Left panel: V_z as a function of the reference optical depth for the ray 1 of the 3D simulation. Middle panel: distribution of formation depths of lines contributing to the mask C6 for the ray 1 weighted (b) and not weighted (a) by the CFLD. Right panel: CCF obtained by cross-correlation of the synthetic spectrum [with (black solid line) and without (black dashed line) including the velocity field in the 3D simulation] for the ray 1 of the 3D snapshot with the mask C6. Green bars show the distribution of velocities corresponding to formation depths of lines contributing to the mask C6.