Vol. 60, n° 11-12, November-December 2005
Content available on Springerlink

Guest editors
Mohamed Daoudi, GET/Télécom Lille 1, France
Gérard Eude, France Télécom R&D, France

Foreword

Mohamed Daoudi, Gérard Eude

High rate compression of CAD meshes based on subdivision inversion

Guillaume LAVOUÉ, Florent DUPONT, Atilla BASKURT

LIRIS UMR 5205 CNRS ; 43, bd du 11 novembre, 69622 Villeurbanne Cedex, France

Abstract In this paper we present a new framework, based on subdivision surface approximation, for efficient compression and coding of 3D models represented by polygonal meshes. Our algorithm fits the input 3D model with a piecewise smooth subdivision surface represented by a coarse control polyhedron, near optimal in terms of control points number and connectivity. Our algorithm, which remains independent of the connectivity of the input mesh, is particularly suited for meshes issued from mechanical or cad parts. The found subdivision control polyhedron is much more compact than the original mesh and visually represents the same shape after several subdivision steps, without artifacts or cracks, like traditional lossy compression schemes. This control polyhedron is then encoded specifically to give the final compressed stream. Experiments conducted on several cad models have proven the coherency and the efficiency of our algorithm, compared with existing methods.

Key words Computer aided design, Three dimensional model, Information compression, Grid pattern, Polygon, Visualization, Approximation, Surface.

Augmented multiresolution Reeb graph for 3D models indexing

Tony TUNG, Francis SCHMITT

GET/Télécom Paris, CNRS UMR 5141 – 46, rue Barrault, 75634 Paris Cedex 13, France

Abstract This article presents an indexing method for 3D mesh models applied to shape and appearance similarity retrieval in database of 3D objects. The approach relies on the multiresolution Reeb graph matching method proposed by Hilaga et al. in 2001 [1]. In our framework, we consider 3D mesh models of various geometrical complexity, different resolution, and sometimes textured. The original approach, based on the 3D object topology, is not accurate enough to obtain satisfying matching. Therefore we propose to reinforce the topological consistency conditions of the matching and to merge within the graph geometrical and visual information to improve the matching and the calculation of the similarity between models. Besides, all these new attributes can be freely weighted to fit the user requirements for object retrieval. We obtain a flexible multiresolutional and multicriteria representation that we called augmented Multiresolution Reeb Graph (aMRG). The approach has been tested and compared with other methods. It reveals very performant for the retrieval and the classi- fication of similar 3D shapes.

Keywords Three dimensional model, Indexing, Multiresolution analysis, Information retrieval, Grid pattern, Database, Geometrical shape, Graph, Similitude.

A framework for 3D CAD models retrieval from 2D images

Tarik FILALI ANSARY, Jean-Philippe VANDEBORRE, Mohamed DAOUDI

GET/INT/ENIC Télécom Lille 1, rue G. Marconi, cité scientifique ; 59658 Villeneuve d’Ascq cedex, France

Abstract The management of big databases of three-dimensional models (used in CAD applications, visualisation, games, etc.) is a very important domain. The ability to characterise and easily retrieve models is a key issue for the designers and the final users. In this frame, two main approaches exist: search by example of a three-dimensional model, and search by a 2D view or photos. In this paper, we present a novel framework for the characterisation of a 3D model by a set of views (called characteristic views), and an indexing process of these models with a Bayesian probabilistic approach using the characteristic views. The framework is independent from the descriptor used for the indexing. We illustrate our results using different descriptors on a collection of three-dimensional models supplied by the car manufacturer Renault. We also present our results on retrieval of 3D models from a single photo.

Keywords Three dimensional model, Indexing, Image, Computer aided design, Database.

Retrieval by content similarity of 3D Models using spin images

Alberto DEL BIMBO, Pietro PALA

Dipartimento Sistemi e Informatica, Università degli studi di Firenze – via S. Marta, 3, 50 139 Firenze, Italy

Abstract Recently, there has been a growing interest in the development of solutions enabling retrieval by content of 3D graphical models. One of the main problems that researchers have addressed is that of finding suitable and robust representations of features that make it possible to describe appearance and structure of 3D models without compromising their discriminative power in the task of similarity matching. Important properties that are expected from model representations are Descriptive power, Conciseness, Invariance under transformations and Insensitiveness to modifications and degeneracies. In this paper we describe an approach to 3D object representation based on spin images, and discuss its properties and performance in comparison with some of the approaches reported in the literature.

Keywords Three dimensional model, Geometrical shape, Similitude, Database, Comparative study.

On the application of 3D technologies to the framework of cultural heritage

Eric PAQUET*, Herna L. VIKTOR**

*Visual Information Technology, National Research Council – M50 Montreal Road, Ottawa, K1A 0R6, Canada
** SITE, University of Ottawa – 800 King Edward Ave., Ottawa, K1N 6N5, Canada

Abstract Unrestricted access to both historical and archaeological sites is highly desirable from both a research and a cultural perspective. With the recent developments in 3D scanner technologies and photogrammetric techniques, it is now possible to acquire and create accurate models of such sites. Through the process of virtualisation, numerous 3D collections are created that need to be visualised, indexed and eventually characterized. This paper presents a mobile virtual environment designed for the visualization of photorealistic high-resolution virtualised cultural heritage scenes and artefacts. In addition, it is shown how it is possible to describe and index the texture and the 3D shape of these artefacts with compact support feature vectors. A data mining system, based on these vectors, allows the characterization and the exploration of the 3D collections, through cluster analysis.

