From: John Stone (
Date: Thu Aug 28 2014 - 11:30:37 CDT

  The "snapshot" renderer can only be used when there is a display
connection, otherwise it gets (as you saw) and "empty" image.

The new test versions of VMD 1.9.2 include a new "-dispdev openglpbuffer"
feature, that allows a batch mode VMD session to use the "snapshot"
renderer, but this still requires a connection to the windowing system,
so although it's a batch job and no GUIs are displayed, VMD has to be
able to talk to the X11 server that controls the attached GPUs.

If you want to render images without any display connection, then you
would need to TachyonInternal, or one of the external renderers instead.
TachyonInternal will give you an image that is very nearly identical to
what you see in the OpenGL window in most cases, so that's the best bet
if you don't want to use the new VMD version and the new
"-dispdev openglpbuffer" flag.

  John Stone

On Thu, Aug 28, 2014 at 08:57:33AM -0700, Philippe Bopp wrote:
> Hi all
> attached two files, a saved state (carfiles.vmd) and a tcl file
> (input.tcl ,
> copied from log).
> If I run VMD 'interactively' (vmd , load save state ... , source
> input.tcl in Tk console)
> everthing works fine (i.e. I get a .ps and a .tga file)
> If I run it from the command line like so:
> vmd -dispdev text -eofexit -e carfiles.vmd < input.tcl > output.log
> The Postscrip file is there, but the .tga file is virtually empty (18
> bytes) (see attached)
> Output.log sais in this case
> Info) Rendering complete.
> Info) Rendering current scene to 'test5.tga' ...
> Info) Rendering complete
> If I change the order of the render commands (i.e. tga first, PostScript
> second)
> nothing changes
> I'm puzzled
> Philippe
> -----------------
> Philippe A. Bopp
> professor of chemistry
> philippebopp AT (ONLY!)
> -----------------
> ---------------------------------------------------------------------------

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