VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Tue Aug 10 2004 - 22:15:44 CDT

Shirley,
  From your first email it wasn't clear that you were talking about
making movies. The only way to reduce the observed trajectory playback
rate below the slowest movie framerate available for the movie format
you've selected, is to duplicate animation frames so that they are
displayed multiple times. This is similar to the way that slow-motion
video is displayed on television. NTSC television always runs at 30 frames
per second regardless what is being shown, so in order to show something
more slowly than this 30fps frame rate, you must show the same frame
multiple times before showing the next one. This is how films which
are recorded at a native frame rate of 24 fps are displayed on
televisions at 30 fps (the technique is often called "telecine".
You need to perform your own version of "telecine" in order to get
the desired frame rate. This means duplicating frames either by
loading the same frame into VMD several times, or by using your own
movie generation script that emits the same picture multiple times, for
a given trajectory timestep. At present there's no means of doing this
with the built-in vmdmovie plugin, though if time allows I may be able
provide an updated version in the not-too-distant future which adds
this and some other useful features.

Thanks,
  John Stone
  vmd_at_ks.uiuc.edu

On Tue, Aug 10, 2004 at 03:13:39PM -0700, Shirley Li wrote:
> Hi John,
>
> Thank you for the animaterealslow scipt. It does help to slow down the view on the SCREEN. While when I re-do the movie creation, it seems that the frame update speed in the MOVIE is still the DEFAULT value: 1sec/frame. How should I make this script be in effect in the ANIMATION?
>
> BTW, what's the official web site for VideoMach, where I could purchase this software?
>
> Thank you for your help. Sorry for bothering you.
>
> Best regards,
>
> Shirley
>
>
> John Stone <johns_at_ks.uiuc.edu> wrote:
>
> Shirley,
> If you want it a lot slower than one frame per second, then you'll
> need to either do it with a script, or by manually clicking the forward
> frame button, depending on how slow you're really wanting here :-)
>
> If you want to do it with a script, you could do it like this:
>
> proc animaterealslow { secondsperframe } {
> animate goto 0
> display update ui
> for {set i 0} { $i < [molinfo top get numframes]} {incr i} {
> animate goto $i
> display update ui
> sleep $secondsperframe
> }
> }
>
> Once you're talking about multiple seconds per frame however, I suspect
> you're probably better off just driving it manually by clicking the frame
> forward button when you're ready to see the next frame.
>
> John Stone
> vmd_at_ks.uiuc.edu
>
> --
> NIH Resource for Macromolecular Modeling and Bioinformatics
> Beckman Institute for Advanced Science and Technology
> University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
> Email: johns_at_ks.uiuc.edu Phone: 217-244-3349
> WWW: http://www.ks.uiuc.edu/~johns/ Fax: 217-244-6078
>
>
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-- 
NIH Resource for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
Email: johns_at_ks.uiuc.edu                 Phone: 217-244-3349              
  WWW: http://www.ks.uiuc.edu/~johns/      Fax: 217-244-6078