Athanasios Gaitatzes received his Master of Science (MSc) in 1989 in Computer Science from Purdue University at W. Lafayette Indiana, with specialization in Computer Graphics and his Bachelor of Science (BSc) in 1991 in Computer Science from the same University. He is currently pursuing his PhD degree in Computer Science at the University of Cyprus.
Additionally he is a Virtual Reality Systems Developer at the Foundation of the Hellenic World (FHW) in Greece where he is responsible for the design and development of both hardware and software infrastructure and content creation for the Virtual Reality exhibits at the Cultural Center of FHW.
From 1991 to 1998 he was employed as a Software Engineer at the Advanced Systems Division of IBM where he was responsible for the design and development of software libraries for 3D programming. He developed patents for security of networks and data on the Internet and systems for the easier navigation of users on the Internet. During this research he filed and received four patents.
Based on his extensive experience in the design and development of software he has taken part in several European research projects as an analyst and technical advisor.
His research interests include real-time computer graphics, photo realistic visualization, rendering techniques, visibility algorithms, real-time walkthroughs and flythroughs of virtual environments, client/server graphics applications and realistic real-time avatars. He has several publications in international journals in the arena of new technologies and cultural heritage. He is also interested in new methods and technologies as they are applied to e-learning.
Abstract: An increasing number of rendering and geometry processing algorithms relies on volume data to calculate anything from effects like smoke/fluid simulations, visibility information or global illumination effects. We present two real-time and simple-to-implement novel surface voxelization algorithms and a volume data caching structure, the Volume Buffer, which encapsulates functionality, storage and access similar to a frame buffer object, but for threedimensional scalar data. The Volume Buffer can rasterize primitives in 3d space and accumulate up to 1024 bits of arbitrary data per voxel, as required by the specific application. The strength of our methods is the simplicity of the implementation resulting in fast computation times and very easy integration with existing frameworks and rendering engines.
Abstract: We present a novel method to accelerate the computation of the visibility function of the lighting equation, in dynamic scenes composed of rigid, non-penetrating objects. The main idea of the technique is to pre-compute for each object in the scene its associated four-dimensional field that describes the visibility in each direction for all positional samples on a sphere around the object, we call this a displacement field. We are able to speed up the calculation of algorithms that trace visibility rays to near real time frame rates. The storage requirements of the technique, amounts from one byte to one bit per ray direction making it particularly attractive to scenes with multiple instances of the same object, as the same cached data can be reused, regardless of the geometric transformation applied to each instance. We suggest an acceleration technique and identify the sampling method that gives the best results based on experimentation.
Abstract: In this paper we present a novel real-time algorithm to compute the global illumination of dynamic scenes with arbitrarily complex dynamic illumination. We use a virtual point light (VPL) illumination model on the volume representation of the scene. Unlike other dynamic VPL-based real-time approaches, our method handles occlusion (shadowing and masking) caused by the interference of geometry and is able to estimate diffuse inter-reflections from multiple light bounces.
Abstract: Educational applications often are slow to leverage and use new interaction devices in order to bring new value and allow new forms of gameplay. Following decades of research on how to use 3D simulation and Virtual Environments in education, attention has recently turned to exploring Multi-User-Virtual-Environments for the educational community. In the following paper we present the results of a pilot simulation battle, created for educational purposes combining the positive aspects of multi-user virtual environments, edutainment VR applications and new Human Computer Interaction (HCI) interfaces. We present the technology used, as well as an evaluation case study of the human-computer interaction results.
Abstract: Research in virtual reality (VR) is a relatively young field, which has shown considerable growth in recent years, as the development of new interactive technologies has inevitably impacted the more traditional sciences and arts. This is more evident in the case of novel interactive technologies that fascinate the broad public, as has always been the case with virtual reality. The increasing development of VR technologies has matured enough to expand research from the military and scientific visualization realm into more multidisciplinary ar-eas, such as education, art and entertainment. Consequently, virtual reality interfaces interaction techniques and devices have improved greatly in order to provide more natural and obvious modes of interaction and motivational elements. In spite of various concerns and objections regarding the appropriateness and educational efficacy of virtual reality, there remain compelling reasons for believing that virtual environments warrant serious investigation and can provide strong tools for learning. This paper analyses the direction taken regarding the development of user friendly interfaces and natural modes of interaction for users of varied technical competencies in virtual environments.
Abstract: In this paper we present a novel real-time algorithm to compute the global illumination of scenes with dynamic geometry and arbitrarily complex dynamic illumination. We use a virtual point light (VPL) illumination model on the volume representation of the scene. Light is propagated in void space using an iterative diffusion approach. Unlike other dynamic VPL-based real-time approaches, our method handles occlusion (shadowing and masking) caused by the interference of geometry and is able to estimate diffuse inter-reflections from multiple light bounces.
