CGAL users discussion list

[Sebastien Loriot <>]

Hello,

could you share a minimal example showing the problem?

Thanks,

Sebastien.

On 5/7/22 13:37, Sebastian Bachmann ( via cgal-discuss 
Mailing List) wrote:
> Hello,
> No one has an idea? Is it not somehow possible to restrict nodes onto a 
> surface? I.e. if I have the polyline of the surface's boundary, can I 
> specify that all nodes must be on that surface?
>
> For now I have written a function to go over all nodes and check if they 
> are near such a boundary face and then "pull" the nodes onto that 
> surface. However, there are certain edge cases were this then yields 
> collapsed triangles etc. Thus, solving this during meshing would be a 
> great enhancement.
>
> Best,
> Sebastian
>
> On 25.04.2022 07:16, Sebastian Bachmann ( via cgal-discuss 
> Mailing List) wrote:
> > Hello,
> >
> > I created an image meshing tool, similar to the one given here in this 
> > example code: 
> > https://doc.cgal.org/latest/Mesh_3/Mesh_3_2mesh_3D_image_with_features_8cpp-example.html 
> > with the only difference, that I extract the surface elements and not 
> > write the full 3D mesh.
> > I noticed, that on the image boundary, the vertices would be not 
> > exactly on the face but roughly +- the relative error bound given in 
> > create_labeled_image_mesh_domain. For examples, nodes on the xy plane 
> > at z=0 are not on z=0 but for example -0.01 to 0.01. While the 
> > protected polylines are exact and have always z=0.
> > I created for example a mesh from the 420.inr example with the same 
> > meshing criteria as given in the example and can see that behaviour 
> > there.
> >
> > While you can control the maximal deviation using the relative error 
> > bound, there will always be some deviation. And if I set the relative 
> > error bound too low, it seems the meshing never finishes.
> > I wonder now, if it is possible to constraint the mesh (similar to the 
> > 1d polylines), such that the vertices for facets on the image 
> > boundary, are always exactly on the image boundary?
> >
> > Best,
> > Sebastian