On this page:
5.12.1 Importing a Mesh
5.12.2 Importing 2D Exodus Files
5.12.3 Importing Abaqus Files
5.12.4 Importing Exodus II Files
5.12.5 Importing Fluent Files
5.12.6 Importing I-DEAS Files
5.12.7 Importing Nastran Files
5.12.8 Importing Patran Files
5.12.9 Lite Meshes
2022.4+26187-e1209cf7 Apr 14, 2022

5.12 Mesh Import

5.12.1 Importing a Mesh

ExodusII finite element data files can be imported into Cubit. Several options for importing the mesh are available, including mesh transformations.

5.12.2 Importing 2D Exodus Files

Cubit has a limited capability to create ACIS Geometry from 2D ExodusII finite element mesh files. (For a more general capability, see the Import Mesh Geometry command, which will create Mesh-Based Geometry).

To import a 2D Exodus II file and create ACIS geometry:

  1. Select File and then Import.

  2. Select the file to be imported.

  3. Select Exodus from the Files of type drop-down menu.

  4. Click Open. A new window will appear.

  5. Optionally specify any appropriate settings from this window.

  6. Click Finish.

Import Free Mesh ’<filename>’ {Time <t> | Step <step#> | Last}

Cubit can create ACIS geometry from 2D Exodus II data files (4, 8, or 9 node QUAD or SHELL element types) that do not have enclosed voids (holes surrounded by mesh) and which were originally generated with Cubit and exported to ExodusII with the Nodeset Associativity option set to on. The Nodeset Associativity command records the topology of the geometry into special nodesets which allow Cubit to reconstruct a new solid model from the mesh even after it has been deformed. The new solid model of the deformed geometry can be remeshed with standard techniques or meshed with a sizing function that can also be imported into Cubit from the same ExodusII file. Cubit’ implementation of the paving and triadvance algorithms can generate a mesh following a sizing function to capture a gradient of any variable (element or nodal) present in the ExodusII file.

In order for this feature to be effective, the following commands must be issued when the mesh is exported and later imported:

nodeset associativity on

set associativity complete on

The first command ensures that the geometry will be correctly recovered from the mesh, while the second ensures that boundary condition and material IDs will be recovered.

5.12.3 Importing Abaqus Files

To import a mesh from an Abaqus format file

  1. Select File and then Import.

  2. Select the file to be imported.

  3. Select Abaqus from the Files of type drop-down menu.

  4. Click Open. A new window will appear.

  5. Optionally select any appropriate specifications from this window.

  6. Click Finish.

Import Abaqus [Mesh Geometry] ’<input_filename>’ [Feature Angle <angle>] [Nobcs]

Including the keyword mesh geometry will instruct Cubit to create mesh-based geometry. This will provide the user with the ability to remesh geometric entities. If the user does not import with the Mesh Geometry flag, he will have to tell Cubit to draw the mesh after the import is done in order to view it.

The feature angle is used when building the surface topology to determine when to split a surface into two surfaces. If the angle between two neighboring element normals is less than Feature Angle, then the two elements will be placed on separate surfaces. If the keyword Feature Angle is not supplied, the default 135 degrees is used. For a description of importing mesh geometry see Importing Exodus II Files.

The keyword nobcs can be included if boundary conditions are not to be imported.

The Abaqus importer can import the following Abaqus file formats: flat file, part-independent, and part-dependent.

It should be noted that Cubit sometimes cannot successfully generate mesh-based geometry for complex models.If this occurs, import the mesh without the Mesh Geometry flag, and draw the mesh to view it.

To list Abaqus cards supported by Cubit:

List Abaqus Import Cards

This command will list out all supported Abaqus cards that Cubit can interpret.

Supported Element Types

1st Order

2nd Order

Triangle

S3
CAX3
CPE3

STRI65
CAX6
CPE6

Quadrilateral

S4
CAX4
CPE4

S8
CAX8
CPE8

Tetrahedron

C3D4

C3D10

Hexahedron

C3D8

C3D20

Line Element

B21
B31
T2D2
T3D2
SPRINGA
SPRING1
SPRING2

B22
B32
T2D3
T3D3

See http://www.simulia.com/ for more information on the ABAQUS file format.

