在分析所测得的双向反射分布函数(BRDF)数据与Phong模型局限性的基础上, 提出了一种适用于描述菲涅耳反射特性的改进Phong模型。在经典Phong模型的基础上增加了两个参数, 分别用来调节不同材质菲涅耳反射的强弱与衰减速率。利用遗传算法对四种空间目标常用材质BRDF数据进行拟合, 对比和分析所提出的改进模型与经典Phong模型的拟合误差。结果表明, 对于具有明显菲涅耳反射现象的材质, 改进模型拟合精度比经典Phong模型高90%, 证实了该改进模型的有效性; 而对于菲涅耳反射现象不明显的材质, 改进模型拟合误差与经典Phong模型相当, 显示了该改进模型的稳健性。改进模型在保证Phong模型原有描述能力的基础上, 对菲涅耳反射现象有了更好的描述效果。

Based on the analysises of the measured bidirectional reflectance distribution function (BRDF) data and the limitations in Phong model, a modified model is proposed to describe the Fresnel reflection properties. On the basis of the classical Phong model, two parameters are added to adjust the strength and the decay rate of Fresnel reflection in different materials, respectively. The genetic algorithm is used to fit the BRDF data from 4 kinds of commonly used materials for space targets, and the fitting errors of the modified model and the classical Phong model are compared and analyzed. The results show that the fitting precision obtained by the modified model is 90% higher than that obtained by the classical Phong model for the materials with an obvious Fresnel reflection phenomenon, which verifies the effectiveness of the modified model. For the materials with a weak Fresnel reflection phenomenon, the fitting errors obtained by the two models are equivalent, which represents the robustness of the modified model. The modified model can better describe the Fresnel reflection phenomenon while keeping the orginal excellent description ability of the Phong model.