Field Driven Meshing#
Fields can serve as design parameters for mesh generation in Artisan. Within this framework, fields can be applied to either modify local material thickness or adjust the size of lattice units.
Scaler Field#
The variation in unit cell size can be achieved using specific keywords: Gen_BasicCartesianHexMesh_MultiSize and Gen_TetBasicMesh_HexSplit. The former keyword allows for the creation of hex elements with varying sizes, while the latter facilitates the generation of tet elements with varying sizes. User shall find all examples below at .\Test_json\MeshLattice\Box_FieldAttractor_MultiSize.
Similar to previously demonstrated applications, users can activate a specific function in Artisan by setting the parameter "Type": "Field_Attractor". This configuration prompts Artisan to import a field, represented as a spatial data cloud containing field values. This potential map are utilized to create an attraction field. This field influences the mesh nodes, driving their deformation. As a result, this process generates elements of varying sizes throughout the mesh. This functionality allows for the tailored manipulation of mesh structures to align with specific design criteria or performance requirements, for example, user may use stress or strain mapping as design parameters to drive the local element size.
The example in the file Box_FA_MS.json demonstrates how the local field changes a box mesh element size, as shown below.
{
"Setup": {
"Type": "Sample",
"Sample": {
"Domain": [
[0.0, 80.0],
[0.0, 80.0],
[0.0, 80.0]
],
"Shape": "Box"
},
"Geomfile": "",
"Rot": [ 0.0, 0.0, 0.0],
"res": [ 0.25, 0.25, 0.25],
"Padding": 4,
"onGPU": false,
"memorylimit": 1073741824000
},
"WorkFlow": {
"1": {
"Gen_BasicCartesianHexMesh_MultiSize": {
"num_elem": [
10,
10,
10
],
"x_range": [
0.0,
80.0
],
"y_range": [
0.0,
80.0
],
"z_range": [
0.0,
80.0
],
"ori": [
0.0,
0.0,
0.0
],
"Normal": [
0.0,
0.0,
1.0
],
"z_angle": 0.0,
"Meshfile": ".//Test_json//MeshLattice//Box_FieldAttractor_MultiSize//BoxHexMesh.med",
"Geomfile": ".//sample-obj//cube_1mm.stl",
"numPrjLayers": 0,
"LayerDepth": 1.0,
"numCoverNodes": 0,
"MultiSize": {
"Type": "Field_Attractor",
"Data": [
[
30,
0.5
]
],
"FieldFile": ".//Test_json//MeshLattice//Box_FieldAttractor_MultiSize//field_data.csv"
}
}
},
"2": {
"Add_Lattice": {
"la_name": ".//Test_json//MeshLattice//Box_FieldAttractor_MultiSize//GenHexMesh.mld",
"size": [
5.0,
5.0,
5.0
],
"thk": 1.0,
"Rot": [
0.0,
0.0,
0.0
],
"Trans": [
0.0,
0.0,
0.0
],
"Inv": false,
"Fill": false,
"Cube_Request": {}
}
},
"3": {
"Export": {
"outfile": ".//Test_results/BoxHexMesh_FieldAttractor_MultiSize.stl"
}
}
},
"PostProcess": {
"CombineMeshes": true,
"RemovePartitionMeshFile": false,
"RemoveIsolatedParts": true,
"ExportLazPts": false
}
}
Here the parameter MultiSize contains three setup parameters:
Parameter |
Details |
|---|---|
|
supports |
|
when |
|
A point-field CSV path or a fitted scalar grid-field ID. CSV points are fitted onto the calculation grid. A grid-field ID created with |
Mesh and field containers#
Gen_BasicCartesianHexMesh_MultiSize uses the mesh interface for both
Geomfile and Meshfile. Geomfile may name a triangle mesh
in the mesh container or a geometry file. Meshfile may name the generated
hex mesh in the mesh container or an output file. The generated mesh ID can be
used by a later mesh-processing or lattice operation, or written to disk with
ExportMeshID.
For Field_Attractor, the field interface resolves FieldFile.
Fitted grid fields keep their own grid shape, origin and spacing, which may
differ from the lattice calculation grid. Gradients use the physical field
coordinates. Nodes sample the lower grid point along each axis, including the
last grid point at the upper domain boundary. Nodes outside a stored field’s
domain stay fixed. Invalid scalar values or inconsistent grid metadata are
reported as errors.
Point-field CSV inputs retain the existing fitting and point-cloud coverage
rule for Cartesian generation. A named fitted grid has its grid domain as its
coverage; it does not retain the original cloud’s sampling gaps. Thus a sparse
CSV and a fitted grid may affect different nodes. The shared deformation
implementation is also used by Proc_Mesh_FieldDrivenMesh and the
Cartesian stage of Gen_TetBasicMesh_HexSplit.
Constant fields and thresholds above all sampled values produce no movement. When the selected values all equal one value but have a nonzero gradient, selected nodes use the full attraction intensity. The existing displacement formula is retained. Correct physical spacing can change the attraction direction for anisotropic grids compared with older versions that assumed equal spacing on all axes.
