就是这它了，如果你继续跟着法向量看，会看到它们实际上，指向上并且指向抛物面里。
It is this guy.If you continue to follow your normal vector, see, they are actually pointing up and into the paraboloid.
那是因为这条线垂直于全部法向量，所以它平行于全部平面，所以它平行于全部平面，为什么它在面内而不是平行于该面？
Well, that's because my line is perpendicular to the normal vectors, so it's parallel to the planes it's parallel to all the planes Now, why is it in the planes instead of parallel to them?
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