QTVR : Viewing Angle

Source: http://www.letmedoit.com/qtvr/qtvr_online/Mod2/m2_covers.html

Mapping of the cylindrical image into the viewing window on a user's monitor

From the central observation point (the node), a viewer may zoom into or out from a particular view by changing the zoom angle of their view. The zoom angle thus represents the mapping of the cylindrical image into the viewing window on a user's monitor. As a user zooms into a panorama, the viewing window on their monitor remains the same size but shows an increasingly smaller area of the cylindrical image.

The ability to zoom into the panorama can lead to a user seeing enlarged individual pixels at very small zoom angle settings. For this reason, most developers will set a minimum and/or maximum value for the zoom angle to prevent either too wide an angle of view, or a view that becomes too pixelated.