# [SOLVED] CCL:Ambiguous rotation values

*From*: Boris Gorelik <bgbg)at(pob.huji.ac.il>
*Subject*: [SOLVED] CCL:Ambiguous rotation values
*Date*: Wed, 2 Jul 2003 08:36:24 +0000

On Tue, 1 Jul 2003 17:53:48 -0400 Rick Venable wrote:
>It occurs to me that for a unit vector and it's inverse, and rotations
>of A that differ by pi, you will get the same relative orientation.
>Try just sampling A from 0 to pi
Yes, that was one part of the problem, but that was not all.
We changed the sampling of phi and theta (angles that define axis direction)
to be from 0 to PI (thus limiting the axis direction to one hemisphere), but
the problem was still present. Then we noted two points:
1. If A (the rotation angle) equals zero then every <phi, theta>
combination
will result in the same rotation (or should I say lack of rotation)
2. If the direction of the rotation axis is parallel to Z (theta==0), for a
given A angle, all phi values will result in the same rotation.
Thanks for help
--
Boris Gorelik
-= ( 2*b || !(2*b)) That's the question =-
Wed, 02/Jul/2003, 2 Tamuz 5763
-------------------------------------------------
! Molecular Modelling Group !
! Pharmacy School, Hadassa Faculty of medicine !
! The Hebrew University of Jerusalem !
! http://www.md.huji.ac.il/models/group.html !
!
!------------------------------------------------