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Netgen python script: use default GUI parameters
3 years 7 months ago #3731
by mleoni
Netgen python script: use default GUI parameters was created by mleoni
Hello everyone! I'm trying to automate a simple meshing procedure, that I follow using Netgen's GUI, into a Python script.
The GUI procedure is as follows:
1. "File -> Import Mesh" to import an STL file [a closed surface]
2. "Generate Mesh"
3. "Optimize Volume"
4. "Export Mesh"
Now, my current script looks like this:
The problem is that the mesh generated by the steps above is different from the mesh generated by this script, and in particular the one generated by my script has much worse quality [aspect ratio].
My understanding was that, by passing a new
instance, Netgen would use the default parameters, which I assumed were also the ones used by the GUI, but it looks like this is not the case.
Can anyone point me in the right direction? I get a very good mesh using the GUI procedure, and I want to reproduce it exactly with my script.
Thanks for any help!
Massimiliano
The GUI procedure is as follows:
1. "File -> Import Mesh" to import an STL file [a closed surface]
2. "Generate Mesh"
3. "Optimize Volume"
4. "Export Mesh"
Now, my current script looks like this:
Code:
import netgen.meshing as meshing
m = meshing.ImportMesh("surfaceMesh.stl")
m.GenerateVolumeMesh()
m.OptimizeVolumeMesh(meshing.MeshingParameters())
m.Export("volumeMesh.gmsh", "Gmsh Format")
My understanding was that, by passing a new
Code:
meshing.MeshingParameters()
Can anyone point me in the right direction? I get a very good mesh using the GUI procedure, and I want to reproduce it exactly with my script.
Thanks for any help!
Massimiliano
- christopher
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3 years 7 months ago #3733
by christopher
Replied by christopher on topic Netgen python script: use default GUI parameters
Hi,
you can get the default meshing parameters by using the `meshsize` object.
```
m.OptimizeVolumeMesh(meshsize.moderate)
```
There are also the other default GUI options like `meshsize.coarse`, ...
Best
Christopher
you can get the default meshing parameters by using the `meshsize` object.
```
m.OptimizeVolumeMesh(meshsize.moderate)
```
There are also the other default GUI options like `meshsize.coarse`, ...
Best
Christopher
3 years 7 months ago #3734
by mleoni
Replied by mleoni on topic Netgen python script: use default GUI parameters
Hello Christopher, thanks for your reply!
I tried following your advice, now my script looks like so:
I can confirm that I get the same mesh after step 2 in the GUI ["Generate Mesh"] and after calling `m.GenerateVolumeMesh(meshing.meshsize.moderate)`. However, I get two different meshes after step 3 ["Optimize Volume"] and after running `m.OptimizeVolumeMesh(meshing.meshsize.moderate)`. In particular, the script command changes the mesh only very little [removes around 300 nodes and doesn't change the quality at all] while the GUI procedure removes 18'000 nodes and significantly improves the mesh quality.
What else can I try?
Thanks a lot for your help!
Massimiliano
I tried following your advice, now my script looks like so:
Code:
import netgen.meshing as meshing
m = meshing.ImportMesh("surfaceMesh.stl")
m.GenerateVolumeMesh(meshing.meshsize.moderate)
m.OptimizeVolumeMesh(meshing.meshsize.moderate)
m.Export("volumeMesh0S.gmsh", "Gmsh Format")
I can confirm that I get the same mesh after step 2 in the GUI ["Generate Mesh"] and after calling `m.GenerateVolumeMesh(meshing.meshsize.moderate)`. However, I get two different meshes after step 3 ["Optimize Volume"] and after running `m.OptimizeVolumeMesh(meshing.meshsize.moderate)`. In particular, the script command changes the mesh only very little [removes around 300 nodes and doesn't change the quality at all] while the GUI procedure removes 18'000 nodes and significantly improves the mesh quality.
What else can I try?
Thanks a lot for your help!
Massimiliano
3 years 7 months ago #3738
by mleoni
Replied by mleoni on topic Netgen python script: use default GUI parameters
To add to the information above, I compared the output I get, in the terminal, when running Netgen via GUI with the output I get when running via Python.
The two outputs are identical for the meshing part, but when the volume optimisation starts, the GUI outputs this
while from the Python script I get
You can see that the output from the GUI says, for the SwapImprove step, `83805 swaps performed`, while the Python script gives `5 swaps performed`.
Is this any helpful? What influences that number?
The two outputs are identical for the meshing part, but when the volume optimisation starts, the GUI outputs this
Code:
Volume Optimization
CombineImprove
2221828 edges
126 edges with improvement
108 elements combined
ImproveMesh
Total badness = 2.72533e+06
Total badness = 2.72509e+06
SplitImprove
2220957 edges
4 edges with improvement
2 splits performed
0 elements split
ImproveMesh
Total badness = 2.72633e+06
Total badness = 2.72613e+06
SwapImprove
83805 swaps performed
SwapImprove2
89 swaps performed
ImproveMesh
Total badness = 2.48466e+06
Total badness = 2.41983e+06
... Lots of other text
while from the Python script I get
Code:
Volume Optimization
CombineImprove
2221828 edges
126 edges with improvement
108 elements combined
ImproveMesh
Total badness = 2.72533e+06
Total badness = 2.72509e+06
SplitImprove
2220957 edges
4 edges with improvement
2 splits performed
0 elements split
ImproveMesh
Total badness = 2.72633e+06
Total badness = 2.72613e+06
SwapImprove
5 swaps performed
SwapImprove2
0 swaps performed
ImproveMesh
Total badness = 2.72612e+06
Total badness = 2.72609e+06
... Lots of other text
You can see that the output from the GUI says, for the SwapImprove step, `83805 swaps performed`, while the Python script gives `5 swaps performed`.
Is this any helpful? What influences that number?
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