Revisiting Physical Sun and Sky Model

This project will improve the current Appleseed's implementation of physical sun and sky models. Fixing the current blue tint present on Appleseed implementation and adding several new features. Such as, a solar disk, ability to configure the Sun with a geographic location, a date and a time and allow users to change atmosphere parameters. Those new features will make the sky models more flexible for artists and will provide a more accurate representation of the appearance and illumination from the day sky. The new features will also make it possible to render other planets skies, from a physically plausible mars sky to an alien sky with multiple suns and a stunning sky's color.