I've been toying around, and trying to cheapen up the shaders a little, especially on the terrain side of things, and I have achieved that pretty much, gained about 20 - 50 fps on the terrain side of things, with a slight improvement in quality to boot. The reason for this is to cater for the cloud rendering as well, I've managed to get it going ok, but the shader isn't giving me the results I want.....
It's not looking too bad from out this far, but they break down when you get close. I'm going to see if I can reduce the overdraw problem that Jabberwocky was talking about, and move to a screen space render system for these clouds I think. Still trying to nut out a cheap way to render this stuff fast, but still look nicer than what they do now. I can see the potential of them, when you fly around the planet, and you see where the pillars and thunderheads are supposed to be, coming over the horizon, it will look great once I've nutted it all out, but it is a tough one. I've had a look at some options out there, but none are going to handle 2000+ square km of them, and on some of the more nicer looking cloud stuff http://www-evasion.imag.fr/Membres/Eric.Bruneton/
, 10 - 20 fps for one small cloud just won't cut with me, I need this thing to be realtime, or it's no good for anyone.
The problem I'm having is the way I have to produce these things, these clouds you see are generated from 1 grey scale image, actually only the alpha channel of that image, the reason for this is that I will be generating these clouds out of a dynamic flow simulation, so they have to self perpetuate, These clouds are designed to be fully procedural in nature, that's the only way I want to do these things, to keep it in the theme of this simulation that started so long ago. I will solve the issues I'm having, but my lack of expertise with shaders and that, is what is making it interesting.
Anyway, I LOVE A CHALLENGE !!!!