July 1, 2026
Physics beef just went 3D
Announcing Box3D :: Box2D
Box2D’s creator drops Box3D and fans instantly start the "Jolt killer or nostalgia trip?" debate
TLDR: Box2D creator Erin Catto has launched Box3D, a new open-source 3D game physics engine built after frustrations with Unreal’s built-in system. The crowd is excited but instantly split between nostalgia for Box2D, curiosity about whether Box3D can beat Jolt, and jokes about surprise Valve lore.
The big news is simple: Box2D, the beloved old-school game physics tool that helped power a ton of indie chaos, has officially gone 3D. Creator Erin Catto says Box3D was born because the physics in Unreal, the giant game-making platform, wasn’t behaving the way his own game needed. Translation for non-engine people: stuff that should fall, spin, and crash naturally was acting weird enough that he decided to build his own answer. And the community reaction? Equal parts hype, side-eye, and nostalgic screaming.
A huge chunk of the conversation immediately turned into "Okay, but how does it compare to Jolt?" That was the loudest debate by far: not whether Box3D is exciting, but whether it can stand toe-to-toe with other respected physics engines. One commenter summed up the mood by noting both projects have serious star power behind them, which is basically the tech version of fans comparing two superhero directors before the movie is even out. Others got sentimental fast, remembering Box2D as the secret sauce behind many clever indie games and wondering if this could spark a comeback for physics-heavy fun.
But the funniest mini-explosion came from one tiny line in the post about Valve’s evolving internal work. A commenter simply replied "wait...." and honestly, that was enough to launch a thousand raised eyebrows. Meanwhile, the wholesome corner of the internet showed up too, with one fan reminiscing about using Box2D to make lily pads drift like raindrops on a pond. So yes, there’s drama, there’s comparison shopping, and there’s also a surprising amount of soft-focus nostalgia for a tool that made digital worlds feel alive.
Key Points
- •Erin Catto announced Box3D, an open source 3D physics engine released on GitHub on June 30, 2026.
- •Box3D is presented as a Box2D-derived engine for 3D games, adding features such as triangle mesh collision, height-field collision, and baked compound collision.
- •The engine keeps Box2D-like architecture while adding features including a C API, C17 codebase, continuous collision, SIMD contact solving, multi-threading hooks, large-world support, and recording/replay.
- •Catto says one major reason for building Box3D was the needs of *The Legend of California*, a survival game he has worked on at Kintsugiyama since 2022 using Unreal Engine.
- •The article cites limitations and issues with Unreal’s Chaos physics engine, plus large-scale server entity-management requirements, as factors that pushed Catto toward creating or adopting a different physics solution.