X-Git-Url: http://git.salome-platform.org/gitweb/?a=blobdiff_plain;f=doc%2Fsalome%2Fgui%2FSMESH%2Finput%2Fconstructing_meshes.doc;h=2a1a0c3aab8bfc97a6f5eb63e17565d687988838;hb=5f4aaf693bb87b8f0b56311c7e602d5d92f07aee;hp=d62feac7cc5102ef33d3a00a1ae361877ac6e11f;hpb=0635c9fc80f67d1e5dc0e94ec85f487286a92070;p=modules%2Fsmesh.git diff --git a/doc/salome/gui/SMESH/input/constructing_meshes.doc b/doc/salome/gui/SMESH/input/constructing_meshes.doc index d62feac7c..2a1a0c3aa 100644 --- a/doc/salome/gui/SMESH/input/constructing_meshes.doc +++ b/doc/salome/gui/SMESH/input/constructing_meshes.doc @@ -2,120 +2,385 @@ \page constructing_meshes_page Constructing meshes -\n Construction of a mesh consists of: +\n Construction of a mesh on some geometry consists of: +\anchor create_mesh_anchor +

Creation of a mesh object

To construct a mesh:
    -
  1. In the \b Mesh menu select Create Mesh or click "Create -Mesh" button in the toolbar. +
  2. Select a geometrical object for meshing.
    3. +
  3. In the \b Mesh menu select Create Mesh or click "Create + Mesh" button in the toolbar. -\image html image32.png -
    "Create Mesh" button
    +
    + \image html image32.png + "Create Mesh" button +
    -The following dialog box will appear: + The following dialog box will appear: -\image html createmesh-inv.png -
    4. -
  4. For example, you need to mesh a 3d object. -\n First, type the name for your mesh in the "Name" box, by default, -it is "Mesh_1". Then select the object you wish to mesh in the Object -Browser and click the "Add" button. + \image html createmesh-inv.png +
    +
    5. +
  5. 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). -\image html image120.png -
    "Add" button
    + Selection of a mesh type hides all meshing algorithms that cannot + generate elements of this type.
    6. -Now you can define 1d Algorithm and 1d Hypotheses, which will be -applied to the edges of your object. (Note that any object has edges, -even if their existence is not apparent, for example, a sphere has 4 -edges). Click the "Add Hypothesis" button to add a hypothesis. +
  6. Apply \subpage basic_meshing_algos_page "meshing algorithms" and + \subpage about_hypo_page "hypotheses" which will be used to compute + this mesh. -\image html image121.png -
    "Add Hypothesis" button
    + "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 and the maximal dimension of elements the algorithms + generate. For example, \b 3D page lists the algorithms that affect + 3D geometrical objects (solids) and generate 3D mesh elements + (tetrahedra, hexahedra etc.) -Click the "Edit Hypothesis" button to define values for the -current hypothesis. + \note + - Some page(s) can be disabled if the source 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 + produce 0D elements. Currently \b 0D page provides only one + algorithm "Segments around vertex" that allows specyfying the required + size of mesh edges about the selected vertex (or vertices). -\image html image122.png -
    "Edit Hypothesis" button
    + For example, you need to mesh a 3D object. -The use of additional hypotheses is optional (i.e. you may leave -"None" in this box). + 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). +
    + \image html image120.png + "Select" button +
    -Proceed in the same way with 2d and 3d Algorithms and Hypotheses, note -that the choice of hypotheses depends on the algorithm. There must be -one Algorithm and one or several Hypotheses for each dimension of your -object, otherwise you will not get any mesh at all. Of course, if you -wish to mesh a face, which is a 2d object, you don't need to define 3d -Algorithm and Hypotheses. -\n In the Object Browser the structure of the new mesh will be -displayed as follows: + 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. +
    + \image html image121.png + "Add Hypothesis" button +
    + Click the "Plus" button to enable adding more additional hypotheses. -\image html image88.jpg + Click the "Edit Hypothesis" button to change the values for the + current hypothesis. +
    + \image html image122.png + "Edit Hypothesis" button +
    -It contains: + 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. + + If you wish you can select different algorithms and/or hypotheses + for meshing some parts 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 + be one Algorithm and zero or several + Hypotheses for each dimension of your object, otherwise you will + not get any mesh at all. Of course, if you wish to mesh a face, + 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 + 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 + 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). + + \image html hypo_sets.png + List of sets of hypotheses. Tag [custom] is + automatically added to the sets defined by the user. + + \note \a "Automatic" in the names of predefined sets of + hypotheses came from previous versions of SALOME where + \ref automatic_length_anchor "Automatic Length" hypothesis + was included in these sets, and not that these sets are suitable for + meshing any geometry. +
    7. +
+ +Consider trying a sample script for construction of a mesh from our +\ref tui_creating_meshes_page "TUI Scripts" section. + +\anchor evaluate_anchor +

