Let's break the name down. The "normal" is a vector perpendicular to a surface, which we can use to calculate lighting.

首先我们从名字上开始分析，所谓“法线”指的是垂直于平面的向量，我们使用这个来计算光照。

youdao

OK, and that's going to be the normal vector to the surface or to the tangent plane.

这就是切平面的，或者说这个曲面的法向量。

youdao

You can remember, if it helps you, that if a surface is to your right then the normal vector will go down.

你也可以这样记，如果曲面在你的右边,那么法向量就向下。

youdao