Given the time I could probably figure out the rotation - I got something working a bit ago but it was rotating around 0,0 instead of the correct origin of the object. I'm in the middle of a work week as well though so I haven't had much time to putz with it.The example Davioware posted here could probably be adapted to allow the planet to be collidable.
From space it wouldn't need a collision mask, when it unwraps, after the transition is complete, the mask would be generated.
As far as art goes - I have no idea where to even begin with that. Like, fundamentally how would that even work. Libnoise (Noise 2.0) has support for spherical and cylindrical noise
. It's built in, Noise 2.0 just doesn't have access to it. Cylindrical is just noise that tiles on one edge rather than two. Spherical is...complicated...to say the least. I figured those two mappings wouldn't be necessary in a 2D engine, but if they would help, let me know and I'll activate them ASAP. I'm not sure if either one of those things would help, though. If the art can't be solved, I'm willing to scale back the graphics to just solid colors and go for a retro type of style, but actual noise would be awesome. In fact, I'm not even sure if noise would work, as the noise color would have to line up with the elevations on the outside, and be solid in the interior. (White peaks, etc.) Maybe it should be done algorithmically rather than with noise, as you suggested.
This was honestly just a crazy idea I had brewing in my head for a while. I didn't think it would actually go anywhere! It's crazy. Imagine my universe populated with these things along with procedural content. It'd be like a ton of Terrarias in one program. I will continue throwing myself at your math and attempting to decipher it - I got a few things down in the little time I had to mess with it tonight, but now is time for sleep and then work. I appreciate the help, and any future help.