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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.

Bug.png Bug: Doesn't work when parented, use env_laser instead or use logic_measure_movement to mimic parenting.

To do: In which games? Works in csgo

Bug.png Bug: <Team Fortress 2> info_target, info_landmark and path_corner might not work as start/end points, info_teleport_destination is a suitable workaround.

In code, it is represented by class CEnvBeam, defined in EnvBeam.cpp.

Usage Notes

The start and end can be any entity, except for internal entities or any other entity that could remove itself automatically, like info_null. If both the 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. The beam's damage will be absorbed by the first solid thing it hits. If Life is greater than 0, the beam will deal this damage only once, while a permanent beam (Life at 0) will inflict damage gradually.



  • 1: Start On - Starts the map with the beam turned on.
  • 2: Toggle - Obsolete. Replaced by the Toggle input in 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 the time set by 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.
  • 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 - Places a decal scorch mark where a damaging beam hits the first solid object (world brush or entity). Refer to the Decal Name keyvalue to set the decal you wish to appear at the end of the beam.
  • 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.


Radius (Radius) <integer>
If the Start Entity and/or Ending Entity 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) (life) <string>
Amount of time before the beam dies. Setting to zero will make the beam stay forever.
Width of beam (BoltWidth) <float>
Pixel width of the beam. Range: 1 to MAX_BEAM_WIDTH.
Frames per 10 seconds (framerate) <integer>
Framerate at which the beam texture should animate, if it has multiple frames.
Strike again time (secs) (StrikeTime) <string>
Refire time between random strikes of the beam. Only used if the 'Random Strike' spawnflag is set.
Start Entity (LightningStart) <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 (LightningEnd) <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 (decalname) <string>
Decal to be applied at the end of the beam
Touch Type (tripwire) (TouchType) <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 (filtername) <filter>
Filter to use to see if activator triggers me.
Endpoint handle (targetpoint) <vector>
If a Ending Entity entity is not specified, use this point as the destination instead. If the beam moves, the destination point will move along with it.


Brightness (1 - 255) (renderamt) <integer>
Misleading name; beam alpha. Invisible when set to 0.
Beam Color (R G B) (rendercolor) <color255>
Beam color.
Damage/second (damage) <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:
  • Easy: 50%
  • Normal: 100%
  • Hard: 150%
HDR color scale (HDRColorScale) <float>
Value to multiply sprite color by when running in HDR mode.
Beam clipping (ClipStyle) <choices>
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
Dissolve Type (dissolvetype) <choices>
If this beam damages and kills something, effects to show around the object.
  • -1: None
  • 0: Energy
  • 1: Heavy Electrical
  • 2: Light Electrical
Amount of noise (0-255) (NoiseAmplitude) <float>
The amount of noise in the beam. 0 is a perfectly straight beam, while the maximum is very jagged. 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 (texture) <sprite>
The material used to draw the beam.
Texture Scroll Rate (0-100) (TextureScroll) <integer>
Rate at which the beam texture should scroll along the beam. Range: 0 to MAX_BEAM_SCROLLSPEED.
Starting Frame (framestart) <integer>
The frame to start the beam texture on.


Classname (classname) <string>
The classname defines the type of entity. Classnames can be changed using AddOutput, which will influence how the engine deals with the entity in certain circumstances.
Name (targetname) <string>
The name that other entities refer to this entity by.
Global Entity Name (globalname) <string>
Name by which this entity is linked to another entity in a different map. When the player transitions to a new map, entities in the new map with globalnames matching entities in the previous map will have the previous map's state copied over their state.
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. Every entity can be parented, even point entities. Entities which are parented will be forced to transition to the next map, such as from a trigger_transition. Some entities which aren't intended to be parented may not function correctly. phys_constraint can be used as a workaround to parenting.
Origin (X Y Z) (origin) <coordinates>
The position of this entity's center in the world. Rotating entities typically rotate around their origin.
Pitch Yaw Roll (X Y Z) (angles) <angle>
This entity's orientation in the world. Pitch is rotation around the Y axis, yaw is the rotation around the Z axis, roll is the rotation around the X axis.
Note.png Note: This works on brush entities, although Hammer doesn't show the new angles.
Flags (spawnflags) <integer>
Toggles features of an entity, its specific number is determined by the combination of flags added.
Response Contexts (ResponseContext) <string>
Pre-defined response system contexts for this entity. Format is key:value,key:value,.... Contexts may be filtered.
Effects (effects) <integer> !FGD
Combination of effect flags to use.
Hammer ID (hammerid) <integer> !FGD
The entity's Hammer ID. Mainly used by plugins and debugging commands, such as ent_keyvalue. Entities spawned at run-time are not assigned any Hammer ID.
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. Try to avoid expensive operations in this function, as it may cause performance problems.
Lag Compensation (LagCompensate) <boolean> (in all games since <Left 4 Dead 2>) !FGD
Set to Yes to lag compensate this entity. Should be used very sparingly!
Disable for Xbox 360 (disableX360) <boolean> (in all games since <Left 4 Dead 2>) !FGD
If this entity should automatically be given the 'Disable' input on the Xbox 360 version of Source.
Is Automatic-Aim Target (is_autoaim_target) <boolean> (in all games since <Counter-Strike: Global Offensive>) !FGD
If set to 1, this entity will slow down aiming movement for consoles and joystick controllers when the entity is under the crosshairs.


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).
Amplitude <float> <Obsolete>
Deprecated. Use Noise instead.


Turns the beam on.
Turns the beam off.
Toggles the beam between on and off.
Width <float>
Set the width of the beam, in pixels.
Noise <float> !FGD
Set how far away from the middle the beam is allowed to deviate.
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).
ScrollSpeed <float>
Set the scroll speed in units per second (0 - 100).


AddOutput <string>
Evaluates a keyvalue/output on this entity.
Format: <key> <value>
Format: <output name> <targetname>:<inputname>:<parameter>:<delay>:<max times to fire, -1 means infinite>
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 thanKillinput.
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.
FireUser1 to FireUser4
Fire the OnUser outputs; see User Inputs and Outputs.
AddContext <string>
Adds to the entity's list of response contexts. Format is <key>:<value>.
RemoveContext <string>
Remove a context from this entity's list. The name should match the key of an existing context.
ClearContext <string>
Removes all contexts from this entity's list.
DispatchEffect <string> (removed since <Left 4 Dead>) !FGD
Dispatches a special effect from the entity's origin. Removed and replaced entirely by the particle system since <Left 4 Dead>.
DispatchResponse <string> !FGD
Dispatches a response to the entity. See Response and Concept.
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> (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.


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.