It now takes approximately 10 seconds to generate a 1024x1024x6 cube map (with heightmap + material + normals data for the planet). It doesn't sound bad, but it actually is.

First thing, to have some good details over the planet, the textures should be 2048x2048 instead of 1024x1024. This means the generation will be 4 times slower, or now take 40 seconds.

Worse, this is assuming the planet calculation loop takes 100% of the CPU, which i cannot afford if it has to run in real-time one day (unless i add "dual CPU system" to the minimum requirements?). By dedicating 20% of the CPU (which is still a lot i think), the generation time will be again increased by a factor of 5: now it will take 200 seconds (or more than 3 minutes) to generate a single planet.

Since the goal is to render a full solar system one day, that means travelling from one planet's ground to another one's should not take less than 3 minutes. That's going to be a problem. Fortunately i still have some ideas in mind to improve the performance a bit, but quality will suffer a bit.