Hoshino Lina (星乃リナ) 🩵 3D Yuri Wedding prep!!!

Hacker & Mad Scientist VTuber!

💍 @cyan 🩵 | We are @TokyoHackerGirls ✨

ママ : https://bsky.app/profile/heripiro.bsky.social | パパ : https://twitter.com/otozuki_teru
All the links: https://lina.yt/me

Public Key

npub14w78207els8vs5fxduhhval0r9zgujpf2khcqyfuhmkt2tlyvcyq2zuequ

NIP-05 Address

lina@vt-social.mostr.pub

Profile Code

nprofile1qqs2h0r48lvlcrkg2ynx7tmkwlh3j3ywfq54ttuqzy7tam949ljxvzqpz4mhxue69uhhyetvv9ujuerfw36x7tnsw43qynefep

Publishing to

relay.ditto.pub

Author Public Key

npub14w78207els8vs5fxduhhval0r9zgujpf2khcqyfuhmkt2tlyvcyq2zuequ

Show more details

Last Notes

2026-10-27 11:50:46 UTC

Is there some easy/reliable UDP/datagram security layer I can use from Rust? Something simple, shared keys or pub/privkey auth (both directions).
If there's nothing better I'm tempted to take wireguard-rs and just remove the routing/tun part...

2026-10-26 14:23:30 UTC

Why is Cyan so cute????
It's not fair, I can't stop looking at her!!!!!! ;;

2026-10-25 06:25:58 UTC

Live vocal production is a hot topic lately so... let's learn how that works and have some fun with Cyan! ✨
Live in 5 minutes~ 🎵
➡️ https://www.youtube.com/watch?v=DzDl5Lc3468
#VTuber #ENVTuber #HoshinoLinaLive
https://media.vt.social/media_attachments/files/117/500/120/756/213/826/original/3c6d7ac154e02410.jpeg

2026-10-24 07:38:41 UTC

📢 You can Just Use Rust and Stop Getting Pwned 📢
Node -C +🦀 = node2shell fixed:
git clone https://github.com/hoshinolina/rust-brotli-decompressor &&
cd rust-brotli-decompressor/c &&
make &&
cp target/release/libbrotli_decompressor.so /lib64 &&
ln -nsf libbrotli_decompressor.so /lib64/libbrotlidec.so.1
Works on Fedora 44 with system node.js v24.
Disclaimer: This is a PoC of how this whole CVE could have been avoided. I stubbed out the brotli metadata support because it was missing that symbol and it's probably useless for HTTP anyway.
rust-brotli-decompressor by Dropbox.
Use Rust, people.
https://media.vt.social/media_attachments/files/117/494/683/161/426/979/original/49ac86d3127d9393.png

2026-10-23 10:49:54 UTC

Is it cheating if we’re both girls⁉️⁉️
Taking the famous test with Cyan in 10 minutes~!!!
➡️ https://youtu.be/KgNgTboExXw
https://media.vt.social/media_attachments/files/117/489/833/925/389/454/original/e47ed7692f12b82a.jpeg

2026-10-22 12:19:11 UTC

The private key was 4.
https://youtube.com/shorts/hIRCmEgGxHQ

2026-10-21 15:22:50 UTC

And there's another one...
https://fedi.katze.sh/@elise/117479383739450605

2026-10-21 15:06:36 UTC

And before I go to sleep: Yes, this PHP vuln is Yet Another Thing That Would Not Happen If It Were Written In Rust.

2026-10-21 14:27:12 UTC

Fedora 43 users install these RPMs to fix PHP:
https://koji.fedoraproject.org/koji/buildinfo?buildID=3125181
Fedora 44 RPMs will be here in ~15 minutes give or take:
https://koji.fedoraproject.org/koji/buildinfo?buildID=3125182
Arch has pushed the fixed packages to mirrors. No word from Alpine yet and I can't hit their git...

2026-10-21 11:07:28 UTC

Ah yes, the wikis documenting how to update things are all down for updates!
https://media.vt.social/media_attachments/files/117/478/578/381/732/871/original/dc5e39d8b2195ff4.png

2026-10-21 10:13:18 UTC

The one funny thing about this PHP bug is that now you know that every service announcing maintenance runs their core infra on PHP ^^;;

2026-10-21 07:36:10 UTC

So what we're learning today is that in the world of LLMs, any time a serious vuln is pre-announced, social media will be flooded with incorrect or incomplete slop about it and make things worse by misleading everyone.
I hate this timeline...

