VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Wed Feb 25 2009 - 15:37:47 CST

Hi,
  There isn't any routine to compute angles from an arbitrary
transformation matrix. The main reason for this is that it's
problematic since one can have matrices that contain shear/scaling
components or a destructive warp transformation, and there'd be
no way to extract angles in such a case. Beyond that, the numerical
precision for angle extraction would be relatively low. If low precision
is all you need, then you could write some scripts to attempt to
either decompose a transformation matrix (on the assumption it only
has translation/rotation components).

  John Stone
  vmd_at_ks.uiuc.edu

On Wed, Feb 25, 2009 at 03:55:27PM -0500, Yinglong Miao wrote:
> Dear VMD developers/users,
>
> >From the user guide, I found matrix routine "transabout" to generate a
> transformation matrix needed to rotate a molecule around an axis by the
> given amount, but no routine on the reverse process: calculate the angle
> from the matrix obtained by fitting structures. Has anyone tried this? It
> would be great if there is something I missed and ready to use. Or I have to
> do the calculations by myself.
>
> Thanks in advance!
>
> --
> Yinglong Miao
> Ph.D. Candidate
> Center for Cell and Virus Theory
> Chemistry Department, Indiana University
> 800 E Kirkwood Ave Room C203A, Bloomington, IN 47405
> Tel: 1-812-856-0981 

-- 
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