iiinova — where your digital self keeps evolving

lucasw @lucasw0.bsky.social · 18/05/2026

"The point is just that the the clean modular picture that you were given of a network stack is a complete lie. These things are complexed together to high heaven."

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lucasw @lucasw0.bsky.social · 18/05/2026

"So there are instances in which TCP actually needs to reach down not just into IP but actually through IP into the boundary layer between IP and Ethernet in order to muck with the neighbor table entries in IPv6..."

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lucasw @lucasw0.bsky.social · 18/05/2026

"That is a beautiful nice simple picture to provide a mental model that we can teach to students. But if you've worked in the real networking world, you know that we violate those those abstraction boundaries all the time."

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lucasw @lucasw0.bsky.social · 18/05/2026

"The Ethernet sits there and doesn't know anything about how IP works and IP sits above Ethernet and doesn't know anything about how Ethernet works and TCP sits above IP and doesn't know how how IP works and doesn't even know that Ethernet exists. That is a complete lie."

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lucasw @lucasw0.bsky.social · 18/05/2026

"if you've taken a a a networking class, you may have seen the the five layer model or the seven layer OSI model and you have this very clean abstraction boundary." youtu.be/THMLDJUFEWI?...

youtu.be

zerocopy with Joshua Liebow-Feeser

YouTube video by Plabayo BV

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lucasw @lucasw0.bsky.social · 12/01/2026

"I don't want to run a piece of code on any of my devices that somebody else wrote outside of sandbox ever again." oxide-and-friends.transistor.fm/episodes/pre...

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lucasw @lucasw0.bsky.social · 21/12/2025

The rmse of curvature error and position error currently gives equal weight to the end points and the interior points, but I'd prefer the end points are more strongly clamped and error in the very middle is less important

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lucasw @lucasw0.bsky.social · 21/12/2025

Next up is finding optimal (or just pretty good) bezier approximations of clothoid curves, and the other way around github.com/lucasw/cloth...

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lucasw @lucasw0.bsky.social · 20/12/2025

(also it's using rust, egui, and an adapted 'stroke' for the cubic bezier curves)

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lucasw @lucasw0.bsky.social · 20/12/2025

It turns out ReciprocalLength was there all along, I just assumed it would be named InverseLength docs.rs/uom/latest/u... - but I still want the AngleLengthRate/Velocity (not PerSecond as above, I keep mixing up the type and particular units)

docs.rs

uom::si::reciprocal_length - Rust

Reciprocal length (base unit reciprocal meter, m⁻¹).

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lucasw @lucasw0.bsky.social · 08/12/2025

I found rust uom ('units of measure' - docs.rs/uom/latest/u...) through sguaba (@jonhoo.eu github.com/helsing-ai/s...) but now I want to make `InverseLength + <inverse_meter>` and next `AngleLengthPerSecond + <radian_meter_per_second>` - so far I'm half way there github.com/lucasw/misc_...

github.com

GitHub - helsing-ai/sguaba: A Rust crate that provides hard-to-misuse rigid body transforms (aka "spatial math") for engineers with other things to worry about than linear algebra.

A Rust crate that provides hard-to-misuse rigid body transforms (aka "spatial math") for engineers with other things to worry about than linear algebra. - helsing-ai/sguaba

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lucasw @lucasw0.bsky.social · 16/10/2025

"I I think it gives people an idea that we're like a Montessori school for systems people. And it's like hey everyone come in and just do whatever you want. Do you wanna eat the Play Doh today? Ok eat the Play Doh... I feel like that's not really accurate"

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lucasw @lucasw0.bsky.social · 16/10/2025

"We can talk about this in kind of our founder mode episode that we about the importance of trust and clarity. And if you've got trust and clarity, then I think you can have autonomy... I think autonomy is important because I think that's when people do the best work"

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lucasw @lucasw0.bsky.social · 04/10/2025

Rust wrapped Jolt Physics visualized in Bevy- each ray-cast simulated lidar point is an individually translated sphere youtu.be/I2yfPAyACps?...

