Images in the Mg ii k line computed from the 3D Bifrost snapshot at μ_Z = 1. Rows: blue emission peak k_2v (top), central depression k₃ (middle), and the red emission peak k_2r (bottom). Columns: computations in 1D PRD (left), 3D PRD (middle), and 3D CRD (right). The intensity is shown as a brightness temperature: B_ν(T_b) = I_ν. Fuchsia-colored spots indicate coordinates where a feature is not present or misidentified. The brightness scale for all images in a row is identical and indicated in the colorbar on the right side.