Search Results

Now showing 1 - 10 of 16
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    An Error Bound for Decoupled Visibility with Application to Relighting
    (The Eurographics Association, 2011) Schwenk, Karsten; Fellner, Dieter W.; N. Avis and S. Lefebvre
    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.
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    A Cut-Cell Geometric Multigrid Poisson Solver for Fluid Simulation
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Weber, Daniel; Mueller-Roemer, Johannes; Stork, André; Fellner, Dieter W.; Olga Sorkine-Hornung and Michael Wimmer
    We present a novel multigrid scheme based on a cut-cell formulation on regular staggered grids which generates compatible systems of linear equations on all levels of the multigrid hierarchy. This geometrically motivated formulation is derived from a finite volume approach and exhibits an improved rate of convergence compared to previous methods. Existing fluid solvers with voxelized domains can directly benefit from this approach by only modifying the representation of the non-fluid domain. The necessary building blocks are fully parallelizable and can therefore benefit from multi- and many-core architectures.
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    EDEN - AN EDITOR ENVIRONMENT FOR OBJECT- ORIENTED GRAPHICS EDITING
    (Eurographics Association, 1990) Fellner, Dieter W.; Kappe, F.
    Systems allowing the creation and manipulation of graphical information (so-called Graphic Editors) have become essential in various fields of applications. At the same time the typical user of such a system has changed. Not computer experts, but designers, secretaries, technicians, teachers etc. are today's typical users of computer graphics, mostly on microcomputers. Obviously it would be desirable to have a common concept of graphics editing covering many applications. The purpose of this paper is a brief survey of the EDEN project started at the IIGb in 1987: the motivation for the project, the major steps, results, current status and future work is presented here. EDEN (short for EDitor ENvironnient) is a generic concept for object-oriented graphics editing, providing device independence at the workstation and graphics output level as well as an application independent file-format for the storage and exchange between different graphics applications.
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    Adapting Precomputed Radiance Transfer to Real-time Spectral Rendering
    (The Eurographics Association, 2010) Schwenk, Karsten; Franke, Tobias; Drevensek, Timm; Kuijper, Arjan; Bockholt, Ulrich; Fellner, Dieter W.; H. P. A. Lensch and S. Seipel
    Spectral rendering takes the full visible spectrum into account when calculating light-surface interaction and can overcome the well-known deficiencies of rendering with tristimulus color models. We present a variant of the precomputed radiance transfer algorithm that is tailored towards real-time spectral rendering on modern graphics hardware. Our method renders diffuse, self-shadowing objects with spatially varying spectral reflectance properties under distant, dynamic, full-spectral illumination. To achieve real-time frame rates and practical memory requirements we split the light transfer function into an achromatic part that varies per vertex and a wavelengthdependent part that represents a spectral albedo texture map. As an additional optimization, we project reflectance and illuminant spectra into an orthonormal basis. One area of application for our research is virtual design applications that require relighting objects with high color fidelity at interactive frame rates.Spectral rendering takes the full visible spectrum into account when calculating light-surface interaction and can overcome the well-known deficiencies of rendering with tristimulus color models. We present a variant of the precomputed radiance transfer algorithm that is tailored towards real-time spectral rendering on modern graphics hardware. Our method renders diffuse, self-shadowing objects with spatially varying spectral reflectance properties under distant, dynamic, full-spectral illumination. To achieve real-time frame rates and practical memory requirements we split the light transfer function into an achromatic part that varies per vertex and a wavelengthdependent part that represents a spectral albedo texture map. As an additional optimization, we project reflectance and illuminant spectra into an orthonormal basis. One area of application for our research is virtual design applications that require relighting objects with high color fidelity at interactive frame rates.
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    Fast Rendering of General Ellipses
    (Eurographics Association, 1991) Fellner, Dieter W.; Helmberg, Christoph
    Even though GKS did not include circles and, in a more general form, ellipses and elliptical arcs in the list of elementary graphics primitives, CGM settled this omission with its standardization in 1987. According to CGM as well as to CGI, ellipses and elliptical arcs are defined in a very general way via endpoints of conjugate diameter pairs (CDP). Based on the algorithm of Maxwell & Baker [5] this paper presents a new algorithm for the rendering of general ellipses (i.e. not aligned to the coordinate axes) and elliptical arcs which is not only fast and very well suited for implementation in hardware but also deals with all degenerate cases of ellipses at no extra cost. Furthermore, the algorithm provides all the information which is necessary for the generation of anti-aliased elliptical curves.
