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generate mesh from overlapping geometries  

 

TheMountain
(@themountain)
Active Member
Joined: 3 months ago
Posts: 7
June 15, 2020 2:31 am  

Hey guys,

 

I have some questions regarding meshing overlapped geometries.

 

I have this geometry with two pieces: the yellow piece and the blue piece, both made of 2D surface mesh. They overlap a bit as shown in the picture.

image.png.1e214dcf3621d53c09ebe26ffdfa1014.png

image.png.64a6246ff41ac5377ceb0f304dea13ac.png
  

My goal is to create continuous solid meshes out of these two pieces. My current approach is: (1) create two solid bodies out of the surface mesh separately, then (2) Boolean Operation merge the two solid bodies into one solid body, then (3) Volume Tetra them. The problem of this approach is that the two merged bodies generate narrow irregular geometry lines at the overlapped part, which leads to really fine mesh at the overlapped region, as shown below, 

image.png.962defbb3dd3fb38bfcfc36fe5bf1031.png

 

I need evenly sized meshes (length ~0.04) for the model to stay stable. I’ve tried to use Check Elements to save the elements smaller than 0.01, then remesh them using Tetra Remesh, but it did not work. 

 

Any suggestions on how to generate solid mesh better in this situation? I’ve attached the model file in this post. Thank you!

 

This topic was modified 2 months ago 3 times by TheMountain

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Negative Volume
(@negativevolume)
Estimable Member Admin
Joined: 2 years ago
Posts: 246
June 15, 2020 4:43 pm  

Hey @themountain

Do you want the bottom region that is not overlapping to be connected as well? Or just the top region? 

So one thing that you can do is to refine the 2D mesh before creating solids from them. That will hopefully eliminate some of the sharp angles that are causing these small elements. 

Do this in 2D, Automesh, then select the current elements of your part and change the mesh size to be relatively small. Make sure your option is set to "elems to original comp" if you plan on just replacing the initial mesh. Then create your solid geometry from these finer meshed parts.

Also, you can use 2D elements to guide the 3D solid mesh. Once you have your solid geometries, create a 2D tria mesh using 2D, Automesh, then change the top left box to surfs instead of elems. Create a 2D mesh that looks coarse enough to you and make sure it's in the same component as the solid geometry. 

Then once you go to volume tetra mesh, check the box "match existing mesh". This will use the 2D mesh as a guide. 

Disclaimer: you may get errors doing this if you create a 2D mesh that is just too large and impossible for the geometry to create 3D elements to fill the geometry. 

Let me know if that helps prevent some of these small elements. 

This post was modified 2 months ago by Negative Volume

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TheMountain
(@themountain)
Active Member
Joined: 3 months ago
Posts: 7
June 15, 2020 7:34 pm  

@negativevolume

Thanks for replying!

I just want the top overlapped region to be connected. Does connecting the bottom region help with the mesh? And How would you connect the bottom region?

I tried meshing existing mesh into a finer mesh, but a finer mesh does not eliminate the small geometry line created due to intersection, as shown in the picture. I tried to toggle those geometry lines before meshing, but it is really hard to find all of them because some are hidden in corners and out of view.

Any suggestions on this?

 

 

1592246057-mesh-inetersect.png

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Negative Volume
(@negativevolume)
Estimable Member Admin
Joined: 2 years ago
Posts: 246
June 15, 2020 7:58 pm  

@themountain

ah I see you are talking about the feature lines that get created. One thing you can do is just skip the geometry creation part all together and connect it using 2d -> ruled. It’ll take a little work but you will have more control. Once you have an enclosed 2d mesh you can create 3D tetrahedrals from them using 3D -> tetramesh and then don’t go to volume tetra, stay in the top tab and select all the 2d mesh.


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TheMountain
(@themountain)
Active Member
Joined: 3 months ago
Posts: 7
June 15, 2020 9:59 pm  

@negativevolume

I am not sure how "2D - ruled" would work on this. Should I delete the overlapped elements first? 


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Negative Volume
(@negativevolume)
Estimable Member Admin
Joined: 2 years ago
Posts: 246
June 24, 2020 5:25 pm  

@themountain

Yeah what you can do if you want to combine the overlapping ends is to basically create a bridge between the two ends and delete the parts inside that are overlapping. This may help show you how to do ruled meshing. 


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TheMountain
(@themountain)
Active Member
Joined: 3 months ago
Posts: 7
June 24, 2020 6:35 pm  

@negativevolume

That's helpful. Thank you!


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