Animated SPH visualisation techniques

A few hours later and I've got this animated. Not as tricky or as slow as I thought it might be.

This is another disc falling through a galaxy cluster. Thanks to its massive dark matter halo it survives pretty much intact even after 5 billion years. It may look like it gets disrupted, and it does a little bit, but only about half its material gets removed. Observationally, that's not significant. Of course there would probably be triggering of star formation happening which I'm not modelling (although that would be possible), so possibly the dark galaxy wouldn't stay dark.

But the point of this is really the difference in visualisations. On the left each particle uses a fixed halo size. On the right the size varies according to the SPH kernel size, which accounts for how diffuse the material is. This completely avoids the problem of very dense regions which otherwise show up as "glowing orbs" (you can see one in the very centre on the right) which looks much larger than they actually are. Both the low density and high density material are shown equally clearly.

Ironically, the old version on the left is probably closer to what could be observationally detected. Sometimes, though, that's not the point - it's more useful to be able to examine all the structures formed in the simulation at all density levels. And it just looks nicer, too.