Where is Adam Nemecek? (https://news.ycombinator.com/user?id=adamnemecek)

/press Quaternion Alert button

> Location: Los Angeles, Prague

It's still a bit early if he's in LA, particularly as it's Sunday.

True dat. Alright, well, I'll help him out with his obligatory link:

http://www.chinedufn.com/dual-quaternion-shader-explained/

Interesting stuff. Maybe there is a connection with the use of quaternion pairs to represent rotations in 4-space (as in the Coxeter paper).

Using quaternion pairs for 4-space rotations relies on the simple fact that each quaternion represents a hyperplane in 4-space (https://en.wikipedia.org/wiki/Transformation_geometry). Using single quaternions to represent rotations in 3-space is geometrically a different mechanism, which AFAIK doesn't have such a simple geometrical explanation.