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    Isogeometric Analysis for Modelling and Design
    (The Eurographics Association, 2015) Riffnaller-Schiefer, Andreas; Augsdörfer, Ursula H.; Fellner, Dieter W.; B. Bickel and T. Ritschel
    We present an isogeometric design and analysis approach based on NURBS-compatible subdivision surfaces. The approach enables the description of watertight free-form surfaces of arbitrary degree, including conic sections and an accurate simulation and analysis based directly on the designed surface. To explore the seamless integration of design and analysis provided by the isogeometric approach, we built a prototype software which combines free-form modelling tools with thin shell simulation tools to offer the designer a wide range of design and analysis instruments.
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    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.
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    Digital Publishing
    (Eurographics Association, 1997) Fellner, Dieter W.
    This presentation covers the general topic of ‘Digital Publishing’ in the context of - the German MEDOC Project and - the German Strategic Digital Library Initiative V3D2 and, more specifically, - in the context of organizing EUROGRAPHICS’97 from the publication point of view. MEDOC is an effort by the German Computer Society (GI) to identify and to address the implications and challenges of digital libraries and electronic publishing on a wide scale. Starting in September 1995 the MEDOC project, partly funded by the German Ministry of Technology, has not only tried to implement a novel architecture for bringing relevant documents to the researcher’s desktop it has also raised the awareness on this important subject within the scientific community as well as within the group of publishers. The scientific counterpart to the application oriented MEDOC project is the strategic initiative V3D2 which is the (German) acronym for ‘Distributed Processing and Delivery of Digital Documents’. This initiative, funded by the German Research Foundation (DFG) over a period of six years and starting in 1997 provides a solid base for researchers from different disciplines (Computer Science, Library Sciences,Applied Sciences, . . . ) to tackle basic research and application issues focusing on ‘generalized electronic documents’. EUROGRAPHICS’97 is the first conference in its series to fully exploit the power of electronic documents and computer networks. This year, the submission of papers, the delivery of papers and attached multimedia material to the IPC members and to the reviewers as well as their online access, the feedback to the authors, and the delivery of the final documents (with the accompanying multimedia data) has been (almost) exclusively carried out electronically. This report briefly describes the architecture behind the work of the program committee from the first call for papers to the production of the printed proceedings and the CD-ROM holding the technical papers, STAR’s and tutorials. The experiences and lessons learned might be valuable to a general audience and not only to those organizing a scientific event in the near future.
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    What Can We Gain from Transdisciplinary Visualization Courses?
    (The Eurographics Association, 2008) Chalmers, Panel Chair: Gitta Domik; Panellists: Alan; Domik, Gitta; Fellner, Dieter W.; Rushmeier, Holly; Steve Cunningham and Lars Kjelldahl
    Transdisciplinary education means going even further in the collaboration with other disciplines than multidisciplinary and interdisciplinary education do. Transdisciplinary education attempts to search for new insights and views that emerge by balancing the importance of each participating discipline. Because most visualization problems are posted by disciplines other than Computer Science and because good solutions to visualization problems span knowledge over different disciplines, we often find interest from students outside the CS area in our visualization courses. This panel will discuss transdisciplinary (as well as interdisciplinary and multidisciplinary) visualization courses from four different viewpoints of the four panellists: What do multidisciplinary, interdisciplinary and transdisciplinary education mean in practical terms for an educator of a visualization course? What benefits does an applied research institute expect from graduates that have experience in interdisciplinary or transdisciplinary versus unidisciplinary collaboration? Will there be enough interest from non-CS students to attend such visualization courses?
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    Mesh Saliency Analysis via Local Curvature Entropy
    (The Eurographics Association, 2016) Limper, Max; Kuijper, Arjan; Fellner, Dieter W.; T. Bashford-Rogers and L. P. Santos
    We present a novel approach for estimating mesh saliency. Our method is fast, flexible, and easy to implement. By applying the well-known concept of Shannon entropy to 3D mesh data, we obtain an efficient method to determine mesh saliency. Comparing our method to the most recent, state-of-the-art approach, we show that results of at least similar quality can be achieved within a fraction of the original computation time. We present saliency-guided mesh simplification as a possible application.