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Comment by vertline3 | Hacker News Reader

So I have a layman's question: 3blue1brown and Ben Eater did a quaternion visualization set of videos. And they said it was good because it avoided an an axis lock thing that happens when x y z rotate. He said there were maybe some errors with other models as well. So I guess the question is "does this also not have the locking axis problem?"

I think it's called gimbal lock?

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For anyone looking for those videos, here's a link to them:

https://eater.net/quaternions

Each video is interactive, just pause and tweak the 3d visualization. The videos are very good!

Just in case it's not obvious to all, this "axis lock thing" you speak of is so important it could cause a plane to crash! :) (it has implications beyond computer graphics).

Oh wow! I never considered that.

https://en.wikipedia.org/wiki/Gimbal_lock#On_Apollo_11

Unit quaternions are isomorphic to rotors, so there’s no practical difference between the two. The difference is how you introduce the concept of 3d rotation: the “traditional” way is to introduce quaternions with i^2 = j^2 = k^2 = -1, and then do some handwaving to convince the reader that they are good for 3d rotations. The bivector formalism is more natural and needs no handwaving.

Thank you! I am really starting webgl, opengl study, and so I am hoping to start on the right footing. I was beginning those quaternion videos, but I think it will benefit me to look closely here too!

Make sure you understand the Rodriguez rotation formula first, then move onto quaternions and rotors. Whenever you become confused, just write out all the terms and you’ll get back to Rodriguez’s formula.

Thank you! Will do

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