The example
.\Test_json\MeshLattice\Box_FieldAttractor_MultiSize\Box_FA_MS_Containers.json
demonstrates ReadMesh -> OP_Fit_GridField ->
Gen_BasicCartesianHexMesh_MultiSize -> ExportMeshID.
It reads the geometry into CubeGeom, fits SizeField, generates
BoxHexMesh in memory, then exports that mesh. Run it from Src.
In the example, the csv file contains many spatial data points, this could lead longer computational time. The example Box_FA_tetmesh_MS.json demonstrates the operations on the tet mesh. The section that defines the field operation is as below.
"1": {
"Gen_TetBasicMesh_HexSplit": {
"Geomfile": ".//sample-obj//cube_1mm.stl",
"size": [
100.0,
100.0,
100.0
],
"Meshfile": ".//Test_json//MeshLattice//Box_FieldAttractor_MultiSize//BoxHexMesh.med",
"ConvertTet2Beam": false,
"MultiSize": {
"Type": "Field_Attractor",
"Data": [
[
30,
0.5
]
],
"FieldFile": ".//Test_json//MeshLattice//Box_FieldAttractor_MultiSize//tetmesh_field_data.csv"
}
}
},
The results is below. Please note that two examples here used different domain size and fields. The field can be either full coverage on the domain, or partially covers the interested areas. It is highly recommend to place more spatial points on the high interested area in order to interpolate the field values at the nodal positions.
Geometry Field#
The geometric distance field can be served as the design parameter that varies the local mesh size. The keyword Gen_ExtHexMesh_Geomfield provides a simple interface that reads the external mesh, projects the exterior nodes on the given geometry’s exterior surface, and then use geometric distance field adjust the interior nodes position. The example .//Test_json//MeshLattice//ExtMesh//Mesh_GeomField.json shows how to read the external mesh (generated using Gen_BoxMesh) and fill a geometry.
{
"Setup": {
"Type": "Geometry",
"Sample": {
"Domain": [
[
0.0,
1.0
],
[
0.0,
1.0
],
[
0.0,
1.0
]
],
"Shape": "Box"
},
"Geomfile": "C:/Users/wangy/Documents/Project-Artisan/Artisan/Artisan/Src/sample-obj/shell_1_of_bdd_.stl",
"Rot": [
0.0,
0.0,
0.0
],
"res": [
0.5,
0.5,
0.5
],
"Padding": 4,
"onGPU": false,
"memorylimit": 1073741824000
},
"WorkFlow": {
"1": {
"Gen_BoxMesh": {
"Normal": [
0.0,
0.0,
1.0
],
"z_angle": 0.0,
"Mesh_file": ".//Test_json//MeshLattice//ExtMesh//Base_Mesh.med",
"y_range": [
0.0,
140.0
],
"z_range": [
0.0,
200.0
],
"ori": [
-190.0,
-68.0,
-2.0
],
"x_range": [
0.0,
200.0
],
"num_elem": [
25,
18,
18
]
}
},
"2": {
"Gen_ExtHexMesh_Geomfield": {
"Geomfile": "",
"out_meshfile": ".//Test_json//MeshLattice//ExtMesh//Base_Mesh_Field.med",
"isPreAttraction": false,
"inp_meshfile": ".//Test_json//MeshLattice//ExtMesh//Base_Mesh.med",
"numCoverNodes": 4,
"AttractionRatio": 0.1
}
},
"3": {
"Add_Lattice": {
"thk": 1.0,
"Rot": [
0.0,
0.0,
0.0
],
"Trans": [
0.0,
0.0,
0.0
],
"Inv": false,
"Fill": false,
"Cube_Request": {},
"la_name": ".//Test_json//MeshLattice//ExtMesh//Bdd_MeshLattice.mld",
"size": [
13.0,
13.0,
13.0
]
}
},
"10000": {
"Export": {
"outfile": ".//Test_results//ExMesh_Geomfield.stl"
}
}
},
"PostProcess": {
"CombineMeshes": true,
"RemovePartitionMeshFile": false,
"RemoveIsolatedParts": true,
"ExportLazPts": false
}
}
The keywords Gen_ExtHexMesh_Geomfield parameters are listed below.
Parameter |
Details |
|---|---|
|
the geometry file path, if empty, it will take the geometry defined in setup; |
|
resultant mesh file; |
|
the read-in external mesh file; |
|
the read-in mesh will check the coverage by using number of nodes, the elements having less number of nodes covered will be removed. |
|
If true, the mesh nodes would adjust using the geometric distance field, if false, the interior nodes will be adjusted after the elements removal. |
|
the multiple scale to the nodal movement magnitude, if 0, field effect will not be applied. |
Above case generates the following infill. In practices, use may consider use other professional mesher to forms a general approximated mesh, and then use this keyword to refine the boundary projection, and the interior nodes positions.
