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The UK Chapter of the Eurographics Association (EGUK) presents:-
Theory and Practice of Computer Graphics 2007

University of Wales, Bangor, UK

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Keynote Speakers

Hendrik Lensch (and Hans-Peter Seidel)

MPI Informatik

Acquisition and Modeling of Global Light Transport using Reflectance Fields

The appearance of real-world objects depends on the incident illumination, on the 3D geometry of the object, and on the reflection properties of the object's surfaces. Reflectance fields capture the resulting global light transport in such a way that the object can be relit in arbitrary virtual environments faithfully reproducing the appearance of the original. In this talk we will present an overview about our current work on acquiring and processing reflectance fields, deriving practical algorithms from theoretical insights. One part will cover acquisition techniques that are able to measure the global light transport within a scene on a ray-to-ray basis allowing for capturing and reproducing effects such as subsurface scattering, refractions and caustics. One remaining problem is that reflectance fields are typically acquired only for a discrete set of incident light directions. A rotation in the incident illumination is likely to produce artifacts due to this coarse sampling. In the second part we will therefore address the problem of upsamling reflectance fields in the light domain allowing for smoothly moving shadows and highlights when light sources rotate around the scene.
Hendrik Lensch is a senior scientist at MPI Informatik where he leads his own independent research group. Hendrik received his PhD from Saarland University in 2003. From 2004 to 2006 he was a visiting assistant professor at Stanford University in the Computer Graphics Lab. His current research focuses on appearance acquisition and computational photography.

For his work on reflectance measurement and dual photography Dr. Lensch was awarded the "Eurographics Young Researcher Award 2005". He was awarded an Emmy Noether Fellowship by the German Research Foundation in 2007.

Hans-Peter Seidel is the scientific director and chair of the computer graphics group at MPI Informatik, and a professor of computer science at Saarland University. Seidel's group has done pioneering work in the newly emerging area of 3D Image Analysis and Synthesis, on the intersection between computer graphics and computer vision. Seidel has co-authored some 200 publications in the field, and more than 20 of his former students and postdocs have meanwhile received faculty positions, in Germany and abroad. Seidel has regularly served on the program committees of all major international graphics conferences, and he has chaired several of these events. He has received grants from a wide range of organizations, including the German Research Foundation (DFG), the German Federal Government (BMBF), the European Community (EU), NATO, and the German-Israel Foundation (GIF).

In 2003 Seidel was awarded the "Leibniz Prize", the highest research award in the German system, by the German Research Foundation (DFG).Seidel is the first computer graphics researcher to receive this award.

Eduard Gröller, Associate Professor

Institute of Computer Graphics and Algorithms (ICGA)

Vienna University of Technology

Focus+Context in Illustrative Visualization

Illustrative Visualization produces computer supported interactive and expressive visualizations through abstractions which are inspired by traditional illustration techniques. These techniques work on different levels: low level abstraction techniques (stylized depiction methods) deal with how objects should be presented, while high level abstraction techniques (smart visibility approaches) are concerned with what should be visible and recognizable. The focus+context principle is an important approach in this respect. It depicts important parts of the scene in great detail (focus) while simultaneously showing a global overview with reduced detail (context). Both focus and context are shown in an integrated view. The talk will deal with several focus+context techniques primarily developed to work with volumetric data. Examples include: importance-driven feature enhancement with an explicit focus specification and illustrative context-preserving volume exploration with an implicit focus specification. The previous two techniques modify the visual appearance of objects. Other approaches change the spatial arrangement of the objects like exploded views or change the object themselves like caricaturistic visualization. There are also techniques to automatically draw the focus of attention to a specific scene region. The techniques have been implemented in VolumeShop, a fully dynamic three-dimensional illustration environment. Further information on the presented techniques is available at
Eduard Gröller is Associate Professor at the Institute of Computer Graphics and Algorithms (ICGA), Vienna University of Technology. In 1993 he received his PhD from the same university. His research interests include computer graphics, flow visualization, volume visualization, medical visualization, and information visualization. He is heading the visualization group at ICGA. The group performs basic and applied research projects in the area of scientific visualization. Dr. Gröller has given lecture series on scientific visualization at various other universities (Tübingen, Graz, Praha, Bahia Blanca, Magdeburg, Bergen). He is a scientific proponent and member of the Scientific Advisory Committee of the VRVis Kplus center of excellence. The center performs applied research in virtual reality and visualization. Dr. Gröller is adjunct professor of computer science at the University of Bergen, Norway (2005-2008). Dr. Gröller co-authored more than 130 scientific publications and acted as a reviewer for numerous conferences and journals in the field. He also serves on various program and paper committees. Examples include Computers&Graphics, IEEE Transactions on Visualization and Graphics, EuroVis, IEEE Visualization conference, Eurographics conference. He has been paper-co chair of Volume Graphics 2005, IEEE Visualization 2005 and 2006, and Eurographics 2006. Dr. Gröller is head of the working group on computer graphics of the Austrian Computer Society and member of IEEE Computer Society, ACM (Association of Computing Machinery), GI (Gesellschaft für Informatik), OCG (Austrian Computer Society).

Dr Simon Wattt

School of Psychology

University of Wales, Bangor

Perceiving depth in virtual scenes: Focus cues do matter

Three-dimensional (3D) displays are playing an increasingly important role in society. As well as research into human depth perception, their applications now include scientific visualization, entertainment and medical procedures such as minimally invasive surgery. A well-known problem with such displays, however, is that perceived depth often differs from the portrayed object or scene, even when the display creates geometrically correct 2D retinal images. One possible reason for these distortions is that conventional displays present stimuli at only one focal distance because the light comes from a single surface. This means that depth information from accommodation and blur - typically not considered significant cues to depth - is inconsistent with the portrayed scene. We report several studies which demonstrate that focus cues do affect 3D percepts, both (i) directly, by providing information about local depth variations and (ii) indirectly, by influencing the process of disparity scaling. These results are consistent with the hypothesis that the visual system makes use of all available sources of depth information (weighted according to their reliability) to estimate scene parameters, and suggest that the design of future 3D displays needs to address the problem of inappropriate focus cues. With this in mind we have devised and implemented a display technique that distributes light across multiple image planes to present stereoscopic stimuli at near-correct focal distances. Preliminary experiments suggest that this approach provides a practical solution to some of the problems created by conventional displays.

Dr Simon Watt is a Lecturer in the School of Psychology, at the University of Wales, Bangor. Much of his work concerns the basic question, how does the brain use information from vision (binocular disparity, vergence, focus cues, perspective etc.) and other sensory modalities (e.g. haptics) to recover the 3D properties of objects in the world? The particular emphasis of this work is on how different sources of depth information are combined by the brain, using a Bayesian statistical approach to cue combination. Before coming to Bangor, Dr Watt was a Postdoctoral Researcher at the University of California, Berkeley where he investigated the role of focus cues in visual space perception and 3D displays; binocular vision; and the visual control of hand movements. He received his PhD in 2000 from the University of Surrey.

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