2026-10-21 06:11:29 UTC

There is an exploit and mitigation floating around.
THAT IS NOT THE EXPLOIT THAT IS EMBARGOED.
It's likely something ELSE someone found in a rush with an LLM.
You are NOT safe just by making a configuration change.

2026-10-21 05:11:20 UTC

I guess we're shutting down PHP today...
https://media.vt.social/media_attachments/files/117/477/177/996/753/884/original/a2a600bdca869589.png

2026-10-21 01:50:00 UTC

Networking zatsu(?) lesson with Cyan!
Starting in 10 min~
➡️ https://www.youtube.com/watch?v=d1iQkxxC_hc
https://media.vt.social/media_attachments/files/117/476/386/366/248/530/original/396448c5c9048e3c.jpeg

2026-10-17 10:19:44 UTC

This is why I'm saying it was probably a regular expression parser. In many regular expression engines, `.` does not match newlines by default.
So, a naive regular expression parser would have failed in this exact way.
And it sounds like something DoCoMo would do.
https://media.vt.social/media_attachments/files/117/455/739/069/548/709/original/d22cddb2b326f2d3.png

2026-10-17 07:31:35 UTC

Whaaaaaaaa
"The format was different"... people are saying there was a trailing line break in the XML after the epicenter location name.
Are DoCoMo parsing XML with regular expressions?????????????
https://www.docomo.ne.jp/info/notice/page/261017_00_m.html
🤦‍♀️🤦‍♀️🤦‍♀️🤦‍♀️
If there is a time to apply the Robustness Principle, it's for earthquake alerts.... this is really sad.

2026-10-16 14:06:12 UTC

So it WAS a bug!
Specifically, to address another false alarm in 2020, they added a threshold to exclude readings more than 700km away from the epicenter when calculating magnitude.
It turns out this new feature was broken and didn't work properly today.
https://www.jma.go.jp/jma/press/2610/16d/kaisetsu202610162240.pdf

2026-10-16 04:10:17 UTC

Ohhhh hold on, the quake was real but it was faaaar into the ocean and a nothingburger.
Did they... miss the P waves, then sensed the S waves up in Hokkaido and misinterpreted them as P waves and therefore thought a Huge One was coming???

2026-10-16 03:48:19 UTC

WELL THAT WAS SCARY... that's the first time I get a crazy earthquake EEW false alarm that even hit the outdoor PA speakers!
https://media.vt.social/media_attachments/files/117/448/540/006/934/555/original/77818f4c6f26b906.png

2026-10-16 03:24:16 UTC

Teaching Cyan fiber networking with a spare 10G pigtail ^^
(It's multimode, eye safe at a reasonable distance)
https://media.vt.social/media_attachments/files/117/448/445/474/809/212/original/1b70c38fcfce1702.jpeg

2026-10-16 02:05:19 UTC

I wrote about how iPhone face tracking is just good software and the Face ID camera thing is a myth on Reddit again.
This time I went into the history of the tech though, which you might find interesting!
https://www.reddit.com/r/vtubertech/comments/1x6mp3t/comment/ph0svny/
https://media.vt.social/media_attachments/files/117/448/130/984/860/544/original/3e45b60831fcacaf.png

2026-10-15 14:00:20 UTC

Guess I'll try NFS for Mac file sharing next. I tried to fix Samba but had *another* bad experience contributing. I don't even know why I try with software in the Linux low level/systems orbit at all any more...

2026-10-15 00:56:21 UTC

Cyan is streaming right now.... what kind of poll is this???????!!!
https://www.youtube.com/live/l2y9NI4Rocc
https://media.vt.social/media_attachments/files/117/442/201/513/535/828/original/e958d55e7647e89c.png

2026-10-14 15:05:45 UTC

OwO what's this
https://media.vt.social/media_attachments/files/117/439/879/192/898/153/original/958cdb3c73f45c27.jpeg
https://media.vt.social/media_attachments/files/117/439/879/166/043/793/original/f9db053ad3646cc1.jpeg

2026-10-14 07:11:03 UTC

## <emoji> is the new em dash.
The code might be good, it might not be... but honestly when I see that now it just makes me look for an alternative project to try first.

