如下是帮助里提供的定义 F4Jc7k2 BRDF：Bi-directional Reflectance Distribution Function. It is the scattered radiance from a surface (reflective scattering) per unit incident Irradiance, and thus has units of inverse steradians (1/sr). The BRDF is defined as the differential scattered radiance per unit incident Irradiance. J.R|Xd BSDF：Bi-directional Scattering Distribution Function and is a generic term which is used to refer to BRDF and BTDF. ~E]ct F BTDF：Bi-directional Transmittance Distribution Function. It is the scattered radiance through a surface per unit incident Irradiance. XN*?<s3 mX4u#$xs: 具体参数怎么选取需要自己去多尝试，手册里虽然有公式，但很抽象。