A three dimension object is expressed mostly using a mathematical model; so, it is topical the question how we
will represent it? Essentially, for this we have two methods:

First is **the representation by a volume model** where the object has a parametric representation.
This method is suitable for subsequent processing and arrangements of a given object.
It is used mainly in mechanical engineering production because it enables the subsequent physical simulation
of the product features. A disadvantage of this method is that model designing is limited only for the use of basic
geometric forms.

The second method is **area representation**. Here we do not depend on geometric forms because the
object is constructed only using polygons of its surface. The surface of an object comprises *vertexes*
(points) interconnected by abscissas into *polygons*. In this way we can represent practically any object
using a polygonal network, which from the point of view of universality is almost ideal.
The most advantageous representation is if there are given *polygons - triangles* because
calculations with these are the simplest.