From: John Stone (
Date: Thu Oct 30 2014 - 08:50:21 CDT

Hi Norman,
  Items 1) and 2) should already be fixed in the next VMD builds.
I believe 1) may have been a bug in OptiX itself, as I was unable to
reproduce that problem with the current OptiX 3.6.3, and I recall
having written code to handle this case almost a year ago.
Item 2) I have improved in the current test versions, although it
could likely still be further improved.

I don't fully understand the issue 3) you describe below, can you
explain what you mean by "background"?

Item 4) is unavoidable. For good performance ray tracing requires
that almost all of the geometry in the scene be directly accessible
in GPU RAM. Representations that are disabled do not take up GPU RAM
in general, but there is one exception to this:

The QuickSurf representation keeps a cache in GPU RAM which can become
quite large in some cases. If the size of the QuickSurf memory cache
gets too large, it doesn't leave much memory for use by OptiX.
You can overcome this issue by setting this environment variable
in your .vmdrc (or in the VMD startup scripts):

This will force QuickSurf to release its memory upon completion of
surface calculations.

I'm working on adding a code path to allow VMD/OptiX to force QuickSurf
to dump its GPU memory cache upon entry into ray tracing.


On Wed, Oct 29, 2014 at 10:10:16AM +0100, Norman Geist wrote:
> Hey,
> seems I encountered two bugs:
> 1. The Tachyon-Optix renderer fails unrecoverable when all
> representations are disabled and also the axis, so in fact there's nothing
> to render.
> It might sound a stupid idea to render _nothing_ in the 1^st place, but
> can IMHO happen when doing user defined animated movies, at least
> it shouldn't crash.
> 2. Tachyon Optix doesn't correctly render msms wireframes compared
> to the traditional Tachyon.
> 3. Saving coordinates in background seems to not be functional, only
> an empty file is created. (Tested from the the GUI only)
> 4. This one might be unavoidable, but VMD seems to have all
> representations in VRAM, also if they are disabled, this makes
> it hard to use Tachyon-Optix for complex video animations as there's not
> enough VRAM left.
> Norman Geist
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> References
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