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func_rotating is a brush entity available in all Source games.

Note.png Note: Team Fortress 2 This entity did not rotate visually until the 19/12/2018 patch, due to bugged implementation of the Client-side rotation spawnflag.

Entity description

A visual guide showing the axis in each viewport (Click to enlarge)

It is used to create rotating brushes. Compare with func_door_rotating.

Friction Explanation & Formula

Fan friction may be a little tricky to understand. Below is an explanation of how it works.

If Hammer has the fanfriction key set to 0 and the game spawns the entity, code sets it to 1 so it doesn't divide by zero.

Friction = fanfriction key / 100

Key Hammer Value Code Value
fanfriction 100 1
fanfriction 50 0.5
fanfriction 0/1 0.01

Note: These formulas get called every 0.1 seconds.

Purpose: Think function: Accelerates a func_rotating to a higher angular velocity. new_speed = fabs( current_speed ) + 0.2 * maxspeed * fanfriction;

Purpose: Decelerates the rotator from a higher speed to a lower one. new_speed = fabs( current_speed ) - 0.1 * maxspeed * fanfriction;


  • A higher 'fanfriction' value will accelerate/deaccelerate faster.
  • A lower 'fanfriction' value will accelerate/deaccelerate slower.


Max Rotation Speed <integer>
The maximum rotation speed of the brushes, in degrees per second. Seems to be limited to a number around 2000, after which the rotational speed ignores the last remaining digits (eg: 2500=250).
Friction (0 - 100%) <integer>
The amount of rotational friction. Value must be between 0 and 100 %. The lower the friction is, the slower it spins up and spins down. This is the opposite of how it would work in real life.
Rotating sound WAV <sound>
Sound to play while rotating.
Volume (10 = loudest) <integer>
The volume of the rotation sound.
Minimum Light Level <string>
The minimum level of ambient light that hits this brush.
Blocking Damage <integer>
Damage done to any entity that blocks the rotation, per frame.
Solid Type <choices>
Brush solidity type
  • 0 : VPhysics
  • 1 : BSP


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.


Origin (X Y Z) (origin) <origin>
The position of this entity's center in the world. Rotating entities typically rotate around their origin.


Pitch Yaw Roll (Y Z X) (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.


Render Mode (rendermode) <choices>
Set a non-standard rendering mode on this entity.

Render FX / Transparency (0 - 255) (renderamt) <integer>
Transparency amount, requires a Render Mode other than Normal. 0 is invisible, 255 is fully visible.
Render Color (R G B) (rendercolor) <color255>
Color tint.
Disable Receiving Shadows (disablereceiveshadows) <boolean>
Prevent the entity from receiving shadows on itself.


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


Disable Shadows (disableshadows) <boolean>
Prevents the entity from creating cheap render-to-texture shadows, or lightmap shadows if the entity is a prop_static. Does not affect shadow mapping.
Disable ShadowDepth (disableshadowdepth) <boolean> (in all games since Portal 2)
Used to disable rendering into shadow depth (for projected textures) for this entity.
Projected Texture Cache (shadowdepthnocache) <choices> (in all games since Portal 2)
Used to hint projected texture system whether it is sufficient to cache shadow volume of this entity or to force render it every frame instead.
  • 0 : Default
  • 1 : No cache - render every frame
  • 2 : Cache it - render only once
Disable flashlight (disableflashlight) <boolean> (in all games since Portal 2)
Used to disable projected texture lighting and shadows on this entity.


Render in Fast Reflections (drawinfastreflection) <boolean> (in all games since Portal 2)
If enabled, this entity will render in fast water reflections (i.e. when a water material specifies $reflectonlymarkedentities) and in the world impostor pass.


  • 1 : Start ON
  • 2 : Reverse Direction
  • 4 : X Axis - If enabled, the entity will spin at the X Axis.
  • 8 : Y Axis - If enabled, the entity spin at the Y Axis.
  • 16 : Acc/Dcc - If enabled, the entity will accelerate and decelerate from maximum speed based on the Friction property.
  • 16 : Team Fortress 2 Client-side Rotation - Intended to simulate the entity entirely on the client.
  • 32 : Fan Pain - With this enabled, the player will be hurt when coming into contact with the brush.
  • 64 : Not Solid
  • 128 : Small Sound Radius
  • 256 : Medium Sound Radius
  • 512 : Large Sound Radius
  • 1024 : Client-side Animation (in all games since Left 4 Dead)


SetSpeed <float>
Set the speed as a ratio of the specified Max Rotation Speed, where 0 is stopped and 1 is the Max Rotation Speed. Negative values rotate backwards.
Start the rotator rotating.
Stop the rotator from rotating.
Stop the rotator from rotating when it gets around to the start position again (on its rotation axis).
Start the rotator rotating forward at maximum speed.
Start the rotator rotating backward at maximum speed.
Toggle the rotator between rotating and not rotating.
Reverse the direction of rotation of the rotator, preserving the current speed.
SnapToStartPos  (in all games since Left 4 Dead 2)
Snap to the initial position and stop moving.
GetSpeed  (in all games since Portal 2)
Causes the func_rotating to fire its OnGetSpeed output with its current speed.


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.


Alpha <integer>
Sets the entity's transparency to a number from 0 (invisible) to 255 (fully visible). Requires the entity to have its Render Mode (rendermode) set to a number other than 0.
Color <color255>
Sets an RGB color for the entity.


Turn dynamic shadows off for this entity.
Turn dynamic shadows on for this entity.
DisableReceivingFlashlight  (in all games since Portal 2)
This object will not receive light or shadows from projected textures.
EnableReceivingFlashlight  (in all games since Portal 2)
This object may receive light or shadows from projected textures.


DisableDrawInFastReflection  (in all games since Portal 2)
Turns off rendering of this entity in reflections when using $reflectonlymarkedentities in water material.
EnableDrawInFastReflection  (in all games since Portal 2)
Turn on rendering of this entity in reflections when using $reflectonlymarkedentities in water material.


OnGetSpeed <integer> (in all games since Portal 2)
Fired when the GetSpeed input is called. The current speed of the func_rotating is passed with this output.


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.