Lyman-alpha emitters and their intensity map are powerful probes of the large-scale structure at optical and near-infrared wavelength as HETDEX plans. However, the fact that the Lyman-alpha photons are scattered due to the neutral hydrogen has non-negligible impact on the observed distribution of Lyman-alpha photons. To study this in detail, we run a suit of radiative transfer (RT) simulations on Illustris and quantify the impact of RT on the real space galaxy clustering (Behrens, CB et al. arXiv: 1710.06171).