0021859: SMESH : Add conversion from QUAD8 to QUAD9 and from HEXA20 to HEXA27

doc/salome/gui/SMESH/input/adding_quadratic_elements.doc

@@ -4,10 +4,22 @@
 
 \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>

doc/salome/gui/SMESH/input/additional_hypo.doc

@@ -23,6 +23,9 @@ Quadratic Mesh hypothesis allows to build a quadratic mesh (whose
 edges are not straight but curved lines and can be defined by three
 points: first, middle and last instead of an ordinary two).
 
+See \ref adding_quadratic_elements_page
+for more information about quadratic meshes.
+
 \anchor propagation_anchor
 <h2>Propagation of 1D Hypothesis on opposite edges</h2>
 

doc/salome/gui/SMESH/input/convert_to_from_quadratic_mesh.doc

@@ -3,13 +3,13 @@
 \page convert_to_from_quadratic_mesh_page Convert to/from Quadratic Mesh
 
 \n This functionality allows transforming linear meshes (or
-sub-meshes) to quadratic (or bi-quadratic) and vice versa. 
-See \ref adding_quadratic_elements_page "Adding quadratic elements" 
-for more information about quadratic meshes.
-Note that conversion of a sub-mesh most probably will
-produce a non-conformal mesh. Elements on the boundary between
-quadratic (or bi-quadratic) and linear sub-meshes become (or remain)
-quadratic (or bi-quadratic).
+sub-meshes) to quadratic and vice versa.
+Note that conversion of a sub-mesh most probably will produce a
+non-conformal mesh. Elements on the boundary between quadratic and
+linear sub-meshes become (or remain) quadratic.
+
+See \ref adding_quadratic_elements_page for more information about
+quadratic meshes.
 
 <em>To produce a conversion:</em>
 <ol>
@@ -19,8 +19,10 @@ Viewer.</li>
 Mesh item </b>, or click <em>"Convert to/from quadratic"</em> button in the
 toolbar.
 
+<center>
 \image html image154.png
-<center><em>"Convert to/from quadratic" button</em></center>
+<em>"Convert to/from quadratic" button</em>
+</center>
 
 The following dialog box will appear:
 
@@ -31,10 +33,12 @@ The following dialog box will appear:
 
 <ul>
 <li>If it is necessary to convert a linear mesh to quadratic or a quadratic
-mesh to linear. Note that the choice is available only if the selected mesh
+  mesh to linear. **Convert to bi-quadratic** option means same as
+  **Convert to quadratic** except that QUAD9 elements are created
+  instead of QUAD8, and HEXA27 elements are created instead of
+  HEXA20. Note that the choice is available only if the selected mesh
   (or sub-mesh) contains both quadratic and linear elements, else the
   direction of conversion is selected automatically.</li>
-
 <li>If it is necessary to place medium nodes of the quadratic mesh on the
 geometry (meshed object). This option is relevant for conversion to
 quadratic provided that the mesh is based on a geometry (not imported from file).</li>