Hi @being_saige, that fieldmap actually looks good!
So those “rays” coming out of the brain are just the extrapolation FSL FUGUE does along the PE axis to ensure that susceptibility correction does not introduce artificial cuts, tearing apart signal at locations with strong inhomogeneity gradients.
I agree it is not the most beautiful plot, and it still requires a fair bit of work (e.g., units?) but I think it clearly conveys how correction will operate.