Evaluating mesh size

+ +After the mesh object is created and all hypotheses are assigned and +before \ref compute_anchor "Compute" operation, it is possible to +calculate the eventual mesh size. For this, select the mesh in +the Object Browser and from the \b Mesh menu select \b +Evaluate. The result of evaluation will be displayed in the following +information box: + +\image html mesh_evaluation_succeed.png + +\anchor preview_anchor +

Previewing the mesh

+ +Before \ref compute_anchor "the mesh computation", it is also possible +to see the mesh preview. + +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 +"Preview" item from the pop-up menu. + +
+\image html mesh_precompute.png +"Preview" button +
+ +Select 1D mesh or 2D mesh preview mode in the Preview dialog. + +\image html preview_mesh_1D.png "1D mesh preview shows nodes computed on geometry edges" +
+\image html preview_mesh_2D.png "2D mesh preview shows edge mesh elements, computed on geometry faces" + +Compute button computes the whole mesh. + +When the Preview dialog is closed, the question about the storage of temporarily +created mesh elements appears: + +\image html preview_tmp_data.png + +These elements can be kept in the mesh. + + +\anchor submesh_order_anchor +

Changing sub-mesh priority

+ +If the mesh contains concurrent \ref constructing_submeshes_page "sub-meshes", +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: + +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 +their priority. + +There is an example of submesh 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 second submesh object Submesh_2 created on Face_2 is: + + +And the last submesh object Submesh_3 created on Face_3 is: + + +The sub-meshes become concurrent if they share sub-shapes that can be +meshed with different algorithms (or different hypotheses). In the +example, we have three submeshes with concurrent algorithms, because +they have different hypotheses. + +The first mesh computation is made with: +
+\image html mesh_order_123.png +"Mesh order SubMesh_1, SubMesh_2, SubMesh_3"
+
+\image html mesh_order_123_res.png +"Result mesh with order SubMesh_1, SubMesh_2, SubMesh_3 "
+ +The next mesh computation is made with: +
+\image html mesh_order_213.png +"Mesh order SubMesh_2, SubMesh_1, SubMesh_3"
+
+\image html mesh_order_213_res.png +"Result mesh with order SubMesh_2, SubMesh_1, SubMesh_3 "
+ +And the last mesh computation is made with: +
+\image html mesh_order_321.png +"Mesh order SubMesh_3, SubMesh_2, SubMesh_1"
+
\image html mesh_order_321_res.png +"Result mesh with order SubMesh_3, SubMesh_2, SubMesh_1 "
+ +As we can see, each mesh computation has a different number of result +elements and a different mesh discretization on the shared edges (the edges +that are shared between Face_1, Face_2 and Face_3) + +Additionally, submesh priority (the order of applied algorithms) can +be modified not only in a separate dialog box, but also in +the Preview. This helps to preview different mesh results, +modifying the order of submeshes. +
+\image html mesh_order_preview.png +"Preview with submesh priority list box"
-There is an alternative way to create a mesh on an object simply by -clicking Assign a set of hypotheses button and selecting between -Automatic Tetrahedralization or Hexahedralization. The program will -automatically generate a 3D mesh with the most appropriate -settings. In the same way you can apply this functionality for meshing -2D objects, in which case 3D algorithms are not applied. -
  • Now, when everything is ready, select your mesh in the Object -Browser. From the \b Mesh menu select \b Compute or click "Compute" button of the -toolbar. +If there are no concurrent submeshes under the Mesh object, the user +will see the following information. +
    +\image html mesh_order_no_concurrent.png +"No concurrent submeshes detected"
    + +\anchor compute_anchor +

