Describe repetitions of geometrical objects.
Regular repetitions (arrays) are based on two lattice vectors, irregular repetitions are based on a list of offsets.
Describe a non-equispaced repetition by storing a list of offsets.
Describe a equi-spaced n*m two-dimensional repetition as a lattice.
The offsets are computed as
(i*a, j*b) for
b the distance vectors between two neighbouring points.
Describe the regular or irregular repetition of a geometrical object.