Unstructured grid

Grids of this type may be used in finite element analysis when the input to be analyzed has an irregular shape.

Unlike structured grids, unstructured grids require a list of the connectivity which specifies the way a given set of vertices make up individual elements (see graph (data structure)).

Ruppert's algorithm is often used to convert an irregularly shaped polygon into an unstructured grid of triangles.

[1] However, there is no such commonly used algorithm for generating unstructured hexahedral grid on a general 3D solid model.

"Plastering" is a 3D version of Paving,[2] but it has difficulty in forming hexahedral elements at the interior of a solid.