X-Git-Url: http://git.salome-platform.org/gitweb/?p=modules%2Fsmesh.git;a=blobdiff_plain;f=doc%2Fsalome%2Fgui%2FSMESH%2Finput%2Fconstructing_meshes.doc;h=2ec8a49878fa121577843d32121c0b28324a3421;hp=0671f89093adc823b03f6249561bcbb44413b72b;hb=54644afede59730525ebb89f87d5e09b620e329c;hpb=3cd8d693a93135ca68e9bfe2d1a8838716c19a80 diff --git a/doc/salome/gui/SMESH/input/constructing_meshes.doc b/doc/salome/gui/SMESH/input/constructing_meshes.doc index 0671f8909..2ec8a4987 100644 --- a/doc/salome/gui/SMESH/input/constructing_meshes.doc +++ b/doc/salome/gui/SMESH/input/constructing_meshes.doc @@ -2,17 +2,67 @@ \page constructing_meshes_page Constructing meshes -\n Construction of a mesh on some geometry consists of: +To create a mesh on geometry, it is necessary to create a mesh object by choosing +- a geometrical shape produced in the Geometry module (main shape); +- meshing parameters, including + - \ref basic_meshing_algos_page "meshing algorithms" and + - \ref about_hypo_page "hypotheses" specifying constraints to be + taken into account by the chosen meshing algorithms. + +Then you can launch mesh generation by invoking \ref compute_anchor "Compute" command. + +\note Sometimes \a hypotheses term is used to refer to both algorithms +and hypotheses. + +Mesh generation on the geometry is performed in the bottom-up +flow: nodes on vertices are created first, then edges are divided into +segments using nodes on vertices; the node of segments are then +used to mesh faces; then the nodes of faces are used to mesh +solids. This automatically assures the conformity of the mesh. + +It is required to choose a meshing algorithm for every dimension of +sub-shapes up to the highest dimension to be generated. Note +that some algorithms generate elements of several dimensions, and +others of only one. It is not necessary to define meshing +parameters for all dimensions at once; you can start from 1D +meshing parameters only, compute the 1D mesh, then define 2D meshing +parameters and compute the 2D mesh (note that 1D mesh will not be +re-computed). + +An algorithm of a certain dimension chosen at mesh creation is applied +to discretize every sub-shape of this dimension. It is possible to +specify a different algorithm or hypothesis to be applied to one or +a group of sub-shapes by creating a \ref constructing_submeshes_page +"sub-mesh". You can specify no algorithms at all at mesh object +creation and specify the meshing parameters on sub-meshes only; then +only the sub-shapes, for which an algorithm and a hypothesis (if any) +have been defined will be discretized. + +\n Construction of a mesh on a geometry includes at least two +(\ref create_mesh_anchor "mesh creation" and +\ref compute_anchor "computing") of the following steps: -Mesh can be \ref use_existing_anchor "computed using your own meshing algorithms" -written in Python. - \anchor create_mesh_anchor

