smesh/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc

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/*!
\page a2d_meshing_hypo_page 2D Meshing Hypotheses
<br>
<ul>
<li>\ref max_element_area_anchor "Max Element Area"</li>
<li>\ref length_from_edges_anchor "Length from Edges"</li>
<li>\ref hypo_quad_params_anchor "Quadrangle parameters"</li>
</ul>
<br>
\anchor max_element_area_anchor
<h2>Max Element Area</h2>
<b>Max Element Area</b> hypothesis is applied for meshing of 2D faces
composing your geometrical object. Definition of this hypothesis
consists of setting the <b>maximum area</b> of meshing elements (depending on
the chosen meshing algorithm it can be <b>triangles</b> or <b>quadrangles</b>),
which will compose the mesh of these 2D faces.
\image html a-maxelarea.png
\n
\image html max_el_area.png "In this example, Max. element area is very small compared to the 1D hypothesis"
<b>See Also</b> a sample TUI Script of a
\ref tui_max_element_area "Maximum Element Area" hypothesis
operation.
<br>
\anchor length_from_edges_anchor
<h2>Length from Edges</h2>
<b>Length from edges</b> hypothesis builds 2D mesh segments having a
length calculated as an average edge length for a given wire.
<b>See Also</b> a sample TUI Script of a
\ref tui_length_from_edges "Length from Edges" hypothesis operation.
<br>
\anchor hypo_quad_params_anchor
<h2>Quadrangle parameters</h2>
\image html hypo_quad_params_dialog.png "Quadrangle parameters creation/edition dialog"
<b>Quadrangle parameters</b> is a hypothesis for Quadrangle (Mapping).
<b>Base vertex</b> parameter allows using Quadrangle (Mapping)
algorithm for meshing of triangular faces. In this case it is
necessary to select a vertex, which will be used as the fourth edge
(degenerated).
\image html hypo_quad_params_1.png "A face built from 3 edges"
\image html hypo_quad_params_res.png "The resulting mesh"
This parameter can be also used to mesh a segment of a circular face.
Please, consider that there is a limitation on the selection of the
vertex for the faces built with the angle > 180 degrees (see the picture).
\image html hypo_quad_params_2.png "3/4 of a circular face"
In this case, selection of a wrong vertex for the <b>Base vertex</b>
parameter will generate a wrong mesh. The picture below
shows the good (left) and the bad (right) results of meshing.
\image html hypo_quad_params_res_2.png "The resulting meshes"
<b>Type</b> parameter has sense on faces with different number of
segments on opposite sides. The following types are available:
<ul>
<li><b>Standard</b> means the default case, triangles and quadrangles
are possible along the longest sides (in the refinement area).</li>
<li><b>Triangle preference</b> forces building only triangles in the
refinement area for transition to higher number of segments.
<i>This type corresponds to <b>Triangle Preference</b> additional
hypothesis, which is obsolete now.</i></li>
<li><b>Quadrangle preference</b> forces building only quadrangles for
transition to higher number of segments. This hypothesis has one
restriction on its work: the total quantity of segments on all
four sides of the face must be even (divisible by 2).</li>
<i>This type corresponds to <b>Quadrangle Preference</b>
additional hypothesis, which is obsolete now.</i></li>
<li><b>Quadrangle preference (reversed)</b> works like
<b>Quadrangle preference</b> (and with same restriction), but
transition is made near the sides with smaller number of
segments.</li>
<li><b>Reduced</b> type forces building only quadrangles, transition
to other number of segments is made layer by layer. This type has
a limitation on number of segments: two opposite edges must have
the same number of segments, two another must have even difference
between their numbers of segments.</li>
</ul>
<b>See Also</b> a sample TUI Script of a
\ref tui_quadrangle_parameters "Quadrangle Parameters" hypothesis.
<br>
*/