I've added an array to hold a variable amount of planets. I also reorganized the code to give to each planet different parameters. I still have a lot to do in that area. For example, even if it's not that visible, the two planets on the following screenshot have the same set of textures/clouds, but because of the atmosphere they look different. The rendering is not correctly done in order (i have to fix quite a few things in the 3D engine for that), so when a part of the atmosphere covers another planet you get strange results.