\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 the same corner nodes as the
+corresponding linear ones, but in addition they have \a midside nodes
+located between the corner nodes on element sides.
+
+If a quadratic 2D element has an additional node at the
+element center, it is a bi-quadratic element (both TRIA7 and
+QUAD9 elements are supported). If a quadratic hexahedral element has 7
+additional nodes: at the element center and at the center of each
+side, it is a tri-quadratic element (or HEXA27).
+
+The convention of nodal connectivity of elements used in SALOME is
+the MED library convention. You can consult the description of nodal
+connectivity of elements in the documentation on MED library or
+\ref connectivity_page "here".
+
+There are several ways to create quadratic elements in your mesh:
+- manually (this way is described below);
+- use \ref quadratic_mesh_anchor "Quadratic Mesh" hypothesis to
+generate a 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
+\note All dialogs for adding quadratic element 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
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".
+combo box lists groups of all the
+\ref grouping_elements_page "three types": both
+\ref standalone_group "standalone groups",
+\ref group_on_filter "groups on filter", and
+\ref group_on_geom "groups on geometry". If the user chooses a
+group on geometry or on filter, he is warned and proposed to
+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>
-(alternatively you can just input numbers in this field without
-selection).The edges formed by the corner nodes will appear in the
-table. To define the middle nodes for each edge double-click on the
-respective field and input the number of the node. All edges and the
-object formed by them will be displayed in the Object browser. When
-all edges are defined you will be able to click \b Apply or <b>Apply and Close</b> button to
+To create any <b>Quadratic Element</b> specify the nodes which will
+form your element by selecting them in the 3D viewer with pressed
+Shift button and click \a Selection button to the right of
+<b>Corner Nodes</b> label. Their numbers will appear in the dialog box
+as <b>Corner Nodes</b> (alternatively you can just input numbers in
+this field without selection; note that to use this way the mesh
+should be selected before invoking this operation). The edges formed
+by the corner nodes will appear in the table. To define the middle
+nodes for each edge, double-click on the respective field and input
+the number of the node (or pick the node in the viewer). For
+bi-quadratic and tri-quadratic elements, your also need to specify
+central nodes.
+As soon as all needed nodes are specified, a preview of a new
+quadratic element will be displayed in the 3D viewer. Then
+you will be able to click \b Apply or <b>Apply and Close</b> button to
add the element to the mesh.
\image html aqt.png
-\b Reverse button for Quadratic Edges switches the first and the last
-nodes. For all other elements it reverses the element.
+\b Reverse button reverses the element.
</li>
</ol>
