Color and atmospheric scattering of the sky

The color of the sky is calculated based on a practical analytic model for daylight.
The atmospheric scattering of terrain colors is calculated using the method described in rendering outdoor Lght scattering in real time.

The model in a practical analytic model for daylight calculates the sky by the sun's orientation and the zenith color (yxy space ).
No direction color. Due to the limitation of shader, in my implementation, the scale is simply implemented in the RGB space.

1. Absorption and out-scattering

2. In-scattering of the sun

3. Comprehensive