After I created a map in OpenLayers 3 (with GeoServer), when I zoomed it out, it duplicated all layers as you can see in the following example:
http://openlayers.org/en/v3.2.1/examples/drag-rotate-and-zoom.html
I don't want the user to be able to drag the map left/right till infinity.
How can I set the extent (to the whole world) so I will not see the duplicated layers?