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These scripts are provided as-is to Pointwise users for performing automated mesh generation from an attributed geometry database and a set of user-defined parameters. The scripts can be used with Pointwise versions 18.1 and higher. Note that the scripts can use some features that were introduced in 18.2, such as Elevate on Export to generate mesh files that support High Order elements. The scripts will ignore meshing parameters and geometry attributes that are not applicable to the version of Pointwise being used.
These scripts were developed under a subcontract from MIT as part of their U.S. Air Force Contract FA8650-14-C-2472.
The objective of this project was to create a set of scripts to be executed within the Pointwise mesh generation program that automatically make a single block unstructured mesh given geometry created using Engineering Sketch Pad (ESP). No foreknowledge of the elements contained in the geometry file is required. If the geometry forms a closed model, then a completed unstructured mesh is the expected result. The scripts create surface meshes that adhere to the geometry and are sized to respect all length scales. A set of default meshing parameters is provided, but can be optionally and selectively superseded by means of a user-defined parameter file. These parameters control the operation of Pointwise during execution. The default parameters were developed to incorporate many best practices that produce a quality unstructured mesh with smoothly varying mesh characteristics.
Note
Even though attribution is not possible with IGES and STEP geometry files, the scripts will attempt to generate a completed unstructured volume mesh for the input geometry. The final mesh will exhibit all the quality characteristics afforded by the processes and best practices, but will not have any characteristics provided through geometry attribution. If the geometry is both closed and of high quality, the likelihood of a completed mesh is high. Once generated, the mesh can be modified using Pointwise to apply problem-specific attributes to meet additional quality criteria.
The main script is GeomToMesh.glf. It can be used either in batch mode from the command line, or in the Pointwise GUI. All of the support scripts must reside in the same directory as GeomToMesh.glf, including:
- GeomToMeshDefaults.glf -- Default parameter values that control the meshing process.
- GMDatabaseUtility.glf -- Functions used for accessing geometry and retrieving attributes.
- GMUtility.glf -- Functions for performing various meshing operations.
- GMSafeUtility.glf -- Functions for isolating loading of user-defined parameter files to prevent malicious commands from being executed by the master script.
- GMMeshParamCoords.glf -- Functions for creating and writing Geometry to Mesh Associativity (GMA) files.
- GMMeshParamCoordsV2.glf -- Functions for creating and writing Geometry to Mesh Associativity (GMA) version 2 files.
The script RefineByFactor.glf can be used to refine or coarsen the current mesh in memory. The factor is defined at the top of the script. This can be used on meshes created with GeomToMesh.glf in a process to create a mesh sequence.
From the Script menu, click Execute... and browse to the directory containing the GeomToMesh.glf and support scripts. Type in or select the geometry file and optional user-defined attributes file, then click Start. A variety of informational messages about the geometry assembly and meshing process are emitted to the message window.
For ease of repeated usage, it is recommended to add GeomToMesh.glf to the Script Toolbar using the Script Toolbar Manager... under the Script menu.
In the directory containing the desired geometry and optional user-defined attributes file, run a command similar to the following:
Windows:
% <path-to-pointwise-install>\win64\bin\tclsh.exe <path-to-scripts>\GeomToMesh.glf geometry-file user-defaults.glf
Non-Windows (Linux and Mac OS/X):
% <path-to-pointwise_install>/pointwise -b <path-to-scripts>/GeomToMesh.glf geometry-file user-defaults.glf
Where:
<path-to-pointwise-install>is the full path to your licensed Pointwise installation directory<path-to-scripts>is the full or relative path to the directory containing GeomToMesh.glf and its support scripts
In either batch or GUI mode, GeomToMesh will write the final mesh file in Pointwise format with a name consisting of the geometry file name with ".GeomToMesh" appended to it. Optionally, a CAE file can be exported for CGNS, Gmsh and UGRID formats, including high order elements if specified and supported by the format.
The meshing process is controlled through either global meshing parameters (which can be customized for each project), or by attributes attached to geometry elements. The global parameters are set via a combination of the provided GeomToMeshDefaults.glf and a customization script that overrides the defaults as needed.
It is highly recommended that the provided GeomToMeshDefaults.glf file remain unaltered. These parameters represent the "best practice" values that generally produce quality unstructured volume grids under normal circumstances. To define a custom set of parameters:
- copy GeomToMeshDefaults.glf to the directory where the geometry (CAD) file is located
- rename the copy to indicate the objective of the customization, e.g. "CoarseSettings.glf"
- edit the values in that file as desired
The custom settings file is specified as input, and is sourced into the main script after the provided default settings (GeomToMeshDefaults.glf) file. So, only the settings that need to be superseded need to be present.
Geometry attributes allow fine-grained control over mesh generation, and supersede the global settings where applicable.
