Describe the Elements of Polyhedral objects

Objects that are often encountered in engineering applications can be classified as either polyhedral or curved objects. A polyhedral object consists of planar faces connected at straight edges, which, in turn, are connected at vertices, e.g. a cube or a tetrahedron. A curved object has curved faces and edges, e.g. a cylinder and a sphere. Polyhedral objects can be classified into following four classes :

Simple Polyhedra

These do not have holes and each face is bounded by a single set of connected edges, i.e. bounded by one loop of edges (Figure ). Polyhedra with Faces of Inner Loops 

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

Polyhedral with Not Through Holes A hole may have a face coincident with the object boundary or an interior hole (Figure(c)).

Polyhedra with Through Holes