基于微面斜率法的粗糙表面半透明介质层光谱散射特性分析

Spectral Scattering Properties Analysis of Semitransparent Medium Layer with Rough Surface by Microfacet Slope Method

对具有一维高斯分布粗糙表面的半透明介质层光谱散射,基于微面斜率法建立了考虑遮蔽效应的粗糙表面光谱辐射传递概率模型,采用蒙特卡罗法模拟光谱辐射能束在粗糙表面、半透明介质层介质与镜反射基底之间的多次反射、折射和吸收等传递过程。通过数值模拟,分析了介质层表面粗糙度、光谱光学厚度、折射率和基底反射率对介质层双向反射分布函数(BRDF)的影响。结果表明,表面粗糙程度不同时,反射峰值随入射角度呈现不同的变化趋势;表面粗糙度增加或折射率增大都将导致漫反射份额增大;介质层光谱光学厚度和基底反射率主要影响BRDF的数值大小,而对BRDF的分布形态影响很小。

For one-dimensional semitransparent medium layer with rough surface and Gaussian distribution, the transfer probability model of the spectral radiation on rough surface with shading effect considered is established with microfacet slope method. Monte Carlo method is used to simulate the radiation transfer. The reflection and refraction of spectral radiation at rough surface, absorption of medium and specular reflection on the substrate are considered along with the effects of shadowing and masking. The effects of roughness, optical thickness, refractive index and reflectivity of substrate on bi-directional reflectance distribution function （BRDF） are investigated. The results show that the change trends of reflection peak with incident angles for different rough levels of surface are different, the diffuse component increases with roughness and refractive index, and reflectivity of substrate and optical thickness change the value mainly instead of the distribution trend of BRDF.