Box3D is a new open source 3D physics engine by Erin Catto, the creator of the widely used Box2D physics engine. Development of the engine began in 2022 and has now resulted in its initial release.
According to the developer, the project was driven by several motivations, one of the primary reasons being issues encountered with Unreal Engine's native physics while developing his own game, The Legend of California. These included the lack of support for simulating gyroscopic torques, falling trees behaving erratically, and the need to perform a fast broad-phase physics pass when simulating very high entity counts, reaching into the hundreds of thousands.
Box3D was created to address these challenges while following the same design principles as Box2D. Developers who enjoy working with Box2D will likely enjoy working with Box3D as well, according to the developer.
Box3D's current feature set can be broadly divided into collision and physics. On the collision side, the engine supports continuous collision detection as well as convex hulls, capsules, spheres, triangle meshes, and height fields. Multiple shapes per body are supported, alongside collision filtering, ray casts, shape casts, and overlap queries.
On the physics side, Box3D includes a robust Soft Step rigid body solver and supports continuous physics for fast translations and rotations. It also uses island-based sleeping to manage inactive bodies efficiently. The engine provides revolute, prismatic, distance, motor, weld, and wheel joints, with support for joint limits, motors, springs, and friction. It also exposes joint and contact forces while generating body movement events and sleep notifications.
Box3D is already being used in several projects, including the s&box and Esoterica game engines, as well as Glenn Fiedler's "1000 player space game."
Despite its adoption in these projects, the developer considers Box3D to still be in an alpha state, requiring additional testing and more complete documentation.
Development will continue, although the goal is not to compete with other physics solutions. Planned areas of improvement include character movement features, mitigation of ghost collisions, improvements to the joint solver, and further performance optimizations.
Box3D is available on GitHub under the permissive MIT license.
For more information and future updates, visit the Box2D website. The developer has stated that this will be the primary channel for Box3D announcements.
