Illustration of the effect of different grid resolution for the reconstructed magnetic field structure using the trilinear method. The magnetic field in the vicinity of the same null point is reconstructed from the 20³ grid data (left) and the 30³ grid data (right). The reconstructed field structure changes from a sink to a divergence-free null point when the resolution is increased. Red and orange field lines are traced in the forward and backward direction, respectively, of the magnetic field.