Issue 4

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    Eurographics 2002
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Scheel, Annette
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    An Efficient Method for Rendering Underwater Optical Effects Using Graphics Hardware
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Iwasaki, Kei; Dobashi, Yoshinori; Nishita, Tomoyuki
    The display of realistic natural scenes is one of the most important research areas in computer graphics. Therendering of water is one of the essential components. This paper proposes an efficient method for renderingimages of scenes within water. For underwater scenery, the shafts of light and caustics are attractive and importantelements. However, computing these effects is difficult and time-consuming since light refracts when passingthrough waves. To address the problem, our method makes use of graphics hardware to accelerate the computation.Our method displays the shafts of light by accumulating the intensities of streaks of light by using hardware colorblending functions. Making use of a Z-buffer and a stencil buffer accelerates the rendering of caustics. Moreover,by using a shadow mapping technique, our method can display shafts of light and caustics taking account ofshadows due to objects.ACM CSS: I. 3.1 Computer Graphics-Hardware Architecture, I. 3.7 Computer Graphics-Three-DimensionalGraphics and Realism
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    Hierarchical Impostors for the Flocking Algorithm in 3D
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) O'Hara, Noel
    The availability of powerful and affordable 3D PC graphics boards has made the rendering of rich immersiveenvironments possible at interactive speeds. The scene update rate and the appropriate behaviour of objects withinthe world are central to this immersive feeling. This paper is concerned with the behaviour computations involvedin the flocking algorithm, which has been used extensively to emulate the flocking behaviour of creatures found innature. The main contribution of this paper is a new method for hierarchically combining portions of the flocksinto groups to reduce the cost of the behavioural computation, allowing far larger flocks to be updated in real-timein the world.ACM CSS: I.3.7 Three-Dimensional Graphics and Realism-Animation
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    Levels of Detail for Crowds and Groups
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) O'Sullivan, C.; Cassell, J.; Vilhjalmsson, H.; Dingliana, J.; Dobbyn, S.; McNamee, B. and Peters, C. and Giang, T.
    Work on levels of detail for human simulation has occurred mainly on a geometrical level, either by reducing the numbers of polygons representing a virtual human, or replacing them with a two-dimensional imposter. Approaches that reduce the complexity of motions generated have also been proposed. In this paper, we describe ongoing development of a framework for Adaptive Level Of Detail for Human Animation (ALOHA), which incorporates levels of detail for not only geometry and motion, but also includes a complexity gradient for natural behaviour, both conversational and social.ACM CSS: I.3.7 Three-Dimensional Graphics and Realism-Animation
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    Eurographics Ireland 2002 Workshop
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) O'Sullivan, Carol
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    New Eurographics Fellow
    (Blackwell Publishers, Inc and the Eurographics Association, 2002)
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    An algorithm for line clipping against a polygon based on shearing transformation
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Huang, Y. Q.; Liu, Y. K.
    Line clipping against a polygon is widely used in computer graphics such as the hidden line problem. A newline-clipping algorithm against a general polygon is presented in this paper. The basic idea of this algorithm is tochange the line to be clipped into a horizontal line by shearing transformation. Then each edge of the polygonalwindow is transformed by a shearing transformation with the same parameters as those used to the line. Eachedge of the polygon is processed against a horizontal line, which makes the clipping process simpler. The result inthis paper shows that less calculation is needed for the new algorithm with a higher speed compared to existingalgorithms.
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    Join Now!
    (Blackwell Publishers, Inc and the Eurographics Association, 2002)
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    Eurographics Spain 11th Conference
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Isern, Jordi Regincos
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    Siggraph 2002
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Laycock, Stephen D.; Laycock, Robert G.
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    Adaptive Zooming in Web Cartography
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Cecconi, Alesandro; Galanda, Martin
    Beyond any doubt much of the current web mapping and web GIS applications lack cartographic quality. Thereasons aren't only the technical limitations related to Internet delivery, but also the neglect of one of the maincartographic principles of digital mapping, namely adaptive zooming. Adaptive zooming describes the adjustmentof a map, its contents and the symbolization to target scale in consequence of a zooming operation. The approachdescribed in this paper proposes the combination of two commonly known concepts: on the one hand levelsof detail (LoD) for those object classes, that require high computational cost for the automated generalizationprocess (e.g. buildings, road network); on the other hand an on-the-fly generalization for those object classeswhich can be generalized by less complex methods and algorithms (e.g. rivers, lakes). Realizing such interactiveand dynamic concept for web mapping requires the use of vector based visualization tools. The data format bestmeeting the criteria is the W3C standard Scalable Vector Graphics (SVG). Thus, it has been used to implementthe presented ideas in a prototype application for topographic web mapping based on the landscape modelVECTOR25 of the Swiss Federal Office of Topography.