Abstract: We present a novel GPU-based method for accelerating the visibility function computation of the lighting equation in dynamic scenes composed of rigid objects. The method pre-computes, for each object in the scene, the visibility and normal information, as seen from the environment, onto the bounding sphere surrounding the object and encodes it into maps. The visibility function is encoded by a four-dimensional visibility field that describes the distance of the object in each direction for all positional samples on a sphere around the object. In addition, the normal vectors of each object are computed and stored in corresponding fields for the same positional samples for use in the computation of reflection in ray-tracing. Thus we are able to speed up the calculation of most algorithms that trace rays to real-time frame rates. The pre-computation time of our method is relatively small. The space requirements amount to 1 byte per ray direction for the computation of ambient occlusion and soft shadows and 4 bytes per ray direction for the computation of reflection in ray-tracing. We present the acceleration results of our method and show its application to two different intersection intensive domains, ambient occlusion computation and stochastic ray tracing on the GPU.
Abstract: Rendering realistic outdoor scenes in realtime applications is a difficult task to accomplish since the geometric complexity of the objects, and most notably of trees, is too high for current hardware to handle efficiently in large amounts. Our method generates trees with self-similarity, and later exploits this property by heavily sharing prerendered textures of similar parts of the tree. The intrinsic tree hierarchy of the trees, combined with their self-similarity, allows generation of multiple levels of detail. Here we present the flow of the processing stage, from the collection of the required input data until the export of the models in all their levels of detail as well as related and additional data.
Abstract: Most dome display systems today employ pre-rendered shows for attracting visitors. In addition since the technology is well established, developers have many tools at their disposal for creating such shows. On the contrary real-time shows for dome displays are just starting to appear. As a result the production of such shows is not a standardized process. Slowly, progress is made. Graphics generator cards are able to support the required SXGA+ resolutions and the supporting cluster systems are able to supply the processing power and memory bandwidth that such real-time systems require. Tools have to be developed and new processes have to be established. The Foundation of the Hellenic World (FHW) having produced numerous real-time productions for immersive flat display systems has great experience in realizing such shows. In this paper we present the technological developments for the production of real time applications for digital dome display systems.
Abstract: As the interest of the public for new forms of media grows, museums and theme parks select real time Virtual Reality productions as their presentation medium. Based on threedimensional graphics, interaction, sound, music and intense story telling they mesmerize their audiences. The Foundation of the Hellenic World (FHW) having opened so far to the public three different Virtual Reality theaters, is in the process of building a new Dome-shaped Virtual Reality theatre with a capacity of 130 people. This fully interactive theatre will present new experiences in immersion to the visitors. In this paper we present the challenges encountered in developing productions for such a large spherical display system as well as building the underlying realtime display and support systems.
Abstract: Occlusion culling is a genre of algorithms for rapidly eliminating portions of three-dimensional geometry hidden behind other, visible objects prior to passing them to the rendering pipeline. In this paper, an extension to the popular shadow frustum culling algorithm is presented, which takes into account the fact that many planar occluders can be grouped into compound convex solids, which in turn can provide fewer and larger culling frusta and therefore more efficient elimination of hidden geometry. The proposed method combines planar and solid occluders using a unified selection approach and is ideal for dynamic environments, as it doesn’t depend on pre-calculated visibility data. The solid occluders culling algorithm has been applied to commercially deployed virtual reality systems and test cases and results are provided from actual virtual reality shows.
Abstract: This paper presents the virtual reality systems, interaction devices and software used at the Foundation of the Hellenic World (FHW). The applications that FHW has produced, associated with the Olympic Games in ancient Greece, are then detailed. The separate virtual reality shows are presented in terms of interactivity and educational value. Technical aspects of the productions are explained, with an emphasis on surround screen projection environments. These techniques were mostly utilized in the recent production regarding the ancient Olympic Games, where much effort has been made to recreate the feeling of the games and help the user/spectator be an interacting part of the edutainment activity.
Abstract: This paper presents the virtual reality applications that the Foundation of the Hellenic World has produced associated with the Olympic Games in ancient Greece. The separate virtual reality shows are presented in terms of interactivity and educational value. The technical aspects of the productions are next explained in detail, with an emphasis on character animation, dynamics and occlusion culling for surround screen projection environments. These techniques were mostly utilised in the recent production regarding the ancient pentathlon, where much effort has been made to recreate the feeling of the games and help the user/spectator be an interacting part of the edutainment activity.
