/*!

\page reorient_faces_page Reorient faces by vector

\n This operation allows changing orientation of a set of neighboring
faces. The desired orientation is defined by a vector. Since direction
of face normals in the set can be even opposite, it is necessary to
specify a control face whose normal will be compared with the vector. This
face can be specified either explicitly or can be found by closeness to
a given point.

Orientation of a face is changed by reverting the order of its nodes.

<em>To change orientation of faces:</em>
<ol>
<li>In the \b Modification menu select the <b>Reorient faces by
    vector</b> item or click <em>Reorient faces by
    vector</em> button in the toolbar.

<center>
\image html reorient_faces_face.png
<em>"Reorient faces by vector" button</em>
</center>

The following dialog box will appear:

<center>
\image html reorient_2d_point.png
\image html reorient_2d_face.png
</center>

<li>In this dialog
<ul>
<li>Specify a way of selection of the control face: by point or
  explicitely.</li>
<li>Select an \b Object containing faces to reorient, either in the Object
  Browser or in the 3D Viewer; it can be either <ul>
    <li>group of faces,</li>
    <li>sub-mesh of faces or</li>
    <li>mesh.</li>
    </ul></li>
<li>Specify either coordinates of a \b Point by which the control face
  will be found or the control \b Face it-self. You can easy specify the \b
  Point by either picking a node in the 3D Viewer or by selecting a vertex
  in the Object Browser. The \b Face can be either picked by mouse in
  the 3D Viewer or its ID can be entered by typing.</li>
<li>Set up a \b Direction to be compared with the normal of the
  control face. You can either pick a node in the 3D Viewer then a \b Direction
  from the coordinate system origin to the selected node will be set,
  or you can pick two nodes (holding Shift button) then a \b Direction
  from the first to the second node will be set.</li>
</ul>
</li>

<li>Click the \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_reorient_faces "Reorient faces by vector" operation. 

*/