youtu.be

Rust Bevy JoltPhysics vehicle simulation

YouTube video by Lucas Walter

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Reposted by lucasw

Jon Gjengset @jonhoo.eu · 29/09/2025

About a month ago, I gave a talk at the Rust Amsterdam meetup about Sguaba (the type-safe spatial math Rust crate), and the recording of that is now online for anyone who wants their head to hurt with frames of reference and coordinate transforms 😅 youtu.be/kESBAiTYMoQ

youtu.be

Sguaba: Type-safe spatial math in Rust

YouTube video by Jon Gjengset

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Reposted by lucasw

RustConf @rustconf.com · 03/10/2025

It's been a month since #rustconf 2025, but the buzz is still strong! 🦀 Revisit the magic via these videos on the @rustfoundation.org YouTube channel, incl. sessions, keynotes, & this highlight reel: www.youtube.com/watch?v=Hw_I... +Don’t miss these event pics 📸 www.flickr.com/photos/rustf...

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lucasw @lucasw0.bsky.social · 18/09/2025

A nice feature with rerun with the buffering of recent data in rerun is that I can build, run a simulation of so many steps faster than real time, replay some then make changes and recompile, but continue to watch the sim in rerun and scrub around in time while waiting (and maybe make more changes).

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lucasw @lucasw0.bsky.social · 18/09/2025

@rerun.io for visualization again, though the movement over the terrain is not obvious- directional lighting and shadows would help (rviz doesn't have shadows but does have camera aligned lighting). I could bake some shading into the mesh triangle colors, or other rerun features could help?

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lucasw @lucasw0.bsky.social · 18/09/2025

The Jolt Physics 'VehicleConstraintsTest C++ wrapped in rust using cxx- it's working as well as I need it to though I'm not sure if wheel friction is right (are wheels spinning faster than vehicle speed over the ground?). The build process isn't ideal but is workable. github.com/lucasw/jolt_...

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lucasw @lucasw0.bsky.social · 16/09/2025

A soon-to-be-released book about iRobot: 'Dancing with Roomba: Cracking the Robot Riddle and Building an Icon' dancingwithroomba.com - via @weeklyrobotics.bsky.social (www.weeklyrobotics.com)