5.12.4 Importing Exodus II Files

The commands to import meshes from an Exodus II format file are:

Import Mesh ’<exodusII_filename>’ No_Geom
[Block <block_ids>] [{genesis_collision_fail|COMBINE_GENESIS_IDS|combine_genesis_names|unique_genesis_ids}] [block_offset <value>] [sideset_offset <value>] [nodeset_offset <value>] [{node_id_collision_fail|UNIQUE_NODE_IDS}] [{element_id_collision_fail|UNIQUE_ELEMENT_IDS}] [node_offset <value>] [element_offset <value>]] [group_name ’<free_elements>’] [[Time <time>|Step <step>|Last] [Scale <value>]]

Import Mesh ’<exodusII_filename>’
[Block <block_ids>] [{genesis_collision_fail|COMBINE_GENESIS_IDS|combine_genesis_names|unique_genesis_ids}] [block_offset <value>] [sideset_offset <value>] [nodeset_offset <value>] [{node_id_collision_fail|UNIQUE_NODE_IDS}] [{element_id_collision_fail|UNIQUE_ELEMENT_IDS}] [node_offset <value>] [element_offset <value>]] [{Group|Body|Volume|Surface|Curve|Vertex} <id_range> | Preview]

Import Mesh Geometry ’<exodusII_filename>’
[Block <id_range>|ALL] [{genesis_collision_fail|COMBINE_GENESIS_IDS|combine_genesis_names|unique_genesis_ids}] [block_offset <value>] [sideset_offset <value>] [nodeset_offset <value>] [{node_id_collision_fail|UNIQUE_NODE_IDS}] [{element_id_collision_fail|UNIQUE_ELEMENT_IDS}] [node_offset <value>] [element_offset <value>]] [Use [NODESET|no_nodeset] [SIDESET|no_sideset] [Feature_Angle <angle>] [surface_feature_angle <angle>][LINEAR|Gradient|Quadratic|Spline|Acis] [Deformed {Time <time>|Step <step>|Last} [Scale <value>] ] [MERGE|No_Merge] [Merge_nodes <tolerance>]

Import Mesh ’<exodusII_filename>’ Lite [{genesis_collision_fail|COMBINE_GENESIS_IDS|combine_genesis_names|unique_genesis_ids}] [block_offset <value>] [sideset_offset <value>] [nodeset_offset <value>] [{node_id_collision_fail|UNIQUE_NODE_IDS}] [{element_id_collision_fail|UNIQUE_ELEMENT_IDS}] [node_offset <value>] [element_offset <value>]]

5.12.4.1 Common Options
5.12.4.1.1 Specifying a Portion of the Mesh to be Imported

The block option in the import mesh command indicates that only the specified element block should be imported from the Exodus II file. If the block option is not specified, then the entire mesh file is read.

5.12.4.1.2 Combine Genesis IDs

The combine_genesis_ids option is used to combine blocks where the ids in the session and the file being imported are identical. This can occur when importing into an active session where Cubit ids have already been assigned. The default behavior is to combine genesis entities based on IDs. If two entities have different IDs but the same names they will not be combined, and the import will fail.

5.12.4.1.3 Combine Genesis Names

The combine_genesis_names option is used to combine blocks where the names in the session and the file being imported are identical. This can occur when importing into an active session where names have already been assigned. If two entities have different names but identical IDs they will not be combined, and the import will fail.

5.12.4.1.4 Unique Genesis IDs

The unique_genesis_ids option is used to renumber genesis entities from the genesis file in the case that id overlap exists when importing into Cubit. The incoming genesis entities are kept unique and are not combined with genesis entities already in the session. In case of colliding IDs a report is displayed in the command window showing the original and new IDs. This renumbering can occur when importing into an active session where Cubit ids have already been assigned. If an entity being imported has the same name as one already in the session, the entity being imported will be renamed with a number suffix ’_N’.

5.12.4.1.5 Genesis Collision Fail

The genesis_collision_fail option allows the user to prevent the genesis file import if any incoming genesis entity ids or names are already used by genesis entities in the session. This can occur when importing into an active session where Cubit ids have already been assigned.

5.12.4.1.6 Block_Offset, Sideset_Offset, Nodeset_Offset

The block_offset, sideset_offset, and nodeset_offset options may be used to modify the IDs of genesis entities being imported. The provided value will be added to the ID in the file.

5.12.4.1.7 Unique Node and Element IDs

The unique_node_ids and unique_element_ids option is used to renumber mesh entities from the genesis file in the case that id overlap exists when importing into Cubit. The incoming genesis entities are kept unique and are not combined with genesis entities already in the session. In case of colliding IDs, a report displayed in the command window showing the original and new IDs. This renumbering can occur when importing into an active session where Cubit IDs have already been assigned. If an entity being imported has the same name as one already in the session, the entity being imported will be renamed with a number suffix ’_N’.

