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<Left 4 Dead 2> sound_mix_layer is a point entity available in Left 4 Dead 2. It is an entity used to set a mix layer to a specific value.

Note.png Note: Developers seeking how to manage priorities of specific sounds should refer to mixgroups found in pak01_dir.vpk: /scripts/soundmixers.txt


Mix Layer Name <string>
Name of the mix layer to be setting the level of.
Level <float>
Set the Mix Layer Level


Name (targetname) <string>
The targetname that other entities refer to this entity by.
Entity Scripts (vscripts) <scriptlist> (in all games since <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 (thinkfunction) <string> (in all games since <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.png Note: Try to avoid expensive operations in this function, as it may cause performance problems.


Level <float>
Set the Mix Layer Level


Removes this entity from the world.
Removes this entity and its children from the world.
Note.png Note: Entities already remove orphaned children upon being removed, but this input removes all children on the same frame, being marginally faster than Kill.
AddOutput <string>
Adds a keyvalue/output to this entity. It can be potentially very dangerous, use with care.
KV Format: <key> <value>
I/O 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 depending on the entity. Can also be invoked by firing an output that does not specify an input.
RunScriptFile <script> (in all games since <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> (in all games since <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.png 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.png 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> (in all games since <Left 4 Dead 2>) !FGD
Execute a VScript function in the scope of the receiving entity.
SetLocalOrigin <coordinates> (in all games since <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> (in all games since <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 <Left 4 Dead><Left 4 Dead 2>)
This output fires when the entity is killed and removed from the game.

Mix layers

More information regarding MixLayers can be found in pak01_dir.vpk: /scripts/soundmixers.txt

These are listed in the dev console commmand snd_list_mixers

  • mobBeatingLayer
  • mobRulesLayer
  • zombatMusicLayer
  • zombatMusic2Layer
  • zombatMusic3Layer
  • witchRageLayer
  • safeRoomLayer
  • unaliveLayer
  • PZVOWarnLayer
  • chargerAttackLayer
  • commentaryLayer
  • undeathLayer
  • adrenalineLayer
  • fluMusicLayer
  • rainLayer
  • stormLayer
  • voipLayer

Entries listed under the dev console command snd_list_mix_groups may work with a "Layer" post-fix, but need further testing.

External links

Audio Mixing (recorded music) - Wikipedia article regarding technical aspects of audio mixing