more detail for "Orientation of faces"
<li><b>2D Quadratic</b> - allows to select between the representation
of quadratic edges as broken <b>lines</b> or as <b>arcs</b></li>
<li><b>Orientation of faces</b> - shows vectors of orientation of
-faces of the selected mesh</li>
+faces of the selected mesh. Vector is shown for each 2D mesh element
+and for each free face of 3D mesh element. Vector direction is calculated by
+the first three nodes of face as a cross product of vectors n1-n2 and n1-n3.</li>
<li><b>Colors / Size</b> - allows to select color and size of
meshes.</li>
<li>\subpage transparency_page "Transparency" - allows to change the
