Node3D Bullet Extension

This is a part of Node3D project.

npm install @node-3d/core @node-3d/plugin-bullet three

@node-3d/plugin-bullet connects the rigid-body simulation in @node-3d/bullet to a Three.js scene managed by @node-3d/core. Use it when bodies should move Three.js objects or when you want simple visible physics debug shapes.

The plugin creates one default Bullet scene and provides a Shape class. A Shape is a regular Bullet Body with optional Three.js integration:

• Give it mesh to keep an existing THREE.Object3D synchronized with physics.
• Give it sceneThree and debug to create a generated solid or wireframe debug mesh.
• It still supports Bullet body options such as type, size, mass, pos, and velocities.

Quick start

Create a static ground shape and a dynamic box, step the Bullet scene each frame, then draw the Core screen. scene below is the Bullet scene; screen.scene is the Three.js scene.

import * as three from 'three';
import { Screen, addThreeHelpers, init } from '@node-3d/core';
import { init as initBullet } from '@node-3d/plugin-bullet';

const { loop } = init();
addThreeHelpers(three);

const screen = new Screen({ three });
const { scene, Shape } = initBullet({ three });

// A zero-mass body is static. The generated wireframe is added to screen.scene.
new Shape({
	sceneThree: screen.scene,
	type: 'plane',
	debug: 'wire',
	color: 0x4f81bd,
});

// A positive mass makes the box fall under the scene's default gravity.
const box = new Shape({
	sceneThree: screen.scene,
	pos: [0, 10, 0],
	mass: 3,
	debug: 'solid',
	color: 0xffb347,
	size: [3, 2, 1],
});

loop(() => {
	scene.update(); // advances Bullet and updates every active Shape
	screen.draw();
});

Use an explicit delta for deterministic/fixed-step simulation:

scene.update(1 / 60);

API

init({ three? })

Initializes the plugin once and returns a cached object. Pass the same three module used by your Core screen if you want Shape to create debug geometry.

| Value | Purpose | | --- | --- | | bullet | The complete low-level @node-3d/bullet module for advanced use, including Joint. | | scene | The default Bullet physics scene. Set scene.gravity, call scene.update(), or use scene.hit() / scene.trace(). | | Shape | A Body subclass that can synchronize an object or generate a Three.js debug mesh. |

Calling init() again returns the first result. Initialize it before creating shapes; later calls cannot replace its three module or default Bullet scene.

new Shape(options)

Shape accepts the normal @node-3d/bullet body properties plus the following plugin options:

| Option | Meaning | | --- | --- | | sceneBullet | Use this Bullet scene instead of the plugin's default scene. | | sceneThree | Three.js scene that receives a generated debug mesh. Required with debug. | | mesh | Existing THREE.Object3D to synchronize with the body transform. | | debug | 'solid' or 'wire' to create a generated debug mesh; omit it for no generated mesh. | | color | Three.js color for the generated debug mesh. |

The ordinary Bullet body options are the physics controls you will use most often:

• type: 'box' (default), 'ball', 'roll', 'pill', or 'plane'.
• size, pos, quat, and rot: shape dimensions and transform. Vectors accept either arrays such as [1, 2, 3] or objects such as { x: 1, y: 2, z: 3 }.
• mass: 0 for static bodies; a positive value for dynamic bodies.
• vell and vela: linear and angular velocity.
• frict, rest, dampl, dampa, and sleepy: contact, damping, and sleep settings.

When Bullet emits a body update during scene.update(), the plugin copies its position and quaternion to mesh and to the generated debug mesh. Changing type or size rebuilds the generated debug geometry. Calling destroy() releases the Bullet body and hides/removes a supplied mesh from sceneThree.

Attach your own mesh

Use mesh when the visual should be a real Three.js model rather than the plugin's simple debug geometry. The plugin only owns transform synchronization; you retain ownership of model materials, geometry, and any additional scene behavior.

const mesh = new three.Mesh(
	new three.BoxGeometry(3, 2, 1),
	new three.MeshStandardMaterial({ color: 0xffb347 }),
);
screen.scene.add(mesh);

const crate = new Shape({
	mesh,
	pos: [0, 10, 0],
	mass: 3,
	size: [3, 2, 1],
});

crate.on('update', ({ pos, quat }) => {
	// Physics has advanced; mesh has already received this transform.
	console.log(pos, quat);
});

For a larger interactive scene, see examples/main.ts.