Supported geometry formats for GeomToMesh include EGADS, IGES, STEP and NMB (Pointwise proprietary geometry format) files. GeomToMesh will attempt to create a single unstructured block volume mesh. IGES and STEP files will not contain GeomToMesh attributes, so the resulting volume mesh will be of the isotropic variety with no viscous boundaries or layers.
NMB or EGADS files may contain GeomToMesh attributes, and thus may include directives that will customize the resulting volume mesh, and may include viscous boundaries and layers. ESP writes EGADS files, and has the ability to assign GeomToMesh attributes to entities in the model. As shown in the table below, GeomToMesh looks for attributes in the form of key-values pairs on faces, curves and nodes in the model that have the prefix "PW:", such as "PW:Name Body" or "PW:WallSpacing 0.001". A list of the possible Pointwise specific attributes is provided below, and also in the provided Excel spreadsheet AttributeVocabulary.xlsx.
When these attributes are found they guide Pointwise to alter the default behavior to produce a mesh that has features of interest to the user, such as boundary conditions and viscous layers.
Note: Preceding $ indicates it is a literal character string
| Key | Value | Geometry Location | Description |
|---|---|---|---|
PW:Name |
Face |
Boundary name for domain or collection of domains. | |
PW:QuiltName |
Face |
Name to give one or more quilts that are assembled into a single quilt. No angle test is performed. | |
PW:Baffle |
$Baffle or $Intersect |
Face |
Either a true baffle surface or a surface intersected by a baffle. |
PW:DomainAlgorithm |
$Delaunay, $AdvancingFront,
$AdvancingFrontOrtho |
Face |
Surface meshing algorithm. |
PW:DomainIsoType |
$Triangle, $TriangleQuad |
Face |
Surface cell type. Global default is Triangle. |
PW:DomainMinEdge |
$Boundary or > 0.0 |
Face |
Cell Minimum Equilateral Edge Length in domain. |
PW:DomainMaxEdge |
$Boundary or > 0.0 |
Face |
Cell Maximum Equilateral Edge Length in domain. |
PW:DomainMaxAngle |
[ 0, 180 ) |
Face |
Cell Maximum Angle in domain (0.0 = NOT APPLIED) |
PW:DomainMaxDeviation |
[ 0, infinity ) |
Face |
Cell Maximum Deviation in domain (0.0 = NOT APPLIED) |
PW:DomainSwapCells |
$true or $false |
Face |
Swap cells with no interior points. |
PW:DomainQuadMaxAngle |
( 90, 180 ) |
Face |
Quad Maximum Included Angle in domain. |
PW:DomainQuadMaxWarp |
( 0, 90 ) |
Face |
Cell Maximum Warp Angle in domain. |
PW:DomainDecay |
[ 0, 1 ] |
Face |
Boundary decay applied on domain. |
PW:DomainMaxLayers |
[ 0, infinity ) |
Face |
Maximum T-Rex layers in domain. |
PW:DomainFullLayers |
[ 0, infinity ) |
Face |
Number of full T-Rex layers in domain. (0 allows multi-normals) |
PW:DomainTRexGrowthRate |
[ 1, infinity ) |
Face |
T-Rex growth rate in domain. |
PW:DomainTRexType |
$Triangle, $TriangleQuad |
Face |
Cell types in T-Rex layers in domain. |
PW:DomainTRexIsoHeight |
> 0.0 |
Face |
Isotropic height for T-Rex cells in domain. Default is 1.0. |
PW:PeriodicTranslate |
"tx; ty; tz" |
Face |
Periodic domain with given translation vector. |
PW:PeriodicRotate |
"px; py; pz; nx; ny; nz; ang" |
Face |
Periodic domain with given point, normal and rotation angle. |
PW:PeriodicTarget |
$true or $false |
Face |
Target domain of a translate or rotate periodic domain. This domain will be deleted before the creation of the periodic domain. |
PW:DomainAdaptSource |
$true or $false |
Face |
Set domain up for adaptation as a source. |
PW:DomainAdaptTarget |
$true or $false |
Face |
Set domain up for adaptation as a target. |
PW:DomainShapeConstraint |
$DataBase or $Free |
Face |
Set domain shape constraint. |
PW:DomainBlunt |
$true or $false |
Face |
Flag the domain as blunt for special dimension handling. |
PW:WallSpacing |
$Wall or > 0.0 |
Face |
Viscous normal spacing for T-Rex extrusion. $Wall uses domParams(WallSpacing) |
PW:TRexIsoHeight |
> 0.0 |
Model |
Isotropic height for volume T-Rex cells. Default is 1.0. |
PW:TRexCollisionBuffer |
> 0.0 |
Model |
T-Rex collision buffer. Default is 0.5. |
PW:TRexMaxSkewAngle |
[ 0, 180 ] |
Model |
T-Rex maximum skew angle. Default 180 (Off). |
PW:TRexGrowthRate |
[ 1, infinity ) |
Model |
T-Rex growth rate. |
PW:TRexType |
$TetPyramid,
$TetPyramidPrismHex, or
$AllAndConvertWallDoms |
Model |
T-Rex cell type. |
PW:BoundaryDecay |
[ 0, 1 ] |
Model |
Volumetric boundary decay. Default is 0.5. |
PW:EdgeMaxGrowthRate |
[ 1, infinity ) |
Model |
Volumetric edge maximum growth rate. Default is 1.8. |
PW:MinEdge |
$Boundary or > 0.0 |
Model |
Tetrahedral Minimum Equilateral Edge Length in block. |
