The effective cross-section, normalised to the number of primary particles, N, for ≈500 aggregates constructed from 81 cubic primary particles on a cubic grid. The symbols (black filled circles and coloured plus signs) are size-scaled by the particle dimensionality, D. The plus signs colour-code (see key at bottom right of the figure) the binned dimensionality (red D = 1–1.5; yellow D = 1.5–2; green D = 2–2.5; blue D = 2.5–2). The orange lines shows some representative analytical fits (see text).