Realistic rendering of sky scene considering atmospheric refraction

Traditional rendering models of sky scenes are mostly based on the light scatter mechanism. They did not consider the affect of atmospheric refraction in detail, thus failing to realistically simulate the change of shape, color and light ring of the scenes of sun and moon. In this paper, a new sky illumination model considering atmospheric refraction is proposed. The authors first derive the quantitative formula of refraction index in the term of air pressure, temperature, and vapor according to the knowledge of atmosphere optics and calculate the refractional track of light through the atmosphere. Then, by adapting a path tracing algorithm considering refraction, the intensity distribution of sky light is calculated. Finally, various sky scenes of sun, moon and stars under different time, different seasons and different viewpoints are realistically rendered.