Abstract: This paper describes the methodological aspects of the application of various established and new graphics techniques in virtual reality applications, in order to visually enrich conventional walkthroughs and extend the common capabilities of virtual environment visualization platforms. The paper describes these techniques and goes to the extent of explaining various practical implementation issues. Examples and application case studies are provided to demonstrate the enhancements.
Abstract: This paper describes the methodological aspects of the application of various established image-based graphics techniques in virtual reality applications, in order to visually enrich and extend the common capabilities of virtual environment visualization platforms. The paper describes these techniques and goes to the extent of explaining various practical implementation issues. Examples and application case studies are provided to demonstrate the enhancements.
Abstract: The use of immersive virtual reality (VR) systems in muse-ums is a recent trend, as the development of new interactive technologies has inevitably impacted the more traditional sciences and arts. This is more evident in the case of novel interactive technologies that fascinate the broad public, as has always been the case with virtual reality. The increas-ing development of VR technologies has matured enough to expand research from the military and scientific visuali-zation realm into more multidisciplinary areas, such as edu-cation, art and entertainment. This paper analyzes the inter-active virtual environments developed at an institution of informal education and discusses the issues involved in de-veloping immersive interactive virtual archaeology projects for the broad public.
Abstract: Shared Miletus is a networked Virtual Cultural Heritage application rst demonstrated at the INET 2000 conference. In this application we sought to explore new tools and techniques, ones that could be useful to create a networked virtual environment which takes the place of a traditional museum. This paper describes the software used to build the environment, and the virtual tools created speci cally to support remote, international visitors to the exhibition.
Abstract: Virtual Reality is a novel and innovative technology which allows us, through its applications, to experience abstract concepts and ideas, visit spaces that are unreachable or no longer exist, and examine objects from diverse and unique points of view. Virtual archaeology refers to the use of 3D computer models of ancient buildings and artifacts visualized through immersive technologies. In this paper we explore issues involved in creating immersive cultural heritage projects enhancing our perspective and understanding of the environments in which our ancestors lived and worked.
Abstract: A method and system are disclosed in a network application for decreasing performance degradation by preventing inadvertent launching of multiple copies of identical network applications. Initially, a remote application is launched from a server to a client in response to a user input event. Next, it is determined if a remote application identical to the remote application has already been launched. If the remote application has already been launched, an elapsed time since the identical remote application was initially launched is determined. Thereafter, the launching of the network application is terminated if the elapsed time is less than a preset value. Alternatively, if the elapsed time is greater than the preset value, the network application is launched. Additionally, if the elapsed time is greater than the preset value, a weighted value of applications running with the client is determined. Thereafter, the network application is launched if the weighted value is small. Alternatively, if the weighted value is large, launching of the network application is terminated.
Abstract: A method and system are disclosed for providing help-data in association with applications launched from a network, such that the applications are displayed within a window of a graphical user interface. Initially, an application is selected from among a number of applications, which are constructed from data generated at a server located within the network. Next, help-data associated with that application is identified. Thereafter, the identified help-data is automatically converted to hypertext data if the identified help-data is derived from a native format other than hypertext format. Hypertext links associated with the identified help-data are then automatically displayed within a window of the graphical user interface. Thereafter, the help-data is automatically displayed within a window of the graphical user interface as a hypertext document, in response to an invocation of the hypertext link by a user of the application. Thus, the hypertext links associated with the identified help-data can be presented to the user in the form of a table and in a graphical user interface window other than the graphical user interface window in which the application is displayed.
Abstract: A method and system are displayed in a computer network for providing a two-dimensional representation of a three dimensional graphic representation to be displayed in association with the three-dimensional graphic representation. The computer network includes a client connectable to a server. Initially, a remote application is transferred from the server to a client. Next, the remote application is displayed within a graphic interface of the client system. Thereafter, the remote application is automatically searched for three dimensional data representative of a three-dimensional graphic representation. If the remote application includes three-dimensional data, then the three-dimensional data is automatically converted to a two-dimensional representation. Thereafter, the two-dimensional representation is displayed within the graphic interface of the client system in association with the remote application.
Abstract: A method and apparatus for improving security for a workstation accessing network resources through a web browser interface. A three step procedure is provided on the workstation for testing the origin and filetype extensions of command files, retrieved by a web browser, to determine whether they may be executed on the workstation. Step one of the invention consists of creating a non-standard command filetype extension on the workstation to be protected. This is followed by step two which isolates specific network or system resources for all approved command files. Finally, step three protects the command file contents and subdirectory locations on the protected workstation. The invention grants execute permission for an application file command files only when all three conditions of the above steps are met.
