Mesh 3D levelset domain and preserve some 2D features

User Help
#1

Hello,

I’m trying to mesh a levelset domain (3D negative part) but also I want to preserve some part of the surface using a given triangulation.

To be more explicit: I have a 3D structured domain (support of my levelset) with a signed distance field, and a stl file (a surface triangulation) of some part of my domain. this triangulation is on the iso-zero of my levelset. I want to create a mesh (surface and volume) conform to my surface triangulation, and as best to my isozero levelset.

Can this be done using the mmg framework?. For example remesh the stl surfaces using the mmgs and then use this mesh as starting point for the mmg3d isozero meshing algorithm. I need this to do a Finite Element Analysis and to impose correctly my boundary conditions (pressure…).

Thanks

#2

Hello,

First, thank you for using our softwares.

I don’t totally understand what you want to do:

  • you want to keep the entities (points and triangles) of your initial surface mesh and to complete it with the missing surface matching with the iso-zero of your levelset?

  • or you can modify your STL surface?

Thanks by advance,

#3

Hi, thanks for the answer,

Yes I can modifie the stl triangulation surface. But I want to keep as best as possible the boundary of the surface defined by the stl.

Example:

Imagine I have signed distance field of a cylinder (my levelset), and also two stl for the top and for bottom caps of my cylinder. I want a 3D triangulation (the bulk of the cylinder), and two 2D meshes of the top and of the bottom of the cylinder (conforming with the 3D mesh of course ). This new mesh can a different from the stl (in general stl triangulation are very bad for finit element analysis).

So at the end I can run my FE code with the 3D mesh and use the 2D mesh to set up the boundary conditions.

thanks

#4

Hi Felipe,
sorry for asking again, but I just want to make sure that I understand clearly your concern…
So you have a surface, described by means of a Level Set function, but you also have STL files corresponding to parts of this implicit surface.
You then want to use the Level Set option of mmg3d to obtain a conforming mesh of your implicit surface, which includes the part you have described by means of STL files as subsurfaces…
Do I get it right ?
Sorry for asking again!

#5

Yes, you are right. maybe this image makes things more clear.

Capture.PNG685×527 86.5 KB

One important thing is that I need the information of the submeshes. For each triangle on the surface I need to know if belongs to a stl surface and with one.

thanks again.

Felipe

#6

Hi Felipe,
so If I get it right, you would like to be able to recognize some parts on the implicit surface by using some STL files of them (and in particular use this information to set boundary conditions in the perspective of FE analyses)?
Unfortunately, mmg3d cannot keep track of some particular part like this… This step of pairing the discretized implicit surface with a STL file is not the task of a meshing software properly speaking, and… to be quite honest, it seems difficult to implement in an automatic, yet robust fashion…
But I understand this is an important question! Food for thought… :wink:
Sorry for not being of much help for this purpose!

#7