An interactive guide to sensor fusion with quaternions
12 comments
·August 15, 2025oneshtein
/* Produce a quaternion from an axis-angle representation.*/
function quat_from_axis(theta: number, x: number, y: number, z: number) {
const halfcos = Math.cos(theta * 0.5);
const halfsin = Math.sin(theta * 0.5);
return new Quaternion(
halfcos,
axis[0] * halfsin,
axis[1] * halfsin,
axis[2] * halfsin,
);
}
noodlejs
Hi! Author here. I hand wrote this website and the source code of the examples mostly comes from my own debugging tools. That method in particular is just a very minimal implementation of section 8.5.2 of this textbook (but I tried to make it friendly for the blog post).
polishdude20
Sorry, but x,y and z are not even being used in that function...
noodlejs
LOL ok yeah, that's a copy-paste issue. I'll fix it up here shortly.
ARob109
I've been seeing "that's vibe coded" comments a lot lately on posts. Comments that call out code that may or may not be vibe-coded. At what point should these types of posts start getting down-voted? It's not constructive, and IMO imparts a negative connotation.
HN: Show HN Awesome New LLM can Code!! Also HN: TFA is vibe coded angry pitchfork or ugh
feoren
What makes you so confident that you can tell that a 3-line function is AI? Especially given that the author denies it, with evidence.
oneshtein
It cannot work, because x,y,z are not used at all.
margalabargala
This looks more like a copy paste error, where the function signature requests xyz, but the function itself uses an undefined array "axis" of which xyz correspond to indexes 0-2.
The code is correct aside from the obvious bug.
Bugs predate the existence of AI by decades. This particular bug doesn't look like one an AI would write.
CamperBob2
Then again, that's just the AI would say...
> a quaternion is a 4D representation of a rotation in 3D space
A unit quaternion represents a rotation in R³.
A quaternion represents the quotient of two vectors in R³. That's what Hamilton had in mind.