From: Axel Kohlmeyer (
Date: Mon Sep 08 2014 - 00:34:10 CDT

On Mon, Sep 8, 2014 at 12:43 AM, Eric Smoll <> wrote:
> Hello VMD users,
> Under "graphics -> representations", the trajectory tab has a option to
> "update selection every frame". From the terminal, I believe this can be
> accomplished with with command "mol selupdate 0 0 on".
> When i use "animate write $TYPE $FILETYPE sel $SEL" on a selection, the
> selection is not updated. I assume the output atoms are those captured when
> the selection is set. "mol selupdate 0 0 on" does not seem to impact the
> output of "animate write." How can I update my selection for every frame
> output by "animate write"?

you cannot. trajectory file input and output in VMD assumes that the
number, identity, and order of atoms doesn't change.
the only way to get the output you desire is to program a loop and
output individual frames and update the selection in between. you'd
then have to postprocess the resulting files. mind you, it may not be
readable by VMD for the reason mentioned above.


> -Eric

Dr. Axel Kohlmeyer
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.