Sorry for late reply. By pre-defining the direction, I mean that the direction of the unit normal is assigned first (I am not sure if I understand it correctly, but assigning “res” to " + " or " - " to me is like assigning the direction of the unit normal - please correct me if I am wrong). However, I would like to know if I do not assign (or restrict) the direction of the unit normal, by default, which direction it is pointing to?
Also, by cell function, do you mean the following part of the script?
i_facets = []
for facet in facets(mesh):
f_index = facet.index()
cells = facet_to_cells(f_index)
if len(cells) >= 2:
if np.isin([m0,m1], marker_array[cells]).all():
print(f_index)
i_facets.append(f_index)