EG2003

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    Freeform Shape Representations for Efficient Geometry Processing
    (Eurographics Association, 2003) Kobbelt, Leif
    The most important concepts for the handling and storage of freeform shapes in geometry processing applications are parametric representations and volumetric representations. Both have their specific advantages and drawbacks. While the algebraic complexity of volumetric representations is independent from the shape complexity, the domain of a parametric representation usually has to have the same structure as the surface itself (which sometimes makes it necessary to update the domain when the surface is modified). On the other hand, the topology of a parametrically defined surface can be controlled explicitly while in a volumetric representation, the surface topology can change accidentally during deformation. A volumetric representation reduces distance queries or inside/outside tests to mere function evaluations but the geodesic neighborhood relation between surface points is difficult to resolve. As a consequence, it seems promising to combine parametric and volumetric representations to effectively exploit both advantages. In this talk, a number of projects are presented and discussed in which such a combination leads to efficient and numerically stable algorithms for the solution of various geometry processing tasks. Applications include global error control for mesh decimation and smoothing, topology control for level-set surfaces, and shape modeling with unstructured point clouds.
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    Open Issues in Photo-realistic Rendering
    (Eurographics Association, 2003) Purgathofer, Werner
    For more than two decades Computer graphics researchers have tried to achieve photo-realism in their images as reliable as possible, mainly by simulating the physical laws of light and adding one effect after the other. The recent years have brought a change of efforts towards real-time methods, easy-to-use systems, integration with vision, modelling tools and the like. The quality of images is mostly accepted as sufficient for real world applications, but where are we really? There are still numerous problems to be solved, and there is notable progress in these areas. No question, the plug-in philosophy of some commercial products has enabled several of these new techniques to be distributed quite fast. But unfortunately, many other of these developments happen in isolated systems for the pure purpose of publication, and never make it into commercial software. This presentation wants to make people more aware of such activities, and evaluate the steps we still have to go towards perfect photo-realism. The talk will start with an attempt to give a brief overview of the rendering history, highlighting the main research directions at different times. It will explain the driving forces of the developments, which are complexity, speed, and accuracy, and maybe also expression in recent years. Solved and unsolved areas are examined, and compared to practically solved but theoretically incomplete topics such as translucency, tone mapping, light source and BTF descriptions, and error metrics for image quality evaluation. The difference lies mainly in the difference between believable, correct, and predictive images. Also, for really realistic images modelling complexity is still an issue. Finally, some recent work on polarization and fluorescence is presented.
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    Industrial and Project Presentations
    (Eurographics Association, 2003) Lozano, Felipe A.; Serón, Francisco
    This volume contains the Industrial and Project Presentations for the 24th annual Conference of the European Association for Computer Graphics, EUROGRAPHICS´03, held in Granada, Spain, between the 1st and 6th of September 2003.
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    Visual Simulation of Lava Flows Employing Particle-based Approach
    (Eurographics Association, 2003) Oda, Yasuyuki; Ota, Shin; Tamura, Machiko; Fujimoto, Tadahiro; Muraoka, Kazunobu; Chiba, Norishige
    This video demonstrates our new particle-based method for visually simulating lava flows. Employing our developed particle-based simulation models of viscous fluid dynamics and heat transfer, this method realizes the visual features of lava flows: lava flows broaden like a fan form; the viscosity of lava changes according to its temperature; cooled lava solidifies into crust or new ground; the color of lava changes according to its temperature; crust is dark; lava of high temperature run out by breaking crust; etc.
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    Goniometric Diagram Mapping for Hemisphere
    (Eurographics Association, 2003) Havran, Vlastimil; Dmitriev, Kirill; Seidel, Hans-Peter
    Describing the light intensity over the hemisphere using a goniometric diagram is a common practice in the lighting industry and is prescribed for instance by IESNA (Illuminating Engineering Society of North America) standards. Goniometric diagram specifies the spatial distribution of the emitted power via a hemispherical surface subdivided by meridians and parallels. Similar tabulated representations are extensively used for complex bidirectional refiectance distribution functions (BRDF) that are difficult to approximate with analytical models. We present an approximative bicontinuous mapping from the unit square to a goniometric diagram on the hemisphere. This mapping has low distortion and the error of the approximation is low. The proposed mapping algorithm is obtained as a composition of four mappings. We outline its use for importance sampling of light sources described by goniometric diagrams and for the representation of BRDF.
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    Extending the Immediate Buckling Model to Triangular Meshes for Simulating Complex Clothes
    (Eurographics Association, 2003) Choi, Kwang-Jin; Ko, Hyeong-Seok
    The immediate buckling model is an essential element for simulating realistic cloth animations without introducing buckling instability. The original model is restricted to structured regular quad meshes, by which its use is severely limited. This paper extends the immediate buckling model from its original formulation in terms of regular quad meshes to irregular triangular meshes, thereby significantly increasing the applicability of the technique. Using a model that included cloth-specific buckling and anisotropy, we produced realistic animations of quite complex clothes.
