如下是帮助里提供的定义 yp*kMC,3 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. _R-#I BSDF：Bi-directional Scattering Distribution Function and is a generic term which is used to refer to BRDF and BTDF. nQ~q -=,L BTDF：Bi-directional Transmittance Distribution Function. It is the scattered radiance through a surface per unit incident Irradiance. xq~=T:>/A J| DWT+$#Z 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。