From: Axel Kohlmeyer (
Date: Wed Apr 18 2012 - 21:10:24 CDT

On Wed, Apr 18, 2012 at 9:08 PM, Andrew DeYoung <> wrote:
> Greetings,
> I am a little embarrassed to be asking this, but somehow I cannot seem to
> find the answer.  The Isovalue Drawing Method in VMD draws surfaces based on
> a volumetric data set.  For example, I have used the Gromacs utility
> g_spatial (
> to compute the spatial distribution function of a set of molecules around
> reference atom(s).  The utility outputs the results in Gaussian 98 cube
> format.  I load the file into VMD and select the Isovalue Drawing Method.  A
> few controls appear, including an Isovalue slider.
> My question is, what are the units of the Isovalue slider?  Is it a length
> (for example, the radius of a sphere in which to consider molecules around
> the reference)?  Or is it a density (for example, a number density in units
> of atoms/Angstrom^3 or atoms/nm^3)?  Or, is this more of a Gromacs question
> than a VMD question?

it is in whatever units the property is in that you are
visualizing (i.e. strictly speaking a gromacs question).

the internet has many resources that can save you from
embarrassing questions, for example this one:


> Thank you for your time!
> Andrew DeYoung
> Carnegie Mellon University

Dr. Axel Kohlmeyer
College of Science and Technology
Temple University, Philadelphia PA, USA.