How to define $vecxzX $vecxzY $vecxzZ in Corotational?

[civilman]

Hi, all
In OpenSees Command Language Manual says "The x-axis is the axis connecting the two element nodes;the y-and z-axes are then defined using a vector that lies on a plane parallel to the local x-z plane--vecxz.The y-axis is defined by taking the cross product of the x-axis and the vecxz vector."
But I can't understand what's the meaning of this sentence.

if nodal coordinates of a beam-column element are nodei(x1,y1,z1),nodej(x2,y2,z2), respectively, how to define the following three parameters, $vecxzX $vecxzY $vecxzZ?
many thanks.

[fmk]

look at the pictures if you don't understand the words.

[civilman]

ou, my god, it's a good idea. thanks a lot.