5.12.4.1.8 Element and Node ID Collision Fail

The node_id_collision_fail and element_id_collision_fail option allows the user to prevent the genesis file import if any incoming mesh entity ids are already used by mesh entities in the session. This can occur when importing into an active session where Cubit ids have already been assigned.

5.12.4.1.9 Node_Offset and Element_Offset

The node_offset and element_offset options may be used to modify the IDs of mesh entities being imported. The provided value will be added to the ID in the file.

5.12.4.2 Importing a Free Mesh Without Geometry

The command to import a free mesh from an Exodus II format file without mesh-based geometry is:

Import Mesh ’<exodusII_filename>’ No_Geom [group_name ’<free_elements>’] [[Time <time>|Step <step>|Last] [Scale <value>]]

When a free Exodus II mesh is imported into Cubit, it contains no geometric or topological information. Previously, the user could either associate that mesh with existing geometry, or build mesh-based geometry to fit the mesh. A third option, as of Cubit 11.1, allows the user to retain the disassociated mesh as a free mesh inside Cubit.

A free mesh may be modified as described in the Free Mesh section of the documentation. This includes limited access to smoothing, renumbering, transformations, refinement, mesh quality, and other mesh centric operations.

When an Exodus II File is imported as a free mesh, Cubit will automatically create a group called "free_elements" to contain the free mesh elements. The ’group_name’ option can be used to give the group a different name.

Deformation information can be read in via the time/step/last and scale parameters.

Note: The import mesh [no_geom] command is not to be confused with the import free mesh command which applies only to 2D Exodus II Files.The term "Free Mesh" in both places of the documentation refers to the same thing - a mesh without geometry. However, in the case of all other import mesh commands, the imported free mesh ends up associated with geometry. The import mesh <filename> [no_geom] is the only way to import a free mesh that remains disassociated from geometry.

5.12.4.3 Importing a Mesh Onto Existing Geometry

The command to import a free mesh from an Exodus II format file and associate it with existing geometry is:

Import Mesh ’<exodusII_filename>’ [{Group|Body|Volume|Surface|Curve|Vertex} <id_range> | Preview]

The user can import a mesh from an Exodus II file and associate the mesh with matching geometry. The resulting mesh may then be manipulated normally. For example, the mesh may be smoothed or portions of it deleted and remeshed. The user can save their work by exporting the geometry and mesh, and then restore the geometry and mesh later. In some cases, saving and restoring can be faster or more reliable than replaying journal files.

Saving and importing a mesh may be useful for teams working on creating a conforming mesh of a large assembly so that they can pass information to one another. For example, a team member can export the mesh on the surfaces between two parts, and another team member import the mesh for use on an adjoining part of the assembly.

As of Cubit version 7.0, any higher order elements, block definitions, nodesets, and sidesets are retained on import.

5.12.4.3.1 Importing a Mesh with Nodeset Associativity

Meshes can be imported into Cubit that contain nodeset associativity data used for defining finite element boundary conditions. If an exported Cubit mesh is going to be imported back onto the same geometry, then before exporting the user should issue the following command:

set export mesh nodeset associativity on

This causes extra nodeset data to be written, which associates every node to a geometric entity, resulting in an import which is more reliable. When importing, if the user does not want to use the nodeset associativity data that exists in a file, then before importing the following command should be used:

set import mesh nodeset associativity off

The user may wish to turn geometry associativity off if, for example, the geometry is no longer identical as a result of curves being composited, or Cubit names changed due to a ACIS version changes.

5.12.4.3.2 Importing a Mesh onto Modified Geometry

Although there are some exceptions, Cubit requires that the mesh be imported onto the same geometry from which it was exported.

Since merge information is not stored with the ACIS representation, care should be taken that the geometry is merged the same way on export and import of the mesh. If not, importing the mesh one block at a time in successive commands may increase the chance of a successful import, at the cost of more memory and time.

Between exporting and importing a mesh, the geometry may be modified slightly by compositing entities. Mesh import will, however not be successful if entities are partitioned or a body is webcut. In some cases mesh import may be successful on modified geometry if the new vertices match up exactly with nodes of the mesh, and the new curves match up exactly with edge chains of the mesh. Unless this criteria is met, associating the mesh with the geometry will be unsuccessful.

