A working group about Shapes


Fourth meeting : Wednesday 19th May 2010
11:00, Coriolis

Shape modelling via phase field higher-order active contours: application to road and river network extraction from remote sensing images.
by Aymen El Ghoul (Ariana team)

Third meeting : Monday 29th March 2010
11:00, Coriolis

Estimating suitable metrics for an empirical manifold of shapes, with application to human silhouettes
by Guillaume Charpiat (Pulsar team)

Second meeting : Tuesday 2nd March 2010
10:00, Euler bleu

Statistical models of currents for measuring the variability of anatomical curves and surfaces
by Stanley Durrleman (Asclepios team)

First meeting : Wednesday 17th February 2010
15:45, Coriolis room (Galois building)
Two presentations (announced here) will be were supposed to be given, and there will be drinks and cakes ;)

Introduction to the Shape Working Group : Shapes and related topics

Here is the e-mail I sent to announce the creation of this working group.


I would like to know who would be interested in the creation of a "working group" about shapes.

The notion of "shape" is rather intuitive, but usually difficult to model and to deal with, both mathematically and practically (it's not just a parameter in R^n). The concept of "shape" is wide, and can be understood differently by different people, depending on the problem of interest where shapes are involved. For example in computer vision, the word "shape", in its continuous interpretation, can stand for "the surface of the object of interest" (in 3D), or for "the (2D) contour of the object in an image", or a gesture (in a video); in its "patch-based" interpretation, it usually stands for a rough geometric model linking a few characteristic patches; shapes can be represented by polygons, meshes, splines, implicitely by level-sets, as zeros of polynomials, by local shape descriptors or small patches... One may be interested into global properties of the shape (principal modes of deformation), or into local ones (precise small deformations along a cell membrane). The concept of "shape" is not specific to computer vision, for instance in molecular biology, shapes may also be decisive for interaction properties.

The precise definition of shape spaces (What is a shape ?) is often an issue, as well as the metrics to consider (What is the distance between two shapes ?) and shape statistics (What is this object supposed to look like, given these previous examples ?). Comparing, optimizing, detecting or recognizing shapes are also important issues.

The aim of the working group would be to understand better the notion of "shape", to review its different aspects, possibly in order to try to unify them into a single framework.

I suggest starting with an overview of the state of the art, for example with a series of presentations by the participants about their own work, where they would emphasize what they mean by "shape", what the precise quantities of interest are (local/global deformations, patches, patterns, movement, curvature, topology, energy to be optimized, etc.), and of course the theories/algorithms/techniques they use/developped.

So far, a few persons from computer vision teams, namely Ariana, Asclepios and Pulsar, have already agreed to participate, but this working group is open to anyone who has to deal with the concept of "shape". Please e-mail me if you are interested, willing to participate actively or just to attend, so that I build a mailing-list and a presentation schedule.

Guillaume Charpiat
Pulsar project

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