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    Building Large Area Multi-Projector Displays
    (Eurographics Association, 2003) Brown, Michael S.; Majumder, Aditi
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    Low-Level Pixel Programming
    (Eurographics Association, 2003) Kraus, Martin
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    Evolutionary Design of BRDFs
    (Eurographics Association, 2003) Meyer-Spradow, Jennis; Loviscach, Joern
    The look of a non-transparent material is determined by its bidirectional reflection distribution function (BRDF). To design 3-D objects for example for games or animation films thus includes to design BRDFs. However, as functions defined on a four-dimensional domain, these form a vast space that is very difficult to explore interactively. Typically, the infinite number of degrees of freedom is reduced to a tractable handful of parameters by introducing simplified physical models or heuristic approximations such as Phongs. As the complexity of such approaches increases, they become difficult to master for a human operator. Even if many parameters are made accessible, an infinite variety of useful and/or interesting BRDFs remains hidden and inaccessible. We therefore propose a method of constructing BRDFs through genetic programming with a human operator making choices based on his or her preferences. With the pixel shader programmability of modern graphics cards this can be performed in real time.
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    GreenArt: A Tool for Non-Photorealistic Rendering of Plants and Trees
    (Eurographics Association, 2003) Campos, C.; Quirós, R.; Huerta, J.; Camahort, E.; Lluch, J.; Vivo, R.
    Plant and tree rendering is critical to many computer graphics applications, like interactive walkthroughs, architectural presentations, entertaintment and computer games. Current research focuses on realistic modeling and rendering of plants and trees. In this paper, however, we focus on non-photorealistic rendering of these models. We introduce GreenArt, a tool for a modeling and rendering non-photorealistic plants and trees. We present GreenArt’s functionality and capabilities and we show some examples of scenes generated using the system.
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    On the characterization of avatars in Distributed Virtual Worlds
    (Eurographics Association, 2003) Morillo, Pedro; Fernandez, Marcos; Orduna, Juan Manuel
    Current Distributed Virtual Environment (DVE) systems run simulations based on a server-network architecture, where the population of avatars should be properly assigned to the servers in the DVE. This goal, called partitioning problem, is a hot research problem in the field of networked 3D real time graphics. Some approaches have been proposed for resolving this problem, all of them based on a very basic model which describes the behaviour of an avatar in a virtual world. This model estimates the workload that a given avatar adds to its server as an independent and static value. In order to design scalable and accurate partitioning schemes we propose a new characterization of the workload generated by the avatars in the system. In this model, the workload is computed as a function of two factors: avatar movement rate and factor of presence. Evaluation results show that this proposed model correlates with real systems properly, providing an accurate abstraction of avatars for load balancing purposes.
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    Learning by doing: A Case for Constructivist 3D Virtual Learning Environment
    (Eurographics Association, 2003) Hu, Weihua; Zhu, Jiejie; Pan, Zhigeng; Li, Yanfeng; Ju, Cunhui
    This paper puts forward an idea that 3D virtual learning environment (3DVLE ) is an effective way to improve the feasibility of implementing constructivist learning theory in distance education. In this paper, we first give an outline of constructivist learning theory and analyze the relationship between 3DVLE and constructivist learning theory. Then we provide a learning and designing scheme on Web-based system. Finally, we briefly describe our 3DVLE system, present system architecture and some implementation considerations. The main goal of our system is to show the potential of designing constructivist virtual learning environment to enable an active, friendly learner-centered learning.
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    Large XML Document Manager and Visualizer
    (Eurographics Association, 2003) Merienne, J. P.; Jacquemin, C.
    This work presents an interactive Graphical User Interface used to display and manipulate collection of large XML documents. It relies on a geometrical model that combines hierarchical and sequential representations. In this interface, XML structures are displayed on an inclined plane in a 3D environment. This interface provides users with a visualization that speeds up searches in collection of documents through simple interaction techniques. Document browsing is facilitated through display space optimization and direct manipulation of document structures. Besides, this approach tries to take advantage of 3D by engaging human 3D spatial cognitive capabilities while using 2D interaction to not disrupt user's habits. A user evaluation for document access is reported that shows that our interface tends to be faster than 2D interface in data searching while taking advantage of the user's natural attraction to 3D interface.
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    Fast Marching farthest point sampling
    (Eurographics Association, 2003) Moenning, Carsten; Dodgson, Neil A.