5.12.4.3.3 Mesh Import Tolerance

To change the tolerance with which imported mesh must line up with geometry issue the command:

Set Import Mesh [Vertex] [Curve] [Surface] Tolerance <distance>

5.12.4.3.4  Specifying a Portion of the Mesh to be Imported

The block option in the import mesh command indicates that only the specified element block should be imported from the Exodus II file. If the block option is not specified, then the entire mesh file is read. The block is not yet supported for lite imports, which currently imports the entire mesh.

If a block is specified without specifying a geometry entity, associativity or proximity is used to determine which volume the block elements should be associated with. If a block and a volume are specified, the block elements are associated with the specified volume, provided they actually match. If a volume is specified without a block, associativity data is used to find a block corresponding to the given volume.

5.12.4.3.5  Unique Genesis IDs and Shell Options

The Unique Genesis IDs option is used to preserve ids in the genesis file in the case that id overlap exists when importing into Cubit. This can occur when importing into an active session where Cubit ids have already been assigned.

The Shell Option is used as a flag to alert the program that there are shell elements in the file. Shell elements can not always be detected by the import program, and this ensures that the shell elements will be included in the model.

5.12.4.3.6  Nodeset Ordering

If the Import mesh NodeSet Order flag is on, the nodesets will be read in a manner which allows them to be associated with existing geometry. This means the nodesets are assumed to be in ascending order. If the flag is set to false, the geometry nodesets in imported mesh files are assumed to be in random order. This value is on by default, and should not need to be changed by the user.

5.12.4.4 Creating Mesh-Based Geometry on Import

Cubit’s mesh generation tools require an underlying geometry representation. In most cases, the ACIS solid modeling engine, compiled with Cubit, is used to represent the geometry. However, in some cases, an ACIS representation is not available, and a previously developed finite element mesh is the only available representation of the model. In order to utilize Cubit’s mesh generation tools, the import mesh geometry command provides an option for creating geometry directly from the finite element mesh.

The import mesh geometry command will create a new volume for every block defined in the Exodus II file. It will also create curves, surfaces and vertices at appropriate locations on the model based on dihedral angles (also called feature angles) and assigned nodesets and/or sidesets. The mesh used to construct the geometry will be owned by the new geometric entities. This means that the mesh can be deleted, remeshed, or smoothed using any of Cubit’s meshing tools by simply using the new geometry definition. Cubit will assign appropriate intervals to the new curves as well as determine an acceptable meshing scheme for surfaces and volumes.

The command to import a finite element mesh from an ExodusII format file and generate geometry from the mesh is:

Import Mesh Geometry ’<exodusII_filename>’
[Block <id_range>|ALL] [Unique Genesis IDs] [Start_id <id>] [Use [NODESET|no_nodeset] [SIDESET|no_sideset] [Feature_Angle <angle>] [surface_feature_angle] [LINEAR|Gradient|Quadratic|Spline] [Deformed {Time <time>|Step <step>|Last} [Scale <value>] ] [MERGE|No_Merge] [Export_facets <1|2|3>] [Merge_nodes <tolerance>]

5.12.4.4.1 File Name

Type the name of file to import in single quotation marks. The file must reside in the current directory. For information on changing the current directory, see Cubit environment commands. To list all the files in the current directory, type ls at the command prompt.

5.12.4.4.2 Blocks

Use this option to select the specific blocks to be imported from the Exodus II file. If no blocks are entered, then all blocks will be read and imported from the file. Standard ID parsing can also be used in this argument to select a range of blocks. For example 1 to 5 or 1, 5 to 10 except 6.

Each unique block selected to be imported will define a new body in the geometric model. Figure 463 shows a simple example of the geometry generated from the 3D finite element mesh.

Figure 463: Example of mesh based geometry (right) created from a finite element mesh (left)

Blocks may be composed of 1D, 2D or 3D elements. For blocks composed of 2D elements (i.e. QUAD4, SHELL etc.), a sheet body will be created. One dimensional elements (i.e.. BEAM, TRUSS, etc.) will define curves. Where a block may be composed of more than one disconnected sets of elements, one body will be created for each continuous region of elements assigned to the same block. Where possible, the ID of the new body will be the same as the block ID. Since IDs must be unique, if a body ID is already in use, the next available ID will automatically assigned by the program.

