I'm a doctor, not a mechanic


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Revision as of 13:46, 11 April 2006 by SuperApe (Talk)

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Trigger (noun)
an actor of class Trigger or one of its subclasses.
Trigger (verb)
to cause an actor's "Trigger" event to be called.


The purpose of this page is to keep the terminology surrounding triggers and events clear. It is important to note that the terms set down here are frequently abused, i.e. the verb "to trigger" is used in a number of ways that may gloss over the actual mechanisms used to a greater or lesser degree.


A Trigger in a map might be activated for a number of different reasons, e.g. the player might touch a trigger, or may hit the USE key whilst in range of the Trigger. This is the role of the Trigger actor - as a sort of "sensor" to detect the conditions that will cause the interaction to take place.

When the Trigger is activated, it raises (or fires) an Event. The Event can be thought of as a message that is broadcast to all actors in the level. NOTE: this is not the same as the event keyword in unrealscript, which means that the function can be called from native code.

All actors whose Tag property matches the trigger's Event property get their Triggered or UnTriggered function called.

Note also that it's possible that some of these actors being triggered are themselves triggers, which may raise further events.

Some abuses[edit]

"The player triggers the light"[edit]

This really means the player activates the trigger, which fires an event, which triggers the light.

"The player triggers the trigger"[edit]

This is just a rubbish sentence! In the scripting world, there is a Touch' function and a Triggered function, so if a trigger is being triggered, do you mean it is being triggered by an event that is raised by another trigger? You probably don't, so try to say activates or touches or uses or fires.


By saying that one actor "triggered" another, we are wrapping up this whole process of detection, event and consequence into a handy little phrase. Unfortunately it's misleading because it implies a one-to-one relationship: one trigger causes one actor to be affected. Of course, any number of actors may have a tag to match the event.

Jump to the Triggers parent page

Related Topics[edit]

Contributors Refactored[edit]





Sweavo: Hope that's a satisfactory refactor for now. When I found the page it was more confusing than helpful. Hopefully it's clearer now. But I'm experienced with triggers so I'd appreciate someone reviewing it for glaring factual errors.

SuperApe: This looks clearer to me.