Utility functions

utils module

n_per_ring(r, d[, phi_ring])	Compute the number of points for a ring at a given radius with specified spacing.
spacing_ring(r, n[, phi_ring])	Compute the spacing between points on a ring given the number of points.
get_wall_ID(i, j, n_ring[, smallest_ID])	Compute the ID of a cylinder wall based on its ring and axis indices.