Qualitative assessment of the redshift-zero density field from sCOLA for different tilings and buffer sizes, with respect to tCOLA. The bottom right panel shows the reference tCOLA density field in a 200 Mpc h⁻¹ box with periodic boundary conditions (the quantity represented is ln(2 + δ_tCOLA) where δ_tCOLA is the density contrast). Other panels show the difference between sCOLA and tCOLA density fields, ln(2 + δ_sCOLA)−ln(2 + δ_tCOLA), for different sizes of tile and buffer region, as indicated above the panels. The tiling is represented by dashed lines, and the central tile’s buffer region is represented by solid lines. In the third dimension, the slices represented intersect the central tile at its centre. As can be observed in this figure, artefacts are predominantly located close to the boundaries of tiles; they are reduced with increasing tile size and buffer region size.