Source PostScript (subv3d.pps)

%% soustraction de deux vecteurs 3d
/subv3d { %% x y z x' y' z'
6 dict begin
        /zp exch def
        /yp exch def
        /xp exch def
        /z exch def
        /y exch def
        /x exch def
        x xp sub
        y yp sub
        z zp sub
end
} def