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volume tetra does not work  

 

TheMountain
(@themountain)
Active Member
Joined: 5 months ago
Posts: 7
May 4, 2020 6:35 pm  

Hey guys,

I have some meshing problems with volume tetra and hope you guys can give me some tips.

1. Lines on geometry surface.

For example, I converted an STL file (surface geometry defined by triangules) into a STEP file (solid body) and the triangular grids stay on the solid body surface.

If I don't toggle (Geometry - quick edit - toggle edge) those surface lines, the 3D mesh (volume tetra) or 2D surface mesh (2D automesh) are gonna follow those surface lines. 

If I toggle those surface lines, volume tetra or 2D automesh won't be able to recognize the surface boundary of the geometry.

I have an example geometry attached here, "file 1 - coccygeus left". Let me know how would you deal with the surface lines if you don't want your mesh to follow those lines.

 

2. Geometry defects.

Still, STEP file converted from STL file.

Sometimes there are defects in the CAD model like the surface lines are messed up, as shown in the figure below. Volume tetra won't work properly. I cannot do 2D automesh either. 

image.png.7ed3e0784ae506c6c8ac7b65115a26b0.png

 I attached the STEP file here, "file 2 - pubococcygeus". How would you mesh this file? Would you clean up the geometry first?

 

3. volume tetra does not work

Still, STEP file coverted from STL file.

I see no obvious messed up surface lines, but still, the volume tetra or 2D automesh won't work. I attached a file here, "file 3 - obturator". Please let me know how would you mesh this solid body.

Thank you!


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Negative Volume
(@negativevolume)
Reputable Member Admin
Joined: 2 years ago
Posts: 285
May 5, 2020 2:46 am  

Hi @themountain

If your goal is to get a 3D tetrahedral mesh then you don’t need to use an .step file. You can 3D tetramesh an enclosed .stl tria mesh and that would skip the problem of the skewed elements after step conversion.


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TheMountain
(@themountain)
Active Member
Joined: 5 months ago
Posts: 7
May 5, 2020 3:12 am  

@negativevolume

Thanks for the tip. I will try that!


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Negative Volume
(@negativevolume)
Reputable Member Admin
Joined: 2 years ago
Posts: 285
May 5, 2020 12:19 pm  

@themountain

So in the 3D toolbar, go to tetramesh -> Tetra mesh, and select all the 2D tria elements of your object. You can mess around with using simple or smooth pyramid. They are slightly different methods of propagating tetrahedral elements through the object. Make sure that your 2D mesh is enclosed or this won't work.

You can check by looking for free edges in Tools -> Edges, and click find edges. This will create a new component called "^edges" and will display red lines everywhere that there is a free edge. These can be things like holes or unconnected elements. An easy way to spot these is to only display this component and use the Fit Model zoom to automatically zoom to the extents of any lines present. 

I hope this works for you!


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TheMountain
(@themountain)
Active Member
Joined: 5 months ago
Posts: 7
May 6, 2020 1:03 am  

@negativevolume

Thank you for the tips. They are really helpful!


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