Box3D open-source 3D physics engine released

Category: Dev tools
Status: confirmed
Sources: announcement, GitHub release, HN discussion
Summary: Erin Catto, the author of Box2D, released Box3D v0.1.0 on 2026-06-30 under the MIT license. Box3D is a 3D physics engine for games written in C17 with a C API and no dependencies beyond the C runtime. It carries over the Box2D solver architecture with a sub-stepping solver, continuous collision detection, SIMD-accelerated contact solving, graph coloring for parallel island groups, and optional multithreading. It adds triangle-mesh and height-field collision, baked compound collision, double-precision coordinates for large worlds, and record and replay. Catto says the 2D and 3D data structures are largely indifferent to spatial dimension, so the two engines share much of their design.
Why it matters: Box2D is a widely used 2D physics library, so a same-author 3D engine gives game and simulation developers an MIT-licensed, dependency-free option in a space dominated by heavier engines.