dancingwithroomba.com

Dancing with Roomba – Cracking the Robot Riddle and Building an Icon

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lucasw @lucasw0.bsky.social · 11/09/2025

``` cxx_build::bridge... .define("JPH_DEBUG_RENDERER", Some("1")) .define("JPH_PROFILE_ENABLED", Some("1")) ``` Now can run the hello world through cxx, can resume with the vehicle example next

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lucasw @lucasw0.bsky.social · 11/09/2025

Need to match these: ``` Version mismatch, make sure you compile the client code with the same Jolt version and compiler definitions! Mismatching define JPH_PROFILE_ENABLED. Mismatching define JPH_DEBUG_RENDERER. ```

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lucasw @lucasw0.bsky.social · 10/09/2025

First question is can I use header files that are pulled in by a dependency (joltc-sys) in my `build.rs`? It looks like it automatically knows about target/release/build/joltc-...hash.../out/lib/libJolt.a, I can link that, but how to include 'joltc-sys-.../out/include/' in cxx_build?

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lucasw @lucasw0.bsky.social · 10/09/2025

Starting over with getting a Jolt physics vehicle simulation into rust- going to try to put a big chunk of it into C++, then use cxx to manage that through a high level interface to supply inputs, step the sim, and get new state after the step update.

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lucasw @lucasw0.bsky.social · 10/09/2025

The next thing needed is a HeightField to drive over, but that isn't in the jolt-rust JoltC currently- github.com/amerkoleci/j... which is a different jolt c wrapper does have it, but making a rust wrapper for that is daunting. Should I just do nearly everything in C++, wrap in rust at high level?

github.com

GitHub - amerkoleci/joltc: JoltPhysics C interface

JoltPhysics C interface. Contribute to amerkoleci/joltc development by creating an account on GitHub.

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lucasw @lucasw0.bsky.social · 10/09/2025

Have a sim vehicle in jolt-rust working with stacked hinges for wheel rotation and steering on two of four wheels, no suspension, visualized in @rerun.io:

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lucasw @lucasw0.bsky.social · 09/09/2025

But now I'm seeing the SixDOFConstraintSettings is missing the MotorSettings... maybe I should just make slider constraints and add separate steering and rolling hinges?

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lucasw @lucasw0.bsky.social · 09/09/2025

What about GroupFilterTable? I see JPC_GroupFilter but no table- what does the table do?

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lucasw @lucasw0.bsky.social · 09/09/2025

But VehicleSixDOFTest.cpp only needs SixDOFConstraintSettings which is already in JoltC, so that's the example to follow for now

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lucasw @lucasw0.bsky.social · 09/09/2025

Now looking at VehicleConstraintTest.cpp there are several things that don't exist in JoltC: VehicleConstraintSettings & WheelSettingsWV (which extends WheelSettings) - the first looks to be easy to add, there are many other *ConstraintSettings in JoltC to follow the example of.

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lucasw @lucasw0.bsky.social · 30/08/2025

Also need to update the joltc submodule with SetGravity: github.com/lucasw/JoltC...

github.com

add PhysicsSystem SetGravity · lucasw/JoltC@5f08a55

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lucasw @lucasw0.bsky.social · 30/08/2025

Have to cargo clean if I add a new function to the Jolt bindings? Or is there a specific file or directory in target I could have deleted for less rebuilding time? Anyhow added SetGravity() github.com/lucasw/jolt-...

github.com

add physics system set_gravity · lucasw/jolt-rust@ed21aad

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lucasw @lucasw0.bsky.social · 29/08/2025

cargo test was strangely sensitive to `build.rs` link order, figured it out by trial and error: github.com/lucasw/jolt-...

github.com

cargo test is very sensitive to the link order (on linux), it has to … · lucasw/jolt-rust@94efc77

…be in this new position

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lucasw @lucasw0.bsky.social · 29/08/2025

linux building is current of jolt-rust was broken, `undefined reference to `JPH::AlignedFree'` and many many others- but adding a `build.rs` to link the built libraries in the hello world examples fixed that- except cargo test has the same problem- how do I link it?

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lucasw @lucasw0.bsky.social · 29/08/2025

The goal is to recreate this car example with the rust bindings- the visualization could be handled by rerun if there's nothing working out of the box from jolt-rust.

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lucasw @lucasw0.bsky.social · 29/08/2025

Also needed `sudo apt install libxcb-cursor-dev`

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lucasw @lucasw0.bsky.social · 29/08/2025

So far compiling Jolt with cmake in Linux on Ubuntu 24.04, but had to edit TestFramework/Utils/AssetStream.cpp and run Samples out of the JoltPhysics/Assets directory so assets load: - mStream((sGetAssetsBasePath() + inFileName).c_str(), inOpenMode) + mStream(inFileName, inOpenMode)

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lucasw @lucasw0.bsky.social · 28/08/2025

I didn't get far with vehicle physics using bevy & rapier physics when I tried a few months ago, but now diving back in- I need physics and I'm willing to wrap C++ for rust, perhaps with bullet, but it turns out there's Jolt github.com/jrouwe/JoltP... and jolt-rust github.com/SecondHalfGa...

github.com

GitHub - SecondHalfGames/jolt-rust: Rust bindings to Jolt Physics

Rust bindings to Jolt Physics. Contribute to SecondHalfGames/jolt-rust development by creating an account on GitHub.

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lucasw @lucasw0.bsky.social · 13/08/2025

There's an embassy task that owns the ntp send and receives over udp, it updates an embassy-sync watch, and then a loop in main gets it and applies it to the systick time, and results look reasonable. I may look into using canbus on this stm32 board but not for a while. docs.rs/embassy-sync...

docs.rs

Watch in embassy_sync::watch - Rust

The `Watch` is a single-slot signaling primitive that allows multiple (`N`) receivers to concurrently await changes to the value. Unlike a `Signal`, `Watch` supports multiple receivers, and unlike a `...

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lucasw @lucasw0.bsky.social · 13/08/2025

Getting sntpc working within embassy was harder than expected, maybe I went about it the wrong way because I ended up forking sntpc to make a very slightly different version of `sntp_process_response()`. github.com/lucasw/misc_...

github.com

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lucasw @lucasw0.bsky.social · 09/08/2025

The boiler plate that was strange was having to set up a random seed for rng and providing an empty Vec of dns_servers, and packetmetas/metadatas. I'd like to find good explanations of all that, also what the bind_interrupts with HASH_RNG is doing (probably it is in the embassy & smoltcp docs)

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lucasw @lucasw0.bsky.social · 09/08/2025

Can send udp packets out of the stm32h753 with embassy now github.com/lucasw/misc_... (and the blinky leds are still blinking, which means the async is still asyncing)

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