Circular mesh includes center as a point, but is not necessarily used as a vertex in the triangulation.

[jorgenriseth]

Python 3.11.0 pacakged by conda-forge
pygmsh 7.1.17 (pypi_0 pypi)

import pygmsh
import gmsh

with pygmsh.geo.Geometry() as geom:
    geom.add_circle([0.0, 0.0], 1.0, mesh_size=0.1)
    gmsh.option.setNumber("Mesh.SaveAll", 0)
    mesh = geom.generate_mesh()

print("Mesh point list includes origin:")
print(mesh.points[:3])
print()
print("Num triangles including the origin:", (mesh.cells[1].data == 0).sum()) # Should be higher than 0

Expected behaviour: All points in a mesh should be used in at least 1 cell.
Actual behaviour: Origin is included in mesh independently of whether it is included in any cells.

[ribesstefano]

I'm also experiencing the same issue (origin included when it shoudn't) with the following code:

import pygmsh

with pygmsh.geo.Geometry() as geom:
    p0 = geom.add_point([0.0, 0.0], lcar)
    p1 = geom.add_point([1.0, 0.0], lcar)
    p2 = geom.add_point([2.0, 0.0], lcar)
    p3 = geom.add_point([2.0, 5.0], lcar)
    p4 = geom.add_point([0.0, 5.0], lcar)
    p5 = geom.add_point([0.0, 1.0], lcar)
    
    l0 = geom.add_line(p1, p2) 
    l1 = geom.add_line(p2, p3)
    l2 = geom.add_line(p3, p4)
    l3 = geom.add_line(p4, p5)
    
    ca1 = geom.add_circle_arc(p5, p0, p1)

    loop = geom.add_curve_loop([l0, l1, l2, l3, ca1])
    surface = geom.add_plane_surface(loop)
    geom.add_physical(l0, 'bottom')
    geom.add_physical(l2, 'top')
    geom.add_physical(l3, 'left')
    geom.add_physical(l1, 'right')
    geom.add_physical(ca1, 'hole')

    mesh = geom.generate_mesh(dim=2)

nodes = mesh.points[:, :2]
cells = mesh.cells_dict['triangle']

For now, I implemented a workaround, but it's not ideal:

nodes_to_remove = [np.array([0.0, 0.0])] # Containing the origin
unconnected_nodes = []
for i, node in enumerate(nodes):
    if node in nodes_to_remove:
        unconnected_nodes.append(i)
for i in unconnected_nodes:
    nodes = np.delete(nodes, i, axis=0) # Remove the node ID/index/pointer
    cells[cells >= i] -= 1 # Make subsequent nodes pointing to the previous node ID/index/pointer

[duhd1993]

This should be asked to Gmsh community. I'm having a different but related problem. I do not want the center point as it's a hole.