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env_screenoverlay in practice with effects/combine_binocoverlay. The following links to a youtube video of these in effect

env_screenoverlay is a point entity available in all Source games. It can display and control a set of screen overlays, to be displayed over the player's view. Useful for view effects like drunkenness, or teleporter afterimages, etc.

Note:An overlay will be applied to all players in multiplayer games, even when the !activator is a player.


You can use any material as an overlay, but UnlitGeneric ones are recommended to avoid artefacting.

Valve provide these materials in the /effects folder:

Combine binoculars
Green teleport shimmer

Red teleport shimmer

Blue teleport shimmer
Drugged distortion
Black. A probable bug makes it so that a thin border around the overlay is still visible.
Flashing animation of three figures. Hardly usable as an overlay.

These materials are not designed as screen overlays, but will work as one:

Monochrome (Black and white)
The combine shield shader effect - refraction with drifting squares.
Red-yellow-green scrolling ground overlay
Green downward haze
Red/Orange Refractive overlay
As if looking through a glass Observation window from Portal


Overlay Name 1 to Overlay Name 10 <string>
Name of the first overlay material to display.
Overlay Duration 1 to Overlay Duration 10 <float>
Amount of time that the overlay should be displayed for, after which it will begin showing the next overlay. Setting this to -1 will make the entity display the overlay indefinitely, until it's forced to change by an input.


Name (targetname) <string>
The targetname that other entities refer to this entity by.
Entity Scripts (vscripts) <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 (thinkfunction) <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.


  • 1 : Allow Suit Zoom


Start displaying the first overlay.
Stop displaying any overlays.
SwitchOverlay <float>
Switch to displaying a specific overlay. Pass in the desired overlay number in the parameter. Entering -1 as the value will cause the overlay to display indefinitely.


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.

See also