It is important to uncheck the "Affect specular" slot, we don't want any specular reflection from that light, only diffuse light.
有一点很重要就是要取消掉“影响高光”的参数。我们不想这盏灯光产生高光，只影响漫反射即可。
2
By regarding a linear light source as a directional rectangular light source with infinitesimal width, a simple formula is derived for calculating the diffusereflection component.
通过将线光源看作一个具有无限细小宽度的有向长方形光源，我们得到了一个计算漫反射分量的简洁公式。
3
The reflection character of a real surface of metalwork is related to the material, light wavelength, scattering and diffusereflection.