Distribution of the cumulative weight factor of all photon packages in the pillar simulations described in Sect. 4.5. The panels in the left column correspond to the cumulative weight factor contribution only due to multiple applications of path length stretching. The panels on the right correspond to the total weight factor, i.e. also including the contribution from other events that alter the weight of a photon package. The top row shows the results of simulations with the composite biasing scheme Eq. (29), the bottom panels correspond to the uniform biasing scheme Eq. (26).