/*!

\page split_to_tetra_page Splitting volumes into tetrahedra

\n This operation allows to split volumic elements into tetrahedra. 
2D mesh is modified accordingly.

<em>To split volumes:</em>
<ol>
<li>Display a mesh or a submesh in the 3D viewer.</li>
<li>In the \b Modification menu select the <b>Split into Tetrahedra</b> item or
click <em>"Split into Tetrahedra"</em> button in the toolbar.

\image html split_into_tetra_icon.png
<center><em>"Split into Tetrahedra" button</em></center>

The following dialog box will appear:

\image html split_into_tetra.png

\par
<ul>
<li>The main list contains the list of volumes. You can click on
a volume in the 3D viewer and it will be highlighted (lock Shift
keyboard button to select several volumes). Click \b Add button and
the ID of this volume will be added to the list. To remove the
selected element or elements from the list click \b Remove button. <b>Sort
list</b> button allows to sort the list of IDs. \b Filter button allows to
apply a definite filter to the selection of volumes.
<br><b>Note:</b> If you split not all adjacent non-tetrahedral volumes, your mesh becomes 
non-conform.</li>
<li><b>Apply to all</b> radio button allows to split all
volumes of the currently displayed mesh or submesh.</li>
</ul>

<ul>
<li>\b Split hexahedron

<ul>
<li><b>Into 5 tetrahedra</b>, <b>Into 6 tetrahedra</b> and <b>Into 24 tetrahedra</b> allows to
specify the number of tetrahedra a hexahedron will be split into. If the specified method does
not allow to get a conform mesh, a generic solution is applied: an additional node 
is created at the gravity center of a hexahedron, serving an apex of tetrahedra, all quadrangle sides of the hexahedron are split into two triangles each serving a base of a new tetrahedron.</li>
</ul>

</li>

<li><b>Select from</b> a set of fields allows to choose a submesh or an
existing group whose elements will be automatically added to the
list.</li>
</ul>

<li>Click the \b Apply or <b>Apply and Close</b> button to confirm the operation.</li>
</ol>
*/