Isosurface of the distribution of Fe (corresponding to a value of Fe density which is at 5% of the peak density) at the age of Cas A for different viewing angles for model W15-IIb-sh-HD-leta; the colors give the radial velocity in units of 1000 km s⁻¹ on the isosurface (color coding defined at the bottom of each panel). The semi-transparent clipped quasi-spherical surfaces indicate the forward (green) and reverse (yellow) shocks. The shocked shell is visualized through a volume rendering that uses the blue color palette (color coding on the right of each panel); the opacity is proportional to the plasma density. A navigable 3D graphic of this model is available at https://skfb.ly/o8FnO.