Density fields (left and middle column) and quasar flux field in the FGP approximation (right column) in physical space (top panels) and in redshift space (bottom panels), with the line-of-sight direction upwards. Leftmost panels: use the Zel’dovich approximation and CIC deposit, the others use the PPT formalism. In all cases we used 256³ resolution elements, the box size (and extent of each image) used for this comparison is 256 h⁻¹ Mpc at z = 2.5. The thickness of the projected slice is 2 h⁻¹ Mpc and white pixels in the CIC panels indicate zero particles deposited.