I am hoping to create a space-orientated sandbox game. Now I do have a rather interesting question. How do I make a procedural terrain generated on a planet (sphere) which a person can fly down to. At the moment, space-to-planet transitions don't bother me, and I don't mind if the terrain is seen from space, I can add Terrain LOD's and what-not later. I am asking, at the moment is. How would I go about procedurally generating terrain (using perlin noise). Then somehow wrapping this around a sphere? I can't use the six-side cube trick method, because my game will be multiplayer, so other people will need to see the planet, etc. Plus you need to be able to fly down into the planet.
So, ideas, suggestions? Anything is greatly appreciated.