Volume 16 (1997)

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Eurographics '97: Budapest, Hungary, September 4-8, 1997
(Blackwell Publishers Ltd and the Eurographics Association, 1997)
Impressions of SIGGRAPH '97: Los Angeles, August 3rd-8th 1997
(Blackwell Publishers Ltd and the Eurographics Association, 1997)
The Personal Interaction Panel - a Two-Handed Interface for Augmented Reality
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Szalavari, Zsolt; Gervautz, Michael
This paper describes the introduction of a new interaction paradigm to augmented reality applications. The everyday tool handling experience of working with pen and notebooks is extended to create a three dimensional two-handed interface, that supports easy-to-understand manipulation tasks in augmented and virtual environments. In the design step we take advantage from the freedom, given by our very low demands on hardware and augment form and functionality to this device. On the basis of examples from object manipulation, augmented research environments and scientific visualization we show the generality of applicability. Although being in the first stages implementation, we consider the wide spectrum of suitability for different purposes.
Polyhedral Surface Modeling with a Diffusion System
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Kuriyama, Shigeru; Tachibana, Keihachiro
This paper presents a method of generating polyhedral surfaces by using a diffusion system that calculates the positional and normal vectors on their vertices. The system generates smooth shapes that satisfy the minimum norm property, and can be extended to imitate the shape controls of curvature continuous surfaces with bias and tension parameters. The shape of a surface is determined by the stable state of nonlinear and local calculations between vertices, and is easily controlled by adding constraints on arbitrary vertices. Such bottom-up calculation of surfaces enhances flexibility in the interactive design of complicated free-form shapes.
A Flexible Architecture for Virtual Humans in Networked Collaborative Virtual Environments
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Sunday Pandzic, Igor; Lee, Elwin; Magnenat Thalmann, Nadia; Capin, Tolga K.; Thalmann, Daniel
Complex virtual human representation provides more natural interaction and communication among participants in networked virtual environments, hence it is expected to increase the sense of being together within the same virtual world. We present a flexible framework for the integration of virtual humans in networked collaborative virtual environments. A modular architecture allows flexible representation and control of the virtual humans, whether they are controlled by a physical user using all sorts of tracking and other devices, or by an intelligent control program turning them into autonomous actors. The modularity of the system allows for fairly easy extensions and integration with new techniques making it interesting also as a testbed for various domains from "classic" VR to psychological experiments. We present results in terms of functionalities, example applications and measurements of performance and network traffic with an increasing number of participants in the simulation.
Network Services
(Blackwell Publishers Ltd and the Eurographics Association, 1997)
EG Eurographics ' 97: Annual Conference of the European Association for Computer Graphics
(Blackwell Publishers Ltd and the Eurographics Association, 1997)
Calender of Events
(Blackwell Publishers Ltd and the Eurographics Association, 1997)
Join Now!
(Blackwell Publishers Ltd and the Eurographics Association, 1997)
Compression Domain Volume Rendering for Distributed Environments
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Lippert, L.; Gross, M.H.; Kurmann, C.
This paper describes a method for volume data compression and rendering which bases on wavelet splats. The underlying concept is especially designed for distributed and networked applications, where we assume a remote server to maintain large scale volume data sets, being inspected, browsed through and rendered interactively by a local client. Therefore, we encode the serverâ s volume data using a newly designed wavelet based volume compression method. A local client can render the volumes immediately from the compression domain by using wavelet footprints, a method proposed earlier. In addition, our setup features full progression, where the rendered image is refined progressively as data comes in. Furthermore, framerate constraints are considered by controlling the quality of the image both locally and globally depending on the current network bandwidth or computational capabilities of the client. As a very important aspect of our setup, the client does not need to provide storage for the volume data and can be implemented in terms of a network application. The underlying framework enables to exploit all advantageous properties of the wavelet transform and forms a basis for both sophisticated lossy compression and rendering. Although coming along with simple illumination and constant exponential decay, the rendering method is especially suited for fast interactive inspection of large data sets and can be supported easily by graphics hardware.
A Procedural Description of Geometric Textures by Spectral and Spatial Analysis of Profiles
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Dischler, J.-M.; Ghazanfarpour, D.
In this paper we describe a method for automatically generating procedural "geometric" textures, using a hybrid (spectral and spatial) analysis of profiles (ID curves). The profile describes a certain height variation for a certain abscissa. We call "geometric" textures a class of textures including "Bump" textures and "hypertextures". In dealing with this challenge (automatic synthesis), we introduce two new key ideas.The first is to compute efficiently a compact and procedural description of the texture, by using a spectral (Fourier transform based) and spatial (histogram based) analytical approach of profiles. The resulting texture is defined as a sum of elementary random functions. This sum is generated according to the profile. The procedural description allows the direct computation of the texture values at any co-ordinates in the Euclidean space and the stochastic aspect of the elementary functions also allows for the processing of highly random textures, with no considerable increase of computation time.The second key idea consists of using analysis in the particular and more complex case of geometric textures. For most analytical methods, underlying geometry is never considered. Using profiles as models, the resulting geometric texture is obtained by extending this profile to 2D or 3D space. The resulting texture directly matches the supplied 1D model. Hence, our method promises to be a very useful tool for easily and efficiently "modelling" any kind of geometric textures including rocks, bumps, peaks, fur, cotton and so on.
