The speed of this system is incredibly high. On my computer, for example it produces 1100 fps at a 1920x1080 resolution, on the DirectX mode.
Currently for Ogre3D engine.
Phases of the moon
The motion of the moon and sun
Changing the color of illumination
Time system with a complete change of the day
The gradient of the sky
Stars at night
Simple atmospheric scattering
Function for time stopping with ability of keeping clouds moving, or not movingI realized my sky system. It can be ported to many modern enough game (or graphics) engines, which are using OpenGL or DirectX.
Updated to current version of graphic engine Ogre (1.7.4)
Ability to change moon phase on the fly
Shadows of the clouds
At this moment there are some ideas about improving this system. But I would like to do this, only if it will make profit.