2026-10-11 05:05:44 UTC

I watched CPK at the cinema again on Friday and when the full version of Reply played after the movie, I cried again.
Every time I watch it, something new clicks and hits even harder ;;

2026-10-10 08:29:46 UTC

Happy birthday to Cyan and meeeee~ 🎂
(Okay I'm technically tomorrow but almost!!)
Send us marshmallows!!!!! https://thgirls.yt/marshmallow

2026-10-09 02:16:24 UTC

Saying coding is not art is like saying architecture isn't art.
Just because the end result is functional and not purely aesthetic doesn't mean it's not creative or artistic.
I suspect a lot of the non-coders (and some coders) who say this kind of stuff think programming is just copying and pasting solutions from Stack Overflow.
That's like saying room design is never an art just because anyone can throw in some IKEA furniture and call it a day.
I don't design my own furniture and most of my furniture is IKEA, and I'm not going to claim I have artistic room design skills... but I'm not going to say artistic room design and architecture doesn't exist. And someone still artistically designed that IKEA stuff I'm using.

2026-10-08 15:29:07 UTC

> My feed is supposed to be SFW
> Joke (maybe half) about R18
> Someone actually comms something cute
> Can't share because SFW
> I've got the freaking editor of the C Programming Language standard liking my tweets about this
My brain is melting what is this timeline aaaaaaaaaaa
https://media.vt.social/media_attachments/files/117/405/996/544/958/141/original/58bd905bc36efe43.png

2026-10-08 15:13:24 UTC

Report: Cyan got what she wanted
😳😳😳😳😳😳😳😳
(Somewhere on Twitter and Bluesky)

2026-10-08 05:17:17 UTC

Cyan: You know when you buttoned my shirt last night?
Me: Yeah?
Cyan: It kinda felt like shibari.

2026-10-07 11:32:12 UTC

I just came home from work and Cyan SAID WHAT ON STREAM???????????????

2026-10-06 13:43:18 UTC

TIL that there is such a thing as a USB2.0 galvanic isolator. It's a relatively recent IC (~2022).
As expected, the obligatory caveat is that it "counts" as one chained hub (despite not being visible to software). So on Macs you get max 3 chained hubs + one of these.
https://media.vt.social/media_attachments/files/117/394/256/496/824/311/original/e16d126fcab8f389.jpeg
https://media.vt.social/media_attachments/files/117/394/256/526/234/547/original/6493cd786df613d8.png

2026-10-05 09:06:53 UTC

Me: I... don't think this is supposed to happen... do I have some weird chord copying setting turned on?
(30 minutes later)
Me: Oh. Yeah that would do it...
https://media.vt.social/media_attachments/files/117/387/499/062/062/027/original/ac0649f0b5a4d904.mp4
https://media.vt.social/media_attachments/files/117/387/504/304/036/677/original/14213761a7882465.png

2026-10-05 03:34:15 UTC

ちょっとまって…
ハニーワークスさんの新曲…
まさに @nprofile…cer5 とあたしじゃない？！？！
https://youtu.be/_v08wKA5ohs

2026-10-05 01:10:34 UTC

Oh my dear @nprofile…cer5... ^^;;
https://media.vt.social/media_attachments/files/117/385/634/266/996/099/original/3d9fbf258f9593b7.png

2026-10-04 08:35:00 UTC

Something something trying to make a CPK medley?!
https://www.youtube.com/watch?v=DHIOO5zf1gM

2026-10-02 11:24:48 UTC

Today I learned that VRChat's anti-cheat blocks VMs...
... and they have *official docs* on how to configure the VM to hide it and evade the block.
I... wh... what? In what world does any of this make sense?!?!?!
https://docs.vrchat.com/docs/using-vrchat-in-a-virtual-machine

2026-09-30 09:37:04 UTC

> panic(cpu 3 caller 0xfffffe0043b5b358): busy timeout[0], (60s): 'Yamaha MX Series' (1,1812001) @ IOService.cpp:5986
Okay, now I really need to get rid of this silly Yamaha kext...