PW:MaxEdge |
$Boundary or > 0.0 |
Model |
Tetrahedral Maximum Equilateral Edge Length in block. |
PW:ConnectorMaxEdge |
> 0.0 |
Edge |
Maximum Edge Length in connector. |
PW:ConnectorEndSpacing |
> 0.0 |
Edge |
Specified connector endpoint spacing. |
PW:ConnectorDimension |
> 0 |
Edge |
Specify connector dimension. |
PW:ConnectorAverageDS |
> 0.0 |
Edge |
Specified average delta spacing for connector dimension. |
PW:ConnectorMaxAngle |
[ 0, 180 ) |
Edge |
Connector Maximum Angle. (0.0 = NOT APPLIED) |
PW:ConnectorMaxDeviation |
[ 0, infinity ) |
Edge |
Connector Maximum Deviation. (0.0 = NOT APPLIED) |
PW:ConnectorAdaptSource |
$true or $false |
Edge |
Set connector up for adaptation as a source. |
PW:NodeSpacing |
> 0.0 |
Node |
Specified connector endpoint spacing for a node. |
Pointwise versions 18.3 and higher provides tools to allow users to edit/add attributes to geometry within the GUI. The geometry can then be exported as an NMB file (Pointwise native geometry) and then processed by the GeomToMesh scripts.
GeomToMesh attributes can exist in EGADS files written by newer versions of ESP. Pointwise V18.3 and higher will be able to import EGADS files which are the native geometry files for ESP. For versions prior to V18.3, geometry attributes can be stored in Pointwise file (.nmb) using a conversion tool called egads2nmb (provided by ESP) that transforms a standard ESP (.egads) file to a Pointwise proprietary geometry format file (.nmb). At this time, there are no plans to support other types of attributed geometry file formats.
The example directory includes several small cases that demonstrate the operation of the scripts.
Baffles are domains that "float" in the interior of a block, and are used to control grid clustering and other aspects of the interior. The surface elements (triangles and quads) in a baffle domain are guaranteed to exist in the isotropic portion of the final volume mesh. Geometric face elements may be attributed with PW:Baffle with a value of "Baffle" or "Intersect". The generated domain for a geometric face element attributed as "Baffle" will be added to the resulting volume grid as a true baffle. If the baffle domain will intersect with another domain, such as an outflow boundary, then boundary geometry element should be attributed as "Intersect".
Periodic domains are created in pairs where one is the "source" and the other (its periodic partner) is an exact copy that has been transformed from the source, typically through either translation or rotation. Only pure translation or rotation periodic domains may be generated by GeomToMesh. The geometric face that represents the source domain should be attributed with PW:PeriodicTranslate or PW:PeriodicRotate with a value component comprised of a translation vector, "tx; ty; tz" or a rotation transform, "px; py; pz; nx; ny; nz; angle", respectively. The translation form includes the three components of the translation from the source domain to the target domain. The rotation transform includes the origin point, normal (rotation axis) and angle used to define the pure rotation from the source domain to the target domain. If there is a geometric face that represents the intended periodic partner domain, it must be attributed with PW:PeriodicTarget and a value of "true". The domain automatically created for this geometric face will be replaced with the periodic domain copy through the designated transformation.
A supplemental source points file can be specified using the parameter genParams(SourcePCDFile) in the UserDefaults.glf file. This is the name of a Point Cloud Data (PCD) file containing points in space and a desired element size. An example file is provided in the ThreeSpheresBox example directory. The entries for each point include the three coordinates, a spacing value, and a decay value. The decay value is optional. If not specified the default background decay will be used. The intent is to permit solution based adaptation. The PCD file can be manually created or created from a flow solution, either using feature-based or output-based (adjoint) adaptation techniques. This is left up to the user. These points will be added to the sources and used to adapt the domains and volume mesh.
The scripts are the subject of an AIAA paper "Automatic Unstructured Mesh Generation with Geometry Attribution", AIAA-2019-1721 presented at AIAA Science and Technology Forum and Exposition 2019 in San Diego, CA. Please refer to that reference for details about the processes followed for automated mesh generation.
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