Switch View Node
The Switch View node combines the views (left and right) into a single Stereo 3D output. This can be useful if for example, you need to treat the view as separate images by combining each of the views.
Left-eye image input.
Right-eye image input.
Stereo 3D image output.
The views to render are defined in the current scene views, in a similar way as you define the composite output resolution in the current scene render panel, regardless of the Image nodes resolutions or Render Layers from different scenes.