Current GiD has two cartesian algorithms implemented: 'Scan convert' and 'zmesher'.
Zmesher is able to generate 3D cartesian meshes of volumes, surfaces, lines and/or points. It is especially suitable for electromagnetic simulations of Finite Differences.
Zmesher has been implemented by a third part partner (University of Granada), and the first time that is used it will require an extra password
Set mesher: Zmesher
and generate again the mesh, disabling the 'User defined' grid and with general size=2.0
If it is the first time that this mesher is used this window ask a password
The password could be freely obtained from the related web (and will be stored in the file scripts/TemporalVariables, to not ask it again)
Enter the password and generate again the mesh. When the mesh is generated is show this information
Now the mesh will have also quadrilateral faces for the isolated surfaces
In fact, this mesher could create some 'degenerated' cells, to preserve topological connections. E.g. 1 line element is generated although there is not any isolated geometrical curve, and also 1 extra quadrilateral is generated from a volume.
If the 'Avoid degeneration' option is set, then these degenerated elements are automatically deleted.