Announcing Box3D

Box3D has been released as an open source 3D physics engine on GitHub, with a design that stays close to Box2D while adding the 3D features game teams actually need. The feature list includes triangle mesh and height-field collision, baked compound collision, continuous collision, sub-stepping, graph coloring for large islands, wide SIMD contact solving, multithreading hooks, optional internal scheduling, doubles for large-world support, cross-platform determinism, and recording/replay.

The engine exists first and foremost because it was needed for The Legend of California, a server-authoritative survival game in development at Kintsugiyama since 2022. Unreal’s Chaos physics caused problems with gyroscopic torque support, erratic tree-fall behavior, and broad-phase concerns for a world with hundreds of thousands of entities. Rather than keep fighting the stock stack, the team replaced it with a custom solution that began as a Rubikon-Lite fork and then absorbed Box2D-style APIs, data structures, and algorithms until it became Box3D.

That custom path also explains some of the engine’s more practical features. Box3D is tuned for fast runtime collision-mesh generation from voxel terrain, large streaming scenes, and compound shapes that can collapse tens of thousands of kitbashed collision pieces into a single optimized structure. For teams shipping open worlds or heavy server simulation, the appeal is less about novelty and more about controlling performance, memory, and determinism at the engine level.

Box3D is still considered alpha, with v0.1 planned next and a path...