Multi-view 3D retrieval using silhouette intersection and multi-scale contour representation

We describe in this paper two methods for 3D shape indexing and retrieval that we apply on two data collections of the SHREC - SHape Retrieval Contest 2007: Watertight models and 3D CAD models. Both methods are based on a set of 2D multi-views after a pose and scale normalization of the models using PCA and the enclosing sphere. In all views we extract the models silhouettes and compare them pairwise. In the first method the similitude measure is obtained by integrating on the pairs of views the difference between the areas of the silhouettes union and the silhouettes intersection. In the second method we consider the external contour of the silhouettes, extract their convexities and concavities at different scale levels and build a multiscale representation. The pairs of contours are then compared by elastic matching achieved by using dynamic programming. Comparisons of the two methods are shown with their respective strengths and weaknesses

Mécanismes économiques à l’œuvre dans les espaces ruraux

Cet article cherche à appréhender les espaces ruraux au travers des mécanismes économiques qui rendent compte de la dispersion dans l’espace des populations et des activités, tels qu’ils sont pris en compte par l’économie spatiale. Deux catégories d’espaces non urbains peuvent alors être distinguées : des espaces ruraux périphériques des villes, où dominent les mécanismes responsables de la dispersion relative de la population urbaine ; des espaces ruraux placés hors influence urbaine et organisés autour de petits pôles d’emploi, où les forces de dispersion des activités sont responsables des dynamiques locales. Le Zonage en aires urbaines et en aires d’emploi de l’espace rural (ZAUER) proposé par l’INSEE rend compte de cette dichotomie de l’espace rural. Il s’avère cependant pertinent de le combiner au découpage en « bassins de vie », également proposé par l’INSEE, en vue de rendre compte des principales logiques de l’intervention publique en milieu rural.This paper suggests definitions of rural areas based on spatial economics theory. We focus on mechanisms that are able to explain the spatial dispersion of population and activities. Two categories of non urban areas are distinguished: on one hand, rural surrounding cities, where changes come from population spread mechanisms; on the other hand, rural areas without urban influence, structured by small employment centres. The French delineation, called “Zonage en aires urbaines et en aires d’emploi de l’espace rural” (ZAUER), takes into account this distinction and allows us to give a relevant description of their development features. It seems to be useful to combine it with another French delineation in “Bassins de vie” in order to understand the main logics of rural development policies

Tatouage fragile d'objets 3D triangulés

Nous proposons une nouvelle méthode de tatouage fragile adaptée au marquage des objets maillés tridimensionnels et triangularisés, basée sur la modification d'invariants géométriques. Nous utilisons une localisation compacte indexée de l'information cachée, et nous vérifions la robustesse du schéma global de tatouage face à l'attaque de coupe

Compensating Printer Modulation Transfer Function in Spatial and Color Adaptive Rendering Workflows

Experiments have shown that the quality of printed images depends on the capacity of the printing system to accurately re- produce details. We propose to improve the quality by compensat- ing for the Modulation Transfer Function (MTF) of the printing system. The MTF of the printing system is measured using a mod- ified version of the method proposed by Jang and Allebach [1]. Then the MTF is adaptively compensated in the Fourier domain, depending on the frequency and on the local mean value. This compensation is included within our mathematical framework for Spatial and Color Adaptive Gamut Mapping Algorithms. Results of a category judgment experiment show significant improvement as the printed MTF compensated images obtain the best scores

Measurement of printer MTFs

In this paper we compare three existing methods to measure the Modulation Transfer Function (MTF) of a printing system. Although all three methods use very distinct approaches, the MTF values computed for two of these methods strongly agree, lending credibility to these methods. Additionally, we propose an improvement to one of these two methods, initially proposed by Jang & Allebach. We demonstrate that our proposed modification improves the measurement precision and simplicity of implementation. Finally we discuss the pros and cons of the methods depending on the intended usage of the MTF