From: Jason Hlozek (
Date: Thu Sep 02 2021 - 10:33:43 CDT

Hi John

The conventional Snapshot OpenGL render does produce the correct '.bmp'.

Re system resources for Tachyon, the GPU is not engaged at all and RAM usage increases by 2GBs but there's still 7GBs of free head room by the time Tachyon aborts.
The external '.dat' scene file is 422MBs and seems to consist predominantly of 3D coordinates so it seems like the grid you reference is at least partially built?

Kind regards

From: John Stone <>
Sent: Thursday, 02 September 2021 15:43
To: Jason Hlozek <>
Cc: <>
Subject: Re: vmd-l: Tachyon not rendering large scenes

Have you checked to ensure that you're not running your system out of
memory? Do you have a conventional OpenGL rendering of the scene in
question for comparison? When you render the scene to an external file,
how large is the scene file? I notice that in the output you included
below, there's no console output indicating that spatial acceleration grid
structures were built, despite the fact that you have the +V flag enabled.
That is one of the reasons I'm wondering about the memory exhaustion
issue. Another possibility is a runaway grid build of some sort, but
I haven't seen a problem like that for a very long time, so the odds
are somewhat against it.

  John Stone

On Thu, Sep 02, 2021 at 12:29:11PM +0000, Jason Hlozek wrote:
> Hi
> I'm trying to render an overlaid view of multiple ligands in the same
> protein pocket (i.e. a very busy scene).
> If I go above 2-3 protein/ligand pairs in the scene, then VMD still writes
> the scene file and calls Tachyon as usual but after a few seconds of
> processing, instead of proceeding to the completion % bar, Tachyon instead
> just ends with VMD saying the render is complete even though it didn't
> run. The same thing happens if I try to call tachyon from the command
> line:
> "C:\Program Files (x86)\University of Illinois\VMD> .\tachyon_WIN32.exe +V
> "C:\Users\user-pc\AppData\Local\VirtualStore\Program Files
> (x86)\University of Illinois\VMD\mmpl3_overlay_test"
> Tachyon Parallel/Multiprocessor Ray Tracer Version 0.99.1
> Copyright 1994-2014, John E. Stone <>
> ------------------------------------------------------------
> C:\Program Files (x86)\University of Illinois\VMD>"
> I thought it might be timing out and tried increasing the windows Timeout
> Detection and Recovery (TDR) registry variables as well as disabling them
> but it made no difference.
> Any suggestions please?
> Kind regards
> Jason

NIH Center for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801           Phone: 217-244-3349