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=126dcfbd905327f434bf7a67510cfbad5307c210;hp=995ee43774abdcd2c90ffa944fbd091afb08a435;hb=88068fce89e10cb32b60ea51cae3440240d42e9f;hpb=79b1ac2b6df9117f16f11d444b1f165d477a1813 diff --git a/doc/salome/gui/SMESH/input/constructing_meshes.doc b/doc/salome/gui/SMESH/input/constructing_meshes.doc index 995ee4377..126dcfbd9 100644 --- a/doc/salome/gui/SMESH/input/constructing_meshes.doc +++ b/doc/salome/gui/SMESH/input/constructing_meshes.doc @@ -2,111 +2,358 @@ \page constructing_meshes_page Constructing meshes -\n Construction of a mesh consists of: +\n Construction of a mesh on some geometry consists of: +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

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 +
    + + The following dialog box will appear: + + \image html createmesh-inv.png +
    +
    4. +
  4. Apply \subpage basic_meshing_algos_page "meshing algorithms" and + \subpage about_hypo_page "hypotheses" which will be used at computation of + 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). + + \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). + + 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). + +
    + \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. + +
    + \image html image121.png + "Add Hypothesis" button +
    + + 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). + + 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. + + 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 +
    5. +
+ +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

-\image html image32.gif -
"Create Mesh" button
+Before \ref compute_anchor "the mesh computation", it is also possible +to see the mesh preview. -The following dialog box will appear: +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 createmesh-inv.png - -
  • 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 mesh_precompute.png +"Preview" button +
    -\image html image120.gif -
    "Add" button
    +Select 1D mesh or 2D mesh preview mode in the Preview dialog. -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. +\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" -\image html image121.gif -
    "Add Hypothesis" button
    +Compute button computes the whole mesh. -Click the "Edit Hypothesis" button to define values for the -current hypothesis. +When the Preview dialog is closed, the question about the storage of temporarily +created mesh elements appears: -\image html image122.gif -
    "Edit Hypothesis" button
    +\image html preview_tmp_data.png -The use of additional hypotheses is optional (i.e. you may leave -"None" in this box). +These elements can be kept in the mesh. -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: -\image html image88.jpg +\anchor submesh_order_anchor +

    Changing sub-mesh priority

    -It contains: +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: -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. +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 discretisation 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"
    -\image html image28.gif -
    "Compute" button
    +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"
    -The Mesh Computation information box appears. + +\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 +
    + +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 mesh elements that cause 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 +\image html failed_computation.png +3D algorithm failed to compute mesh on a box shown using Show + Sub-shape button -Publish Subshape button allows importing it in a separate MED -or UNV file. +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. -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. +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). -Consider trying a sample script for construction of a mesh from our -\ref tui_creating_meshes_page "TUI Scripts" section. -
    • +Bad Mesh to Group button creates groups of the bad mesh entities, +thus allowing you for more comfortable analysis of these entities. + +\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 the information box, show only if an error occurs or never. +By default, the information box is always shown after mesh computation operation. + +

    + +\anchor use_existing_anchor +

    "Use existing edges" and "Use existing faces" algorithms

    + +It is possible to create a 1D or a 2D mesh in a python script +(using AddNode, AddEdge and AddFace commands) and +then use such sub-meshes in the construction of a 2D or a 3D mesh. For +this, there exist two algorithms: Use existing edges and Use + existing faces. +For example, you want to use standard algorithms to generate 1D and 3D +meshes and to create 2D mesh by your python code. Then you +
      +
    1. create a mesh object, assign an 1D algorithm,
      2. +
    2. invoke \b Compute command, which computes an 1D mesh,
      3. +
    3. assign Use existing faces and a 3D algorithm,
      4. +
    4. run your python code, which creates a 2D mesh,
      5. +
    5. invoke \b Compute command, which computes a 3D mesh.
    -*/ \ No newline at end of file +Consider trying a sample script demonstrating the usage of +\ref tui_use_existing_faces "Use existing faces" algorithm for +construction of a 2D mesh using Python commands. + +\image html use_existing_face_sample_mesh.png + Mesh computed by \ref tui_use_existing_faces "the sample script" + shown in a Shrink mode. + +*/