Using a mini depth buffer to approximate visibility sounds smart, got to keep that in mind instead of doing traditional culling.
Hmmm, I tried soft particles before, but usually in narrow crowded spots they wouldn't be visible much, because they would always (almost) collide and therefore fade out. Well, that could be a matter of tweaking.
The biggest problem I had with glow-sprites, soft or not, were rectangular shaped lights such as fluorescent "tubes". The sprite can't rotate with the camera in this case, unless it scales itself depending on the view vector or something. Keep it a fixed rotation did the job for most angles, but as soon as you stand in a 90 degree angle, you still notice the flatness, if you can see the sprite at all.
That's why I was thinking about defining a 3D shape (such a sphere or cube) around lamps and then render a view dependant sprite in it. But I didn't implement anything yet, neither do I have a battle plan. But maybe someone else has experience?
That's a lot of formula's, usually my brains crash then But I'll give it a try and read, I always thought that Atmospheric Scattering, at least in games, was more for bigger scaled (outdoor) fog and skies, rather than doing glow sprites which are a very local effect? Either how, it needs to be a relative cheap effect as in my case I have many lights that can appear everywhere.
Anyway, thanks for the links!
Btw, maybe useful for others, I found this about implementing lens-flares
Works for unlimited lights, err, and highlights, and it's basically what the sprites would be approximating in the first place. But if you need cheap, better atmospheric scattering might not be the way to go.