Well, my problem for 2 days (or was that 3?) has been a matter of generating the right random numbers! How do you like that?
The impostor system is working very nicely, will be plenty fast and should give a pretty neat look as you fly around. Lots of (fake) detail as far as the eye can see.
The problem was actually generating the points with an even distribution. Hard to explain very easily but it was good experience, I got to refresh my math skills, well develop them in the first place is probably more like it, especially calculus which I had to use a lot. I still missed something I think either in my models or my actual calculus, I don't know, but it's close enough for me.
So last night I started the render-to-texture code; actually it doesn't use RTT. It's not strictly speaking realtime so speed doesn't matter that much, I'd rather have it maximum compatibilities than the 20% or so increase that RTT seems to give over my current technique. Also, the textures I'm genning are very small, like, 32 pixels or so, so it won't probably make a difference. glCopyTexSubImage2D is very very useful, and very easy to use...