基于辐射传输理论和分形理论的云场景仿真

 基于云的边缘特征和天空亮度分布特征，对有云天空场景的仿真方法进行了研究。分析了云对天空亮度影响，并据此提出了一种基于分形原理的云场景仿真方法。通过辐射传输理论，给出了有无云天空的光谱亮度分布计算方法。在分析了云边缘具有自相似分形特征基础上，利用有云天空亮度分布特征、二次随机法和分形几何的Diamond-Square算法设计了云纹理生成算法。利用混合修正δ-Eddington近似计算出了观察视场2°×2°内640×480单元的2维天空亮度数组。利用该理论模型得到有云天空的2维亮度数组，并用VC++实现了云场景的动态仿真，得到了较为逼真的结果。

Cloud scene simulation based on radiative transfer theory and fractal theory

Methods for cloud scene simulation are analyzed and studied based on the properties of real cloud edge and distribution of sky radiance.A model is used to simulate cloud scene by means of fractal geometry algorithm after effects on the sky radiance of cloud are analyzed.Firstly,spectral radiances of cloud free sky and cloudy sky are respectively calculated according to the radiative transfer theory.A simulation method for cloud edge is developed based on the improved random generator after studying the properties of real cloud edge and self similar character of the fractal principle.Finally, a kind of algorithm implemented to create cloud texture is designed by making full use of radiance distribution of cloud sky,quadric random method and Diamond-Square interpolation.Consequently,some dynamic cloud scenes are successfully simulated.