The general formula for a perovskite is ABO3 where A and B are cations. The easiest way to visualize the structure is in terms of the BO6 octahedra which share corners infinitely in all 3 dimensions, ...

TiO2 (titanium dioxide, download cif) is the nominal rutile structure. It can be thought of as infinite columns of edge sharing TiO6 octahedra. In addition, each edge-shared oxygen is corner-shared ...