Atmospheric Rayleigh scattering in 3D with Unity 3D : The blue color of the sky is caused by the scattering of sunlight off the molecules of the atmosphere. This scattering, called Rayleigh scattering, is more effective at short wavelengths (the blue end of the visible spectrum). Therefore the light scattered down to the earth at a large angle with respect to the direction of the sun’s light is predominantly in the blue end of the spectrum.
This demo is made with Unity 3D and use almost only GPU shaders to compute the light scattering.