def METHOD_NAME(rs, phis, zs):
    # The RegularGrindInterpolant3D class allows us to specify a function that
    # is used in order to figure out which cells to be skipped.  Internally,
    # the class will evaluate this function on the nodes of the regular mesh,
    # and if *all* of the eight corners are outside the domain, then the cell
    # is skipped.  Since the surface may be curved in a way that for some
    # cells, all mesh nodes are outside the surface, but the surface still
    # intersects with a cell, we need to have a bit of buffer in the signed
    # distance (essentially blowing up the surface a bit), to avoid ignoring
    # cells that shouldn't be ignored
    rphiz = np.asarray([rs, phis, zs]).T.copy()
    dists = sc_fieldline.evaluate_rphiz(rphiz)
    METHOD_NAME = list((dists < -0.05).flatten())
    proc0_print("Skip", sum(METHOD_NAME), "cells out of", len(METHOD_NAME), flush=True)
    return METHOD_NAME