From: t.shivam_at_iitg.ernet.in
Date: Thu Jan 04 2018 - 23:28:16 CST

> Dear Vmd users,
>
> I am wondering how can I get a line (vector) in TCL code which will pass
> through the center of mass of protein and will be parallel to the z axis.
> Thanks.
>
> Rabeta Yeasmin
>
you can use orient package

http://www.ks.uiuc.edu/Research/vmd/script_library/scripts/orient/

regards
shivam