考虑大气折射的天空场景真实感绘制

传统的天空场景绘制方法大都是基于大气对天空光和太阳光的散射，它们没有细致考虑大气折射的影响，因此无法绘制出太阳和月亮场景在不同观测条件下形状、色泽、光晕的变化，文章提出了一种考虑大气折射的天空光模型，首先基于大气光学知识推导出大气折射率与气压、温度和水汽压的定量关系，详细计算了光线在大气中的折射轨迹，采用一种考虑折射的路径跟踪方法计算天空光强度的分布，并绘制出不同时间、不同季节、不同观测地点下更具真实感的太阳、月亮和星星的天空场景。

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.