Hello Robert, nice job and thanks for sharing this 
I have some question if you want to answer it’s would be appreciate.
What will happen If I try to start playing with my character on the planet? What I mean is, did this include king of gravity so I can run every where on the planet? If yes, when you are out of the atmosphere, the player will be attract by the gravity or out of range? I plain to have 8 planets so if there a kind of gravity (It’s realy important to have a gravity in my case) I don’t want them to kill each other.
Also, I want to know if I can create a little real planet, exemple: have many lod’s (1000 polygon , 4000, 15 000, 60 000, 250 000 and maybe for a bigger planet 1 000 000 [Divide in many piece so we only see a maximum of polygon]) and have acceptable performance (For a non-realistic scene like a cartoon game and basique material that fade quality with distance, etc)?
Last question hehe, Do you know if there is a trick to create a spherical landscape, if no, maybe a trick to gradually fade the polycount of an object like the landscape do (base on distance). That would be !
Thanks for the answer and I apologize for my poor english, I learned english as a second language.