3 \page about_meshes_page About meshes
5 \n \b MESH represents a discrete approximation of a subset of the
6 three-dimensional space by \ref mesh_entities "elementary geometrical elements".
8 Mesh module provides several ways to create the mesh:
10 <li>The main way is to \subpage constructing_meshes_page "construct the mesh"
11 on the basis of the geometrical shape produced in the Geometry
12 module. This way implies selection of
13 - a geometrical object (<em> main shape</em>) and
14 - <em>meshing parameters</em> (\ref
15 basic_meshing_algos_page "meshing algorithms" and
16 characteristics (e.g. element size) of a
17 required mesh encapsulated in \ref about_hypo_page "hypothesis"
20 Construction of \subpage constructing_submeshes_page "sub-meshes"
21 allows to discretize some sub-shapes of the main shape, for example a face,
22 using different meshing parameters than other sub-shapes.<br>
23 Meshing parameters of meshes and sub-meshes can be
24 \subpage editing_meshes_page "edited". (Upon edition only mesh entities
25 generated using changed meshing parameters are removed and will be
27 \note Algorithms and hypotheses used at mesh level are referred as
28 \a global ones and those used at sub-mesh level are referred as \a
31 <li>Bottom-up way, using \ref modifying_meshes_page "mesh modification"
32 operations, especially \ref extrusion_page "extrusion" and \ref
33 revolution_page "revolution". To create an empty mesh not based on
34 geometry, use the same dialog as to \ref constructing_meshes_page
35 "construct the mesh on geometry" but do not specify any geometry
36 nor meshing algorithm.
38 <li>The mesh can be \ref importing_exporting_meshes_page "imported" from
39 (and exported to) the file in MED, UNV, STL, CGNS, DAT, GMF and
42 <li>The 3D mesh can be generated from the 2D mesh, \ref
43 importing_exporting_meshes_page "imported" or manually created. To
44 setup the meshing parameters of a mesh not based on geometry, just
45 invoke \ref editing_meshes_page "Edit mesh / sub-mesh" command on
48 <li>Several meshes can be \subpage building_compounds_page "combined"
51 <li>The whole mesh or its part (sub-mesh or group) can be
52 \subpage copy_mesh_page "copied" into a new mesh.
54 <li>A new mesh can be created from a transformed, e.g. \ref
55 translation_page "translated", part of the mesh.</li>
58 Meshes can be edited using the MESH functions destined for
59 \ref modifying_meshes_page "modification" of meshes.
61 Attractive meshing capabilities include:
62 - 3D and 2D \ref viscous_layers_anchor "Viscous Layers" (boundary
63 layers of highly stretched elements beneficial for high quality
64 viscous computations);
65 - automatic conformal transition between tetrahedral and hexahedral
68 The \b structure of a SALOME mesh is described by nodes and elements based on
69 these nodes. Geometry of the element is defined by the sequence of
70 nodes constituting it and
71 the <a href="http://www.code-aster.org/outils/med/html/connectivites.html">
72 connectivity convention </a> (adopted from MED library). Definition of
73 the element basing on elements of lower dimension is NOT supported.
76 The mesh can include the following entities:
78 <li>\b Node — an entity of a mesh defining a position in 3D
79 space with coordinates (x, y, z).</li>
80 <li>\b Edge (or segment) — 1D element of a mesh linking two nodes.</li>
81 <li>\b Face — 2D element of a mesh representing a part of
82 surface bound by links between face nodes. A face can be a
83 triangle, quadrangle or polygon.</li>
84 <li>\b Volume — 3D element of a mesh representing a part of 3D
85 space bound by volume facets. Nodes of a volume describing each
87 the <a href="http://www.code-aster.org/outils/med/html/connectivites.html">
88 MED connectivity convention.</a> A volume can be a tetrahedron, hexahedron,
89 pentahedron, pyramid, hexagonal prism or polyhedron.</li>
90 <li>\b 0D element — element of a mesh defined by one node.</li>
91 <li>\b Ball element — discrete element of a mesh defined by a
92 node and a diameter.</li>
95 Every mesh entity has an attribute associating it to a sub-shape it is
96 generated on (if any). The node generated on the geometrical edge or
97 surface in addition stores its position in parametric space of the
98 associated geometrical entity.
100 SALOME supports elements of second order, without central node
101 (quadratic triangle, quadrangle, tetrahedron, hexahedron, pentahedron
102 and pyramid) and with central nodes (bi-quadratic triangle and
103 quadrangle and tri-quadratic hexahedron).<br>
104 Quadratic mesh can be obtained in two ways:
105 - Using a global \ref quadratic_mesh_anchor "Quadratic Mesh"
106 hypothesis. (Elements with the central node are not generated in this way).
107 - Using \ref convert_to_from_quadratic_mesh_page operation.