As can be seen from the illustration, the sum of the values from a given ray crossing the segments in its path is zero.

从图中可看出，给定射线与其路径中的段的交叉值总和是零。

youdao

As can be seen from the illustration, the sum of the values from a given ray crossing the segments in its path is zero.

从图中可看出，给定射线与其路径中的段的交叉值总和是零。

youdao