Orthogonal Decomposition of Non-Uniform Bspline Spaces using Wavelets
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Kazinnik, Roman; Elber, Gershon
We take advantage of ideas of an orthogonal wavelet complement to produce multiresolution orthogonal decomposition of nonuniform Bspline (NUB) spaces. The editing of NUB curves and surfaces can be handled at different levels of resolutions.Applying Multiresolution decomposition to possibly C1 discontinuous surfaces, one can preserve the general shape on one hand and local features on the other of the free-form models, including geometric discontinuities. The Multiresolution decomposition of the NUB tensor product surface is computed via the symbolic computation of inner products of Bspline basis functions. To find a closed form representation for the inner product of the Bspline basis functions, an equivalent interpolation problem is solved.As an example for the strength of the Multiresolution decomposition, a tool demonstrating the Multiresolution editing capabilities of NUB surfaces was developed and is presented as part of this work, allowing interactive 3D editing of NUB free-form surfaces.
An Analysis of Quasi-Monte Carlo Integration Applied to the Transillumination Radiosity Method
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Szirmay-Kalos, Laszlo; Foris, Tibor; Neumann, Laszlo; Csebfalvi, Balazs
This paper presents an enhanced transillumination radiosity method that can provide accurate solutions at relatively low computational cost. The proposed algorithm breaks down the double integral of the gathered power to an area integral that is computed analytically and to a directional integral that is evaluated by quasi-Monte Carlo techniques. Since the analytical integration results in a continuous function of finite variation, the quasi-Monte Carlo integration that follows the analytical integration will be efficient and its error can be bounded by the Koksma-Hlawka inequality. The paper also analyses the requirements of the convergence, presents theoretical error bounds and proposes error reduction techniques. The theoretical bounds are compared with simulation results.
Tunnel-Free Supercover 3D Polygons and Polyhedra
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Andres, Eric; Nehlig, Philippe; Francon, Jean
A new discrete 3D line and 3D polygon, called Supercover 3D line and Supercover 3D polygon, are introduced. Analytical definitions are provided. The Supercover 3D polygon is a tunnel free plane segment defined by vertices and edges. An edge is a Supercover 3D line segment. Two different polygons can share a common edge and if they do, the union of both polygons is tunnel free. This definition of discrete polygons has the "most" properties in common with the continuous polygons. It is particularly interesting for modeling of discrete scenes, especially using tunnel-free discrete polyhedra. Algorithms for computing Supercover 3D Lines and Polygons are given and illustrated.
Synthesizing Novel Views from Unregistered 2-D Images
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Havaldar, Parag; Lee, Mi-Suen; Medioni, Gerard
Synthesizing the image of a 3-D scene as it would be captured by a camera from an arbitrary viewpoint is a central problem in Computer Graphics. Given a complete 3-D model, it is possible to render the scene from any viewpoint. The construction of models is a tedious task. Here, we propose to bypass the model construction phase altogether, and to generate images of a 3-D scene from any novel viewpoint from prestored images. Unlike methods presented so far, we propose to completely avoid inferring and reasoning in 3-D by using projective invariants. These invariants are derived from corresponding points in the prestored images. The correspondences between features are established off-line in a semi-automated way. It is then possible to generate wireframe animation in real time on a standard computing platform. Well understood texture mapping methods can be applied to the wireframes to realistically render new images from the prestored ones. The method proposed here should allow the integration of computer generated and real imagery for applications such as walkthroughs in realistic virtual environments. We illustrate our approach on synthetic and real indoor and outdoor images.
A Multiscale Approach to Integrated Volume Segmentation and Rendering
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Westermann, Rudiger; Ertl, Thomas
A number of techniques have been proposed for rendering volumetric scalar data sets. Techniques have also been proposed for analyzing the three dimensional information contents of the underlying domain, but traditionally the data analysis part is left as a post-processing step which only involves the rendered two dimensional images. In this paper, we describe a visualization method for scalar volume data which integrates explicit knowledge of the underlying domain into the rendering process. The key of this approach lies in a hierarchical description of the discrete signal, which is decomposed into a sequence of multiscale representations. We describe a technique for the analysis of structures within the data. This allows for the segmentation and classification of the relevant features and can be used to improve their visual sensation. We also address the problem of accelerating the final rendering pass by integrating the extracted object space information into the ray traversal process.
Computing Volumes of Solids Enclosed by Recursive Subdivision Surfaces
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Peters, Jorg; Nasri, Ahmad
The volume of a solid enclosed by a recursive subdivision surface can be approximated based on the closed-form representation of regular parts of the subdivision surface and a tight estimate of the local convex hull near extraordinary points. The approach presented is efficient, i.e. non-exponential, and robust in that it yields rapidly contracting error bounding boxes. An extension to measuring higher-order moments is sketched.
An Efficient Code-Based Voxel-Traversing Algorithm
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Zalik, Borut; Clapworthy, Gordon; Oblonsek, Crtomir
Calendar of Events
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Greiner, Gunther
Book Reviews
(Blackwell Publishers Ltd and the Eurographics Association, 1997) Howard, Toby

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