现在，垂直于同一个平面的，有两个方向。

Now, there's two different possible directions that are perpendicular to a plane.

youdao

因为画是平面的两度空间，山石是立体的三度空间，所以须有原则才使画中之石有立体感。

Because painting is the plane twice the space, stone is three dimensional space. So it is necessary to have principles to make painting the stone, there is a sense of three-dimensional.

youdao