the clouds are, in effect, tori with circular cross sections. In our 3D runs, which are done in cartesian coordinates, the clouds are true spheres.

The actual cloud size distribution in the Galaxy is poorly constrained and so our adopted parameters of the cloud size distribution may not accurately reflect the true cloud size distribution, [though others have found similar results, e.g. @Gosachinskij+Morozova_1999; @Chieze+Lazareff_1980]. There is evidence that interstellar clouds have a morphology that is closer to filamentary or “clumpy sheets” [@Heiles+Troland_2003], though more regular clouds are observed as well. We do not expect the cloud geometry to have a very substantial effect on SNR evolution or observables since, once shocked, the complex flows inside the remnant create large distortions of the clouds in any case. However, if a remnant encounters a cloud that is comparable in size to the remnant, both the appearance and evolution of the remnant would be strongly affected. In such cases the remnant would have a strongly asymmetric appearance. Exploration of such cases is beyond the scope of this paper.

WL found that their solutions could be parametrized by just two parameters: $C$, the ratio of the mass in clouds to that in the intercloud 