Azimuthal rotation angle plotted as a function of radial location and time. Areas in the same connected disc precess together, and create a distinct horizontal band. By the end of the simulation, three different bands are visible, corresponding to the three discs in the simulation. The disc surface density profile at |$t=1500 T_\mathrm{ b}$| (same as Fig. 12) is also shown on the right to compare the locations of the observed gaps. A detailed time evolution of the disc surface density and warp profile is also available as an online video (https://www.youtube.com/watch?v=GHrsw9brblc).