The Delaunay triangulation of a spatial point pattern X
is defined as follows. First the Dirichlet/Voronoi tessellation of X
computed; see dirichlet. Then two points of X
are defined to be Delaunay neighbours if their Dirichlet/Voronoi tiles
share a common boundary. Every pair of Delaunay neighbours is
joined by a straight line. The result is a tessellation, consisting of
disjoint triangles. The union of these triangles is the convex hull of
X.