2026-09-29 13:42:56 UTC

私たちのコミュニケーション
https://media.vt.social/media_attachments/files/117/354/618/894/234/485/original/258f0b7418b2c18c.png

2026-09-29 13:11:17 UTC

I'm really liking this microservice thing. This is the code for the whole Discord stream notification service ^^
https://media.vt.social/media_attachments/files/117/354/494/401/340/905/original/b766fa1992c525b4.png

2026-09-28 13:45:27 UTC

Microservice ALL THE THINGS!
https://media.vt.social/media_attachments/files/117/348/966/443/769/382/original/ed73d37580a409e6.png

2026-09-28 04:40:24 UTC

I could've sworn I pushed this a year ago but apparently I'd been sitting on it so...
pypi.org/project/rmectl
Python module to control the RME Digiface. Low effort, but it works. In case anyone finds it useful ^^

2026-09-25 02:35:25 UTC

Anyway, Live2D model security / cmo3 drama over on birdsite if anyone wants to follow: https://x.com/Lina_Hoshino/status/2103282334724448365

2026-09-25 02:33:38 UTC

OMG BUFFER FINALLY HAS THREADS!!!!!!!
I'd been giving up on crossposting anything long lately because it's such an enormous pain to do manually...!!!!!
https://media.vt.social/media_attachments/files/117/329/337/835/219/896/original/163bc4397d779752.png

2026-09-21 09:20:54 UTC

Cyan: I can't imagine R18 of that.
Me: Well, you know Rule 34 exists so...
Cyan: What's tha... ohhh that one
Me: Yeah
Cyan: Why isn't it applied to us yet???

2026-09-14 04:09:50 UTC

I've said it before. Vibe/AI coding is a symptom of the software industry's problem with tech debt, bloat, over-complexity, and feature creep.
If you are using AI to write "boilerplate"... why are you writing boilerplate? Good tooling doesn't need boilerplate.

2026-09-11 15:00:58 UTC

Too sleepy to schedule the stream but: Testing out OpenVT tomorrow @ 1PM JST (in 13h)!
OpenVT is an open source alternative to VTube Studio, built on Godot using Ayagami! ✨
We're going to make it better, faster, lighter, & with more features than VTS! Native Win/Mac/Linux!

2026-09-11 12:22:30 UTC

I wish Time Machine sparse bundles stored data and metadata separately. I can't afford to back up to SSD, but having everything on a networked HDD array is agonizingly slow...
I store my *NAS* meta itself on SSDs. If the sparsbundle had meta separately, I could just move that...

2026-09-11 12:15:39 UTC

Notes on restoring a network Time Machine backup to a new/wiped Mac via USB:
- Place the .sparsebundle at the *root* of the USB filesystem, or it won't find it
- Recovery mode does not work, boot normally and use Migration Assistant (on firstboot flow)
- If correct, USB drive will pop up in backup source list

2026-09-11 09:14:45 UTC

Is anyone interested in a chatting stream about Live2D technology?
I learned a lot writing Ayagami, and I wonder if any riggers would be interested in talking about it! ^^

2026-09-02 03:49:41 UTC

After last night's stream I think I want to do a handcam stream teaching digital logic with real logic gates... and I realized that good digital logic demo/learning kits just don't seem to exist any more. Nothing like what I had when I was young.
I might have to design my own...

2026-08-30 15:51:52 UTC

⋱ Mad Scientist Hacker VTuber ⋰
Dev by day, pianist by night 🍎✨
I’m Lina, the cool-headed part of the yuri tech duo @nprofile…nrqq
〜〜〜〜〜〜〜〜〜〜〜
YouTube：https://lina.yt
Links：https://lina.yt/me
Art：https://twitter.com/heripiro
Rig：https://twitter.com/otozuki_teru
Live：#HoshinoLinaLive
FA：#HoshinoLinaArt
〜〜〜〜〜〜〜〜〜〜〜
https://media.vt.social/media_attachments/files/117/185/256/432/726/882/original/e71ae5de62493586.png
https://media.vt.social/media_attachments/files/117/185/256/536/645/983/original/3ac13336ec46d494.png

