function PolarGridHelper( radius, radials, circles, divisions, color1, color2 ) {

		radius = radius || 10;
		radials = radials || 16;
		circles = circles || 8;
		divisions = divisions || 64;
		color1 = new Color( color1 !== undefined ? color1 : 0x444444 );
		color2 = new Color( color2 !== undefined ? color2 : 0x888888 );

		var vertices = [];
		var colors = [];

		var x, z;
		var v, i, j, r, color;

		// create the radials

		for ( i = 0; i <= radials; i ++ ) {

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

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

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

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

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

		}

		// create the circles

		for ( i = 0; i <= circles; i ++ ) {

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

			r = radius - ( radius / circles * i );

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

				// first vertex

				v = ( j / 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 );

				// 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 );

			}

		}

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

		var material = new LineBasicMaterial( { vertexColors: VertexColors } );

		LineSegments.call( this, geometry, material );

	}
@author mrdoob / http://mrdoob.com/
@author Mugen87 / http://github.com/Mugen87
@author Hectate / http://www.github.com/Hectate