This is the C2-Ray code for time-dependent photo-ionization calculations. This version is for 3D, multiple sources, and for hydrogen only. It runs under both MPI and OpenMP. The factorization branch is a new version which tries to reduce the length of subroutines to make the code more manageable and easier to read. This branch has now passed a range of tests and will be the one in which future developments will take place. Please see https://docs.google.com/document/d/1fPoOdxj3CxIzRi8RowFQFKf2KHKYi_rnoLD7X2T-J18/edit?usp=sharing for documentation about compiling and running this code.