# Automatic Meshing for Faces and Edges

The automatic mesh sizes faces and edges when using the coarse, standard and fine mesh options are dependent on the solver method.

If any bounding regions of a face have user-defined local mesh sizes, the face will inherit the smallest of the local mesh sizes. An edge will inherit the smallest mesh size from its bounding faces.
• Bounding face of a FEM region: The first order automatic mesh size of that region is used.
• Bounding face of a VEP region: The mesh size of that region is used.
• Metal face bounding a SEP region: The smallest wavelength in the media bounding the face is used to determine the mesh size.

In all other cases the largest wavelength for the bounding media is used to determine the mesh size. When higher order basis functions are used for the MoM, junction edges (where multiple faces share an edge) and open edges (where an edge only has one face bordering it) are meshed as for RWG or order 0.5.

Type Fine Standard Coarse
MoM (RWG or 0.5 order basis function) $\frac{\lambda }{16}$ $\frac{\lambda }{12}$ $\frac{\lambda }{8}$
MoM (1.5 order basis function) $\frac{\mathrm{3\lambda }}{16}$ $\frac{\lambda }{4}$ $\frac{\mathrm{3\lambda }}{8}$
MoM (2.5 order basis function) $\frac{\lambda }{3.2}$ $\frac{\lambda }{2.4}$ $\frac{\lambda }{1.6}$
MoM (3.5 order basis function) $\frac{\lambda }{1.6}$ $\frac{\lambda }{1.2}$ $\frac{\lambda }{0.8}$
Physical optics (PO) $\frac{\lambda }{10}$ $\frac{\lambda }{8}$ $\frac{\lambda }{6}$
Large element PO (LE-PO) $\frac{\mathrm{9\lambda }}{5}$ $\frac{\mathrm{9\lambda }}{5}$ $\frac{\mathrm{9\lambda }}{5}$
Ray launching geometrical optics (RL-GO)
Faceted UTD
Note: The symbol indicates that the mesh should accurately represent the geometry, for both flat and curvilinear mesh elements.