Comparison between a galaxy processed with CRASH-RT (left) and one processed with the semianalytic model (right). On the left we depict from top to bottom the average gas density (n_gas), the average ionisation fraction (x_HII) and the distribution and ionising emissivity of sources (Q_sources). On the right we depict the hydrogen optical depth (τ_HI), ionising emissivity F_ion and the location based escape fraction (f_esc).