The PolarGridHelper is an object to define polar grids. Grids are two-dimensional arrays of lines.
var radius = 10;
		var radials = 16;
		var circles = 8;
		var divisions = 64;
		var helper = new THREE.PolarGridHelper( radius, radials, circles, divisions );
		scene.add( helper );
		
		[example:webgl_helpers Example using various helpers]
		
		radius -- The radius of the polar grid. This can be any positive number. Default is 10.
		radials -- The number of radial lines. This can be any positive integer. Default is 16.
		circles -- The number of circles. This can be any positive integer. Default is 8.
		divisions -- The number of line segments used for each circle. This can be any positive integer that is 3 or greater. Default is 64.
		color1 -- The first color used for grid elements. This can be a [page:Color], a hexadecimal value and an CSS-Color name. Default is 0x444444 
		color2 -- The second color used for grid elements. This can be a [page:Color], a hexadecimal value and an CSS-Color name. Default is 0x888888
		
Creates a new [name] of radius 'radius' with 'radials' number of radials and 'circles' number of circles, where each circle is smoothed into 'divisions' number of line segments. Colors are optional.
[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]