SALOME documentation central

Constructing meshes


Construction of a mesh consists of:

To construct a mesh:

  1. In the Mesh menu select Create Mesh or click "Create Mesh" button in the toolbar.

    image32.png
    "Create Mesh" button

    The following dialog box will appear:

    createmesh-inv.png
  2. For example, you need to mesh a 3d object.
    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.

    image120.png
    "Add" button

    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.

    image121.png
    "Add Hypothesis" button

    Click the "Edit Hypothesis" button to define values for the current hypothesis.

    image122.png
    "Edit Hypothesis" button

    The use of additional hypotheses is optional (i.e. you may leave "None" in this box).

    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.
    In the Object Browser the structure of the new mesh will be displayed as follows:

    image88.jpg

    It contains:

    • a reference to the geometrical object on the basis of which the mesh has been constructed;
    • Applied hypotheses folder containing the references to the hypotheses applied to the construction of the mesh;
    • Applied algorithms folder containing the references to the algorithms applied to the construction of the mesh.

    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.

  3. After the mesh object is created and all hypotheses are assigned and before the mesh computation, it is possible to see the mesh preview.

    For this, select the mesh in the Object Browser. From the Mesh menu select Preview or click "Preview" button in the toolbar or activate "Preview" item from the pop-up menu.

    mesh_precompute.png
    "Preview" button

    Select 1D mesh or 2D mesh preview mode in the Preview dialog.

    preview_mesh_1D.png

    1D mesh preview shows nodes computed on geometry edges

    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 appers:

    preview_tmp_data.png

    These elenents can be reused in the next mesh computation.

  4. It is equally possible to skip the Preview and Compute the mesh after the hypotheses are assigned. For this, select your mesh in the Object Browser. From the Mesh menu select Compute or click "Compute" button of the toolbar.

    image28.png
    "Compute" button

    The Mesh Computation information box appears.

    meshcomputationsucceed.png

    If the mesh computation failed, the information about the cause of the failure is provided.

    meshcomputationfail.png

    After you select the error, Show Subshape button allows visualizing the geometrical entity that causes it.

    failed_computation.png

    Example of the invalid input mesh

    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. 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.

    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.

  5. It is possible to calculate the eventual mesh size before Compute operation. For this, select the mesh in the Object Browser and from the Mesh menu select Evaluate. The result of evaluation will be displayed in the following information box:

    mesh_evaluation_succeed.png

    Consider trying a sample script for construction of a mesh from our TUI Scripts section.


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