copy( source, recursive = true ) {

		this.name = source.name;

		this.up.copy( source.up );

		this.position.copy( source.position );
		this.rotation.order = source.rotation.order;
		this.quaternion.copy( source.quaternion );
		this.scale.copy( source.scale );

		this.matrix.copy( source.matrix );
		this.matrixWorld.copy( source.matrixWorld );

		this.matrixAutoUpdate = source.matrixAutoUpdate;

		this.matrixWorldAutoUpdate = source.matrixWorldAutoUpdate;
		this.matrixWorldNeedsUpdate = source.matrixWorldNeedsUpdate;

		this.layers.mask = source.layers.mask;
		this.visible = source.visible;

		this.castShadow = source.castShadow;
		this.receiveShadow = source.receiveShadow;

		this.frustumCulled = source.frustumCulled;
		this.renderOrder = source.renderOrder;

		this.animations = source.animations.slice();

		this.userData = JSON.parse( JSON.stringify( source.userData ) );

		if ( recursive === true ) {

			for ( let i = 0; i < source.children.length; i ++ ) {

				const child = source.children[ i ];
				this.add( child.clone() );

			}

		}

		return this;

	}
Copies the values of the given 3D object to this instance.

@param {Object3D} source - The 3D object to copy.
@param {boolean} [recursive=true] - When set to `true`, descendants of the 3D object are cloned.
@return {Object3D} A reference to this instance.