Touch Marker
 | Touch Marker | Receiver for unique marker objects such as fiducial, bar-coded objects, and so on. |
Camera based MultiTouch systems often support the recognition of uniquely marked objects. For example, a glass might have a barcode underneath it and when placed on the tracking surface, a special menu shows the user a selection of dishes that go well with exactly this drink.
The interpretation of markers - if supported at all - and which ID corresponds to which pattern is done by the tracking software that comes with the MultiTouch hardware, not Ventuz. Please refer to your hardware's manual to find out more about marker support and what IDs are generated.
Ventuz supports marker objects sent by the TUIO protocol (i.e. 2Dcur messages) in that it recognizes them as no ordinary touches. Since TUIO only transmits position information - not camera images - a touch marker is transmitted as a touch position update with a unique ID (integer) that identifies the marker.
A Touch Marker node is bound to a specific touch marker by setting the MarkerID property to the respective ID assigned by the touch hardware. The node will fire events when the marker is placed on the table or lifted from it. It also provides the X/Y position in screen coordinates and the angle of rotation. Unlike the other interaction nodes, the Touch Marker currently has no implicit behavior and therefore only acts as a value provider.
Ventuz only supports one object for a certain ID at the same time. The behavior if multiple objects with the same ID are placed on the tracking surface is undefined.
The Touch Marker node is a special node as it is the only node that reacts to marker objects. Marker touches also cannot be used to activate any of the other interaction nodes.