activator Last edited 4 months ago2024-06-28 14:34:06 UTC

In GoldSrc entity system, the activator is the initiator of the entity events. Usually that means players walking into triggers or "use"-ing things. If such triggers have the "monsters" flag set then monsters could be activators too. Some entities can also trigger other entities on its own e.g. a func_train that passes a path_corner with a "Fire on pass" set will trigger the targeted entity with itself as the activator.

The activator is one of two entity references passed to an entity being triggered, the other being the caller. Whereas the caller is the immediate entity that triggers another entity, the activator reference is preserved and passed along when entities trigger other entities (aka a trigger chain). This allows a chaining of triggers e.g. a trigger targets a trigger_relay, which targets a game_text, which displays text to only the activator by default. Scenarios where activator is used:

• Some entities such as func_healthcharger and game_text acts on the activator by principle or by default. Others like env_fade can be set to affect activators instead of globally.
• NPCs get aggravated by the activator if it's a valid entity.
• In multiplayer, it is used to award points to players who uses environmental traps or something like func_tank.

The activator chain however will be broken (i.e. the original activator reference lost) in the following entities:

• trigger_relay - sends itself as activator (however in Spirit of Half-Life it does forward the activator)
• scripted_sequence - sends no activator
• scripted_sentence - sends no activator
• func_breakable - sends no activator
• monstermaker - sends itself as activator

Therefore, care should be taken to make sure entities that affect activators aren't targeted in the above ways. For example, a trigger_relay targeting a game_text will crash the game unless "All Players" flag is checked.