2026-08-30 13:24:25 UTC

Huh, I think I just invented something kinda cool (I'm sure I'm not the first to come up with it?). A way to render "layer groups" with a shared opacity (without internal overlaps being revealed), like offscreen rendering, without actually doing any offscreen rendering or switching framebuffers.
The tradeoff is you have to render those groups twice (once for an alpha pre-pass) and your framebuffer alpha needs to be expendable (so, opaque background behind everything). But you can have as many such groups as you want (single level deep, no nesting).
The trick is to first render such a group as alpha mask only (clearing FB alpha and then accumulating the group alpha into it, standard blending with alpha write only), then render a couple quads to compute:
(pass 1)
Adst' = Adst * Asrc
(pass 2)
Cdst' = Cdst * (1 - Adst)
A = 1 - Asrc
Where Asrc is the layer group opacity (which can in fact be any arbitrary mask, not necessarily a constant).
Then finally render the group again, front to back, with front to back blending formulas:
Cdst = Cdst + Csrc * Adst
Adst = Adst + Asrc * (1 - Adst)
The first part leaves the FB RGB as a combined semitransparent "front layer" (background at 1 - layer group opacity) + pre-accumulated "back layer" in the RGB channels (background at (layer group opacity * (1 - layer group alpha))).
The second part renders the layer group "in between".
Repeat for more layer groups, back to front.
Surely I'm not the first to come up with this?

2026-08-29 03:05:33 UTC

I think I'm going to start working on NekoDeck again soon. But less so the frontend first... the new plan is to use MQTT to tie all our streaming setup together.
Originally I was thinking of doing a Redis thing but then I realized... I already have MQTT for Home Assistant!

2026-08-26 11:08:05 UTC

Sudden cleaning stream with Cyan??? Our office is a mess!!!!!!!
https://www.youtube.com/watch?v=gZw0DdWwQRw

2026-08-24 09:57:06 UTC

- reply

@nprofile…9qfw They aren't, but yes it's probably related. It's a bug in their TIFF loader.
The explanation consistent with my tests is that the image is straight alpha, and expected as such on both ends, and there are no unexpected conversions, BUT along the way it transitions an object *tagged* as premultiplied, and in at least the macOS implementation that object implicitly clamps RGB to A (removing emissivity when premultiplied), which corrupts the color values in straight alpha.

2026-08-23 15:55:42 UTC

Live2D Reverse Engineering is
✨ COMPLETE ✨!!
With Cubism 5.3 blend modes implemented and known bugs fixed, that wraps up all the features! Thank you Maruseu for the lovely test model! 🩵
Try it out at https://demo.ayagami.dev 🚀
https://media.vt.social/media_attachments/files/117/145/635/475/084/023/original/71621c60759c27dc.png

2026-08-23 05:59:44 UTC

Guerrilla stream! Wrapping up the Live2D reverse engineering!
Starting now~
https://youtube.com/live/CycQJcMy3Uk
https://media.vt.social/media_attachments/files/117/143/292/039/533/363/original/866f6f3afc8fd65b.jpeg

2026-08-22 14:43:49 UTC

Linux hackers are safe, Windows and macOS hackers will steal your data... and you'd better call police if you meet a GPU hacker?!?!
https://media.vt.social/media_attachments/files/117/139/690/443/125/918/original/e825a519baeeba46.png
https://media.vt.social/media_attachments/files/117/139/690/466/411/417/original/2801a7186e40e88a.png
https://media.vt.social/media_attachments/files/117/139/690/447/377/836/original/2a893f5c49c0250c.png
https://media.vt.social/media_attachments/files/117/139/690/432/709/322/original/62589a7b98b255db.png

2026-08-22 09:05:26 UTC

Ayagami does screenshots now! Just drop your model in, pose it however you like, and copy/save as transparent PNG (current view or full model resolution)
https://demo.ayagami.dev
Tomorrow I'll stream again and wrap up work on the 5.3 blending/color issues ^^

2026-08-21 16:22:22 UTC

- reply

@nprofile…pmn8 I gave them some hints but I'm not going to fully debug it.

2026-08-21 15:55:25 UTC

Sooo I'm writing a copy to clipboard feature for demo.ayagami.dev, and I couldn't get the alpha to work properly.
I was pasting into GIMP and Inkscape.
Turns out pasting images is broken in GIMP and Inkscape on macOS.
Since 2021 🤦‍♀️
https://gitlab.gnome.org/GNOME/gimp/-/work_items/6569

2026-08-16 08:27:08 UTC

- reply

@nprofile…vs3g The FAQ has some examples of permitted usage: https://www.irasutoya.com/p/faq.html
For non-commercial use it's more liberal than CC BY-NC (more like CC NC if that existed, no need to credit). For commercial use there is a limit of 20 free images per work.
There are some restrictions on usage (no political, illegal, discriminatory use, no commercial redistribution of the images themselves on their own) but that's the gist of it.

