A [page:Layers] object assigns an [page:Object3D] to 1 or more of 32 layers numbered 0 to 31
			- internally the layers are stored as a [link:https://en.wikipedia.org/wiki/Mask_(computing) bit mask], and by default all
			Object3Ds are a member of layer 0.
			This can be used to control visibility - an object must share a layer with a [page:Camera camera] to be visible when that camera's
			view is renderered.
			All classes that inherit from [page:Object3D] have an [page:Object3D.layers] property which is an instance of this class.
		
[example:webgl_layers WebGL / layers]
Create a new Layers object, with membership initially set to layer 0.
A bit mask storing which of the 32 layers this layers object is currently a member of.
			layer - an integer from 0 to 31.
			Remove membership of this *layer*.
		
			layer - an integer from 0 to 31.
			Add membership of this *layer*.
		
			layer - an integer from 0 to 31.
			Set membership to *layer*, and remove membership all other layers.
		
			layers - a Layers object
			Returns true if this and the passed *layers* object are members of the same set of layers.
		
			layer - an integer from 0 to 31.
			Toggle membership of *layer*.
		
Add membership to all layers.
Remove membership from all layers.
[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]