What would the user want the information for? (Sorry if this has been explained before, but as I said I didn't follow the early part of this thread, and although I looked at the archive I may have missed something.)
I take it that the user might need the information to reproduce the same view again, or to drive some other program to produce the same view. In that case RxRyRz information would be useful only if JMol or some other program could understand it as input, and that seems unlikely. Jmol could presumably interpret 3 successive rotations, but in that case it would cope just as well with RzRxRz or RzRyRz. The transformation to Euler angles is singular if the rotation is around the z axis, so there are numerical problems if the rotation axis is close to the z axis, though in practice that can be handled as a special case. The advantage of the angle-axis representation is that it can be obtained straightforwardly from the rotation matrix via the quaternion representation. If Euler angles are to be used, I would advocate RzRyRz, which is used in quantum mechanics and hence in most applications concerning molecules, rather than RzRxRz, which is mainly used in classical mechanics. But the relationship between them is very simple so it's not a big issue. Anthony At 08:54 on 5 October, Bob Hanson wrote: > Miguel, we have this book at St. Olaf. I'll take a look. > > Anthony, do you see any practical problems with delivering > RxRyRz information to the user, or is this more of a concern > in principle? Does it make any difference, since Jmol doesn't use > RxRyRz for anything right now and wouldn't except for > informing the user of a simple set of rotations that will > generate one specific structure? Probably when output, these > would be rounded to the nearest integer anyway. > (Though I don't have Miguel's thoughts on that.) > > No one is suggesting that Jmol use RxRyRz for representing arbitrary > rotations internally. > > Bob -- Anthony Stone http://www-stone.ch.cam.ac.uk/ University Chemical Laboratory, Email: [EMAIL PROTECTED] Lensfield Road, Phone: +44 1223 336375 Cambridge CB2 1EW Fax: +44 1223 336362 ------------------------------------------------------- This SF.net email is sponsored by: IT Product Guide on ITManagersJournal Use IT products in your business? Tell us what you think of them. Give us Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more http://productguide.itmanagersjournal.com/guidepromo.tmpl _______________________________________________ Jmol-developers mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/jmol-developers
