/*!

\page prism_3d_algo_page 3D extrusion meshing algorithm

3D extrusion algorithm can be used for meshing prisms, i.e. <b>3D Shapes</b>
defined by two opposing faces having the same number of vertices and
edges and meshed using the \ref projection_algos_page "2D Projection"
algorithm. These two faces should be connected by quadrangle "side"
faces.

The opposing faces can be meshed with either quadrangles or triangles,
while the side faces should be meshed with quadrangles only.

\image html image157.gif

As you can see, the <b>3D extrusion</b> algorithm permits to build and to
have in the same 3D mesh such elements as hexahedrons, prisms and
polyhedrons.

*/