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

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/*!
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\page constructing_submeshes_page Constructing sub-meshes
By purpose, the sub-mesh is an object used to assign to a sub-shape
different meshing parameters than those assigned to the main shape.
Structurally, the sub-mesh is a mesh on a certain sub-shape, or a group of
sub-shapes, possibly generated using different meshing algorithms
and/or hypotheses than those used to generate the mesh on other
sub-shapes.
Creation of a sub-mesh allows to control individually meshing of a
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certain sub-shape, thus to get a locally coarser or finer mesh, to get
elements of different types in the same mesh, etc.
A sub-shape to create a sub-mesh on should be retrieved from the main shape
in 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>
<li> In Mesh module, by clicking <em>Publish Sub-shape</em> button in a
dialog showing \ref meshing_failed_anchor "meshing errors".</li>
</ul>
Internally, definition of meshing parameters to apply for
discretization of a certain sub-shape, for example an edge of a
compound of solids, starts from searching an algorithm, 1D as for the
edge. The following sub-shapes are sequentially checked for presence
of a sub-mesh where 1D algorithm is assigned:
<ul>
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<li> the \b edge itself</li>
<li> <b>groups of edges</b> containing the edge, if any</li>
<li> \b wires sharing the edge</li>
<li> \b faces sharing the edge</li>
<li> <b>groups of faces</b> sharing the edge, if any</li>
<li> \b shells sharing the edge</li>
<li> \b solids sharing the edge</li>
<li> <b>groups of solids</b> sharing the edge, if any</li>
<li> the <b>main shape</b></li>
</ul>
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(This sequence of sub-shapes defines the priority of sub-meshes. Thus more
local, i.e. assigned to sub-shape of lower dimension, algorithms and
hypotheses have higher priority during the search of hypotheses to
apply.)
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As soon as a 1D algorithm is found, the search stops and the same
sequence of sub-shapes is checked to find the main and additional 1D
hypotheses, which can be taken into account by the found 1D algorithm.
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The multi-dimensional algorithms have a higher priority than
uni-dimensional ones if they are assigned to sub-meshes of the
same priority.
If meshing parameters are defined on sub-meshes of the same priority,
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for example, different 1D hypotheses are assigned to two faces sharing
an edge, the hypothesis assigned to a sub-shape with a lower ID will
be used for meshing. You can \ref submesh_order_anchor "change" mutual
priority of such concurrent sub-meshes.
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\n Construction of a sub-mesh consists of:
<ul>
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<li>Selecting a mesh which will encapsulate the sub-mesh</li>
<li>Selecting a sub-shape for meshing</li>
<li>Applying one or several
\ref about_hypo_page "hypotheses" and
\ref basic_meshing_algos_page "meshing algorithms" which will be used
for discretization of this sub-shape.</li>
</ul>
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<br><em>To construct a sub-mesh:</em>
\par
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From the \b Mesh menu select <b>Create Sub-mesh</b> or click <em>"Create
Sum-mesh"</em> button in the toolbar.
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<center>
\image html image33.gif
<em>"Create Sub-mesh" button</em>
</center>
\par
The following dialog box will appear:
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\par
\image html createmesh-inv2.png
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 define meshing algorithms and hypotheses in the same way as
in \ref constructing_meshes_page "Create mesh" dialog.
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Later you can change the applied hypotheses or their parameters in
\ref editing_meshes_page "Edit mesh/sub-mesh" dialog. Mesh entities
generated using changed hypotheses are automatically removed.
\anchor subshape_by_mesh_elem
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If the parent mesh is already computed, then you can define the
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\b Geometry by picking mesh elements computed on a sub-shape of interest
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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
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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
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following pop-up menu allowing to choose a way of geometry definition will
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appear.
\image html choose_geom_selection_way.png
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<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.
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\image html find_geom_by_mesh_elem.png
In this dialog, <b> Element Type </b> defines a kind of element to pick in the
Viewer.
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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).
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In the Object Browser the structure of the new sub-mesh will be
displayed as follows:
\image html image10.jpg
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><em>Applied hypotheses</em> folder containing the references to the
hypotheses assigned to the sub-mesh;</li>
<li><em>Applied algorithms</em> folder containing the references to the
algorithms assigned to the sub-mesh.</li>
</ul>
<br><b>See Also</b> a sample TUI Script of a
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\ref tui_construction_submesh "Construct Sub-mesh" operation.
*/