From Valve Developer Community
Revision as of 11:56, 15 March 2017 by Yolobongsmoker69 (talk | contribs) (Inputs)

Jump to: navigation, search
Headcrab Canister

<Half-Life 2> env_headcrabcanister is a point entity available in the Half-Life 2 series.

The canister is a mortar shell containing a payload of headcrabs. The mortar shell inflicts damage within a radius of where it lands and releases headcrabs after impact. Inputs and entity options offer control over impact damage and when the headcrabs are released, among other options.

For an example of their use, see the shantytown in d1_canals_05.

Dedicated Console Variables

sk_env_headcrabcanister_shake_amplitude <float>
Crash effect's shake amplitude.
sk_env_headcrabcanister_shake_radius <float>
Crash effect's shake radius.
sk_env_headcrabcanister_shake_radius_vehicle <float>
Crash effect's shake radius for vehicles.



Name <string>
The targetname that other entities refer to this entity by.
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.


Parent (parentname) <targetname>
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.


Pitch Yaw Roll (Y Z X) <angle>
This entity's orientation in the world. Pitch is rotation around the Y axis, yaw is the rotation around the Z axis, roll is the rotation around the X axis.
Wich headcrab to Spawn? <choices>
Select wich headcrab will jump out the canister.
  • 1 : Normal headcrabs
  • 2 : Fast Headcrabs
  • 3 : Poison Headcrabs
Headcrab count <integer>
Number of headcrabs to spawn on impact.
Flight Speed <float>
Speed to fly through the air.
Flight Time <float>
Time to fly through the air in seconds.
Starting Height <float>
Relative height from the landing position at which the canister should be launched. Positive values mean launch it above the impact point, negative values mean launch it below.
Min Refire time <float>
Min number of seconds before the canister is refired. This will only work for canisters placed in the skybox.
Max Refire time <float>
Max number of seconds before the canister is refired. This will only work for canisters placed in the skybox.
Canister count <integer>
Number of canisters to fire in the skybox (0 means fire continuously, forever).
Impact damage <float>
Max damage the canister applies on impact.
Impact damage Radius <float>
Max radius of the impact damage for the canister.
Smoke duration <float>
Duration that the canister smokes. -1 means always smoke.
Launch Position Name <targetname>
If the canister should launch to its origin from another point within the world, this should specify an info_target at the launch origin.


  • 1 : No Impact Sound
  • 2 : No Launch Sound
  • 4096 : Start Impacted
  • 8192 : Land at initial position
  • 16384 : Wait for input to open
  • 32768 : Wait for input to spawn headcrabs
  • 65536 : No smoke
  • 131072 : No shake
  • 262144 : Remove on impact
  • 524288 : No impact effects



Removes this entity and any entities parented to it from the world.
Functions the same as Kill, although this entity and any entities parented to it are killed on the same frame, being marginally faster than Kill.
AddOutput <string>
Evaluates a keyvalue/output on this entity. It can be potentially very dangerous, use with care.
Format: <key> <value>
Format: <output name> <targetname>:<inputname>:<parameter>:<delay>:<max times to fire, -1 means infinite>
FireUser1 to FireUser4
Fire the OnUser outputs; see User Inputs and Outputs.
Use  !FGD
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.
RunScriptFile <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.
RunScriptCode <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 <Left 4 Dead 2>, 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.
CallScriptFunction <string> (New with Left 4 Dead 2) !FGD
Execute a VScript function in the scope of the receiving entity.
SetLocalOrigin <coordinates> (New with Alien Swarm) !FGD
Send this entity to a spot in the map. If the entity is parented to something, it will be offset from the parent by this amount.
SetLocalAngles <angles> (New with Alien Swarm) !FGD
Set this entity's angles.


SetParent <string>
Move with this entity. See Entity Hierarchy (parenting).
SetParentAttachment <string>
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.
SetParentAttachmentMaintainOffset <string>
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.
Fires the canister.
Opens the canister (must be called after the OnImpacted output is fired).
Spawns headcrabs (must be called after the OnImpacted output is fired and after OpenCanister is triggered, if the Wait for Input to open spawnflag is checked.)
Causes the smoke effect to stop.



OnUser1 to OnUser4
These Outputs each fire in response to the firing of the like-numbered FireUser1 to FireUser4 Input; see User Inputs and Outputs.
OnKilled  (Only in the Left 4 Dead series)
This Output fires when the entity is killed and removed from the game.
OnLaunched <targetname>'
Fired when the canister is launched. The targetname is of the canister.
Fires when canister hits the ground.
Fires when canister has finished opening.