opposite vector

基本解释

If you took the opposite vector field that contracts everything to the origin that will have negative divergence.
如果每点处取负的向量的话,就会得到负的散度了。
But it could be that, well, imagine that my vector field accidentally goes in the opposite direction then this part of the curve, while things are flowing to the left, contributes negatively to flux.
的确有可能出现往两个方向流动的情况,可以想象到，这一小部分往相反方向流动，当流体向左流时，就只能算作负值了。
This value can be negative to extrude in the direction opposite the Face object's normal vector.
这个值可以为负，从而在 Face 对象的法向量的反方向上挤压。

So the minus vector is the same vector flipped over, pointing the opposite way.
因此负矢量即为同一矢量的翻转,指向相反的方向
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