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Green boxes represent occluded props, red boxes unoccluded ones.

func_occluder is a brush entity available in all Source games.

Entity description

It hides models that are entirely covered by it in the player's view, according to how it has been textured. They are used to control visibility in places where func_areaportals or world brushes are unsuitable. Calculations of model visibility ingame is done in real time and is not in the final compile process. Use func_occluders wisely because they do calculations in real time and can cost a lot of CPU if there are too many in a map.



This entity works according to how materials has been applied to it:

  • All sides covered with the occluder or trigger materials will occlude.
  • All sides covered with the nodraw material will not occlude.

Occluders and Areaportals

There are several important differences between occluders and areaportals:

  • An occluder only hides props, not world geometery or static brushes.
  • An occluder does not split visleaves.
  • An occluder can be free standing and does not need to separate two areas.

Debugging commands

Activate/deactivate the occlusion system.
Activate/deactivate wireframe rendering of what the occlusion system is doing.
Show the occlusion proxies
Prevents occlusion testing for entities that take up more than X% of the screen. 0 means use whatever the level said to use.
Prevents this occluder from being used if it takes up less than X% of the screen. 0 means use whatever the level said to use.
Activate/deactivates spew about what the occlusion system is doing.
At least this many occluders will be used, no matter how big they are.


Start Active <bool>
If the entity starts inactive, use the Activate or Toggle inputs to turn it on.


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.


Control the state of the occluder.


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.



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.

External Links