I am trying to convert my triangular surface meshes into gid volumetric meshes;
Any idea? I’ve tried a lot programs, but still not find the correct way.
Thanks~
Hello,
I don’t understand clearly your question. What do you mean with ‘convert triangular surface meshes into gid volumetric meshes’? Are you trying to generate tetrahedra meshes of volumes, which contour surfaces are triangles? Or do you want to create prismatic elements from triangular ones?
If do you want to create the tetrahedra enclosed by your triangular surfaces (the boundary faces of tetras exactly matching your triangles), you can do it writting this:
Mescape Meshing MeshFromBoundary
and select the triangles that form a closed region to be filled with tetras.
This is not the normal flow of use of GiD, it is more natural to have a geometric volume, apply boundary conditions/materials and then generate the mesh.
As trick, you can create a gometrical surface for each triangle
Mescape Geometry Create Reconstruct OneSurfForEachElement
and select the triangles to create surfaces from them
then you can create a geometric volume, assign boundary conditions to geometric entities and generate a mesh
(as trick to create a triangle by surface assign a structured number of divisions=1 to all lines. Menu:Mesh->Structured->Lines->Assign number of cells)
To create thin prisms from triangles you can do a similar think, and use the copy tool with an operation of ‘offset’, and extruding volumes.
You can do it in mesh or geometry (it is better to do it in geometry, to allo use more edition tool, allow re-mesing, and handle assign calculation conditions.
thank you so much escolano!!! It helps a lot~~~
In addition, escolano, after applying the first code, the GiD asking me about the size of elements to be generated, then how should i decide it?
Thank you so much~
It is asking for the element size (edge size) to try to be reached by the tetrahedra
Hi escolano:
I really appreciate your help, and i just have a small concern here; for the command:
Mescape Geometry Create Reconstruct OneSurfForEachElement
was unknown to the GiD.
You have any idea about it?
Thank you a lot~
This command (Geometry Create Reconstruct OneSurfForEachElement) is recent and only exists in last GiD 12.1.xd developer versions.
Dowload the last available developer version.
With old GiD’s without this command you can try to do a trick to create a surface by triangle:
1- Export your current triangles with: Files->Export->Using template .bas (only mesh)->DXFSAP2000
2- Import again the .dxf file with Files->Import->DXF…
If ‘automatic collapse after import’ was not set while importing the DXF do you need to do a model collapse with a small tolerance (else surfaces are unconnected)
Hi escolano:
i’ve tried your suggestions and i am still have some questions about the mesh generated by using the code:Mescape Meshing MeshFromBoundary.
is the mesh generated by applying this code will be a volume mesh?
if not, then should i use the code: Mescape Geometry Create Reconstruct OneSurfForEachElement?
the attached picture is for the one i generated by using the first code. after this the second one cannot be applied to it.
I would really appreciate if you take a look and provide me some help on how to generate it into a volumetric mesh by steps.
Thanks a lot!!
Mescape Meshing MeshFromBoundary
will generate the volume mesh (tetrahedra) from a closed surface boundary (of triangles).
Depending on other contextual words (click righ-mouse button to show the contextual menu) the original triangles will be deleted or not,
and different volume mesher algorithms and parameters could be selected: advancing front, delaunay (tetgen),…
You can check the kind and amount of elements of your current mesh for example with Utilities->Status…
Hi escolano:
Thank you again for helping out, and those are really helpful.
I just wondering if you know after the converting, how to generate those tetrahedral meshes into 10-node tetra? Since from the process you mentioned i can only generate 4-node tetras.
Best regards.
Siyang
Unfortunately we don’t have a command to elevate the degree of the mesh from linear to quadratic or vice-versa to decrease the degree.
The command doesn’t exits because direct edition of mesh is not the normal workflow of GiD. The normal way is to edit the geometry and then generate the mesh in a single step.
Elevate the degree with new nodes located in the mid-egde is a relativelly operation simple, maybe you could do it internally in your solver or writting some Tcl macro do do it in GiD. A detail that must be taken into account is to try to preserve, as better as possible, the attached data (conditions, materials, groups, layers)
We will think to add this feature to new GiD versions.
Hi escolano:
I got some problems when using the command “Mescape Meshing MeshFromBoundary” for generating the tet mesh from triangulated meshes that i have.
First one is showing that there is a mesh error as shown in the attached picture as “first error” (for mesh 0001r-10000.obj), and if it requires the mesh to be moved to another specific point to be meshed?
The second one is about “Bad selection, exists 1 gaps…” (as shown in the attached picture as the second error) which I don’t quite understand about how to fix this problem?(for mesh 0002r-10000).
Thank you for your time on helping me about this.
Simon
objfiles.rar (693 KB)
Hi escolano:
First, i really appreciate your continuous help to my concerns, and they are really helpful.
I was using the command code as you mentioned in this post, which is the “Mescape Meshing MeshFromBoundary” for converting my surface meshes to tet mesh, and it is pretty useful until few minutes ago. The GiD just suddenly stopped working every time after i enter the code and selected the mesh. I even reinstalled the program, while the same problem was popped out as the program stopped running after selecting the mesh.
Any idea about what’sss going on with the program?
Thanks a lot!!!
Simon
Hi escolano:
Since i had some problem with using the code “Mescape Meshing MeshFromBoundary” for converting some of my particles to tetra, so i’m trying to use the second way as you mentioned as:
"This is not the normal flow of use of GiD, it is more natural to have a geometric volume, apply boundary conditions/materials and then generate the mesh.
As trick, you can create a gometrical surface for each triangle
CODE: SELECT ALL
Mescape Geometry Create Reconstruct OneSurfForEachElement
and select the triangles to create surfaces from them
then you can create a geometric volume, assign boundary conditions to geometric entities and generate a mesh
(as trick to create a triangle by surface assign a structured number of divisions=1 to all lines. Menu:Mesh->Structured->Lines->Assign number of cells)
To create thin prisms from triangles you can do a similar think, and use the copy tool with an operation of ‘offset’, and extruding volumes.
You can do it in mesh or geometry (it is better to do it in geometry, to allo use more edition tool, allow re-mesing, and handle assign calculation conditions."
Can you explain a bit more about some part of it? After applying the code to the particle, the surfaces are created, and as you said i did Menu:Mesh->Structured->Lines->Assign number of cells and in the window that shows “enter number of cells to assign to lines” i entered “1”.
After this i am not clear about what you said, and in the “offset” operation, what type of entities should i choose? and how to decide the "Factor’? And i’m really confused about the last sentence about “do it in mesh or geometry…”
Thank you so much if you can provide me a more detailed explanation.
Sincerely,
Simon