Importing 3MF, PLY, STL, and VRML Meshes

) to import a mesh from a , , , or file. When you import a mesh, you can position, rotate, and scale the mesh by using one or several Transform attributes.

Figure 8-22: The fluid region in the tutorial Analyzing Porous Structures on the Microscopic Scale is imported from an STL file.


	These formats can be imported in 3D models only.

To import additional meshes, add another node. Then COMSOL Multiphysics adds the elements of the newly imported mesh to the existing mesh.


	Meshes from different Import nodes form an assembly. See Conforming, Nonconforming, and Nonmatching Meshes for more information about assembly type meshes.

See also:

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Imported Meshes and Element Orders for information about curved elements.

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Importing Meshes from Files with Length Unit

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Importing Externally Generated Mesh Data

Files of the formats 3MF, PLY, STL, and VRML typically contain triangle elements with small angles, large angles, and the mesh elements often vary a lot in size. Such meshes are not well suited for simulations and need to be remeshed or modified before generating a volume mesh.


	For information on remeshing an imported mesh, see Remeshing Imported Meshes and Creating Geometry from Mesh.


	Note that importing a mesh modifies the number of geometric entities. Thus when you are adding this operation to a meshing sequence that is conforming with the component’s geometry, a new meshing sequence that is defining its own geometric model is automatically created, and the Import node is added to this new sequence. For more information, see The Mesh Node.

Enter the properties for the import using the following sections:

Import

Specify the filename in the field or click the button. You can also click the downward arrow beside the button and choose (

) to open the fullscreen window. Click the downward arrow for the menu (

) to choose (

) to move to the row for this file in the window, (

), and (if you have copied a file location) (

Select the check box (selected by default) to automatically form domains for each (connected) finite void region that is defined by the imported surface mesh and analyze these domains with respect to the mesh that might already exist in the sequence.


	Most physics require a mesh on the domains. Use the Free Tetrahedral, Swept, and Boundary Layers operations to fill the domains with domain elements.

Boundary Partitioning Properties

When a mesh is imported into COMSOL Multiphysics, the operation automatically determines a partitioning of the mesh into domains, boundaries, edges, and points. If the automatically performed partitioning does not match the requirements, you can modify the face partitioning by manually adjusting the corresponding parameters. For details, see the section Boundary Partitioning Properties.

Repair Tolerance and Selection for STL (Stereolithography) Files

These settings are available when the list is set to for import of stereolithography files in 3D. Such files contain data for an unstructured triangulated surface.

The check box is selected by default to create a boundary selection of every solid section in the file during import. Typically, there is only one such section. In that case, a selection of the entire boundary is created. This happens also when the STL file is binary and can by definition have no solid sections. The created selections appear in a table in the section that appears below the section. The table has two columns. In the right column, the name of the solid section that the selection has been created from appears. If the section is named or if the file is binary, the name is empty. If the check box is selected and domains was successfully created, a table with selections for the domains appear under the section. The domain selection typically get the same name as the boundary selection for the boundaries that enclose the domain. The selections appear in the same order as the corresponding sections in the file. In the left column, the name of the selection appears. By this name, which can be changed, as well as dimension of the selection, you can find the selection in the model.

The repair tolerance assures that the imported mesh contains no holes and no triangles with sides shorter that the tolerance. Specify the by selecting one of these options:

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(the default), to use a default tolerance value (10−8).

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, to specify a (default: 10−8). The relative tolerance value must be smaller or equal to 1.

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, to specify an (default: 10−8) in the length unit specified in the Settings window for the node.

Tolerance for Merging of Vertices for 3MF, PLY, and VRML Files

These settings are available when the list is set to , , or for import of files of the 3MF, PLY, or VRML formats. Such files contain data for a surface mesh containing triangle or quadrilateral (PLY only) elements.

Select the check box to merge mesh vertices that coincide within the merge tolerance during import. Specify the by selecting one of these options:

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(the default), to use a default tolerance value (10−8).

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, to specify a (default: 10−8). The relative tolerance value must be smaller or equal to 1 and it translates to an absolute value by multiplying it with the largest coordinate in the mesh.

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, to specify an (default: 10−8) in the length unit specified in the Settings window for the node.

Entity Selections

The sections , , , and appear after building the operation. The selections are generated during the import based on selections defined in the source. In the column, the name of each selection appears. For STL file import, the source of each selection appears in column (that is, which information in the imported file that was used to generate the selection). Select the name in the column to highlight the selection in the window. You can change the name of a selection by editing the corresponding table entry in the column. Note that not all of these selection sections are available for all space dimensions.

The selections can be used to specify entity selections in operations and attributes within the same meshing sequence and, if the mesh defines the component’s geometric model, for physics and material settings. For more information about the component’s geometric model, see The Mesh Node.