constructor( plane, size = 1, hex = 0xffff00 ) {

		const color = hex;

		const positions = [ 1, -1, 0, -1, 1, 0, -1, -1, 0, 1, 1, 0, -1, 1, 0, -1, -1, 0, 1, -1, 0, 1, 1, 0 ];

		const geometry = new BufferGeometry();
		geometry.setAttribute( 'position', new Float32BufferAttribute( positions, 3 ) );
		geometry.computeBoundingSphere();

		super( geometry, new LineBasicMaterial( { color: color, toneMapped: false } ) );

		this.type = 'PlaneHelper';

		/**
		 * The plane being visualized.
		 *
		 * @type {Plane}
		 */
		this.plane = plane;

		/**
		 * The side length of plane helper.
		 *
		 * @type {number}
		 * @default 1
		 */
		this.size = size;

		const positions2 = [ 1, 1, 0, -1, 1, 0, -1, -1, 0, 1, 1, 0, -1, -1, 0, 1, -1, 0 ];

		const geometry2 = new BufferGeometry();
		geometry2.setAttribute( 'position', new Float32BufferAttribute( positions2, 3 ) );
		geometry2.computeBoundingSphere();

		this.add( new Mesh( geometry2, new MeshBasicMaterial( { color: color, opacity: 0.2, transparent: true, depthWrite: false, toneMapped: false } ) ) );

	}
Constructs a new plane helper.

@param {Plane} plane - The plane to be visualized.
@param {number} [size=1] - The side length of plane helper.
@param {number|Color|string} [hex=0xffff00] - The helper's color.