5.12.4.4.3 Unique Genesis IDs

The unique genesis Ids option is used to preserve ids in the Cubit session in the case that id overlap exists when importing an Exodus II file. This can occur when importing into an active session where ids for blocks, nodesets or sidesets have already been assigned. The default behavior, when ID collisions occur, is to include any new entity into the existing block nodeset or sideset. If the unique genesis Ids option is used, Cubit will automatically generate a unique ID for any block, nodeset or sideset imported. A report of the collisions and their new IDs will be displayed on import in the command window.

5.12.4.4.4 Start ID

Use this option to specify an alternate ID value for imported mesh entities. The specified value will be used as the starting ID for BOTH nodes and mesh elements. The new IDs will be assigned consecutively from the starting value. If the new ID values for any of the imported entities would conflict with existing IDs, the command does not abort but moves the starting ID for all element types to the same useable starting ID value.

5.12.4.4.5 Nodesets/Sidesets

Use the nodeset and sideset options to use any nodeset and sideset information in the Exodus II file in constructing geometry. Recall that nodesets and sidesets are generic boundary condition data assigned to nodes, edges or faces of the finite elements. It is useful to group mesh entities belonging to unique boundary conditions into geometric entities. This permits the user to remesh a particular region of the model without having to reassign boundary conditions.

If the nodeset and sideset arguments are given, geometric entities will be generated for each unique set of nodes, edges or element faces assigned to a nodeset or sideset. The default is to use any nodeset and sideset information available in the file. Figure 464 shows an example of how nodeset and sideset information might be used to generate geometry.

Figure 464: Example of geometry created from mesh entities assigned to nodesets (3) and sidesets (1 and 2).

Upon import, nodesets and sidesets are automatically created with the appropriate geometric entities assigned to them. The IDs of the new geometric entities, if generated from boundary condition data, will be the same as the nodeset and sideset IDs. Where doing so would conflict with existing geometric IDs, the program will automatically select the next available ID.

5.12.4.4.6 Feature Angle

Use this option to specify the angle at which surfaces will be split by a curve or where curves will be split by a vertex. 180 degrees will generate a surface for every element face, while 0 degrees will define a single, unbroken surface from the shell of the mesh. The default angle is 135 degrees.

mbg005.gifmbg006.gifmbg007.gif

Figure 465: Example use of Feature Angle

Figure 465 shows an example of the use of different feature angles. On the left is a simple two-element hex mesh. Specifying a feature angle greater than 120 degrees would create the geometry in the center image. Using a feature angle less than 120 degrees and greater than 90 degrees would define the geometry on the right.

It is possible to independently control the feature angle for surfaces and curves. If surface_feature_angle is specified, it controls the angle at which surfaces will be split by a curve, while Feature_Angle controls the angle at which curves will be split by a vertex. If surface_feature_angle is not specified, feature_angle will control the angle for both surfaces and curves.

5.12.4.4.7 Smooth Curves and Surfaces

This argument allows the option of using a higher-order approximation of the surface when remeshing/refining the resulting geometry. Default is to use the original mesh faces themselves as the curve and surface geometry representation. If the finite element model to be imported is to represent geometry with curved surfaces, it may be useful to select this option. If selected, it will use a 4th order B-Spline approximation to the surface [Walton,96]. Figure 466 shows the effect of the smooth curve and surface option.

Figure 466: Effect of Smooth Curve and Surface Option for remeshing of mesh-based geometry

In this figure the top image is the original finite element mesh imported into Cubit. In this example both models have been remeshed with the same element size. The difference is that the figure on the right uses the smooth curve and surface option. While this option can improve the surface representation, it should be noted that memory requirements and meshing times can sometimes be affected.

If importing the Exodus II file using the command line, other options for surface representations are also available.

[LINEAR|Gradient|Quadratic|Spline]

The method used from the GUI is either linear or spline. The gradient and quadratic methods are still somewhat experimental and may not be as general purpose as the spline representation.

5.12.4.4.8 Apply Deformations

This option permits the user to import time-dependant deformation information from the Exodus file. For this option, any vector data in the Exodus II file is assumed to be deformation information. If selected, deformations will be applied to the nodes upon import. Enter a specific time step value, integer step, or the last time available in the file. If time-dependant data is available in the Exodus II file, selecting the down arrow in the edit field will display the available time steps in the file. Default time is the last time step.

