And the way it will work is that you have to choose an orientation of a surface, which just means choosing one of the two possible unit normal vectors.

具体方法是，先给曲面定向，也就是选择两个单位法向量中的一个。

youdao

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

Your body is use to normal walking on a flat surface, thus you don't really get any noticeable results from it.

你的身体习惯于正常走在平坦的表面，这就使你不会真正得到显而易见的效果。

youdao

Storm surges have the potential to be dangerous because they involve a great upwelling of a stretch of ocean - intense low pressure at the heart of a storm literally tugs the sea surface above its normal level to create a massive bulge.

BBC: Legacy of Britain's great flood

In this, the stream of video and audio data is recorded as a series of minuscule spots on the disc's surface that have been gently fried by a laser beam and turned from their normal crystalline condition to an amorphous state that has different reflective properties.

ECONOMIST: Digital video discs