如下是帮助里提供的定义 $eHYy,, 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. 8J|2b; Vf BSDF：Bi-directional Scattering Distribution Function and is a generic term which is used to refer to BRDF and BTDF. U9"g;t+/ BTDF：Bi-directional Transmittance Distribution Function. It is the scattered radiance through a surface per unit incident Irradiance. b9nTg _y:-_q 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。