説明
Deterministic 3D rigid-body physics for Unreal Engine 5.8, powered by Box3D — the 3D sibling of Erin Catto's Box2D. A fixed-timestep simulation that runs independently of Chaos, but can also work alongside it in the same scene. Native recording and replay, a full joint set, sensors, conveyor surfaces, static-mesh collision, and a suite of ready-made demo maps.
Try before you buy — download the free compiled sample project (UE 5.8, Win64):
WHY BOX3D?
• Deterministic by design. Driven by a world subsystem on a fixed 60 Hz / 4-substep clock rather than by your frame rate. The same scene, stepped from the same state with the same inputs, produces the same result run after run on the same build — verified by an automated test suite, not just asserted.
• Runs alongside Chaos, not instead of it. Simulate what needs to be deterministic in Box3D and leave the rest of your game on the engine's physics, or drive individual actors with it. No project physics settings change.
• Records and replays natively. Simulations write .b3rec files that play back exactly, in-engine. Separately, Take Recorder can capture simulated actors into a Level Sequence for cinematics.
• Scales. Bodies sleep and islands collapse as scenes settle, and an instanced-mesh path handles scenes with thousands of bodies.
• C++ source included, and the whole runtime surface is exposed to Blueprint — a Blueprint-only project can use all of it once the plugin is installed.
FEATURES
• Rigid bodies with sphere, box-hull and capsule shapes
• Static-mesh collision mirroring — convex and triangle-mesh shapes taken from a Static Mesh's own authored collision, with an offline bake commandlet for packaged builds
• Revolute, distance, spherical and weld joints, with break events and live motor setters
• Sensors with begin and end overlap events
• Conveyor surfaces driven by surface tangent velocity
• Contact hit events carrying impact point, normal and approach speed
• Line trace, overlap and sweep queries
• Instanced-mesh path for scenes with thousands of bodies
• Solver statistics: body and island counts, step time, substep and step rate
• Simulate-In-Editor support
• Take Recorder integration for baking simulated actors into a Level Sequence
INCLUDED DEMO SUITE
A hub map, eight demo scenes and a framework smoke test, all built from engine primitives — no third-party content and nothing to import.
• Dominoes — a thirty-ring spiral, sequential contacts at scale
• Large Pyramid — a thousand-body stack, settling and sleeping
• Jenga Tower — friction, and pulling a block out without toppling the rest
• Inclined Plane and Restitution — Coulomb friction and bounce, side by side
• Ball and Chain — thirty-two revolute links carrying a heavy ball with no visible stretch
• Rope Bridge — a sixty-plank hinged span that sags under load and recovers
• Ragdoll Pile — fourteen-bone figures on cone-limited ball sockets
• Conveyor Circuit — cargo carried around a closed loop by static belts
• Smoke Stack — the framework's own smoke test
Every scene is interactive. Right-click to grab, left-click to shoot a ball. Point at any dynamic body and it lights up; grab it, wheel it nearer or further, and let go mid-sweep to throw it. Hard impacts leave fading marks on static surfaces. Each demo exposes its tuning as editable properties and ships named camera angles. Two further scenes are registered as experimental and documented as such.
COMPATIBILITY
• Unreal Engine 5.8
• Windows 64-bit (Win64)
• C++ source included; no third-party plugin dependencies — it enables only Takes and Enhanced Input, both bundled with the engine
• Works in Blueprint-only projects once installed
KNOWN LIMITATIONS
Stated up front, so there are no surprises after purchase.
• Triangle-mesh shapes collide on Static bodies only — a Box3D engine constraint, not a wrapper gap. Moving objects need convex or primitive shapes. There is no dynamic-body bake path: a dynamic prop mirroring its mesh collision works in editor and PIE, but receives no shapes when packaged.
• No height-field collision — no Landscape class in UE 5.8 exposes collision data to third-party engines. Approximate terrain with primitives or a Static Mesh proxy.
• No vehicle or wheel joint wrapper yet.
• No .b3rec import into Sequencer — Take Recorder captures live actor transforms instead.
• Box3D and Chaos do not interact. A Box3D body is static as far as Chaos is concerned, and vice versa; objects that must collide with each other need to live in the same engine.
• Windows only — no Mac, Linux or console builds in this release.
DOCUMENTATION AND SUPPORT
Usage, installation, limitations, Tutorials and a page per demo ship in the plugin's Docs folder and are published at the documentation link on this listing.
ATTRIBUTION
Includes Box3D by Erin Catto, used under the MIT license (github.com/erincatto/box3d), built from the publisher's fork. The MIT notice
and full build provenance ship with the plugin at Source/ThirdParty/Box3DLibrary/.
Development was AI-assisted throughout. The C++ implementation, automated tests, demo scenes, and documentation were written by a human developer working with AI coding assistants; all code was reviewed, compiled, and validated against an automated test suite (198 passing) and Epic's own RunUAT BuildPlugin toolchain before release. No generative AI was used to produce art, audio, or textures — the plugin ships no such assets, only C++ source, procedurally generated demo levels, and a small set of hand-authored materials.