Ensure mesh has only Tet-10 elements

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I have a new app for the Apple Vision Pro that shows FE mesh and FE results in an immersive environment, but only for tet-10 elements. I have figured out how to use LiveLink Matlab to export all tet-10 elements that are created using the "Free Tet" mesher. However, when I display the mesh with the Vision Pro app, it shows a large portion of the mesh, but not all. I believe that's because of the "boundary and edge elements" that are created with the "Free tet" mesher. These are, possibly, triangular and line elements? Can I force the "Free tet" mesher (or another mesher in Comsol) to only generate tet-10 elements?


4 Replies Last Post 2025/07/03 4:21 JST
Henrik Sönnerlind COMSOL Employee

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Posted: 1 week ago 2025/06/25 18:39 JST

You are correct in that there are always elements of lower dimensions generated on boundaries, edges (and points, actually). But since you are using a Matlab script to extract the mesh, it should be possible to filter out only the solid elements.

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Henrik Sönnerlind
COMSOL
You are correct in that there are always elements of lower dimensions generated on boundaries, edges (and points, actually). But since you are using a Matlab script to extract the mesh, it should be possible to filter out only the solid elements.

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Posted: 1 day ago 2025/07/02 9:04 JST

Thanks. I had done that, but the model looked like a Picasso abstract with fractal outcroppings superimposed on the actual model! So I thought that having boundary elements (and edge elements, and maybe even vertices) was the key to successfully exporting the tet model. Based on your response, I made a tet primitive and meshed it with one just 1 tet element. It had a completely different tet-10 element connectivity than what I had seen in the Comsol description of a quadratic tet element. But, once I got the actual element connectivity from my single tet-10 element incorporated into my Matlab script for exporting the geometry, I've been able to extract models (with more than 1 element :) without having to use the boundary, edge, or vertex elements. Thanks for your help. (I think that the documentation, however, needs some clarification.)

Thanks. I had done that, but the model looked like a Picasso abstract with fractal outcroppings superimposed on the actual model! So I thought that having boundary elements (and edge elements, and maybe even vertices) was the key to successfully exporting the tet model. Based on your response, I made a tet primitive and meshed it with one just 1 tet element. It had a *completely different tet-10 element connectivity than what I had seen in the Comsol description of a quadratic tet element*. But, once I got the actual element connectivity from my single tet-10 element incorporated into my Matlab script for exporting the geometry, I've been able to extract models (with more than 1 element :) without having to use the boundary, edge, or vertex elements. Thanks for your help. (I think that the documentation, however, needs some clarification.)

Bjorn Bretz COMSOL Employee

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Posted: 19 hours ago 2025/07/02 20:17 JST
Updated: 17 hours ago 2025/07/02 21:21 JST

Which method did you use to extract the mesh data, including the second order element information, from the COMSOL model?

Which method did you use to extract the mesh data, including the second order element information, from the COMSOL model?

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Posted: 10 hours ago 2025/07/03 4:21 JST

I've attached the OneTet model generation .m file, and the Matlab file I'm working on to extract the node and element connectivity for the input model to the Vision Pro app. Also included in the file is the extraction of nodal displacement data, stress data, and strain data. Note that if this is run, the nodes are: 1,0,0,0 2,0.5,0,0 3,1,0,0 4,0,0,0.5 5,0,0,1 6,0.5,0,0.5 7,0,0.5,0 8,0,0.5,0.5 9,0,1,0 10,0.5,0.5,0 and the extracted connectivity (ElementConnectivityTET.txt) is: Element number, tet-10 connectivity 1,1,2,3,7,10,9,4,6,8,5 I have "fixed the connectivity" to match the Vision Pro app (I don't know if I should say the name, as I wrote it; it's on the App store) with (ITS_ElementConnectivityTET.txt).
Element number, ITS_tet10 connectivity 1,1,3,9,5,2,10,7,6,8,4 This now works with 1 element and with a few thousand elements to see the model appropriately (no Picasso abstract with fractal outcroppings!)

So this may help with documentation, if I am using this correctly, or maybe it's there and I've not found it....

The new problem is that the stresses and strains that I extract with this to plot do not match the Comsol stresses and strains plots. I'm not sure where I've gummed that up...

Once I have that all worked out, I will include it on the website associated with the Vision Pro app to help users coming from Comsol. (The example models currently there are from ABAQUS/Calculix).

Thanks.

I've attached the OneTet model generation .m file, and the Matlab file I'm working on to extract the node and element connectivity for the input model to the Vision Pro app. Also included in the file is the extraction of nodal displacement data, stress data, and strain data. Note that if this is run, the nodes are: 1,0,0,0 2,0.5,0,0 3,1,0,0 4,0,0,0.5 5,0,0,1 6,0.5,0,0.5 7,0,0.5,0 8,0,0.5,0.5 9,0,1,0 10,0.5,0.5,0 and the extracted connectivity (ElementConnectivityTET.txt) is: Element number, tet-10 connectivity 1,1,2,3,7,10,9,4,6,8,5 I have "fixed the connectivity" to match the Vision Pro app (I don't know if I should say the name, as I wrote it; it's on the App store) with (ITS_ElementConnectivityTET.txt). Element number, ITS_tet10 connectivity 1,1,3,9,5,2,10,7,6,8,4 This now works with 1 element and with a few thousand elements to see the model appropriately (no Picasso abstract with fractal outcroppings!) So this may help with documentation, if I am using this correctly, or maybe it's there and I've not found it.... The new problem is that the stresses and strains that I extract with this to plot do not match the Comsol stresses and strains plots. I'm not sure where I've gummed that up... Once I have that all worked out, I will include it on the website associated with the Vision Pro app to help users coming from Comsol. (The example models currently there are from ABAQUS/Calculix). Thanks.

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