# Volume : 2D meshing to 3D meshing

Hi

I had a volume part meshing in 2D. I want to mesh it in 3D (in volume). I can realize it by choosing 4 points and make a volume element, using the function "Add Tetra". But it just can be realized one by one element. Do you know if there is a function which can make all the part become volume meshed in one shot ?

Thanks

TH.

Hi Thomas,

If you already have a closed 2D mesh, you can assign Tetrahedron (Netgen) algorithm to this 2D mesh and compute 3D mesh.

St.Michael

Thanks for your answer St.Michael

I have already tried it but the following message displays : "Invalid input mesh. Intersecting triangles."

(I tried it not with only one part)

Hello Thomas,

I am trying to create a 3D volume mesh (Tetrahedron Netgen) from a 2D surface mesh. In doing so, I encountered some of the free edges and faces which I removed by removing the corresponding elements and nodes causing it (sometimes by merging the nodes in order to correct the similar error again and again). However, I do have the same problem as you have mentioned long back. Did you find the solution for the displayed message : "Invalid input mesh. Intersecting triangles." ?

It would be a great support for replying my queries. Thank you for your time and consideration.

Best regards,

Aroj

Hi Aroj

Tetrahedron (Netgen) algorithm can't work with

- interfering 3D domains.
- non-manifold 2D mesh.

All these can be a reason of "Invalid input mesh. Intersecting triangles." error. In such cases there only way is to change 2D input mesh of Netgen. For example, 3D domains can be meshed separately (in different meshes) and then merged together into one mesh.

St. Michael

Hi Saint Micheal. Is there a way to see if there are 3d interfering domains and/or there is 2d non-manifold mesh?Because i'm encoutering the same problems, and the mesh seems ok, a simple wing inside a domain....

Previously Saint Michael wrote:

Hi Aroj

Tetrahedron (Netgen) algorithm can't work with

- interfering 3D domains.
- non-manifold 2D mesh.
All these can be a reason of "Invalid input mesh. Intersecting triangles." error. In such cases there only way is to change 2D input mesh of Netgen. For example, 3D domains can be meshed separately (in different meshes) and then merged together into one mesh.

St. Michael

If you encounter "Invalid input mesh. Intersecting triangles" error, a right way is to first look at those triangles to understand where they come from. In a dialog showing errors of mesh generation there is "Show bad mesh" button which shows the intersecting triangles in the Viewer in magenta. Usually these triangles are hidden by other elements, and to see them it's useful to show only segments or to hide the mesh at all.

The reasons I specified in my preceding post are actual for the 3D mesh built from 2D mesh shell without geometry, i.e. when one e.g. imports 2D mesh from a file and tries to generate 3D mesh from it.

St.Michael