Creation of a mesh object

@@ -32,70 +82,103 @@ written in Python. \image html createmesh-inv.png
+
  • To filter off irrelevant meshing algorithms, you can + select Mesh Type in the corresponding list from Any, + Hexahedral, Tetrahedral, Triangular and \b Quadrilateral (there + can be less items for the geometry of lower dimensions). + + Selection of a mesh type hides all meshing algorithms that cannot + generate elements of this type.
    • +
  • Apply \subpage basic_meshing_algos_page "meshing algorithms" and - \subpage about_hypo_page "hypotheses" which will be used at computation of + \subpage about_hypo_page "hypotheses" which will be used to compute this mesh. "Create mesh" dialog box contains several tab pages titled \b 3D, \b 2D, \b 1D and \b 0D. The title of each page reflects the - dimension of the CAD model (geometry) the algorithms listed on - this page affect. For example, \b 3D page lists the algorithms - that affect 3D geometrical objects (solids). + dimension of the sub-shapes the algorithms listed on + this page affect and the maximal dimension of elements the algorithms + generate. For example, \b 3D page lists the algorithms that affect + 3D sub-shapes (solids) and generate 3D mesh elements + (tetrahedra, hexahedra etc.) + + As soon as you have selected an algorithm, you can create a + hypothesis (or select an already created one). A set of accessible + hypotheses includes only the hypotheses that can be used by the + selected algorithm. \note - - Some page(s) can be disabled if the source geometrical + - Some page(s) can be disabled if the geometrical object does not include shapes (sub-shapes) of the corresponding dimension(s). For example, if the input object is a geometrical face, \b 3D page is disabled. - Some algorithms affect the geometry of several dimensions, - i.e. "1D-2D" or "1D-2D-3D". If such an algorithm is selected by the - user, the dialog box pages related to the corresponding lower level - dimensions are disabled. - - \b 0D page does not refer to the 0D elements, but to 0D - geometry (vertices). Mesh module does not provide algorithms that + i.e. 1D+2D or 1D+2D+3D. If such an algorithm is selected, the + dialog pages related to the corresponding lower dimensions are + disabled. + - \b 0D page refers to 0D geometry (vertices) rather than + to 0D elements. Mesh module does not provide algorithms that produce 0D elements. Currently \b 0D page provides only one - algorithm "Segments around vertex" that allows specyfying the required + algorithm "Segments around vertex" that allows specifying the required size of mesh edges about the selected vertex (or vertices). For example, you need to mesh a 3D object. - First, type the name of your mesh in the \b Name box, by default, - it is "Mesh_1". Then select the geometrical object you wish to - mesh in the Object Browser and click "Select" button near \b Geometry - field (if the name of the object has not yet appeared in \b Geometry field). - + First, you can change a default name of your mesh in the \b Name + box. Then check that the selected geometrical object indicated in + \b Geometry field, is what you wish to mesh; if not, select + the correct object in the Object Browser. Click "Select" button + near \b Geometry field if the name of the object has not yet + appeared in \b Geometry field.
    \image html image120.png "Select" button
    Now you can define 3D Algorithm and 3D Hypotheses, which will be - applied to the solids of your geometrical object. Click the "Add - Hypothesis" button to add a hypothesis. - + applied to discretize the solids of your geometrical object using + 3D elements. Click the "Add Hypothesis" button to create + and add a hypothesis.
    \image html image121.png "Add Hypothesis" button
    + Click the "Plus" button to enable adding more additional hypotheses. Click the "Edit Hypothesis" button to change the values for the current hypothesis. -
    \image html image122.png "Edit Hypothesis" button
    - Most standard 2D and 3D algorithms can work without hypotheses - using some default parameters. The use of additional hypotheses - is optional (i.e. you may leave "None" in this box). + Most 2D and 3D algorithms can work without hypotheses using + default meshing parameters. Some algorithms do not require any + hypotheses. After selection of an algorithm "Hypothesis" field of + the dialog can contain: + + After selection of an algorithm Add. Hypothesis field can contain: + Proceed in the same way with 2D and 1D Algorithms and Hypotheses that will be used to mesh faces and edges of your geometry. (Note that any object has edges, even if their existence is not apparent, for example, a sphere has 4 edges). Note that the choice of hypotheses and lower dimension algorithms depends on - the higher dimension algorithm. + the higher dimension algorithm. + + If you wish you can select other algorithms and/or hypotheses + for meshing some sub-shapes of your CAD model by \ref constructing_submeshes_page. Some algorithms generate mesh of several dimensions, while others produce mesh of only one dimension. In the latter case there must @@ -105,36 +188,62 @@ written in Python. which is a 2D object, you do not need to define a 3D Algorithm and Hypotheses. - In the Object Browser the structure of the new mesh will be + In the Object Browser the structure of the new mesh is displayed as follows: - -
    \image html image88.jpg -
    - It contains: There is an alternative way to assign Algorithms and Hypotheses by clicking Assign a set of hypotheses button and selecting among - pre-defined sets of hypotheses. In addition to the standard + pre-defined sets of algorithms and hypotheses. In addition to the built-in sets of hypotheses, it is possible to create custom sets by editing CustomMeshers.xml file located in the home directory. CustomMeshers.xml file must describe sets of hypotheses in the same way as ${SMESH_ROOT_DIR}/share/salome/resources/smesh/StdMeshers.xml - file does (sets of hypotheses are enclosed between - tags). - + file does (sets of hypotheses are enclosed between \ + tags). For example: +~~~~~~{.xml} + + + + + + + +~~~~~~ + If the file contents are incorrect, there can be an error at + activation of Mesh module: "fatal parsing error: error + triggered by consumer in line ..." +
    +
    \image html hypo_sets.png List of sets of hypotheses. Tag [custom] is - automatically added to the sets defined by the user + automatically added to the sets defined by the user. +
    + \note + - \a "Automatic" in the names of predefined sets of hypotheses + does not actually mean that they are suitable for meshing any + geometry. + - The list of sets of hypotheses can be shorter than in the + above image depending on the geometry dimension.
    • @@ -157,7 +266,9 @@ information box:

    Previewing the mesh

    Before \ref compute_anchor "the mesh computation", it is also possible -to see the mesh preview. +to see the mesh preview. This operation allows to incrementally +compute the mesh, dimension by dimension, and to discard an +unsatisfactory mesh. For this, select the mesh in the Object Browser. From the \b Mesh menu select \b Preview or click "Preview" button in the toolbar or activate @@ -192,31 +303,31 @@ it is possible to change the priority of their computation, i.e. to change the priority of applying algorithms to the shared sub-shapes of the Mesh shape. -To change submesh priority: +To change sub-mesh priority: -Choose "Change submesh priority" from the Mesh menu or a pop-up -menu. The opened dialog shows a list of submeshes in the order of +Choose "Change sub-mesh priority" from the Mesh menu or a pop-up +menu. The opened dialog shows a list of sub-meshes in the order of their priority. -There is an example of submesh order modifications taking a Mesh created on a Box +There is an example of sub-mesh order modifications taking a Mesh created on a Box shape. The main Mesh object: -The first submesh object Submesh_1 created on Face_1 is: +The first sub-mesh Submesh_1 created on Face_1 is: -The second submesh object Submesh_2 created on Face_2 is: +The second sub-mesh Submesh_2 created on Face_2 is: -And the last submesh object Submesh_3 created on Face_3 is: +And the last sub-mesh Submesh_3 created on Face_3 is: