/*!

\page symmetry_page Symmetry

\n This geometrical operation allows to perform a symmetrical copy of
your mesh or some of its elements.

<em>To create a symmtrical copy of the mesh:</em>

<ol>
<li>From the \b Modification menu choose \b Transformation -> \b Symmetry item  or click
<em>"Symmetry"</em> button in the toolbar.

\image html symmetry.png "Symmetry button"

One of the following dialogs will appear:

It is possible to mirror a mesh or some of its elements through:
\image html symmetry1.png "a point (defined by a point and a vector)"
\image html symmetry2.png "an axis"
\image html symmetry3.png "a plane (defined by a point and a normal to the plane)"

</li>

<li>
In the dialog:
<ul>
<li>specify the IDs of the elements for the symmetry operation:

<ul>
<li><b>Select the whole mesh, submesh or group</b> activating this
checkbox; or</li>
<li>choose mesh elements with the mouse in the 3D Viewer. It is
possible to select a whole area with a mouse frame; or</li> 
<li>input the element IDs directly in <b>ID Elements</b> field. The selected elements will be highlighted in the
viewer; or</li>
<li>apply Filters. <b>Set filter</b> button allows to apply a filter to the selection of elements. See more
about filters in the \ref selection_filter_library_page "Selection filter library" page.</li>
</ul>
</li>

<li>depending on the nature of the mirror object: 
<ul>
<li>if the mesh is mirrored through a point, specify the coordinates
of the point</li>
<li>if the mesh is mirrored through an axis: 
<ul>
<li>specify the cooordinates of the start \b Point of the axis vector;</li>
<li>specify the axis \b Vector through the coordinates of its
end point with respect to the coordinates of the start point;</li>
</ul>
</li>

<li>if the mesh is mirrored through a plane:
<ul>
<li>specify the cooordinates of the \b Point lying on the plane;</li>
<li>specify the axis \b Vector through the coordinates of its
end point with respect to the coordinates of the start point.</li>
</ul>
</li>

<li>specify the conditions of symmetry operation:
<ul>
<li>activate <b>Move elements</b> radio button to create  the source
mesh (or elements) at the new location and erase it from the previous location;</li>
<li>activate <b>Copy elements</b> radio button to create the source
mesh (or elements) at the new location, but leave it at the previous
location, the source mesh will be considered one and single mesh with the result of the rotation;</li>
<li>activate <b>Create as new mesh</b> radio button to leave the
source mesh (or elements) at its previous location and create a new
mesh at the new location, the new mesh appears in the Object Browser
with the default name MeshName_rotated (it is possible to change this
name in the adjacent box);</li>
<li>activate <b> Copy groups </b> checkbox to copy the groups of elements of the source mesh to the newly created mesh.</li>
</ul>
</li>

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

</ol>

<br><b>See Also</b> a sample TUI Script of a 
\ref tui_symmetry "Symmetry" operation.  

*/