    We introduce the Fast Marching farthest point sampling (FastFPS) approach for the progressive sampling of planar domains and curved manifolds in triangulated, point cloud or implicit form. By using Fast Marching methods2, 3, 6 for the incremental computation of distance maps across the sampling domain, we obtain a farthest point sampling technique superior to earlier point sampling principles in two important respects. Firstly, our method performs equally well in both the uniform and the adaptive case. Secondly, the algorithm is applicable to both images and higher dimensional surfaces in triangulated, point cloud or implicit form. This paper presents the methods underlying the algorithm and gives examples for the processing of images and triangulated surfaces. A companion report4 provides details regarding the application of the FastFPS algorithm to point clouds and implicit surfaces.
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    Realtime Ray Tracing and its use for Interactive Global Illumination
    (Eurographics Association, 2003) Wald, Ingo; Purcell, Timothy J.; Schmittler, Jörg; Benthin, Carsten; Slusallek, Philipp
    Research on realtime ray tracing has recently made tremendous advances. Algorithmic improvements together with optimized software implementations already allow for interactive frame rates even on a single desktop PC. Furthermore, recent research has demonstrated several options for realizing realtime ray tracing on different hardware platforms, e.g. via streaming computation on modern graphics processors (GPUs) or via the use of dedicated ray tracing chips. Together, these developments indicate that realtime ray tracing might indeed become a reality and widely available in the near future. As most of todays global illumination algorithms heavily rely on ray tracing, this availability of fast ray tracing technology creates the potential to finally compute even global illumination – the physically correct simulation of light transport – at interactive rates. In this STAR, we will first cover the different research activities for realizing realtime ray tracing on different hardware architectures – ranging from shared memory systems, over PC clusters, programmable GPUs, to custom ray tracing hardware. Based on this overview, we discuss some of the advanced issues, such as support for dynamic scenes and designs for a suitable ray tracing API. The third part of this STAR then builds on top of these techniques by presenting algorithms for interactive global illumination in complex and dynamic scenes that may contain large numbers of light sources. We believe that the improved quality and the increased realism that global illumination adds to interactive environments makes it a potential “killer application” for future 3D graphics.
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    Skeleton Subspace Deformation with Displacement Map
    (Eurographics Association, 2003) Liu, Feng; Liang, Ronghua; Ye, Dahai
    Skeleton Subspace Deformation (SSD) is a novel Free Form Deformation technology (FFD), and plays an important role in character animation, interactive game and other fields. In this paper, we present a new layered algorithm of SSD. After a preliminary conventional SSD, a displacement map is constructed based on the pose of the skeleton and the original surface. And then synthesize the displacement map with the defectively deformed surface and thus solve the inherent problems of conventional SSD, called "collapse" and "pinch". The experiment shows the effectiveness of this algorithm to create the realistic skin for an animated character.
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    PREFACE
    (Eurographics Association, 2003)
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    Beyond Image Quality Comparison
    (Eurographics Association, 2003) Bornik, Alexander; Cech, Peter; Ferko, Andrej; Perko, Roland
    We solve the problem of quantitative measuring of image quality, beyond the widely used MSE (mean square error) or even visual comparison. We combine eight feature-based and perceptually-oriented image quality metrics. The need for this comes from virtual archaeology, where various image acquisitions, antialiasing, multiresolution, image reconstruction or texturing methods produce very similar images. The proposed evaluation framework is suitable for any image quality decision-making, being not restricted to virtual archaeology. In particular, we compare a representative database of visually indistiguishable image pairs from different cameras, anisotropic texture filters and various antialiasing methods. For image registration we propose a modified video processing step. The results support the selection beyond commonly used visual comparison.
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    Persepolis: Recovering history with a handheld camera
    (Eurographics Association, 2003) Sainz, M.; Susin, A.; Cervantes, A.; Bagherzadeh, N.
    In this paper we present new improvements to our novel pipeline for image based modeling of objects using a camcorder. Our system takes an uncalibrated sequence of images recorded around a scene, it automatically recovers the underlying 3D structure and camera path and then a volumetric scene reconstruction is performed using a hardware accelerated voxel carving approach. Finally a triangular mesh is obtained and the available information from the images is combined to generate a full 3D photo-realistic reconstruction. As an application, we use this system to reconstruct parts of the archeological site of Persepolis (Iran).
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    Occlusion Culling for Image-Based Rendering withWarping
    (Eurographics Association, 2003) Soner, I. Sen; Atalay, Volkan
    The basic idea of the proposed algorithm is to reduce the number of depth pixels in Layer Depth Images (LDI) by culling the occluded ones before warping. The method combines the octree spatial subdivision concept with LDI concept, using the implicit geometry stored in depth pixels. The algorithm uses an octree to group depth pixels in a hierarchical way. The proposed algorithm is very effective when used in highly occluded scenes, and the density of the depth pixels should be high enough to get a high performance from the algorithm