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Env_beam in action

env_beam is a point entity available in all Source games. It creates a visible energy beam running between two entities, in either a line or ring shape. Similar to env_laser.

Usage Notes

Start and end points should (ideally) be info_targets, though almost any entity is acceptable, with the exception of info_null (which is removed during map compile), and entities that cannot be named (prop_static, func_detail and prop_detail). If both / all start and end point entities are destroyed in-game, the beam will no longer work.

Developers can specify a group of multiple starting / ending entities by giving them the same name. The env_beam will then randomly select one of these entities to use for each strike. If entity names for either points is omitted, a random point on a solid surface within the radius (specified in its Radius property) will be selected for each strike instead. If both points are omitted, the center will be the env_beam entity itself. Such randomized beams do not cause damage.

The beam will always visibly run from start to end, even through solid brushes. However, beam damage will be absorbed by the first solid thing it hits, such as props, players, or solid brushes. When blocked in this manner, a striking env_beam (Life > 0) will immediately discharge all damage upon impact of each strike (which means that players can walk into a beam strike after impact and not take damage), while a permanent beam (Life = 0) will inflict damage gradually.


Brightness (1 - 255) <integer>
Beam brightness. Useless when set to 0.
Beam Color (R G B) <color255>
Beam color.
Radius <integer>
If the LightningStart and/or LightningEnd values are omitted, this radius determines the area within which the endpoints will randomly strike. A new random position will be appointed for every strike.
Life (seconds 0 = infinite) <string>
Amount of time before the beam dies. Setting to zero will make the beam stay forever.
Width of beam <float>
Pixel width of the beam. Range: 1 to MAX_BEAM_WIDTH.
Amount of noise (0-255) <float>
The amount of noise in the beam. 0 is a perfectly straight beam. Range: 0 to MAX_BEAM_NOISEAMPLITUDE.
Note.png Note: The name says the maximum is 255, but by default the maximum value is 64. Values higher than 64 will default to 64.
Sprite Name <sprite>
The material used to draw the beam.
Texture Scroll Rate (0-100) <integer>
Rate at which the beam texture should scroll along the beam. Range: 0 to MAX_BEAM_SCROLLSPEED.
Frames per 10 seconds <integer>
Framerate at which the beam texture should animate, if it has multiple frames.
Starting Frame <integer>
The frame to start the beam texture on.
Strike again time (secs) <string>
Refire time between random strikes of the beam. Only used if the 'Random Strike' spawnflag is set.
Damage / second <string>
How much damage this beam does per second to things it hits when it is continually on, or instantaneously if it strikes. For continuous damage, the value should be greater than 10 or it may not work.
Note.png Note: Damage is scaled to the difficulty setting:
  • The "Easy" (skill 1) setting causes 50% of the Damage / second value.
  • The "Normal" (skill 2) setting causes 100% of the Damage / second value.
  • The "Hard" (skill 3) setting causes 150% of the Damage / second value.
Start Entity <targetname>
Entity that the beam starts at. If omitted the entity will instead use a random position on any surface within its Radius value. A new random position will be appointed for every strike. See usage note above.
Ending Entity <targetname>
Entity that the beam ends at. If omitted the entity will instead use a random position on any surface within its Radius value. A new random position will be appointed for every strike. See usage note above.
Decal Name <string>
Decal to be applied at the end of the beam
HDR color scale. <float>
float value to multiply sprite color by when running in HDR mode.
Touch Type (tripwire) <choices>
If you want the beam to fire an output when touched by entities, choose the entity type here.
  • 0 : Not a tripwire
  • 1 : Player Only
  • 2 : NPC Only
  • 3 : Player or NPC
  • 4 : Player or NPC or Physprop
Filter Name <filter>
Filter to use to see if activator triggers me. See filter_activator_name for more explanation.
Endpoint handle <vector> (in all games since <Alien Swarm>)
If a LightningEnd entity is not specified, use this point as the destination instead. If the env_beam moves, the destination point will move along with it.
Beam clipping <choices> (in all games since <Alien Swarm>)
Select whether you want the beam to clip against geometry or characters
  • 0 : Do not clip (default)
  • 1 : Clip to geometry
  • 2 : Clip to everything solid


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.


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.


Render FX (renderfx) <choices>
Preset pattern of appearance effects.


  • 1 : Start On
Starts the map with the beam turned on.
  • 2 : Toggle
Obsolete. Replaced by the Toggle input of the Source I/O system. Used to toggle the beam on and off.
  • 4 : Random Strike
When the beam has died, it will strike again randomly within a delay interval of 0 to the value in Strike again time (secs).
  • 8 : Ring
Uses the starting and ending points as a diameter, drawing a beam ring between them instead of a straight line.
Note.png Note: info_targets cannot be used for ring beams; the ring will not show at all. Instead, use brush entities (like func_brushes or func_trains) or models.
  • 16 : StartSparks
Every time the beam strikes or is turned on, the beam temporarily emits a small shower of sparks at its Start Entity.
  • 32 : EndSparks
Every time the beam strikes or is turned on, the beam temporarily emits a small shower of sparks at its Ending Entity.
  • 64 : Decal End
Do not use. Places a decal scorch mark where a damaging beam hits the first solid (world brush or entity). Unfortunately this decal is enormous as a crater, obviously a square decal and horribly ugly.
  • 128 : Shade Start
The beam fades out toward its Start Entity. Overrides Shade End. Does not work on striking beams or beam rings.
  • 256 : Shade End
The beam fades out toward its Ending Entity. Is overridden by Shade Start. Does not work on striking beams (Life > 0) or beam rings.
  • 512 : Taper Out
Makes the beam taper out into a point towards its Ending Entity. Does not work on striking beams (Life > 0) or beam rings.


Turns the beam on.
Turns the beam off.
Toggles the beam between on and off.
Causes the beam to strike once. It will stay on for its set Life and then turn off (it will never turn off if Life is set to zero).
Alpha <integer>
Sets the beam's alpha (0 - 255).
Color <color255>
Sets the beam's render color (R G B).
ColorRedValue <float>
Sets the red color channel's value (0 - 255).
ColorGreenValue <float>
Sets the green color channel's value (0 - 255).
ColorBlueValue <float>
Sets the blue color channel's value (0 - 255).
Amplitude <float>
Set the amplitude of beam noise (0 - 255).
ScrollSpeed <float>
Set the scroll speed in units per second (0 - 100).
Width <float>
Set the width of the beam, in pixels.


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.


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.


Fired when an entity touches the beam. Only fired if the entity passes the 'Touch Type' choice.


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.

See Also