So if I understand this right you've got 2 points in space, call them C and
D, and you want to use the vector from C to D as the axis of rotation of
your molecule-portion...  It sounds like all you need to do is subtract C
from D and then that gets you an appropriete single <X,Y,Z> vector you can
use to use (along with the origin as you mentioned). (Either have the
moving portion built relative to the origin or translate it temporarily to
the origin by translating -C.)  Then after rotating, translate the
molecule-portion over to location C.
not sure if this helps
Charles



"Charlie" <crr### [at] hotmailcom> wrote:
> Hello, and Thanks ahead of time for any help!!
>
> I'm a chemist and use Povray to render my molecules and it works great.
> I've also made short animations of molecules spinning in space, no problem.
>  Now I have hard one that I need help with.  I made a simple structure and
> I manage to define it into pieces. I want piece 1 to remain stationary, but
> I want piece 2 to rotate 180 degrees about and axis.  Sounds easy, but I
> can't define this axis, whenever I rotate the molecule, it always uses the
> origin (where my wanted rotating piece 2 is no where near) and a second
> point that I can define. This generates images of bonds breaking and atoms
> flying off.  Can anyone help??  The povray guides keep talking of vectors
> and I want to define a vector (<X, Y, Z>, <x, y, z>) as my axis to rotate
> around.
>
> Thanks again,
>
> Charlie R.
> Univ of NV, Reno

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