lume/src/core/Object3DWithPivot.ts

Build next-level interactive web applications.

import {Vector3} from 'three/src/math/Vector3.js'
import {Object3D} from 'three/src/core/Object3D.js'

// Augment the Object3D class definition with a new pivot property.
//
// XXX In order for this augmentation to work, Object3D must be imported from
// the file it originates from, not from the 'three' index module (i.e. `from
// 'three/src/core/Object3D'` instead of `from 'three'`). Otherwise we get this
// bug: https://github.com/microsoft/TypeScript/issues/18877. See also the
// report on Three.js: https://github.com/mrdoob/three.js/issues/19468.
declare module 'three/src/core/Object3D.js' {
	interface Object3D {
		pivot: Vector3
	}
}

const pivot = Symbol('pivot')

export class Object3DWithPivot extends Object3D {
	override type = 'Object3DWithPivot';

	[pivot]?: Vector3

	override get pivot(): Vector3 {
		if (!this[pivot]) this[pivot] = new Vector3()
		return this[pivot]
	}
	override set pivot(v: Vector3) {
		this[pivot] = v
	}

	// This overrides Object3D to have a `.pivot` property of type
	// THREE.Vector3 that allows the origin (pivot) of rotation and scale to be
	// specified in local coordinate space. For more info:
	// https://github.com/mrdoob/three.js/issues/15965
	override updateMatrix() {
		this.matrix.compose(this.position, this.quaternion, this.scale)

		const pivot = this.pivot

		if (pivot.x !== 0 || pivot.y !== 0 || pivot.z !== 0) {
			const px = pivot.x,
				py = pivot.y,
				pz = pivot.z
			const te = this.matrix.elements

			te[12] += px - te[0] * px - te[4] * py - te[8] * pz
			te[13] += py - te[1] * px - te[5] * py - te[9] * pz
			te[14] += pz - te[2] * px - te[6] * py - te[10] * pz
		}

		this.matrixWorldNeedsUpdate = true
	}
}

// Override updateMatrix for all Three.js Object3D derivatives.
Object3D.prototype.updateMatrix = Object3DWithPivot.prototype.updateMatrix
// Give all Three.js Object3D derivatives the pivot property.
Object.defineProperty(
	Object3D.prototype,
	'pivot',
	Object.getOwnPropertyDescriptor(Object3DWithPivot.prototype, 'pivot')!,
)