smesh/doc/salome/gui/SMESH/input/constructing_submeshes.doc

/*!

\page constructing_submeshes_page Constructing sub-meshes

Sub-mesh is a mesh on a geometrical sub-object (sub-shape) used to assign
different meshing algorithms and/or hypotheses than the algorithms and
hypotheses assigned to the parent mesh on the parent geometrical
object, that allows getting a local mesh refinement.

A sub-shape to create a sub-mesh on should be retrieved from the shape
of the parent mesh one of the following ways: <ul>
<li> In Geometry module, via <em>New Entity > Explode</em> menu.</li>
<li> In Geometry module, by creation of a group (<em>New Entity >
    Group > Create Group</em> menu).</li> 
<li> In Mesh module, by
  \ref subshape_by_mesh_elem "selecting a mesh element" generated on a
  sub-shape of interest. This way is accessible if the mesh is
  already computed.</li> 
</ul>

If a geometrical sub-object belongs to several geometrical objects
having different meshes or sub-meshes, it will be meshed with the
hypotheses of a sub-mesh of a lower dimension.<br>
For example, a face of a box is meshed with a sub-mesh using algorithms
and hypotheses other than the parent mesh on the whole box. The face
and the box share four edges, which will be meshed with algorithms and
hypotheses of the sub-mesh on the face, because the face is a 2D object
while the box is a 3D object.  <br>
 If the dimensions are the same, an arbitrary algorithm/hypothesis
 will be used. This means that an edge shared by two faces each having
 its own different sub-mesh, will be meshed using algorithms and
 hypotheses of any of the two, chosen randomly. This indeterminacy can
 be fixed by defining \ref submesh_order_anchor "Sub-mesh priority". The
 default sub-meshes priority is such that multi-dimensional algorithms
 are processed first.
<br>

\n Construction of a sub-mesh consists of:
<ul>
<li>Selecting a mesh which will encapsulate your sub-mesh</li>
<li>Selecting a geometrical object for meshing</li>
<li>Applying one or several previously described 
\ref about_hypo_page "hypotheses" and 
\ref basic_meshing_algos_page "meshing algorithms" which will be used
at computation of this sub-mesh</li>
</ul>

<br><em>To construct a sub-mesh:</em>
\par
From the \b Mesh menu select <b>Create Sub-mesh</b> or click <em>"Create
Sum-mesh"</em> button in the toolbar.

<center>
  \image html image33.gif
  <em>"Create Sub-mesh" button</em>
</center>

\par
The following dialog box will appear:

\par
\image html createmesh-inv2.png

\par
It allows to define the \b Name, the parent \b Mesh and the \b
Geometry (e.g. a face if the parent mesh has been built on box) of the
sub-mesh. You can select meshing algorithms and hypotheses in the same way as
in \ref constructing_meshes_page "Create mesh" menu.

\par
\anchor subshape_by_mesh_elem
If the parent mesh is already computed, then you can define the
\b Geometry by picking mesh elements computed on a sub-shape of interest
in the 3D Viewer, i.e. you do not have to extract this sub-shape
in Geometry module beforehand. To start element selection, press \a
Selection button to the right of \b Geometry label. If this button is
already down, then click it to release and then click it again. The
following pop-up menu allowing to choose a way of geometry definition will
appear.

\par
\image html choose_geom_selection_way.png

\par
<b>Direct geometry selection</b> enables selecting the sub-shape in the Object
Browser.
<b>Find geometry by mesh element selection</b> activates the following dialog.

\par
\image html find_geom_by_mesh_elem.png

\par
In this dialog, <b> Element Type </b> defines a kind of element to pick in the
Viewer.
Instead of picking an element in the Viewer, you can type its
ID in <b> Element ID</b> field. 
<b> Geometry name </b> field allows defining a name of the sub-shape
with which the sub-shape will appear in the Object Browser (if not yet
there).

\par
In the Object Browser the structure of the new sub-mesh will be
displayed as follows:

\image html image10.jpg

\par
It contains:
<ul>
<li>a sub-mesh name (\a SubMeshFace1)
<li>a reference to the geometrical object on the basis of which the
  sub-mesh has been constructed (<em>Cylindrical Face_1</em>);</li>
<li><b>Applied hypotheses</b> folder containing the references to the
hypotheses selected at the construction of the sub-mesh;</li>
<li><b>Applied algorithms</b> folder containing the references to the
algorithms selected at the construction of the sub-mesh.</li>
</ul>

<br><b>See Also</b> a sample TUI Script of a 
\ref tui_construction_submesh "Construct Sub-mesh" operation.

*/