VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Mon Feb 25 2013 - 15:11:51 CST

Hi,
  You say you want to compute "intermediate steps" in a rotation.
What is it that you plan to do with them? Depending on what it is, you
might be able to interpolation between the starting and final orientation
using a quaternion, or something similar, without having to reverse-engineer
the RMS alignment code in VMD -- the fitting routines in VMD internally
compute a translation matrix and rotation matrix in two discrete steps,
but the rotation matrix is computed in an iterative Jacobi solver,
not in terms of a sequence of separate rotation steps.

Cheers,
  John Stone
  vmd_at_ks.uiuc.edu

On Fri, Feb 22, 2013 at 05:16:23PM +0100, Daniel Klose wrote:
> Dear VMD users and developers,
>
> I'm interested in decomposing the rotation matrix returned by measure fit into its components so that I can do intermediate steps in the given rotation.
>
> I assume the matrix is a product of a translation matrix and a rotation matrix around an arbitrary point (or three rotations about the origin and a translation?), but writing down the matrix equations I found that I seem to need to know a more exact convention ... Could someone tell me?
>
> And is there maybe an independent way to figure out the translation vector and/or the rotation center? Without, this problem may be underdetermined.
>
> Thank you for your help!!
> Daniel
>
> --
> Daniel Klose
> University of Osnabrück
> Department of Physics, Room 32/341
> Barbarastr. 7
> 49076 Osnabrück
> Germany
>
> daniel.klose_at_uos.de
> phone +49 541 969 2465 

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