VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Thu Jan 26 2006 - 14:21:37 CST

Marco,
  There's no way to do this with the built-in features of the existing
and upcoming versions of VMD at present. One could solve this pretty
easily by doing ray casting against the extracted isosurfaces, returning
the hit points and their respective positions along the ray. You could
then evaluate distances between any points on any sets of isosurfaces
extracted from your data. The main issues are extracting the data
(probably doable by exporting the scene as an STL model) and performing
the ray casting test. Ray-triangle intersection is relatively simple,
and since you'd only be doing one ray, you could just implement a brute
force loop to test the ray against all of the triangles. For any reasonable
isosurface sets this would be quite fast. Let me know if you need help
with this.

  John Stone
  vmd_at_ks.uiuc.edu

On Wed, Jan 25, 2006 at 07:28:09PM +0100, Marco Neves wrote:
> Dear all,
>
> I'm using VMD to plot a GRID (.kont) isosurface contour.
> VMD works perfect on this task but now I have the following problem: I
> want to calculate the distance between couples of points displayed.
> Does anyone have any suggestion about how to do this?
> Thanks a lot!
> Regards,
>
> marco 

-- 
NIH Resource for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
Email: johns_at_ks.uiuc.edu                 Phone: 217-244-3349
  WWW: http://www.ks.uiuc.edu/~johns/      Fax: 217-244-6078