Hacker News Reader

mattivcon Ask HN: Which air quality monitor to buy?

I have two Airthings View Plus and I am very happy with them. I have them set up in Home Assistant to turn some fans on and off based on air quality.

mattivcon Show HN: Obsidian Canvas – An infinite space for your ideas

Just purchased the "Early bird tier" to give it a try. I just get a "500 Server Error" when clicking the "View Content" link in gumroad.

mattivcon Harvard mandates the bivalent Omicron-specific Covid-19 booster

That is not quite the whole story. They are making it available for anyone in Oslo, at least. [1] I live in Oslo and have an appointment to get a booster tomorrow. I have multiple friends and family members in the healthcare sector, and they are all warning me that we are likely to see a significant spike in the winter. At the same time we are seeing more and more sign that each repeated infection has increased risks. [2]

- [1] https://www.oslo.kommune.no/english/coronavirus/corona-vacci...

- [2] https://time.com/6232103/covid-19-reinfections-effects/

mattivcon FreeTube – A Private YouTube Client

I have had a love-hate relationship with YouTube for a long time. On the one hand, many channels put out great content that I want to watch. But the recommended videos feature is exceptional at hooking into my reptilian brain and getting me to waste a lot of time on junk that I later regret as a big waste of time.

I looked into a lot of alternative clients, including FreeTube, in an attempt to solve this. I use Tube Archivist[1], an open-source project that allows you to subscribe to and auto-download YouTube channels and playlists or download individual videos and watch them in a minimal web interface. It works fine on iOS as long as you set it up to download in an iOS-compatible format. I currently have it running in a Docker container on my Synology NAS.

[1] https://www.tubearchivist.com/

mattivcon Ask HN: What is the most complex concept you understand?

The problem with quaternions for optimizations is that they are over-constrained. Meaning the norm of the 4 values must sum to 1 for it to be a valid 3D rotation. So you need to ether penalize a rotation with a norm different from 1 or constantly remap the quaternion back to a valid one in each iteration of the optimization. Neither solutions is very elegant.

A 3 valued so3 lie algebra vector is however always a valid 3D rotation, no matter what the values are. That makes it an ideal parameterization of the optimization problem.

The mapping from so3 lie algebra to SO3 lie group (which could be represented as a rotation matrix or quaternion) is a smooth differentiable function, which allows us to compute the jacobian we need for the gradient in the optimization.

mattivcon Ask HN: What is the most complex concept you understand?

Lie theory is, among other things, a very elegant way to parameterize an energy function involving rotations in 3D space. For example the translation and rotation of multiple camera frames that observe the same set of 3D points. This is the basis of how Visual Odometry, SLAM or 3D reconstruction problems are solved.

There are other cool things like representing a probability distribution over a 3D rotation with an multivariate gaussian vector interpreted as a so3 or se3 vector. Using this you can for implement a very elegant extended kalman filter estimating a 3D rotation. Which usually can be a tricky thing to do.

In robotics we pretty much only use the SO3, SE3 and SIM3 groups so my knowledge is limited to those groups.

mattivcon Ask HN: What is the most complex concept you understand?

Probably Lie Theory, or at least the small subset of it that is relevant for robotics.

It has taken me a long time and a lot of work to understand it to the level I have, and I still have a lot more to learn. But it is a fascinating subject and a very elegant way to represent some very complex optimization problems.

mattivcon Ask HN: What are you working on?

https://github.com/matiasvc/Toucan A Computer Vision and Robotics visualization library.

It is way to hard and complex to do 2D and 3D visualization in C++. Toucan is my attempt to solve that. It can be called from anywhere with minimal code and gives you interactive 2D and 3D visualization.

mattivcon Ask HN: Show me your half baked project

https://github.com/matiasvc/Toucan

I work in robotics and have for a long time been frustrated with how hard it is to visualize data in C++. I created Toucan to try to solve that. The project is still in a very early stage but has already started to become a useful tool.

The API still needs work but it’s getting there. Toucan can be called from anywhere in your code, and runs in its own thread to always remain interactive and responsive.

mattivcon Ask HN: Who is hiring? (January 2021)

When you say “remote possible”, are you open to Europe based candidates or only US based?

mattivcon Bug drone for UK army that weights 196g, has 40 mins autonomy and 2km range

I work with nano-UAVs. I am very skeptical that the 40 minute flight time is even close to being real.

Especially with a quadcopter design. They are way to inefficient.

mattivcon Ask HN: Good C++ code bases to read?

One of the C++ project that have influence my programming the most recently, which is to move to a style that is something between C and C++, is Dear ImGUI: https://github.com/ocornut/imgui

mattivcon New study suggests handwriting engages the brain more than typing

The cloud sync is optional. You could use the SSH access you get when connecting to it over USB, and possibly roll your own backup solution.

mattivcon New study suggests handwriting engages the brain more than typing

The experience is very close. Much more so than with an iPad and Apple Pencil.

