PieFed
Box3D | A revolutionary new physics engine developed by Erin Catto in collaboration with a Valve dev
https://x.com/erin_catto/status/2072326622590730604?s=20
After seeing its announcement a few days ago I didn’t think much of it, but after looking into it a bit this looks awesome !
Box3D was released a few days ago by legendary developer Erin Catto accompanied by a blog post, this is the person behind the popular Box2D engine.
In the blog post he explains that his work stems from his collaboration with Dirk Gregorius, “Principal Software Engineer II and Physics Architect” at Valve, the person behind Half-Life: Alyx’s physics engine “Rubikon”, which Box3D is based off.
Facepunch has also revealed that they have been using Box3D for about a year now as well in s&box. Showcasing a cool demo
An interesting quote from the blog post:
On the Valve side, Rubikon continues to evolve and Dirk has developed optimizations (similar to those in Box3D) in a new engine called Ragnarok. Look for that in future Valve games.
👀
Did he just reveal Valve’s next physics engine ?
+HL3 confirmed
- cool showcase 1
- showcase 2
- showcase 3 in gmod (already??)
Tweet transcript
I’m happy to announce the release of a new open source 3D physics engine called Box3D. I’ve been working on this project for a few years now, but it represents over 20 years of experience writing physics engines for games. Read more here: [blog post link]
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In what way is it revolutionary? Genuinely asking. Is there something Box3D can do that all the other 3d physics engines can’t?
Having more options is always good. Box3d uses box2d’s api which is familiar for a lot of developers. Box3d also adapts a lot of Erin catto’s latest research. He’s pretty foundational to game physics, with many physics engines being built off his work and research, like jolt. Box3d is also very fast with a blazingly fast broad phase collision pass.
Also Box3d is one of very few physics engines that simulates proper gyroscopic torques.
MrSoupDidn’t watch whole demo, but one thing: rotational gyroscopic torque
He showed Box3D correctly modelling: https://www.youtube.com/watch?v=1VPfZ_XzisU
And compared it to a game in Unreal when a spinning rifle had an unnatural perpetual motion spinning quality to it
Check out out: https://box2d.org/posts/2026/06/announcing-box3d/
- Large world support with doubles for position
This should be a standard on all physics engines
Does box3d work with godot?
woelkchenIt’s really cool, Box2D is still sort of the golden standard for 2D physics engines, and maybe Box3D can be that with enough support.
But since announcement I’m still wondering what it offers versus other open source 3D physics engines. How does it compare to something like Jolt or Rapier? I only saw one person saying that Box3D is faster than Rapier when compiled to WASM, but we definitely need good comparisons at some point to know if this is a big deal or not.
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This sounds like a big selling point to me.
From what I understand, many of the existing physics engines are non-deterministic, which can make networking physics interactions in certain types of games pretty difficult.
Difficult to say, but I see points against this being a silver bullet of any sort.
A competitive game like starcraft wouldn’t be responsive enough if they transferred all unit data every tick. So they use a lockstep model, where only player commands are transferred, and they are relying on a deterministic system (not just physics) playing out the same on all connected machines.
However, a guideline for software companies is generally don’t reinvent the wheel, but “the secret sauce” should be your own. I imagine for competitive online games, the code that makes the network interaction crisp is part of the secret sauce. Such games, StarCraft, MMORPGs etc, also tend to have simpler game-relevant physics. Colliders so characters don’t clip through each other, some simple raycasting and instant collision checks for area effects, usually.
The angle a pebble flies away from an explosion is usually not made game-relevant even in single player games - so it’s not because they can’t, it’s because it doesn’t mesh with the game.
It might open up faster online play for some indie games, but I don’t know if it will have an impact otherwise.
Yep, yep!
What is revolutionary about it?
Using it isn’t supporting human rights violations?
https://xcancel.com/erin_catto/status/2072326622590730604?s=20
Pretty sure most game engines already have 3D physics engines… Which is why this news keeps falling flat. I don’t really get what’s being offered.
Is it free? Is it vastly more efficient? Is it being incorporated into one of the big three game engines?
Alyx’s physics were genuinely groundbreaking. If this includes all the features they showed off in that game, it’ll be one hell of a contender in the physics engine market.
Though it would have been more impactful (ha) if they had released it six years ago alongside Alyx, back when the free physics options were all kind of crap compared to the commercial ones. Jolt has become the de facto free 3d physics solution within the past few years and it’s also a huge step up over the old offerings.
Edit: sadly it seems Box3D is based on a stripped-down version of Rubikon and doesn’t really do much beyond extend Box2D to the third dimension. I guess its selling point is that it’s probably much, much easier to integrate than Jolt, and that the API will be familiar to Box2D users.
This guy made Box2D before, a high performant 2D physics engine that is free and open source and has been used in a shit ton of 2D games. So ofcourse devs are excited with this 3D physics engine. Yes it’s free and open source as well. It’s deterministic across different CPUs, which Unreal’s Chaos physics engine and Unity’s PhysX physics engine are not. This means that simulations with the exact same starting conditions will end up having the same result no matter the device the sim is running on. This a huge benefit for multiplayer games. And benchmarks say it’s performant. Someone already implemented it in Unity and it’s faster than the built in PhysX engine in most cases.
It’s basically a free alternative to Havok. Havok is also a high performant deterministic physics engine, but costs tens of thousands to hundreds of thousands of dollars per game to use. Havok is what many triple A studios use in their games. Like Breath of the Wild uses Havok.
A small addendum: Jolt, the other new-ish free physics engine this would be competing against, is also deterministic (with some caveats that Box3D hopefully avoids) and more performant than contemporary commercial offerings (the benefit of being new and not held back by decades of accumulated cruft and early design decisions such as obsolete threading models).
What sets Box3D apart is that, like you said, many devs are already familiar with the 2d version of this engine and Box3D mimics its APIs aside from the added dimension. This makes it very easy to pick up for a large portion of the indie crowd.
Usually they aren’t very good, and proprietary way. This is fully open source and has some really good features like determinism and multi-threaded. It is much more precise and performant as well.
If you check the blog post you can see that the impetus for making this game engine was how buggy Unreal Engine’s “Chaos” physics engine was.
Its FOSS. It does some things better, specifically than Unreal. Box2D is quite famous and well supported. Read the blog post if you want to know more details.
I’ve said what I’ve said, and asked what I’ve asked. The answers aren’t in the link. “Maybe one day” is the answer.
Answers are in the link though. Unreal’s physics engine did not meet his expectations so he rolled his own.