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Equipe de recherche MIRAGES

Rapports d'activité

Overall Objectives

The MIRAGES project research activity is oriented towards the development of model-based approaches with feedback. It is the way that MIRAGES has chosen to develop Computer Vision/Computer Graphics collaboration techniques since 1984 when this approach was chosen by the members of the project.Its activity is concentrated on the manipulation of 3D objects in image sequences with an application domain oriented towards new services (related to those 3D objects) which will appear in future communication networks as well as new products for objects customization. Our research activity is carried out in three directions:

First Research Activity: 3D Analysis of Image Sequences

We are interested in the determination of properties such as structure, movement and photometry of 3D objects (especially human beings) in image sequences. Our approach differs from traditional methods as we mainly look for feedback model-based methods to guide the analysis. The main problems we are handling are:

3D object tracking in image sequences when the geometry of the object is known but its movement has to be determined. Both rigid, articulated and deformable objects are considered: particularly human body and face tracking.

Interactive, semi-automatic and automatic camera calibration: Here, we use 3D object models (very often, generic models) as calibration tools, in order to perform calibration. Calibration is necessary for 3D model specification.

Automatic and semi-automatic object model specification: starting from a generic model of an object (for example a human body or a face) and an image sequence, this task consists in constructing the specific model which will be used for tracking in image sequences (see above).

Collaboration is carried out with Electronic Arts (Vancouver, Canada), the major video game company worldwide, interested by our 3D face expression tracker, with AXIATEC (a French company interested in products customization) on face modeling. The Golf-STREAM contract (RIAM funding) started in June 2002 in collaboration with the French Symah Vision production company. The task was to study complete human body 3D tracking and more specifically professional golfers from image sequences in order to allow them to improve their technique and also enrich journalists comments on television broadcasts of professional golf tournaments. This task was not entirely accomplished during the period of the contract but we are continuing this research with our own funding and in collaboration with NTU. We hope to extend this work to other types of applications such as video-surveillance, tele-conferencing, while mixing real and synthetic images.

Second Research Activity: 3D Garment Simulation

The second research direction is the creation and deformation of soft objects, particularly non linear and hysteretic ones. Presently, our research activity is applied to the 3D simulation of garments. In this research area, we are mainly studying:

The control of the mechanical properties of soft 2D structures (like textile materials) modeled by mass/spring systems, or using meshless approaches.

The automatic construction of garments from 2D patterns around a human body modeled as an articulated mechanical system.

Potential applications are realistic synthesis of 3D garments on 3D numerical mannequins applied to future e-commerce of garments for the textile industry. We obtained an important funding source from ANR for this application.

Third Research Activity: 3D cities modeling and reconstruction

This research direction is related to an activity in the TERRA NUMERICA French competitivity network coordinated by Thalès. The aim of this research is to produce a 3D representation from Ile De France from aerial photos (produced by IGN) and from videos and 3D scans obtained from cars which are sensing facades from the ground. The activity of Mirages consists in using an analysis/synthesis approach to replace the raw data obtained from our partners as well as building models in order to replace raw data by compact 3D representations suitable for new services.

"TERRA NUMERICA" is a federated project of the French competitive cluster "Cap Digital" focused on Digital Content Creation. TERRA NUMERICA has been labeled on February, 2006 and is funded by the French Ministry of Industry and the territorial institutions of the Ile-de-France area. Dedicated to the modeling and visualization of large urban areas, this collaborative project gathers 17 industrial and academic partners under the governance of Thalès for an overall budget of 15M euros. Planned over a 3 years period, this project started on January 2007. Within this project, the Mirages team is responsible for the coordination and technical direction of technological developments targeting the 3D reconstruction of geo-specific buildings : Work Package WP3.1.4 also gathering TRIMBLE, IGN, THALES, ENSMP-CMM, ENST.

Modeling of large urban areas drains significant stakes both from an economical (developement of new geo-localized services targeting mass and business markets segments in the field of city planning, territory management, tourism, security/defense simulations) and societal (control of numerical heritage) perspectives. Yet, focusing on buildings, the definition of realistic visual representations implied in such numerical model predominantly comes down to several man years of labor when dealing with large-scale reconstruction areas. The work package 3.1.4 of TERRA NUMERICA aims to develop and integrate new technologies fulfilling this problematic. Based upon the analysis of various acquisitions and on the formalization of architectural a priori, these developments are intended to automate the reconstruction process while certifying the compliancy and fidelity of a 3D representation both at the geometric and semantic level.

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