constructor( radius = 10, sectors = 16, rings = 8, divisions = 64, color1 = 0x444444, color2 = 0x888888 ) {

		color1 = new Color( color1 );
		color2 = new Color( color2 );

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

		// create the sectors

		if ( sectors > 1 ) {

			for ( let i = 0; i < sectors; i ++ ) {

				const v = ( i / sectors ) * ( Math.PI * 2 );

				const x = Math.sin( v ) * radius;
				const z = Math.cos( v ) * radius;

				vertices.push( 0, 0, 0 );
				vertices.push( x, 0, z );

				const color = ( i & 1 ) ? color1 : color2;

				colors.push( color.r, color.g, color.b );
				colors.push( color.r, color.g, color.b );

			}

		}

		// create the rings

		for ( let i = 0; i < rings; i ++ ) {

			const color = ( i & 1 ) ? color1 : color2;

			const r = radius - ( radius / rings * i );

			for ( let j = 0; j < divisions; j ++ ) {

				// first vertex

				let v = ( j / divisions ) * ( Math.PI * 2 );

				let x = Math.sin( v ) * r;
				let z = Math.cos( v ) * r;

				vertices.push( x, 0, z );
				colors.push( color.r, color.g, color.b );

				// second vertex

				v = ( ( j + 1 ) / divisions ) * ( Math.PI * 2 );

				x = Math.sin( v ) * r;
				z = Math.cos( v ) * r;

				vertices.push( x, 0, z );
				colors.push( color.r, color.g, color.b );

			}

		}

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

		const material = new LineBasicMaterial( { vertexColors: true, toneMapped: false } );

		super( geometry, material );

		this.type = 'PolarGridHelper';

	}
Constructs a new polar grid helper.

@param {number} [radius=10] - The radius of the polar grid. This can be any positive number.
@param {number} [sectors=16] - The number of sectors the grid will be divided into. This can be any positive integer.
@param {number} [rings=16] - The number of rings. This can be any positive integer.
@param {number} [divisions=64] - The number of line segments used for each circle. This can be any positive integer.
@param {number|Color|string} [color1=0x444444] - The first color used for grid elements.
@param {number|Color|string} [color2=0x888888] -  The second color used for grid elements.