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<Left 4 Dead> <Left 4 Dead 2> func_nav_blocker is a brush entity available in the Left 4 Dead series. It is a brush entity that can block nav areas touching its AABB used to restrict NPCs from crossing over nav areas.

Note.png Note: The entity will NOT start to block automatically: it must first be activated with the BlockNav input.
Note.png Note:  In l4d2, func_nav_blocker behaves slightly different than in L4D1. To block a nav area, you must use a logic_relay triggered by a logic_auto on map spawn and send an unblocknav input to all func_nav_blockers, then selectively send an input again .5 seconds or so after and block the ones needed. Failure to unblock them before blocking them will produce the error in the console that says "Area # already blocked by a different team id". In l4d2 func_nav_blocker may also ignore your "team(s) to block", and will block both teams if the func_nav_blocker brush resides in a prop_door_rotating , func_physbox and perhaps others entites which may break your flow if you have it set to "Affects Flow: Yes."


Team(s) to block <choices>
Team(s) this entity should block
  • -1 : Everyone
  • 2 : Survivors
  • 3 : Infected
Affects Flow? <boolean>
Does this func_nav_blocker block flow in the level? Only func_nav_blockers with this enabled will cause flow recomputation on blocking/unblocking.


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.


Start Disabled (StartDisabled) <boolean>
Stay dormant until activated (with theEnableinput).
Note.png Note: This KeyValue is not available in Smart Edit and must be added manually.
Warning.png Warning: Enabled/disabled state does not block or unblock NAV areas. Use BlockNav/UnblockNav

Recheck Breakables <Boolean>
Appears to respond to any changes to breakables even though a BlockNav/UnblockNav input is fire anyway from the breakable prop anyway.
Note.png Note: This KeyValue is not available in Smart Edit and must be added manually.


BlockNav <string>
Starts blocking nav areas.
Stops blocking nav areas.


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.


Enable/disable this entity from performing its task. It might also disappear from view.
Warning.png Warning: Enabled/disabled state does not block or unblock NAV areas.



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.