I tried to understand quaternions, it didn't work. I know, why I have to use them (no singularities, …). But I can't visualize how they work.
I have a spatial. When I rotate this spatial local, it will be always rotated around it's (0,0,0)-coordinate. Am I right? Let's assume, I want to rotate the spatial around it's (1,2,3)-coordinate. HOW??? Do Quaternions make this job?
They don't… Quaternions always rotate about the Nodes centre.
Thus you must attach the Node in question to another Node positioned at coordinates 1.0f, 2.0f, 3.0f, and apply the Quaternion's rotation to the parenting node.
There's an article about this on the Wiki if you search for it. Rotating or Pivotting about a point.
ok, i hope this is the correct solution, i had the same idea. thank you!!!
i have no idea how quaternions work either, but i use them anyway 
you just have to know what they do, not how.
Who's life done miserable by quaternions and rotating about any points, too:
/home/jmonke2/public_html/wiki/data/pages/rotate_about_a_point.txt
source code of the illustrated example: jmetest/scene/TestRotateAboutPoint.java
thanks to adamgp for wiki hint!