Setting the mesh size for an edge in 3d

Main Forum Old-Forum - do not post here
1

Hi,

in the tutorials the setting of the mesh size for a surface and for a point is demonstrated.
How can this be done for an edge, for example for a cube (for local refinement towards an edge) either in a python file or in the gui (How can I select an edge in the “Refinement dialog …”)?

Best regards,
Gerhard

2

Hi,

since the geometry is modeled by 3d objects and planes, you can not directly set the mesh size on an edge.
But you can restrict the mesh size in an arbitrary point. I would suggest a loop over points on the edge and using the “RestrictH(…)” function as in the following code.

from netgen.csg import *

cube = OrthoBrick(Pnt(-1,-1,-1),Pnt(1,1,1))
geo = CSGeometry()
geo.Add(cube)

maxh = 0.5
mp = MeshingParameters (maxh=maxh)
n = 40
for i in range(n+1):
    loc_h = 2/n # edge length devided by number of points
    mp.RestrictH(x=1,y=-1+i*loc_h,z=1,h=loc_h) # restrict local mesh size at a point

ngmesh = geo.GenerateMesh(mp=mp)

from ngsolve import *
Draw(Mesh(ngmesh))

Best
Christoph