Keywords Three dimensional model, Culture, History, Archeology, Photogrammetry, Database, Visualization, Indexing, Information retrieval, Cluster analysis.

PBTree – A new progressive and hierarchical representation for network-based navigation in densely built urban environments

Jérôme ROYAN, Christian BOUVILLE, Patrick GIOIA

France Telecom R&D, 4 rue du Clos Courtel, 35510 Cesson-Sévigné, France

Abstract This paper describes a novel progressive and hierarchical representation for densely built urban areas. It aims at navigating through huge urban environments with network-based client-server systems. Thanks to this method, navigation is no longer limited to walkthrough, but allows flying over the city. This can be achieved through a set of dedicated algorithms allowing the decomposition of city into a multi resolution representation. The method effi- ciently exploits the fact that automated modelling technologies of urban scenes are generally based on the processing of 2D data (video, photographs, cadastral map, …), to model 2D1/2 data (building footprint, height, altitude, …) which turns out to be more compact. From this pre-computed representation of buildings, the server progressively sends the perceptible details to the client for all the regions visible from a given viewpoint.

Keywords Three dimensional model, Three dimensional representation, Urban area, Hypermedia navigation, Interactive mode, Multiresolution analysis, Visualization, Client-server architecture.

Open Topics

Application of the simulated annealing to the synthesis of ring printed antennas arrays

Méhadji ABRI, Noureddine BOUKLI-HACENE, Fethi Tarik BENDIMERAD

Laboratoire de Télécommunications, Département d’Electronique, Faculté des Sciences de l’Ingénieur, Université Abou-Bekr Belkaïd – BP 230, Pôle Chetouane, 13 000 Tlemcen, Algérie

Abstract This publication consists of an analysis and a synthesis by the amplitude law of linear and planar ring printed antennas array. The analysis of the structure is based on the modified cavity model which allows taking into account the fringing fields effects. The synthesis problem is solved by the simulated annealing method based on a random process research controlled by temperature parameter. The feeding network amplitude permitting to produce an optimal radiation pattern is then given. Various synthesis results for linear and planar arrays are presented.

Keywords Antenna array, Printed antenna, Cavity resonator, Annular resonator, Antenna synthesis, Simulated annealing, Radiation pattern.

A methodology to measure the security level of a data provider network

Cédric LLORENS*,**, Ahmed SERHROUCHNI*

* GET/Télécom Paris, LTCI-UMR 5141 CNRS – 46, rue Barrault 75013 Paris, France.
** Equant-Network Security – 18, rue Paul Lafarge, 92 904 Paris La Défense 10 cedex, France

Abstract This paper presents a methodology to measure the security level of a data provider network. This methodology consists of defining a network security policy, of checking the network security policy through a reverse engineering analysis performed on the network devices configurations, of building an event tree based on the vulnerabilities found, of quantifying the event tree probabilities, and of computing the resulting risk.

Keywords Telecommunication network, Multiple service network, Risk, Communication security, Packet transmission, Internet protocol, Availability, Stochastic method, Policy, System evaluation.

Email automatic filtering an adaptive and multi-level approach

Omar NOUALI*,**, Philippe BLACHE**

* Laboratoire de logiciels de base, CE.R.I.S.T., rue des 3 frères Aïssiou, Ben Aknoun, Alger, 16 030, Algérie
** LPL – Université de Provence, 29, Av. Robert Schuman, F-13621 Aix-en-Provence, France

Abstract This article proposes an electronic mail system with several levels of filtering: a simple filtering based on contents analysis of the message header fields; a Boolean filtering based on the existence or not of key words in the body of the courriel; a Vectorial filtering based on weight of key words; a linguistic filtering based on the linguistic properties characterizing structure and contents of courriel. We propose an adaptive solution by using an automatic learning method which allows the filtering system to learn from data, to modify its knowledge and to adapt to user’s interests. Moreover, we use a lexical network to improve message representation and to take into account the semantic aspect.

Keywords: Electronic mail, Filtering, Adaptive method, Machine learning, Linguistic model, Spam message.

Modeling long term memory effects in microwave power amplifiers for system level simulation

Arnaud SOURY, Edouard NGOYA

IRCOM-CNRS Institute, University of Limoges – 123 av. Albert Thomas, 87060 Limoges, France

Abstract Accurate and dynamic behavioral models of SSPAs become of prime importance in system level analysis and design of modern communication and detection systems. This paper describes a new method to characterize and reproduce nonlinear memory effects in behavioral models of SSPAs. We highlight, in a first section, the detailed mathematical development, whose the starting point is the Volterra series expansion, and ends to the nonlinear impulse response notion. The new model extraction relies on envelope transient simulations or timedomain measurements of complex envelopes at extern DUT reference accesses. This modeling technique is simple and enables a good prediction of nonlinear memory effects and especially long term memory effects and nonlinear transient behaviors. Simulations and measurements based extractions of this model are presented through significant amplifier examples.

Keywords Microwave amplifier, Power amplifier, Modeling, Long term, Memory effect, Dynamic model, System simulation, Non linear effect, Volterra series.