From: John Stone (
Date: Mon Feb 02 2009 - 10:41:09 CST

  VMD renders the potential on surfaces using 3-D texture mapping.
As each pixel is drawn in a constituent triangle composing the surface
being rendered, the GPU performs a texture lookup on the potential value
at that 3-D location. Depending on the texturing mode, the texture
lookup is either simply plulling the "nearest" potential value, or it
does a trilinear interpolation from the 8 nearest potential values to
compute the potential at that point. There are some other complexities
involved in how the image appears depending on how the surface was generated
versus the way the potential map was computed, but I'll hold off on explaining
all of that unless you need to know more. Let us know if that answers
your question.

  John Stone

On Mon, Feb 02, 2009 at 04:57:02PM +0100, Emeline Leproult wrote:
> Dear VMD developers,
> After a run of APBS, how is the electrostatic potential mapped on the
> surface ?
> How do you translate the electrostatic potential information (contained in
> each point of the grid .dx generated by APBS) on the surface ? Do you
> simply map the electrostatic potential of the nearest point of the grid
> on a given surface coordinate ? Or is it more complicated ?
> Perhaps you use the multivalue.exe (or multivalue.o) in APBS/tools to do
> this job ?
> Thanks in advance for your explanation,
> Emeline

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