Spherically symmetric dust geometries used in RADMC-3D, centred on the star. Colour bars show the logarithm of dust density in g cm⁻³. Top: single continuous shell of dust (S). Middle: continuous dust shell with an overdense shell at the outer edge (D). Bottom: two-shell model with a cavity (CD). The labelled arrows indicate the size parameters used in the model, except for r_in, which is unresolved at this resolution.