Departmental Seminar

Delaunay triangulations on orientable surfaces of low genus

Professor Monique Teillaud
INRIA Nancy-Grand Est, LORIA

Earlier work on Delaunay triangulation of point sets on the 2D flat torus, which is locally isometric to the Euclidean plane, was based on lifting the point set to a locally isometric 9-sheeted covering space of the torus. Under mild conditions the Delaunay triangulation of the lifted point set, consisting of 9 copies of the input set, projects to the Delaunay triangulation of the input set.

We improve and generalize this work [SoCG’16, joint work with Mikhail Bogdanov and Gert Vegter]. First we present a new construction based on an 8- sheeted covering space, which shows that eight copies suffice for the standard flat torus. Then we generalize this construction to the context of compact orientable surfaces of higher genus, which are locally isometric to the hyperbolic plane. We investigate more thoroughly the Bolza surface, homeomorphic to a sphere with two handles, both because it is the hyperbolic surface with lowest genus, and because triangulations on the Bolza surface have applications in various fields such as neuromathematics and cosmological models. While the general properties (existence results of appropriate covering spaces) show similarities with the results for the flat case, explicit constructions and their proofs are much more complex, even in the case of the apparently simple Bolza surface. One of the main reasons is the fact that two hyperbolic translations do not commute in general. 

We also present an implementation for the Delaunay triangulation of the Bolza surface [SoCG’17, joint work with Iordan Iordanov], to be integrated into the CGAL library. 

Date & time

Thu 22 Jun 2017, 10.30–11am



Le Couteur Seminar Room (3.17)


Members of RSPE welcome