ATTALI , Dominique

Delaunay triangulations and Voronoi diagrams have found numerous applications in surface modeling, surface mesh generation, deformable surface modeling and surface reconstruction. Many algorithms in these applications begin by constructing the three-dimensional Delaunay triangulation of a finite set of points scattered over a surface. Their...

It is well known that the complexity of the Delaunay triangulation of $n$ points in $R ^d$, i.e. the number of its simplices, can be $\Omega (n^\lceil \frac{d{2}\rceil })$. In particular, in $R ^3$, the number of tetrahedra can be quadratic. Differently, if the points are uniformly distributed in a cube or a ball, the expected complexity of the...

We show that the Delaunay triangulation of a set of n points distributed nearly uniformly on a p-dimensional polyhedron (not necessarily convex) in d-dimensional Euclidean space is O(n^((d-k+1)/p)), where k = ceil(d+1)/(p+1)$. This bound is tight, and improves on the prior upper bound for most values of p.

We show that the Delaunay triangulation of a set of points distributed nearly uniformly on a polyhedron (not necessarily convex) of dimension p in d-dimensional space is of order n to the power (d-1)/p for p between 2 and d-1. This improves on the well-known worst-case bound of n to the power ceiling of d/2.

We show that the Delaunay triangulation of a set of $n$ points distributed nearly uniformly on a $p$-dimensional polyhedron (not necessarily convex) in $d$-dimensional Euclidean space is $O(n^{\frac{d-k+1}{p}})$, where $k = \lceil \frac{d+1}{p+1} \rceil$. This bound is tight in the worst case, and improves on the prior upper bound for most...

Assume that Y is a noisy version of a point set X in convex position. How many vertices does the convex hull of Y have, that is, what is the number of extreme points of Y? We consider the case where X is an (epsilon,kappa)-sample of a sphere in Rd and the noise is random and uniform: Y is obtained by replacing each point x in X by a point...

We show that the Delaunay triangulation of a set of points distributed nearly uniformly on a polyhedron (not necessarily convex) of dimension p in d-dimensional space is O(n^(d-1)/p))$. For all p between 2 and d-1, this improves on the well-known worst-case bound of $O(n^ceil(d/2))$.

The medial axis of a geometric shape captures its connectivity. In spite of its inherent instability, it has found applications in a number of areas that deal with shapes. In this survey paper, we focus on results that shed light on this instability and use the new insights to generate simplified and stable modifications of the medial axis.

We say that a simplicial complex is shrinkable if there exists a sequence of admissible edge contractions that reduces the complex to a single vertex. We prove that it is NP-complete to decide whether a (two-dimensional) simplicial complex is shrinkable. Along the way, we describe examples of contractible complexes that are not shrinkable.