Qualitative comparison of different synthesized results. The images in each column are one slice-view along z-axis in the 3D volume. Real: real enhanced LLSM experimental 3D images, which contain three average biofilm local densities (D), 54.8%, 59.0% and 64.6%, and three signal-to-background ratios (SBR), 2.2, 1.8 and 1.3 (Zhang et al., 2020). Label: label images obtained by CellModeller with comparable local density conditions to the first column. The synthetic outputs for comparison are from model-based simulation (Zhang et al., 2020), original SpCycleGAN (Fu et al., 2018), SpCycleGAN loss in 3D, CycleGAN loss (Zhu et al., 2017) in 3D and our modified 3D cyclic GAN with $(p1,p2)=(2,1)$ and $(α,β)=(2,1)$ in Equation (3). More visual comparisons can be found in Supplementary Figure S2