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Not detracting from this post, but has anyone else noticed there's a front page post about Quaternions or Kalman filters on about a monthly cadence? Wonder why that is?

I have noticed too that HN has an enduring fascination with quaternions, and they seem to reach front page surprisingly frequently (considering that there's not a huge amount of discussion of other geometry topics). I'm certainly not complaining though - I love quaternions too!

Maybe because it intersects deeply with game dev?

yes, that's the module i learnt about them in during college.

IMHO I think for me they're interesting because it felt like mathematically they straddle the line of being nearly impossible for me.

I could just barely do them and felt very accomplished when I could. Anything else was either impossible or easy by comparison.

assuming my maths skills are average here then most people have similar experiences with them.


What in particular did you find difficult about dealing with them?

HN's going to need a windscreen cleaner and a bucket if 3blue1brown and Terence Tao ever collaborate on using adaptive Kalman filters for optimal paths in Quaternion spaces.

Maybe it's aspirational: things that people don't know, and would like to learn, and perhaps use one day.

I never noticed it until I read Pynchon's Against the Day, I assume I just ignored quaternion posts before then. Great book, enjoyed the way he used quaternions and vectors towards literary ends.

Edit: just noticed we also have a thread on bifurcation, another big topic in Against the Day.


They're both simple to motivate and complicated enough to have an allure.

At least this is a topic that the average HN reader is likely to be able to understand and which is closely related to software. Several years ago there was a period where there were periodic posts about things like homotopy type theory and research-level algebraic geometry which inevitably spark only inane misunderstandings and uninformed speculation in the comments. I can only attribute it to some kind of fetish for the frontiers of pure math.

AG maybe isn't so connected to software, but HoTT connects to the "functional programming" crowd. https://youtu.be/MVtlD22Y8SQ is me doing some examples.

no worries, quaternions just make the usual rotations. It’s cyclic.

Because quaternions are awesome? :) it definitely feels like a discovery when you learn about them first.

Because quaternions are so cool yet under-appreciated. Unfortunately not many octonion posts.

Octonions are cool! The one application I’m familiar with is in crystallography - you can represent the interface between two crystals with a unit octonion https://doi.org/10.1016/j.actamat.2018.12.034

(Open access pdf: https://par.nsf.gov/servlets/purl/10098941)

Can you give some pointers to other interesting applications?


Quaternions and spherical trigonometry - https://news.ycombinator.com/item?id=42880242 - Jan 2025 (48 comments)

Visualizing quaternions (2018) - https://news.ycombinator.com/item?id=38043644 - Oct 2023 (42 comments)

Visualizing quaternions: an explorable video series (2018) - https://news.ycombinator.com/item?id=31083042 - April 2022 (15 comments)

Visualizing quaternions: An explorable video series - https://news.ycombinator.com/item?id=18310788 - Oct 2018 (32 comments)


It's because the quaternion is part of the state of the Kalman filter.

Not in any intrinsic way, it’s just a mildly better way of representing attitude if your state vector includes attitude.

They are posted by the Quaterminions.

They’re both quite basic building blocks in state estimation and as SV’s focus shifts from web apps to drone warfare it will only increase in frequency.

In my experience in a university ECE program, you'd start with understanding the high level properties of transistors, then combining transistors to make AND and OR gates, then XOR and other gates, then MUXes and half/full adders, then flip-flops and eventually into synchronous (clocked) logic.

The lab component of such coursework did start with TTL chips but the timing of the coursework was such that you'd have most of the asynchronous logic theory taught by the time the chips came out.


Was it an Electrical Engineering, Electronics Engineering or Electrical Engineering Technology Program? My digital course skipped over transistor level and spent that time on basic FPGA's instead.


Not OP but I did Electrical and Electronic Engineering undergrad and we started with diodes at the materials level, then BJT and FET transistors, then logic gates, flip flops, timers, ALUs and eventually working up to build a Motorola 68K micro controller from mid level components. There was some VHDL and FPGA in the later stages as well from memory.


Very cool.

Looks similar to my own project. I think we even used the same case for the display.

https://github.com/Mrjohns42/WeatherDash


Very nice! I like!

I would comment the difference is I have GUIs to set things up, for non-technical users. I did a survey of various projects and found most of them had a configuration step such as "now SSH into the box and input your API key". My mum is never going to do that I'm afraid.

Edit: not to poop on this mode of setting things up, it's good for personal projects but I'm trying to take another step here.


Of course! A setup GUI is almost a required feature if you intend to sell or give it to a non-programmer. That just wasn't the case for me.


This is a big feature and one that most hackers don't bother with because they consider it the least fun part. Advertise it!


Not sure you can eliminate it, but you can certainly reduce the impact and scale by fighting anti-competitive behavior . A major reason this sort of mass manipulation is so lucrative and effective is because you only have operate on a couple of platforms to reach a majority of eyeballs.


Reminded me of the Amazon show called Upload. Sort of a lighter, more humorous take than Black Mirror, but the darker philosophical complexities still surface regularly.


It almost did. There was a hostile takeover bid from Broadcom a few years back, and the US gov intervened to block it.

https://www.reuters.com/article/us-qualcomm-m-a-broadcom-tim...


It totally was a Silicon Valley b-plot, Season 5 Ep 5


The key specifier word was "whitebox". They aren't speaking generally about cryptography.


Very cool. Shamelessly linking my own weather display: https://github.com/Mrjohns42/WeatherDash

Supporting EINK on mine could potentially help make it more visually compelling like yours, but I've done other EINK display projects in the past (see https://github.com/Mrjohns42/DoggieClock) and screen burn-in was definitely an issue.


> and screen burn-in was definitely an issue.

I find this very surprising, I was aware that you can sometimes get ghosting-effects, but I did not think permanent burn-in was possible on EINK tech.


Burn-in is very possible. It is ink particles inside a solvent. Drive it the wrong way and you'll damage the ink or the solvent. Just like LCD where if you drive it the wrong way, the liquid crystal gets damaged. The difference is LCD voltage waveforms are built into hardware and are much simpler since there's no moving components.


Thanks for the insights


The world always needs more 3D platformers.


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