\page adding_quadratic_elements_page Adding Quadratic Elements
-\n MESH modules allows you to work with <b>Quadratic Elements</b>.
+\n MESH module allows you to work with <b>Quadratic Elements</b>.
-Quadratic Edge is not a straight but a broken line and can be defined
-by three points: first, middle and last. All more complex \b Quadratic
-\b Elements differ from ordinary ones in that they consist of Quadratic
-Edges.
+Quadratic elements are defined by same corner nodes as the
+corresponding linear ones, and in addition they bear \a midside nodes
+located between the corner nodes on element sides.
+
+The quadratic quadrilateral element can bear an additional node at the
+element center, then it is referred as bi-quadratic one (or
+QUAD9). The quadratic hexahedral element can bear 7 additional nodes:
+at the element center and at centers of sides, then it is referred as
+tri-quadratic one (or HEXA27).
+
+There are several ways you can create quadratic elements in your mesh:
+- manually create quadratic elements (the way described below);
+- use \ref quadratic_mesh_anchor "Quadratic Mesh" hypothesis to
+generate quadratic mesh on your geometry;
+- convert an existing linear mesh to a quadratic one
+(see \ref convert_to_from_quadratic_mesh_page).
<em>To add a quadratic element to your mesh:</em>
<ol>
\image html image152.png
+\note All dialogs for quadratic element adding to the mesh
+provide the possibility to automatically add an element
+to the specified group or to create the group anew using
+<b>Add to group</b> box, that allows choosing an existing group for
+the created node or element or giving the name to a new group. By
+default, the <b>Add to group</b> check box is switched off. If the user
+swiches this check box on, the combo box listing all currently
+existing groups of the corresponding type becomes available. By
+default, no group is selected. In this case, when the user presses
+<b>Apply</b> or <b>Apply & Close</b> button, the warning message box
+informs the user about the necessity to input a new group name. The
+combo box lists both \ref standalone_group "standalone groups"
+and \ref group_on_geom "groups on geometry". If the user chooses a
+group on geometry, he is warned and proposed to
+\ref convert_to_standalone "convert this group to standalone".
+If the user rejects conversion operation, it is cancelled and
+a new quadratic element is not created.
+
+
To create any <b>Quadratic Element</b> specify the nodes which will form your
triangle by selecting them in the 3D viewer with pressed Shift
button. Their numbers will appear in the dialog box as <b>Corner Nodes</b>
