Basic Elements and Polyhedra with Faces of Inner Loops:

Basic Elements

Objects that are frequently encountered in engineering applications may be classified as either polyhedral or curved objects. A polyhedral object contains planar faces associated at straight edges, which, in turn, are linked at vertices, for example a cube or a tetrahedron. A curved object has curved faces and edges, for example a cylinder and a sphere. Polyhedral objects might be classified into following four classes:

Simple Polyhedra

These do not have holes and each of face is bounded by a single set of associated edges, i.e. bounded by one loop of edges

Polyhedra with Faces of Inner Loops

These are same to the first with the exception that a face might be bounded by more than one loop of edges (Figure (b)).

Polyhedral with Not Through Holes

A hole might have a face coincident along with the object boundary or an interior hole (Figure (c)).

Polyhedra with Through Holes

These are called  as handles (Figure (d)).

(a) Simple Polyhedra

(b) Polyhedra with Faces of Inner Loops

                   (c) Polyhedra with Not Through Holes

(d) Polyhedra with Handles (Through Holdes)