denizen-bulletphys

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Status: 1.0.0-alpha. The falling-blocks command and the vehicle/suspension command are both implemented and working on a live server. What's still missing for a real 1.0: Denizen ObjectTags/events for bodies and vehicles (right now they're addressed by a plain numeric id).

How it works

The actual physics runs on libbulletjme (a JNI binding to Bullet) on its own thread, stepped at a fixed 60 Hz — decoupled from server TPS. Once per game tick, the main thread reads an immutable snapshot of every body's transform and reflects it into the world through block_display entities with client-side interpolation. MC blocks around active bodies are streamed into a static Bullet collider (loaded/unloaded as bodies move, not a fixed radius around a spawn point) — that's what falling blocks and vehicle wheels actually rest and collide against.

main thread (20 TPS)  ──commands/terrain──►  physics thread (60 Hz, Bullet)
       ▲                                              │
       └──────────  transform snapshot  ◄─────────────┘
       │
   block_display (client-side interpolation)

Using it from Denizen

- physicsbody spawn [<location>] (material:<material>) (size:<#.#>) (mass:<#.#>) (count:<#>)

- physicsvehicle spawn [<location>] (mass:<#.#>) (size:<#.#>,<#.#>,<#.#>) (material:<material>) (save:<name>)
- physicsvehicle <#(id)> addwheel offset:<#.#>,<#.#>,<#.#> (radius:<#.#>) (resting:<#.#>) (steering:<boolean>)
- physicsvehicle <#(id)> drive (wheel:<#>) (steer:<#.#>) (throttle:<#.#>) (brake:<#.#>)
- physicsvehicle <#(id)> remove

Why libbulletjme, not ode4j/jbullet

jBullet has been abandoned since 2008. ode4j is pure Java, but its raycast vehicle suspension would have had to be hand-rolled. libbulletjme is actively maintained, ships PhysicsVehicle with working suspension out of the box, and is already used by the DynamX physics mod for Minecraft.

Requirements

Java	21+ (one jar runs on both 1.21.x / Java 21 and 26.x / Java 25)
Server	Paper 1.21.x+ (tested on Leaf 26.2)
Denizen	1.3.3+
Engine	libbulletjme 23.1.0 — natives for Linux x64/ARM64, Windows x64, macOS x64/ARM64 bundled in the jar

License

All Rights Reserved.