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    SVG Linearization and Accessibility
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Herman, Ivan; Dardailler, Daniel
    The usage of SVG (Scaleable Vector Graphics) creates new possibilities as well as new challenges for theaccessibility of Web sites. This paper presents a metadata vocabulary to describe the information content ofan SVG file geared towards accessibility. When used with a suitable tool, this metadata description can helpin generating a textual ('linear') version of the content, which can be used for users with disabilities or withnon-visual devices.Although this paper concentrates on SVG, i.e. on graphics on the Web, the metadata approach and vocabularypresented below can be applied in relation to other technologies, too. Indeed, accessibility issues have a muchwider significance, and have an effect on areas like CAD, cartography, or information visualization. Hence, theexperiences of the work presented below may also be useful for practitioners in other areas.ACM CSS: I.3.4 Graphics Utilities-Graphics Packages, I.3.6 Methodology and Techniques-Graphics datastructures and data types, Standards, K.4.2 Social Issues-Assistive technologies for persons with disabilities
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    Computer Graphics forum
    (Blackwell Publishers, Inc and the Eurographics Association, 2002)
    Eurographics and Computer Graphics forum offer a variety of services on the international networks. You can find details ofour latest events, how to prepare a paper for the conference or for the journal and much more besides. This information can beaccessed mainly through the EG website but we also offer some support for ftp and mail server access.
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    Feature Model Visualization
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Bronsvoort, Willem F.; Bidarra, Rafael; Noort, Alex
    Feature modelling is now the predominant way of modelling products. Feature visualization is an important aspect here that can still be considerably improved. In this paper, an integrated way of visualizing feature models is presented, using new techniques for both the geometry and the structure of models. For the geometry of feature models, techniques are presented to visualize a selected subset of form features in a way that clearly distinguishes them from the rest of the model, as well as functional information such as closure faces of subtractive form features. For the structure of features models, techniques are presented to visualize several types of graphs. The different visualization techniques are used in an integrated way. Implementation of some of the techniques requires a non-manifold representation of the geometry of the feature model. This representation, and some other implementation aspects, are briefly described. Throughout the paper, numerous examples of images of feature models are given which show that the new visualization techniques can indeed improve the effectiveness of feature modelling.ACM CSS: I.3.7 Three-Dimensional Graphics and Realism-visible line/surface algorithms, J.6 Computer-AidedEngineering-feature modelling
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    Visualizing Crowds in Real-Time
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Tecchia, Franco; Loscos, Celine; Chrysanthou, Yiorgos
    Real-time crowd visualization has recently attracted quite an interest from the graphics community and, asinteractive applications become even more complex, there is a natural demand for new and unexplored applicationscenarios. However, the interactive simulation of complex environments populated by large numbers of virtualcharacters is a composite problem which poses serious difficulties even on modern computer hardware. In thispaper we look at methods to deal with various aspects of crowd visualization, ranging from collision detectionand behaviour modeling to fast rendering with shadows and quality shading. These methods make extensive useof current graphics hardware capabilities with the aim of providing scalability without compromising run-timespeed. Results from a system employing these techniques seem to suggest that simulations of reasonably complexenvironments populated with thousands of animated characters are possible in real-time.ACM CSS: I.3.7 Three-Dimensional Graphics and Realism-Animation
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    Author Index Volume 21 (2002)
    (Blackwell Publishers, Inc and the Eurographics Association, 2002)
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    Erratum: Artistic Surface Rendering Using Layout of Text
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Surazhsky, Tatiana; Elber, Gershon
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    A Spoken Dialogue System for Navigation in Non-Immersive Virtual Environments
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) McNeill, M.D.J.; Sayers, H.; Wilson, S.; Mc Kevitt, P.
    Navigation is the process by which people control their movement in virtual environments and is a corefunctional requirement for all virtual environment (VE) applications. Users require the ability to move, controllingorientation, direction of movement and speed, in order to achieve a particular goal within a VE. Navigation israrely the end point in itself (which is typically interaction with the visual representations of data) but applicationsoften place a high demand on navigation skills, which in turn means that a high level of support for navigationis required from the application. On desktop systems navigation in non-immersive systems is usually supportedthrough the usual hardware devices of mouse and keyboard. Previous work by the authors shows that many usersexperience frustration when trying to perform even simple navigation tasks - users complain about getting lost,becoming disorientated and finding the interface 'difficult to use'. In this paper we report on work in progressin exploiting natural language processing (NLP) technology to support navigation in non-immersive virtualenvironments. A multi-modal system has been developed which supports a range of high-level (spoken) navigationcommands and indications are that spoken dialogue interaction is an effective alternative to mouse and keyboardinteraction for many tasks. We conclude that multi-modal interaction, combining technologies such as NLP withmouse and keyboard may offer the most effective interaction with VEs and identify a number of areas where furtherwork is necessary.ACM CSS: I.3.6 Computer Graphics Methodology and Techniques-Interaction and Techniques, I.3.7 Three-DimensionalGraphics and Realism-Virtual Reality, I.2.7 Natural Language Processing-Speech Recognitionand Synthesis
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    Editorial
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Duke, David; Scopigno, Roberto
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    A Skeleton-based Approach for Detection of Perceptually Salient Features on Polygonal Surfaces
    (Blackwell Publishers, Inc and the Eurographics Association, 2002) Hisada, Masayuki; Belyaev, Alexander G.; Kunii, Tosiyasu L.
    The paper presents a skeleton-based approach for robust detection of perceptually salient shape features. Given ashape approximated by a polygonal surface, its skeleton is extracted using a three-dimensional Voronoi diagramtechnique proposed recently by Amenta et al. [3]. Shape creases, ridges and ravines, are detected as curvescorresponding to skeletal edges. Salient shape regions are extracted via skeleton decomposition into patches.The approach explores the singularity theory for ridge and ravine detection, combines several filtering methodsfor skeleton denoising and for selecting perceptually important ridges and ravines, and uses a topological analysisof the skeleton for detection of salient shape regions.ACM CSS: I.3.5 Computational Geometry and Object Modeling