    Computing the mesh

    + +It is equally possible to skip \ref evaluate_anchor "the Evaluation" +and \ref preview_anchor "the Preview" and to \b Compute the mesh after +the hypotheses are assigned. For this, select your mesh in +the Object Browser. From the \b Mesh menu select \b Compute or +click "Compute" button of the toolbar. + +
    \image html image28.png -
    "Compute" button
    +"Compute" button +
    -The Mesh Computation information box appears. +After the mesh computation finishes, the Mesh Computation information +box appears. In case of a success, the box shows +information on number of entities of different types in the mesh. \image html meshcomputationsucceed.png If the mesh computation failed, the information about the cause of the -failure is provided. +failure is provided in \b Errors table. \image html meshcomputationfail.png -After you select the error, Show Subshape button allows -visualizing the geometrical entity that causes it. +After you select the error, Show Sub-shape button allows +visualizing in magenta the geometrical entity that causes the error. + +\image html failed_computation.png +3D algorithm failed to compute mesh on a box shown using Show + Sub-shape button + +Publish Sub-shape button publishes the sub-shape, whose meshing +has failed, in GEOM component as a child of the mesh geometry, which +allows analyzing the problem geometry and creating a submesh on it in +order to locally tune the hypotheses. + +If the failure is caused by an invalid input mesh and the algorithm has +found which mesh entities are bad, Show bad Mesh +button appears in the dialog. Clicked, it shows the bad mesh entities in +the Viewer in magenta. Sometimes the shown mesh entities are too small +or/and hidden by other mesh elements. They can be seen after +switching the mesh to Wireframe visualization mode or switching off +the visualization of faces and volumes (if any). -\image html failed_computation.png "Example of the invalid input mesh" +Bad Mesh to Group button creates groups of bad mesh entities +to facilitate their analysis. -\Note Mesh Computation Information box does not appear if you set +\image html show_bad_mesh.png +Edges bounding a hole in the surface are shown in magenta using Show + bad Mesh button + +\note Mesh Computation Information box does not appear if you set "Mesh computation/Show a computation result notification" preference to the "Never" value. This option gives the possibility to control mesh computation reporting. There are the following possibilities: always -show information box, only if an error occurs or never. +show the information box, show only if an error occurs or never. By default, the information box is always shown after mesh computation operation. -Publish Subshape button publishes the subshape, whose meshing -failed, in GEOM component as a child of the mesh geometry, which -allows analyzing the problem geometry and creating a submesh on it in -order to locally tune hypotheses. +

    +\anchor edit_anchor +

    Editing the mesh

    -NOTE It is possible to define a 1D or a 2D mesh in a -python script and then use such submeshes in the construction of a 3D -mesh. For this, there exist two algorithms: Use existing edges and Use -existing faces. They are not entirely usable from the GUI, so a -mesh created using these algorithms should be exported into a python -script, edited and then imported into the GUi. +It is possible to \ref modifying_meshes_page "edit the mesh" of +lower dimension before generation of mesh of higher dimension. -Consider trying a sample script for construction of a mesh from our -\ref tui_creating_meshes_page "TUI Scripts" section. -
    • - +For example you can generate 2D mesh, modify it using e.g. +\ref pattern_mapping_page, and then generate 3D mesh basing on the +modified 2D mesh. The workflow is following: +- Define 1D and 2D meshing algorithms. +- Compute the mesh. 2D mesh is generated. +- Apply \ref pattern_mapping_page. +- Define 3D meshing algorithms without modifying 1D and 2D algorithms +and hypotheses. +- Compute the mesh. 3D mesh is generated. + +\note Nodes and elements added \ref adding_nodes_and_elements_page +"manually" can't be used in this workflow because the manually created +entities are not attached to any geometry and thus (usually) can't be +found by a mesher paving some geometry. + +See Also a sample TUI Script demonstrates the possibility of +\ref tui_editing_while_meshing "Intermediate edition while meshing" -*/ \ No newline at end of file +*/