I guess what I love about it is that in many ways combines the best of both physical and digital writing. It feels very much like writing with a real piece of paper, and it does not have any distracting apps like social media or a web browser. It also brings the benefits of being a digital device, in that you can edit things after the fact. Such as rearranging pages. Selecting portion of a text or drawing and then move it within the page, or to another page. Do copy and paste, and things like that.

mattivcon New study suggests handwriting engages the brain more than typing

I can attests to this. I quickly forget that I am not writing on a real piece of paper when using it. It feels very natural.

mattivcon New study suggests handwriting engages the brain more than typing

I recently got a reMarkable 2 tablet( https://remarkable.com/store/remarkable-2 ), and I am absolutely loving it.

I have for along time carried around notebooks for note taking and journaling, because I felt the process of handwriting improve my experience of organizing my thoughts. But it was cumbersome and I ended up carrying multiple notebooks for different purposes.

Since I got the reMarkable 2 tablet it has replaced all my notebooks while retaining all the benefits of handwriting. With the added bonus of much easier organizing, backup and being able to view the notes on other devices.

mattivcon Google Maps Hacks

I use an app called Arc for this: https://apps.apple.com/us/app/arc-app-location-activity/id10...

I am pretty happy with it, so i can recommend giving it a try.

mattivcon Ask HN: Your favourite outstandingly creative/informative YouTube channels?

3Blue1Brown: https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw He makes mathematical concepts amazingly intuitive and easy to understand using visualizations.

Brian Douglas: https://www.youtube.com/user/ControlLectures Some of the absolute best material I have found on control theory.

mattivcon Ask HN: Anyone else getting calendar spam?

I recently got spam that looked very similar, through a shared iPhoto album invitation. Seems some spammer have gotten quite inventive recently.

mattivcon Quick, How Might the Alien Spacecraft Work?

I think you misunderstood a bit. The circular symbol is not correlated to the landing sites in any way. It's just a example of the alien's writing system, which large parts of the movie centers around deciphering.

It's a pretty good movie, i can recommend watching it.

mattivcon Ask HN: Self Driving Car Engineer Nanodegree

Hey Dhruv, thanks for answering questions.

In what degree is the material tailored for cars vs other forms of autonomous vehicles? Would you say the knowledge transferable to, for example, autonomous drones?

mattivcon Typora – A cross platform markdown editor

I have been using MacDown for a while now, which again was a replacement for Mou. But this looks even better.

mattivcon Ask HN: Who works in (mobile) robotics on HN?

I am still just a undergrad student, but i am hoping for a career in robotics research or R&D.

I am however one of the founders of my university aerial robotics team, we are planning the attend the IARC (http://www.aerialroboticscompetition.org/) competition this summer.

One of the big unsolved problems in aerial robotics is high-resolution localization without external sensors. Al the drone acrobatics videos out there use a external tracking system. The current IARC mission aims to push this by requiring complex interaction between flying and ground robots without any external sensors. We are currently trying to solve this by using camera and LIDAR sensors. You can read more on our progress here: http://www.ascendntnu.no/blog/

I would love some sort of email group, i have been looking for something like that for some time. Pleas sign me up if you end up creating one: mattivc[at]gmail.com

mattivcon Haskell and floppy disks in Norwegian government

The reason a lot of Norwegian doctors cling to their DOS interfaces is not because of age, or a resistance to upgrade.

I have discussed the topic of medical software with my father extensively, who is a M.D. in a rural town in Norway.

The reason is efficiency. As a doctor you are required to look up a lot of information on the patient, while maintaining a conversation with them. This is only really possible with a keyboard only interface. The older DOS systems does this, and the newer GUI based packages largely does not.

mattivcon Telepresence Robot Crosses Atlantic Seven Times Trying to Get Home

Makes me think physical packets needs a TTL or something.

mattivcon Ask HN :What is the best business book you read and helped you a lot?

Do you have a suggestion for a specific book or books?

mattivcon Why Is American Teaching So Bad?

I imagine it is because all the other countries close to the US in population size are even worse.

Granted, it is not based on very much, but i sort of feel that the US has gained the dominance it has today by being really big, and not horribly corrupt or impoverished.

mattivcon Ask HN: What's your favourite sci-fi/fantasy book?

A great one that haven't already been mentioned is "Stranger in a Strange Land" by Robert Heinlein.

http://en.wikipedia.org/wiki/Stranger_in_a_Strange_Land

It's one of those books that just takes a while to digest after you are done reading it. I highly recommend it.

mattivcon RC fighter model UAV build in Jet engine 360+mph [video]

I have been toying with the idea of trying to create a small Pulsejet[1] engine and stick it on a UAV frame. It's a very simple design and shouldn't be to hard to make with, i think.

[1]: http://en.wikipedia.org/wiki/Pulsejet