht und klassifiziert. Weiterhin werden VRML-Editoren betrachtet und ihre Vor- und Nachteile hinsichtlich der Erzeugung von VR-Szenen untersucht. Ausgehend von dieser Untersuchung wird ein Prototyp zur Darstellung und Bearbeitung von Applikationen vorgestellt, der sich in das an der Z2 entwickelte VR-System Avalon integriert und es ermöglicht, VR-Applikationen interaktiv, d.h. während die Anwendung läuft, darzustellen und zu bearbeiten, so daß die Änderungen sofortige Auswirkung auf die laufende Szene haben. Das System kann die die Szene beschreibenden Knoten und ihre Verbindungen untereinander darstellen und erlaubt das interaktive Erstellen neuer und das Entfernen von bestehenden Verbindungen. Der der Anwendung zugrunde liegende Szenengraph wird in einer baumartigen Struktur angezeigt und zu einem speziellen Knoten werden detaillierte Informationen bereitgestellt.

Moderne Virtual Reality-Systeme erlauben dem Anwendungsentwickler, Szenen aus einer Vielzahl unterschiedlicher Elemente und Komponenten aufzubauen. Nahezu alle Systeme unterstützen statische Szenengraphen zur Beschreibung der räumlichen und logischen Organisation dieser Elemente. Darüber hinaus erlauben viele Systeme die Einbindung einfacher dynamischer Elemente, wie Filme oder Audiosequenzen, in die Szenenbeschreibung. Dieser Arbeit liegt die Anforderung zugrunde, ein bestehendes System zur Erstellung von Prototypen für Virtual Reality-Anwendungen zu erweitern, um das Streaming audiovisueller Informationen zu unterstützen. Zusätzlich können aber auch andere Informationen als Datenstrom übertragen werden. Beispielsweise können Szenenbeschreibungen zur Laufzeit dynamisch in die bestehende virtuelle Umgebung eingefügt werden und damit eine grössere Flexibilität der Szenenbeschreibung erreichen. Für das Einbinden solcher Informationsströme fehlte es jedoch an einem Basisformat, das neben der räumlichen und logischen Organisation auch die zeitliche Abfolge beschreibt und so den Zusammenhang zwischen Multimediadaten und der Szenenbeschreibung einer virtuellen Umgebung herstellt. Im Rahmen dieser Arbeit wurden bestehende Beschreibungsformate für Multimediapräsentationen anhand der Anforderungen verglichen. Darüber hinaus wurde analysiert, welche Anforderungen in Zukunft zu erwarten sind, um ein möglichst flexibles System zu erhalten. Dafür wurde ein Bogen von der aktuellen multimedialen Konvergenz zum nächsten Entwicklungsschritt im Bereich Graphik und interaktive Systeme gespannt. Die Überlegung ist, dass der Konversion der multimedialen Datenformate eine Konversion im Bereich der Darstellungs- und Kommunikationssysteme zur Folge hat. Diese zweite Konversion wird mit dem Begriff der Mixed Reality gleichgesetzt, welcher per Definition die Bereiche der Virtual Reality, des Teleconferencings, der Telepresence und der Augmented Reality umfasst. Darüber hinaus werden die möglichen Auswirkungen auf Ausdrucksformen und Präsentation von Informationen beleuchtet und an Beispielen verdeutlicht. Das Ergebnis der Untersuchung favorisiert MPEG-4 gegenüber anderen Beschreibungsformaten wie MHEG oder SMIL. Zusätzlich wurden auch die Anforderungen an Übertragungsprotokolle im Hinblick auf multimediale Informationen betrachtet. Auch auf diesem Gebiet zeigte sich eine Überlegenheit des MPEG-4 Systems durch seine Flexibilität und Modularität. Aufgrund des Umfangs des MPEG-4-Systems, blieb die Implementierung eines Prototypen rudimentär. Trotzdem konnte die Machbarkeit der Integration sowie die Schwächen bestehender MPEG-4 Implementierungen gezeigt werden, die deren Einsatz bislang unmöglich machen.

