从而法向量的方向是竖直向上或向下的。

The normal vector is just sticking straight up or straight down.

youdao

它垂直于其表面指向外面，但这与球面法向量的指向的方式有点不同，圆柱的边缘是竖直的。

Well, it is sticking straight out, but sticking straight out in a slightly different way from what happens with a sphere. See, the sides of a cylinder are vertical.

youdao

你用了法向量i，而不是竖直向量。

K instead of using the vertical vector k, you use the normal vector I.

youdao