Gas surface density as a function of the radius for a disc generated with Diskpop at different times as the colour bar shows. The four models are purely viscous (top left, α_SS = 10⁻³), viscous including internal photoevaporation (top right, ${\alpha }_{\mathrm{S}\mathrm{S}}={10}^{-3},{\dot{M}}_{\mathrm{w}}=4\times {10}^{-10}{M}_{\odot }{\mathrm{y}\mathrm{r}}^{-1}$). wind-driven (bottom left, α_DW = 10⁻³, λ = 3, ω = 0.25) and viscous including external photoevaporation (bottom right, α_SS = 10⁻³, FUV = 100 G₀) respectively.