From Valve Developer Community
trigger_once is a brush entity available in all Source games. It is a trigger volume that removes itself after it has been triggered (touched by a qualifying entity) once. A trigger uses outputs to activate an event in another entity.
- Filter Name
- A filter entity to test potential activators against.
- Entity Scripts
<scriptlist>(New with Left 4 Dead 2)
- Space delimited list of VScript files (without file extension) that are executed after all entities have spawned. The scripts are all executed in the same script scope, later ones overwriting any identical variables and functions.
- Script think function
<string>(New with Left 4 Dead 2)
- Name of a function in this entity's script which will be called automatically every 100 milliseconds (ten times a second) for the duration of the script. It can be used to create timers or to simulate autonomous behavior. The return value (if present) will set the time until the next call. Note:Try to avoid expensive operations in this function, as it may cause performance problems.
- Specifies a movement parent. An entity will maintain its initial offset from its parent. An attachment point can be added to the end of the name, separated by a comma. Warning: If a trigger does not start out with a parent but rather is assigned one dynamically, choose another entity and add it here as a dummy. Otherwise the trigger will stop colliding properly when it gets its real parent. Warning: In Counter-Strike: Source
- Origin (X Y Z)
- The position of this entity's center in the world. Rotating entities typically rotate around their origin.
- Start Disabled (StartDisabled)
- Stay dormant until activated (probably with the
- Global Entity Name
- Name by which this entity is linked to another entity in a different map. When the player transitions to a new map, entities in the new map with globalnames matching entities in the previous map will have the previous map's state copied over their state.
- 1 : Clients
- 2 : NPCs
- 4 : Pushables
- 8 : Physics Objects
- 16 : Only player ally NPCs
- 32 : Only clients in vehicles
- 64 : Everything (not including physics debris)
- 512 : Only clients *not* in vehicles
- 1024 : Physics debris
- 2048 : Only NPCs in vehicles (respects player ally flag)
- 4096 : Disallow Bots
- 4096 : Correctly account for object mass (trigger_push used to assume 100Kg) and multiple component physobjs (car, blob...) (New with Alien Swarm)
- Toggles this trigger between enabled and disabled states.
- Enable/disable this entity from performing its task. It might also disappear from view.
- Move with this entity. See Entity Hierarchy (parenting).
- Change this entity to attach to a specific attachment point on its parent. The entity will teleport so that the position of its root bone matches that of the attachment. Entities must be parented before being sent this input.
- As above, but without teleporting. The entity retains its position relative to the attachment at the time of the input being received.
- Removes this entity from the the movement hierarchy, leaving it free to move independently.
- Removes this entity and any entities parented to it from the world.
- Functions the same as
Kill, although entities with a large number of children are killed marginally faster.
- Evaluates a keyvalue/output on this entity. It can be potentially very dangerous, use with care.
<output name> <targetname>:<inputname>:<parameter>:<delay>:<max times to fire, -1 means infinite>
- Fire the
OnUseroutputs; see User Inputs and Outputs.
- Same as a player invoking +use; may not do anything. Can also be invoked by creating an output that does not specify an input.
This input is not included in Valve's FGDs.
<script>(New with Left 4 Dead 2)
- Execute a VScript file from disk, without file extension. The script contents are merged with the script scope of the receiving entity.
<string>(New with Left 4 Dead 2)
- Execute a string of VScript source code in the scope of the entity receiving the input. String quotation may be needed when fired via console. Bug: In , the code is executed in the script scope of the entity that fires the output, not the one receiving the input.Warning: Never try to pass string parameters to a script function with this input. It will corrupt the VMF structure because of the nested quotation marks, which then must be removed manually with a text editor.
<string>(New with Left 4 Dead 2) !FGD
- Execute a VScript function in the scope of the receiving entity. Note:This input is missing from some games FGD files.
<origin>(New with Alien Swarm) !FGD
- Set this entity's origin in the map. Note:This input is missing from some games FGD files.
<angles>(New with Alien Swarm) !FGD
- Set this entity's angles in the map. Note:This input is missing from some games FGD files.
- Fired when an entity starts touching this trigger. The touching entity must pass this trigger's filters to cause this output to fire. (activator is the toucher)
- Fired whenever the trigger is activated. (activator is the activator)
- These Outputs each fire in response to the firing of the like-numbered
FireUser4Input; see User Inputs and Outputs.
OnKilled(New with Left 4 Dead)
- This Output fires when the entity is killed and removed from the game.