Figure 467: Example of remeshing of a deformed finite element mesh

Figure 467 shows an example of using Mesh-Based Geometry for a large deformation analysis. In this case, the analysis [Attaway et. al.,98] began and continued until mesh quality became unacceptable. At that point, the mesh was imported into Cubit and geometry re-created from the computed deformations. The finite element mesh could then be removed, remeshed or improved and written back to an Exodus II file. After remapping [Wellman,99] the appropriate analysis variables back to the mesh, the analysis could then be restarted. This process was repeated multiple times until the desired results were achieved.

Note: Care should be taken when using large deformations, as inverted elements (negative Jacobians) may produce unpredictable results with the resulting geometric representation.

Also available is an optional scale factor. This applies the indicated scale to all deformations. Default is 1.0.

5.12.4.4.9 Merge

This option allows the user to either merge or not merge the resulting volumes. The default option is to merge adjacent volumes. This results in non-manifold topology, where neighboring volumes share common surfaces. Using the no_merge option, adjacent volumes will generate distinct/separate surfaces.

5.12.4.4.10 Merge Nodes

The merge_nodes option will allow the user to specify a different tolerance for merging nodes on import. The default value is 1e-6.

Note: Care should be taken when setting import merge tolerances. Setting a tolerance too low will not merge adjacent nodes. Setting the tolerance too high can produce undesirable results, and severely tangle the mesh.

5.12.4.5 Importing a Lite Mesh

The command to import a lite mesh from an Exodus II format file is:

Import Mesh ’<exodusII_filename>’ lite

When an Exodus II mesh is imported into Cubit using the lite option it contains no geometric or topological information.

The lite mesh import may be an option for users wanting to quickly view the mesh without gaining all the abilities to modify the mesh.

More information on how a lite mesh may be viewed or modified is described in the Lite Mesh section of the documentation.

5.12.5 Importing Fluent Files

To import a mesh from a fluent format file

  1. Select File and then Import.

  2. Select the file to be imported.

  3. Select Fluent from the Files of type drop-down menu.

  4. Click Open. A new window will appear.

  5. Optionally select any appropriate specifications from this window.

  6. Click Finish.

Import Fluent [Mesh Geometry] ’<input_filename>’ [Feature Angle <angle>] [nobcs]

Including the keyword mesh geometry will instruct Cubit to create mesh-based geometry. This will provide the user with the ability to remesh geometric entities. If the user does not import with the Mesh Geometry flag, he will have to tell Cubit to draw the mesh after the import is done in order to view it.

The feature angle is used when building the surface topology to determine when to split a surface into two surfaces. If the angle between two neighboring element normals is less than Feature Angle, then the two elements will be placed on separate surfaces. If the keyword Feature Angle is not supplied, the default 135 degrees is used. For a description of importing mesh geometry see Importing Exodus II Files.

The keyword nobcs can be included if boundary conditions are not to be imported.

It should be noted that Cubit sometimes cannot successfully generate mesh-based geometry for complex models.If this occurs, import the mesh without the Mesh Geometry flag, and draw the mesh to view it.

5.12.6 Importing I-DEAS Files

To import a mesh from an I-DEAS format file

  1. Select File and then Import.

  2. Select the file to be imported.

  3. Select Ideas from the Files of type drop-down menu.

  4. Click Open. A new window will appear.

  5. Optionally select any appropriate specifications from this window.

  6. Click Finish.

Import Ideas [Mesh Geometry] ’<input_filename>’ [Feature Angle <angle>] [Nobcs]

Including the keyword mesh geometry will instruct Cubit to create mesh-based geometry. This will provide the user with the ability to remesh geometric entities. If the user does not import with the Mesh Geometry flag, he will have to tell Cubit to draw the mesh after the import is done in order to view it.

The feature angle is used when building the surface topology to determine when to split a surface into two surfaces. If the angle between two neighboring element normals is less than Feature Angle, then the two elements will be placed on separate surfaces. If the keyword Feature Angle is not supplied, the default 135 degrees is used. For a description of importing mesh geometry see Importing Exodus II Files.

The keyword nobcs can be included if boundary conditions are not to be imported.

It should be noted that Cubit sometimes cannot successfully generate mesh-based geometry for complex models.If this occurs, import the mesh without the Mesh Geometry flag, and draw the mesh to view it.

To see more information on the I-DEAS file format, visit their website at http://www.siemens.com.

