constructor( camera ) {

		const geometry = new BufferGeometry();
		const material = new LineBasicMaterial( { color: 0xffffff, vertexColors: true, toneMapped: false } );

		const vertices = [];
		const colors = [];

		const pointMap = {};

		// near

		addLine( 'n1', 'n2' );
		addLine( 'n2', 'n4' );
		addLine( 'n4', 'n3' );
		addLine( 'n3', 'n1' );

		// far

		addLine( 'f1', 'f2' );
		addLine( 'f2', 'f4' );
		addLine( 'f4', 'f3' );
		addLine( 'f3', 'f1' );

		// sides

		addLine( 'n1', 'f1' );
		addLine( 'n2', 'f2' );
		addLine( 'n3', 'f3' );
		addLine( 'n4', 'f4' );

		// cone

		addLine( 'p', 'n1' );
		addLine( 'p', 'n2' );
		addLine( 'p', 'n3' );
		addLine( 'p', 'n4' );

		// up

		addLine( 'u1', 'u2' );
		addLine( 'u2', 'u3' );
		addLine( 'u3', 'u1' );

		// target

		addLine( 'c', 't' );
		addLine( 'p', 'c' );

		// cross

		addLine( 'cn1', 'cn2' );
		addLine( 'cn3', 'cn4' );

		addLine( 'cf1', 'cf2' );
		addLine( 'cf3', 'cf4' );

		function addLine( a, b ) {

			addPoint( a );
			addPoint( b );

		}

		function addPoint( id ) {

			vertices.push( 0, 0, 0 );
			colors.push( 0, 0, 0 );

			if ( pointMap[ id ] === undefined ) {

				pointMap[ id ] = [];

			}

			pointMap[ id ].push( ( vertices.length / 3 ) - 1 );

		}

		geometry.setAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );
		geometry.setAttribute( 'color', new Float32BufferAttribute( colors, 3 ) );

		super( geometry, material );

		this.type = 'CameraHelper';

		/**
		 * The camera being visualized.
		 *
		 * @type {Camera}
		 */
		this.camera = camera;
		if ( this.camera.updateProjectionMatrix ) this.camera.updateProjectionMatrix();

		this.matrix = camera.matrixWorld;
		this.matrixAutoUpdate = false;

		/**
		 * This contains the points used to visualize the camera.
		 *
		 * @type {Object<string,Array<number>>}
		 */
		this.pointMap = pointMap;

		this.update();

		// colors

		const colorFrustum = new Color( 0xffaa00 );
		const colorCone = new Color( 0xff0000 );
		const colorUp = new Color( 0x00aaff );
		const colorTarget = new Color( 0xffffff );
		const colorCross = new Color( 0x333333 );

		this.setColors( colorFrustum, colorCone, colorUp, colorTarget, colorCross );

	}
Constructs a new arrow helper.

@param {Camera} camera - The camera to visualize.