An ol.View2D object represents a simple 2D view of the map.
+
This is the object to act upon to change the center, resolution,
+and rotation of the map.
+
The view states
+
An ol.View2D is determined by three states: center, resolution,
+and rotation. To each state corresponds a getter and a setter. E.g.
+getCenter and setCenter for the center state.
+
An ol.View2D has a projection. The projection determines the
+coordinate system of the center, and its units determine the units of the
+resolution (projection units per pixel). The default projection is
+Spherical Mercator (EPSG:3857).
+
The constraints
+
setCenter, setResolution and setRotation can be used to change the
+states of the view. Any value can be passed to the setters. And the value
+that is passed to a setter will effectively be the value set in the view,
+and returned by the corresponding getter.
+
But an ol.View2D object also has a resolution constraint and a
+rotation constraint. There's currently no center constraint, but
+this may change in the future.
+
As said above no constraints are applied when the setters are used to set
+new states for the view. Applying constraints is done explicitly through
+the use of the constrain* functions (constrainResolution and
+constrainRotation).
+
The main users of the constraints are the interactions and the
+controls. For example, double-clicking on the map changes the view to
+the "next" resolution. And releasing the fingers after pinch-zooming
+snaps to the closest resolution (with an animation).
+
So the resolution constraint snaps to specific resolutions. It is
+determined by the following options: resolutions, maxResolution,
+maxZoom, and zoomFactor. If resolutions is set, the other three
+options are ignored. See ol.View2DOptions for more information.
+
The rotation constaint is currently not configurable. It snaps the
+rotation value to zero when approaching the horizontal.
+
+