/*!

\page extrusion_page Extrusion

\n Extrusion is used to build mesh elements of plus one
dimension than the input ones. Any line or planar element can be
extruded. Line elements will extrude into quadrilateral plane elements.
Triangular and Quadrilateral plane elements extrude into Pentahedron
and Hexahedron solids respectively.

<em>To use extrusion:</em>
<ol>
<li>From the \b Modification menu choose the \b Extrusion item or click
<em>"Extrusion"</em> button in the toolbar. 

\image html image91.gif
<center><em>"Extrusion" button</em></center>

The following dialog box will appear:

\image html extrusionalongaline1.png

\image html extrusionalongaline2.png
</li>

<li>In this dialog box you should select:
<ul>
<li>the type of elements which will be extruded (1D or 2D),</li>
<li>specify the IDs of the elements which will be extruded by
selecting them in the 3D viewer or select the whole mesh or
submesh,</li>
<li>specify the vector along which the elements will be extruded,</li>
<li>number of steps.</li>
</ul>
<li> <b>Generate Groups</b> checkbox allows copying the groups of
elements of the source mesh to the newly created one. </li>
</li>

<li>Click the \b Apply or \b OK button.</li>
</ol>

\image html image77.jpg

\image html image76.jpg

<br><b>See Also</b> a sample TUI Script of an 
\ref tui_extrusion "Extrusion" operation. 

*/