Quad dominant or all Quad mesh in 2D (preserving grain boundaries) about neper

[MiguelVCarvalho]

To use the subdivision algorithm All Quads, the checkbox Recombine all triangular meshes has to be activated also. Otherwise, it will only break all triangles into 4 quads.

[rquey]

How would it translate in terms of entries in the .geo file? For tri/tet meshing, Neper uses this:

/* Options for the meshing: */
[...]
Mesh.Algorithm      = 6;
Mesh.Algorithm3D    = 4;
[...]
Mesh.SaveAll = 1;
Mesh.Optimize       = 1;

[MiguelVCarvalho]

Quad Dominant:

Mesh.RecombinationAlgorithm = 3; (blossom full-quad)
Mesh.RecombineAll = 1;

All Quads:
Mesh.RecombinationAlgorithm = 3; (blossom full-quad)
Mesh.RecombineAll = 1;
Mesh.SubdivisionAlgorithm = 1; (All quads)

Something like this might work.

[rquey]

@MiguelVCarvalho - As of version 3.5.3-29, a mesh can be written under format msh version 4, using -format msh4. The mesh file can then be processed externally (by Gmsh) to get a full-quad mesh.

Here is an example:

neper -T -n 2 -dim 2
neper -M n2-id1.tess -format msh4
gmsh -2 n2-quad.geo

This is only a start - it will be integrated to Neper more thoroughly.

n2-quad.geo:

Merge "n2-id1.msh4";
Mesh.RecombinationAlgorithm = 1;
RecombineMesh;
Mesh.SecondOrderLinear = 1;
Mesh.SubdivisionAlgorithm = 1;
RefineMesh;