To triangulate a region is to describe it as the union of a collection of simplices whose interiors are pairwise disjoint. The region is then decomposed into elementary cells of bounded complexity. The words to triangulate and triangulation originate from the two-dimensional problem, but are commonly used in a broader context for regions and simplices of any dimension.

Triangulations and related meshes are ubiquitous in domains where the ambient space needs to be discretized, for instance in order to interpolate functions of several variables, or to numerically solve multi-dimensional differential equations using finite-element methods. Triangulations are largely used in the context of robotics to decompose the free configuration space of a robot, in the context of artificial vision to perform three-dimensional reconstructions of objects from their cross-sections, or in computer graphics to solve problems related to windows or to compute illuminations in rendering an image. Finally, in the context of computational geometry, the triangulation of a set of points, a planar map, a polygon, a polyhedron, an arrangement, or of any other spatial structures, is often a prerequisite to running another algorithm on the data. For instance, this is the case for algorithms performing point location in a planar map by using a hierarchy of triangulations, or for the numerous applications of triangulations to shortest paths and visibility problems.

Triangulations form the topic of the next three chapters. Chapter 11 recalls the basic definitions related to triangulations, and studies the combinatorics of triangulations in dimensions 2 and 3.