That's the analog of the position vector.

那是和位矢相似的情况

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I think it's clear, the position of the object with respect to the ground, this vector is the same as the position of the object with respect to the plane, plus the position of the plane with respect to the ground.

我觉得很明显,物体相对于地面的位置,这个矢量等于,物体相对于平面的位置矢量,加上物体相对于地面的位置矢量

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