Any plane actually has infinitely many normal vectors.
每一个平面都有无数条法向量。
The first unit about cross-products,normal vectors and so on is actually useful now.
第一单元学得叉积、法向量这些,现在就有用了。
Normal vectors are vectors perpendicular to the face of each triangle that defines a mesh.
法向量是与构成网状结构的所有三角形表面都垂直的向量。
Remember, the Angle between two planes is the same thing as the Angle between the normal vectors.
记住两个平面之间的夹角和，两个法向量之间的夹角是一样的。
Taking gauss curvatures and normal vectors as random variables, Lorentz Curve was extended to 3d Lorentz Surface.
以高斯曲率和法向量为随机变量，将洛伦兹曲线扩展为三维，得到洛伦兹曲面。
Here we don't have a notion of orienting the surface other than by precisely choosing one of the two possible normal vectors.
这里我们并没有曲面定向的概念，能做的就是，从两个法向量中选出一个作为正方向。
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。
If the two level curves are tangent to each other that means they have the same tangent line. That means that the normal vectors should be parallel. Let me maybe draw a picture here.
如果两个等高线相切，说明它们的切线相同，也就是说他们的法向量应该平行，我再在这里画个图。
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?
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？
So, remember, when we set up the divergence theorem, we need the normal vectors to point out of our region, which means that on the top surface, n But, on the bottom face, we want n pointing down.
当我们建立散度定理时，我们要使法向量指向区域外，即在上表面时，要指向上方。，we，want，n，pointing，up。,但是，在下表面，要使n指向下面。
When we know two vectors in a plane, it let us find the normal vector to the plane, and that is what we need to find the equation.
当我们已知平面上的两个向量，我们就可以找到，这个平面的法向量，然后我们就可以用法向量来找到方程。
Another way to do it, of course, would provide actually parametric equations of these lines, get vectors along them and then take the cross-product to get the normal vector to the plane.
当然也有另一种方法，就是用参数方程表示这两条直线，用两条直线的方向向量作外积，从而得到切平面的法向量。
The feature vectors extracted by this method are repeated and stable, and they differentiate the normal and the diseased effectively.
构造的特征向量具有较好的重复性与稳定性，可以较有效地区分正常人与心脏病人。
The feature vectors extracted by this method are repeated and stable, and they differentiate the normal and the diseased effectively.
构造的特征向量具有较好的重复性与稳定性，可以较有效地区分正常人与心脏病人。
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