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func_tanktrain is a brush entity available in all Source games. It was meant to be a train that follows a target entity (such as the player). It was never finished and doesn't work correctly.

It was meant to be used in combination with a tanktrain_ai entity.

In code it is represented by class CFuncTankTrain, defined in hl2_dll\tanktrain.cpp.

Bug: This entity has a hard-coded damage filter and will never die as is not properly configured to take damage in the first place. (See talk page)


Health <integer>
Health of the tank.


First Stop Target <targetname>
The name of the first path_track in the train's path. The train will spawn at this path_track. It will also turn to face direction indicated by the 'Orientation Type' setting.
Max Speed (units / second) <integer>
The maximum speed that this train can move. Any speeds applied to this train, such as by path_tracks or SetSpeed inputs, will be clipped to this maximum value.
Initial Speed (units / second) <integer>
The speed that the train will move at after it spawns, 0 = stopped.
Change Velocity <choices>
The method through which this train changes its velocity as it moves along the path.
  • 0 : Instantaneously
  • 1 : Linear blend
  • 2 : Ease in/ease out
Change angles <choices>
The method through which this train changes its orientation as it moves along the path.
  • 0 : Never (always fixed orientation)
  • 1 : Near paths
  • 2 : Linear blend
  • 3 : Ease in/ease out
Distance Between the Wheels <integer>
Used for turning and stopping.
Tip:Increase the value for smoother turns.
Height above track <integer>
The height above the track that this train moves.
Bank Angle on Turns <string>
The angle at which the train will "bank" or tilt when approaching a turn. Use positive or negative angle numbers close to 0 (ie. between -5 and +5, depending on left or right) to achieve realistic tilt angles.
Damage on Crush <integer>
The amount of damage this train does to entities that block it.
Minimum Light Level <string>
The minimum level of ambient light that hits this brush.
Move Sound <sound>
A sound that is played (and looped) while the train is moving.
Move Ping Sound <sound>
A sound that is played more frequently as the train speeds up.
Start Sound <sound>
A sound played when the train starts moving.
Stop Sound <sound>
A sound played when the train stops moving.
Volume (10 = loudest) <integer>
Volume of the sound when the train is moving.
Min pitch (1-255, > 100 = higher) <integer>
The sound pitch value that the train will approach as it comes to a stop.
Max pitch (1-255, > 100 = higher) <integer>
The sound pitch value that the train will approach as it approaches its max speed (or 1000 inches/second if the 'Use max speed for pitch shifting move sound' flag is not set).
Min move sound interval <float>
Minimum interval at which to play the move ping sound.
Max move sound interval <float>
Maximum interval at which to play the move ping sound.


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


Parent <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>
The position of this entity's center in the world. Rotating entities typically rotate around their origin.


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.
To do: 18-21, 25


Global Entity Name <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.


Disable shadows (disableshadows) <boolean>
Prevent the entity from creating cheap render-to-texture shadows. Does not affect shadow mapping.
Disable ShadowDepth (disableshadowdepth) <boolean> (New with Portal 2)
Used to disable rendering into shadow depth (for projected textures) for this entity.
Projected Texture Cache (shadowdepthnocache) <choices> (New with 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> (New with Portal 2)
Used to disable projected texture lighting and shadows on this entity.



  • 1 : No Pitch (X-rot)
  • 2 : No User Control
  • 8 : Passable - It disables the collision from the object
  • 16 : Always Fixed Orientation
  • 128 : Rideable Train* - Does not knock entities off or cause damage.
  • 256 : Use max speed for pitch shifting move sound
  • 512 : Not blockable by players



SetSpeed  <float>
Set the speed of the train, as a ratio of max speed [0, 1]
SetSpeedDir  <float>
Set the speed of the train, as a ratio of max speed. Negative values reverse the direction [-1, 1]
SetSpeedReal  <float>
Set the speed of the train. Must be a positive value from 0 to max speed.
SetSpeedDirAccel  <float>
Accel/Decel to the specified speed, as a ratio of max speed. Negative values reverse the direction [-1, 1]
SetSpeedForwardModifier  <float>
Applies the given modifier to all forward speeds. [0, 1]
TeleportToPathTrack  <targetname>
Teleport the train to the designated path track.
Stop the train.
Start the train moving forward.
Start the train moving backward.
Bug: If the train's corresponding path_tracks do not have "New Train Speed" set to a nonzero number, StartBackward will exhibit undesired behavior including the train freezing or moving in the wrong direction. This bug can be a pain if the train needs to ride through the path_track again at a different speed. This can be fixed by firing an "addOutput speed '#'" input at the path_track in question.
Resume the train moving in the current direction after it was stopped via the Stop or Toggle input.
Reverse the direction of the train.
Toggle the train between start and stop.


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.


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 shadow off.
Turn shadow on.
DisableReceivingFlashlight  (New with Portal 2)
This object will not receive light or shadows from projected textures.
EnableReceivingFlashlight  (New with Portal 2)
This object may receive light or shadows from projected textures.


Fired when the tank is killed.
Bug: This entity can never die without code modification. (See talk page)
Fired when the train starts moving in either direction.
Fires continuously every frame when the train is moving to its next destination.
Note:This is incorrectly listed as "OnNext" AND its description is completely wrong in the default FGD!


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.