2026-08-15 04:01:32 UTC

Starting now!!! Let's wrap things up!!!

2026-08-14 15:34:20 UTC

STREAM: Reverse engineering Live2D: Wrapping up!
Let's look at 5.3 advanced blend modes and other loose odds and ends!
✨ Important FAQ✨
https://lina.yt/moc3faq
🕐 Aug 15 13:00 JST / 04:00 UTC
▶️ https://youtube.com/live/HbF6ci7EK9g
#VTuber #ENVTuber #Live2D
https://media.vt.social/media_attachments/files/117/094/590/677/604/989/original/4fbaa049de42af95.png

2026-08-13 21:29:00 UTC

- reply

@nprofile…3tsk I'm not surprised... on APUs there's also fun stuff like changing the GPU "VRAM" memory carveout too, I wouldn't be surprised if that short circuits the IOMMU and a lot of other things... maybe someone should try that one on SMM memory.

2026-08-13 14:30:55 UTC

- reply

@nprofile…dn2p I'd rather the jank my way, MIT licensed ^^

2026-08-13 09:03:50 UTC

( https://youtube.com/playlist?list=PL8S0yfRexZULmW9fhF2gcMsuPBi6jeVhZ )
https://media.vt.social/media_attachments/files/117/087/392/897/614/420/original/6461e31e3d36afcc.jpg

2026-08-12 20:32:00 UTC

- reply

@nprofile…8zly If any of your devices came with a Type C charge cable it probably wasn't USB3 ^^;; (unless the device itself requires USB3 to function normally).

2026-08-12 19:24:51 UTC

- reply

@nprofile…8zly That's the vast majority of USB PD cables, including e.g. all the default Apple charge cables. You can't have USB3 support keeping the cable thin and flexible, since that needs a lot of extra wiring.

2026-08-12 14:27:29 UTC

I love Cyan so much~ 🩵🩵🩵🩵🩵

2026-08-12 11:48:24 UTC

- reply

@nprofile…40y0 It's Japanese, so certainly means it doesn't ^^

2026-08-12 06:22:59 UTC

Go watch my lovely waifu stream!!!!! She's all lonely while I'm at work!! 🩵
https://www.youtube.com/live/4p7rAt8IRBg

2026-08-12 01:46:59 UTC

I wish all USB cables were labeled like this!!!
(Elecom brand, if anyone's wondering)
https://media.vt.social/media_attachments/files/117/080/012/755/372/916/original/cc138ae07331b5db.jpeg

2026-08-11 15:55:41 UTC

- reply

@nprofile…qadx A month. That's less than US$1600.

2026-08-11 12:08:55 UTC

- reply

@nprofile…rt5d Given the horrors I've seen in Live2D (broken vector rotation code in the physics engine)... I'm not sure how much actual thinking goes into it...

2026-08-11 11:36:01 UTC

- reply

@nprofile…rt5d I mean, it's essentially the minimum wage for flipping burgers with no relevant experience in Tokyo.
The 2x difference is the market. The flipping burgers part, apparently Live2D think that's what programming is worth...

2026-08-11 10:58:47 UTC

- reply

USD equivalent: $11/h or so.
This is barely above minimum wage in Tokyo.
For a software engineer.
All the jank in Live2D makes a lot of sense now...

2026-08-11 10:53:29 UTC

- reply

You could *barely* afford a tiny studio apartment on that salary... years ago. It's gotten more expensive since.

2026-08-11 10:49:44 UTC

The Live2D ad targeting is on the nose www
I checked their jobs site... 250000 JPY starting salary for programmers. With 25h overtime.
You can barely survive in Tokyo on that.
No thanks... ^^;;
https://media.vt.social/media_attachments/files/117/076/484/602/181/867/original/8174230e2f3f3f81.png
https://media.vt.social/media_attachments/files/117/076/484/612/011/984/original/67f1fd991c4d6470.png

2026-08-11 06:46:21 UTC

- reply

Docs: https://docs.live2d.com/en/cubism-editor-manual/physical-operation-setting/
They document gravity as "Speed of convergence", but in the screenshots it says "Overall acceleration" instead, and the actual editor caption these days seems to be "Convergence speed".
I guess they can't afford a competent l10n team...?