5.12.7 Importing Nastran Files

To import a mesh from an Nastran format file

  1. Select File and then Import.

  2. Select the file to be imported.

  3. Select Nastran from the Files of type drop-down menu.

  4. Click Open. A new window will appear.

  5. Optionally select any appropriate specifications from this window.

  6. Click Finish.

Import Nastran [Mesh Geometry] ’<input_filename>’ [Feature Angle <angle>] [Nobcs]

Including the keyword mesh geometry will instruct Cubit to create mesh-based geometry. This will provide the user with the ability to remesh geometric entities. If the user does not import with the Mesh Geometry flag, he will have to tell Cubit to draw the mesh after the import is done in order to view it.

The feature angle is used when building the surface topology to determine when to split a surface into two surfaces. If the angle between two neighboring element normals is less than Feature Angle, then the two elements will be placed on separate surfaces. If the keyword Feature Angle is not supplied, the default 135 degrees is used. For a description of importing mesh geometry see Importing Exodus II Files.

The keyword nobcs can be included if boundary conditions are not to be imported.

It should be noted that Cubit sometimes cannot successfully generate mesh-based geometry for complex models.If this occurs, import the mesh without the Mesh Geometry flag, and draw the mesh to view it.

See http://en.wikipedia.org/wiki/Nastran for more information on the NASTRAN file format.

5.12.8 Importing Patran Files

To import a mesh from an Patran format file

  1. Select File and then Import.

  2. Select the file to be imported.

  3. Select Patran from the Files of type drop-down menu.

  4. Click Open. A new window will appear.

  5. Optionally select any appropriate specifications from this window.

  6. Click Finish.

Import Patran ’<neutral_filename>’

Import Patran Mesh Geometry ’<neutral_filename>’ [Use [Feature_Angle <angle>] [Linear|Gradient|Quadratic|Spline] ]

See Importing Exodus II Files for a description of the import options.

For more information on the Patran file format, see their website at http://www.mscsoftware.com.

5.12.9 Lite Meshes

Cubit has the ability to represent mesh using either a lightweight or heavy representation. The lightweight representation option is new for Cubit 16.3, and can be referred to as lite. The heavy representation is useful for supporting all the various mesh manipulation operations available in Cubit. While still under development, the lite representation option is intended to be a quick way to display larger meshes while supporting a smaller subset of mesh manipulation operations.

The following items are not yet supported:

5.12.9.1 Creating a lite mesh

To use the lite mesh representation one may import a mesh file using the ’lite’ option. There is not currently another way to create lite mesh other than importing from a file. The command to import a lite mesh is:

Import mesh "<filename>" lite

Additional options for lite import can be found under the Import Mesh Lite command.

5.12.9.2 Graphics

Generally, the graphical features for lite meshes are supported at the same level as for heavy mesh. This includes the ability to draw, pick, and zoom, among other operations. The coloring of the mesh is based on blocks and may be adjusted by the user. Toggling visibility of all sidesets and nodesets can be done by clicking the Display Boundary Conditions toolbar button or with the bc visibility {on|off} command. Toggling visibility of all blocks can be done by clicking the Display Mesh toolbar button or with the mesh visibility {on|off} command.

Figure 468:

The draw, zoom and select commands work on blocks, sidesets and nodesets. Selecting those genesis entities in the graphics window will result in them being highlighted in both the graphics window and in the tree. The selection of nodes and elements has not yet been implemented for mesh imported as lite meshes.

5.12.9.3 Information

There are several ways to view information about the lite mesh. The tree and the property page can show information about the blocks, sidesets and nodesets. The list command can print information about individual blocks, sidesets, and nodesets. The list element command will print out the ID space used by elements. The list node command will show the ID space used by nodes. Listing of individual elements and nodes is not yet supported.

5.12.9.4 Modification to lite mesh

Some modifications to genesis entities are supported. Blocks, sidesets and nodesets may have names assigned to them. Blocks may have their attributes modified, and materials may be assigned to blocks. Not supported is the ability to modify the contents of blocks, nodesets and sidesets.

5.12.9.5 Exporting a lite mesh

Exporting a lightweight mesh to an Exodus file is supported. This includes writing out blocks, nodesets, sidesets, element ids, node ids, etc... Not all Exodus data is read in, and if there is some data not recognized by Cubit, it will not be exported. Field data is an example of Exodus data not recognized by Cubit, nor exported. Importing multiple Exodus files and exporting a single file is supported. Importing a single Exodus files and exporting a portion of it is supported.