addAxesHelper() {
		this.axesDiv = document.createElement('div');
		this.el.appendChild(this.axesDiv);
		this.axesDiv.classList.add('axes');

		const { clientWidth, clientHeight } = this.axesDiv;

		this.axesScene = new Scene();
		this.axesCamera = new PerspectiveCamera(50, clientWidth / clientHeight, 0.1, 10);
		this.axesScene.add(this.axesCamera);

		this.axesRenderer = new WebGLRenderer({ alpha: true });
		this.axesRenderer.setPixelRatio(window.devicePixelRatio);
		this.axesRenderer.setSize(this.axesDiv.clientWidth, this.axesDiv.clientHeight);

		this.axesCamera.up = this.defaultCamera.up;

		this.axesCorner = new AxesHelper(5);
		this.axesScene.add(this.axesCorner);
		this.axesDiv.appendChild(this.axesRenderer.domElement);
	}
Adds AxesHelper.

See: https://stackoverflow.com/q/16226693/1314762