Improved algorithm for simulations of divergent-light halos.

Divergent-light halos are produced when light from nearby light sources is scattered by ice crystals in the atmosphere. We present a theory of divergent-light halos leading to an improved algorithm for the simulation of such halos. Contrary to the algorithm that we presented earlier for simulating such halos, the new algorithm includes a mathematically rigorous weighting of the events. The computer implementation is very compact, and the whole procedure is elegant and conceptually easy to understand. We also present a new simulation atlas showing halos produced by crystals of different shapes and orientations for a set of elevations of the light source.