Mmg3d Lagrangian motion: controlling the number of elements

User Help
#1

Hi,

I am testing the Lagrangian motion (option 2, since I have large deformation in the mesh) functionality.
The problem that, after motion, the number of elements (tetra) increases significantly from 1M to 33M.
Using the -noinsert option works, however, since the deformation is large, this doesn’t produce a suitable mesh.
I tried the -hmin, -hmax and -hgrad options, but I didn’t notice any difference.

So, how I can control/limit the number of elements in the mesh after displacement?

Another question please, do you have a plan to include the Lagrangian motion in Parmmg?

Regards,
Saleh

#2

Hello,
With option 2 in Lagrangian mode, point insertion and collapse are performed but mesh control is achieved only by means of the “geometric” parameters:

  • -hausd (roughly, the maximum size on boundary surfaces) and
  • -hgrad (the ratio between consecutive edges).

The rational being that for small displacements most users re-compute a metrics on the displaced mesh with no or little topology changes (options 0 and 1), while for large displacements (option 2) all the remesher efforts are devoted at returning a valid mesh with good surface approximation.

If your case is heavily refined, you could try to increase the -hausd in order to reduce the number of elements, or increasing -hgrad could help to reduce the propagation of small sizes from the boundary to the interior of the domain.

For the moment, extending the support of the Lagrangian motion to ParMmg is not foreseen.

Hope this helps,
Regards,
Luca

1 Like
#3

Thank you Luca

I will try again the hausd and hgrad options.

Regards,
saleh