Re: [PyMOL] CGO rotate vs quaternion

Hi Pawel,

Have a look here:
http://euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/index.htm

It should provide some insight into what quaternions are and how you can
use them to rotate or obtain an axis-angle representation.

Cheers,

Tsjerk


On Sun, Nov 24, 2013 at 11:31 PM, Павел Томашевский <cro...@gm...>wrote:

> Hi all,
>
> Ok, so today I have to admit that I don't know what quaternions are
> but I <probably> will need to use them.
> I'm working on PyMOL and Sensable Phantom Omni haptic device
> integration using Virtual Reality Peripherial Network (VRPN).
>
> So far I have a nicely working plugin for PyMOL that can retreive
> X,Y,Z coordinates and vector of four quaternion values.
>
> My CGO pointer (cone) can smoothly move according to X,Y and Z
> changes. Now I need to do some rotations of the pointer. AFAIK
> 'rotate' function accepts only degree value of rotation around axis.
>
> My question is: is there any build in PyMOL function that accepts four
> quaternion values and do rotation (instead of degree for each axis)?
>
> If not: do you have any simple hint or math formulas for me :) to
> calculate angles for rotation of CGO out of four quaternion value?
>
> Cheers
> Pawel 'crooveck' Tomaszewski
>
>
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-- 
Tsjerk A. Wassenaar, Ph.D.