Top-left panel: AMR level used to perform the calculation in one quarter of the computing box. The zooming strategy is clearly visible. The first levels use nearly uniform refinement while the last ones are based on the Jeans length and follow the dense gas. Top-right panel: column density for the whole computing box and along the x-axis. Second, third and fourth rows display a series ofzooms, going from 250 to 0.25 pc, showingthe column density along the y-axis. From the bottom rows, the interest and limit of the calculation clearly appear. The cores as entities are reasonably described but their internal structure is poorly described.