当x的值变化时，将所有的阴影面积相加，就会得到阴影部分的体积，再解释一遍。

And then, when I add all of these areas together, as the value of x changes, I will get the volume. OK, let me try to explain that again.

youdao

颗粒和昆虫的体积阴影都应该远离光源，并有助于建立一个很好的空间感和透视。

The volumetric shadows from the particles and insects should all point away from the light source, and helps creating a nice sense of space and perspective.

youdao