A novel point rendering algorithm is presented using surfels as rendering primitives. A surfel is a discrete 3D surface element consisting of the attributes position, normal, and color. It is shown, that a 3D object representation by surfels can be created directly from point clouds of 3D scanners, from polygonal meshes, and from implicit surfaces. The surfels are compressed using quantization schemes for each of the three attributes, and stored in a full binary space partitioning tree in order to render the 3D object in various level-of-details which are view-dependently defined. Three rendering speed-up techniques are presented: hierarchical view frustum culling, hierarchical backface culling using normal masks, and the exploitation of view coherence.

Spencer, Stephen N.: Web3D - VRML 2000. Proceedings : Fifth Symposium on the Virtual Reality Modeling Language. New York: ACM Press, 2000, pp. 29-34

We discuss potential and limitations of a Morph Node, inspired by the corresponding construct in Java3D. A Morph Node in Java3D interpolates vertex attributes among several homeomorphic geometries. This node isa promising candidate for the delivery of 3D animation in avery compact form. We review the state-of-the-art in Web 3D techniques with respect to the possibility of interpolating among several geometries. This review leads to a simple extention for VRML-97 as well as a recommendation for necessary changes in Java3D. Furthermore, we discuss various optimization issues for Morph Nodes.

Der Radiologe, Vol.40 (2000), 3, pp. 256-261

Die Entwicklung einer neuen Generation bildgebender Geräte ermöglicht die Akquisition hochauflösender tomographischer Datensätze. Als Ergebnis liegt eine grosse Anzahl der Schichten vor, sodass neue, ausgereifte Methoden für deren effiziente Auswertung erforderlich werden. Wünschenswert ist das computerunterstützte Generieren von dynamischen 3D-Modellen der Anatomie des Patienten aus dem Bildmaterial. Da der Betrachter in der Lage sein sollte, schnell sensible Entscheidungen treffen zu können, ist für die Modellierungs- und Visualisierungstechniken ein hoher Grad an Genauigkeit in kürzester Zeit notwendig. In diesem Beitrag präsentieren wir Techniken, die in der Cardiac Station realisiert wurden und veranschaulichen diese anhand von kardiologischem Bildmaterial. Neben der Darstellung der Morphologie können die im Ergebnis vorliegenden Bilder auch Aufschluss über die Funktion geben. Daher werden Funktionsparameter aus dem Bildmaterial ermittelt und zusammen mit dem Modell visualisiert. Um die Genauigkeit des Modells anhand der Original-Bilddaten verifizieren zu können und um darüber hinaus Eingriffe anhand eines Modells zu planen, präsentieren wir experimentelle Interaktionstechniken.

Computers & Graphics, Vol.24 (2000), 5, pp. 741-753

Due to the development of new imaging devices, which produce a large number of tomographic slices, advanced techniques for the evaluation of large amounts of data are required. Therefore, computer-supported extraction of dynamic 3-D models of patient anatomy from temporal series is highly desirable. Since the diagnostician must be able to quickly make rational decisions based on the models, a high degree of accuracy is required within a minimum amout of time. We present modelling and visualization techniques that are realized within the Cardiac Station. Results for the application of these techniques to cardiac image data are given. In addition to providing information about the patient's morphology, functional parameters can be derived from the data and visualized together with the model. In order to verify the model with the original image data and to plan for real intervention, interaction techniques are presented.

Kim, Myoung-Hee et al.: Advanced Medical Image Processing. Proceedings 1998. Seoul, 1998, Session IV, No. 4

Volume visualization is rapidly becoming the preferred tool for the estimation of anatomical features for volume modalities such as MRI, CT or 3-D ultrasound. Although traditional volume visualization systems provide quite adequate results they are not applicable for interactive VR applications. Since volume visualization implies processing of an enormous amount of data, this technique usually leads to insufficient frame rates. To counteract these drawbacks, a dedicated hardware or super-computer for rendering in real-time is used quite frequently. This paper presents an approach usind 3-D textures and standard rendering hardware, which allows real-time rendering of volume and polygonal data in VR applications. The proposed environment enables the user to navigate through - and interact with - the VR scene, which combines volume and surface model data sets.