This source tree contains the hydrogen + helium version of C2-Ray,
the radiative transfer / photo-ionization code.
It combines the 1D and 3D versions of the code, although they need
to be build in different ways.

The original C2-Ray was developed by Garrelt Mellema & Ilian Iliev.
This version was developed by Martina Friedrich.

Different tests of the code and a description of the algorithms can
be found in
Radiative transfer of energetic photons: X-rays and helium ionization in C2-Ray
M. M. Friedrich, G. Mellema, I. T. Iliev, P. R. Shapiro, 2012,
MNRAS 421, 2232 (arXiv:1201.0602)

The original C2-Ray paper (hydrogen only) is
C2-Ray: A new method for photon-conserving transport of ionizing radiation
G. Mellema, I. Iliev, M. Alvarez, P. R. Shapiro, 2006
New Astronomy 11, 374 (astro-ph/0508416)