Jean-Daniel Boissonnat, a life of research dedicated to geometry

© inria / Photo G. Scagnelli

Varied and sometimes far-removed applications like 3D mapping of cities, medical imaging of the heart, numerical modelling of cars and cinematographic creations have benefited over recent years from the fruit of research into geometry and computational topology. Jean-Daniel Boissonnat is now a director of research of the highest grade at Inria Sophia Antipolis - Méditerranée research centre. He has guided the development of this emerging digital discipline, of which he is today one of the experts.

A pioneering scientific discipline

"I began my career at Inria in the Paris centre in 1980. At the time, two areas facilitated the emergence of computational geometry. The first was Information Technology, in which the need for ways of sorting, comparing and reconstituting numerical objects was beginning to be felt. The second was the development of new 3D sensors invented at Inria, which simplified the measurement of geometrical objects compared with the techniques of the time. The goal then was to develop algorithms that utilised these data to reconstitute surfaces. " This task meant finding answers to various theoretical questions, such as determining the two closest points within a cluster of points. "A seemingly simple geometrical problem led to many of the algorithmic solutions from new research."

Initially, the research was mathematical and mainly concerned the development of next-generation algorithms to simply and effectively solve the problems posed. It also aided in the creation of the CGAL Library (Computational Geometry Algorithms Library) which coded and implemented these geometrical algorithms. "CGAL is widely used today and applied in different fields, for instance in scientific computing to generate the meshes used by industrial engineers, and in robotics for planning the motion trajectory of articulated systems."

A researcher and innovative spirit

The development of CGAL over many years was supported by European funding and stimulated the creation of GeometryFactory, a startup founded in 2003 by Andreas Fabri, to expand the library's developments, maintain it and open it to new users. Nowadays, a dozen or so engineers are maintaining CGAL by offering a range of consultancy and service solutions to various clients like businesses, local authorities and research centres.

As a researcher, Jean-Daniel has constantly reshaped his discipline. Having won a European Research Council grant, he undertook a new project in 2014. GUDHI (Geometry Understanding in Higher Dimensions) aimed to expand proven, effective methods to 3D applications. "We wanted to find methods for solving problems of a larger scale, like those in physics which incorporate time and space, or those in image analysis which entail processing a great quantity of data, often from a few million data to hundreds of millions. This 'dimensional challenge' is a current topic in data science."

Passing on knowledge and experience

Although today this research is being applied in many scientific fields, Jean-Daniel himself is now working to share this knowledge through teaching and published works. It is with gratitude that he looks back on the path he has trodden.

I've been very lucky in my career! Like working with students or colleagues of the highest level, or receiving European grants. At the beginning of my career, many scientists conducted their research in the United States, but European funding reversed that trend. In particular, it enabled us to form multidisciplinary teams to work on long-term projects.

The results of those projects have been communicated to a wide scientific community. And as the researcher admits, they rarely ended up stuck down blind alleys.

In my research, things often moved forward! Obviously we encountered diverse problems, some unsolvable, but the number of open questions was even greater, and we always found a way around the obstacles.

After an exemplary career, Jean-Daniel delivers a message of optimism to young scientists. He advises them above all to fulfil their dreams – so long as they remain reasonable! – and not to hesitate about embracing a career in research.

Research is not a waste of time. It is often difficult, it is still demanding and it can sometimes be intimidating, but most importantly it opens up new areas of exploration. From applied and fundamental mathematics to IT development, the diversity of subjects within computational geometry, for instance, has something to suit all tastes and it can benefit from all skills.