This class can be used to start or to synchronize a network of field connections. It is the "null" field –a field with no values. It is typically used as the "start button" for engines that change over time.

Triggers can be connected from any other type of field, and will notify any engines or nodes they are part of (or any other triggers they are connected to) whenever the value of the field is set (even if it is set to its current value) or the field is touch()'ed.

Since they have no value, SoSFTriggers are not written to file. A node or engine containing an SoSFTrigger field will write only the field's name.