A Multi-Target consists of multiple Image Targets in a defined geometric arrangement. The position and orientation of each Image Target within a Multi-Target is defined relative to the origin of the Multi-Target, which is at its volumetric center.
All of the faces of a Multi-Target can be tracked at the same time because they possess a pre-defined pose relative to Multi-Target origin. This enables the entire Multi-Target to be tracked when any of its child targets has been detected. In this way, a Multi-Targets provides a common tracking reference for its child targets. The corresponding TrackableResult (in this case a MultiTargetResult) provides a common pose, as opposed to the individual status and pose information provided for the individual Image Targets.
Multi-targets are created by defining a relationship among multiple existing Image Targets using the Vuforia Target Manager or by directly manipulating the Dataset Configuration XML file. The spatial relationship of the individual parts is stored in the XML file using simple transformations, See How To Modify a Multi-Target Using its Config XML File. You can also configure Multi-Targets at runtime, See How To Add Images to a Multi Target at Runtime