2026-08-11 06:46:21 UTC

Live2D physics is bizarre.
"Duration" (JSON: "Radius"): Pendulum length. Mistranslation of 長さ (length).
"Ease of swinging" (JSON: "Mobility"): Reversed damping factor.
"Reaction time" (JSON: "Delay"): Time dilation factor.
"Convergence speed" (JSON: "Acceleration"). Gravity.

2026-08-10 22:45:31 UTC

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@nprofile…s6dx Not exactly, what you're describing has more to do with tracking. For example, my new model overdoes it and I actually want to turn it down or remap it a bit. All that is configurable and adjustable by the user already, it's just a lot of people don't bother to dig through the settings and just use whatever the defaults were.
What I'm describing is specifically about the physics (hair, clothes, things like eye bounce, etc.) feeling more "bouncy" than you'd expect.

2026-08-10 16:27:46 UTC

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@nprofile…9zph I did notice that ~3.02 was closer at some speeds, and I don't think I ever did as high as 1 rad/frame, so that tracks!

2026-08-10 15:50:42 UTC

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@nprofile…t6v8 Someone else brought that up on Twitter! That makes sense but it doesn't explain how we go from that to what the diagram is describing and why it works...

2026-08-10 15:46:52 UTC

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@nprofile…u326 The units are already radians, there's no extra pi needed anywhere.

2026-08-10 10:27:54 UTC

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@nprofile…qlh2 It's whatever. I tested at multiple FPSes and velocities. It's always 3.
The double multiplication is intentional.
velocity per second -> velocity per frame
(adjust)
velocity per frame -> velocity per second
Now this velocity loss is applied at a rate of emu_fps, which means that the *instantaneous acceleration* that generates it is the velocity loss, times the frame rate, giving radians per second squared.

2026-08-10 10:06:42 UTC

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@nprofile…qlh2 Frame rate at which the diagrammed operation would happen.

2026-08-10 09:30:38 UTC

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Note that the 3 is NOT in the original Live2D implementation anywhere. I have an exact (to FP precision) black-box re-creation of that, and it's doing what is shown in the diagram I posted above. There is no 3 anywhere in that code.

2026-08-10 09:30:38 UTC

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I don't know why it's 3 yet, but 3 seems to be ~exact by all appearances. No, it's not pi...
The diagram above should be what actually happens. You can write out the vector math for that, but I don't know why that arctan thing with a fudge factor of 3 works out in practice... anyone want to try to solve the math and see if it really ends up like that?

2026-08-10 09:30:37 UTC

One thing I haven't figured out yet is where this mystery factor of 3 comes from.
These two lines of code are emulating what happens when the Live2D physics engine applies velocity as linear motion, then clamps down to a fixed radius, every frame.
The arctan thing was a first approximation (taking the velocity vector as tangent to the current position, length = angular velocity), but then the factor of 3 makes it correct.
https://media.vt.social/media_attachments/files/117/070/511/220/454/352/original/50755c6cb76bd056.png
https://media.vt.social/media_attachments/files/117/070/511/230/292/208/original/6acd14b9611cc56f.png

2026-08-10 07:11:08 UTC

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This doesn't make ANY sense hard-coded, but it's useful behavior if you want it.
I think what I will do for Ayagami is add it as a configurable per-pendulum parameter. That way you can tune how much "free energy" is created when it moves, instead of having a fixed, poorly chosen value imposed upon you.

2026-08-10 07:11:07 UTC

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One interesting thing I verified is that the "1/5 angle input momentum boost" thing Live2D does is absolutely essential to having it behave as designed.
I suspect that behavior is part of what people call the "Live2D physics feel". It basically creates energy from thin air!
So for example, if you rotate a still pendulum by 45 degrees, it will swing over MORE than 45 degrees on the opposite side, because energy was created. Sometimes a lot more. With some settings it'll even loop around!

2026-08-10 02:54:17 UTC

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The plushies are super cute~!!!!!

2026-08-09 04:09:40 UTC

Starting now!! We're going to do ✨MATH✨!!

2026-08-08 12:07:33 UTC

STREAM: Reverse engineering Live2D Physics! (part 3)
We've got a model of the physics engine! Now let's see if I can design an engine that works better than the original ^^
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2026-08-02 04:11:27 UTC

I'm live with Cyan @ THG~!
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2026-08-01 14:30:19 UTC

We are...
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