addLevel( object, distance = 0, hysteresis = 0 ) {

		distance = Math.abs( distance );

		const levels = this.levels;

		let l;

		for ( l = 0; l < levels.length; l ++ ) {

			if ( distance < levels[ l ].distance ) {

				break;

			}

		}

		levels.splice( l, 0, { distance: distance, hysteresis: hysteresis, object: object } );

		this.add( object );

		return this;

	}
Adds a mesh that will display at a certain distance and greater. Typically
the further away the distance, the lower the detail on the mesh.

@param {Object3D} object - The 3D object to display at this level.
@param {number} [distance=0] - The distance at which to display this level of detail.
@param {number} [hysteresis=0] - Threshold used to avoid flickering at LOD boundaries, as a fraction of distance.
@return {LOD} A reference to this instance.