Compute the number of points for a ring at a given radius with specified spacing.
Shortest import: from geoparticle import n_per_ring
r (float or np.ndarray) – Radius of the ring(s).
d (float) – Desired spacing between points.
phi_ring (float) – Total angle of the ring in radians (default is 2π for a full circle).
Number of points per ring. Returns an integer if r is scalar.
np.ndarray or int