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func_tracktrain is a brush entity available in all Source games. It functions as a moving platform that the player can ride. It follows a path of path_track entities.

Note.png Note: Unless the Fixed Orientation flag is set, build your train so that the front of the train is facing down the X axis. (This means that the front of the train is visible in the front view, etc..) When it spawns it will automatically rotate to face the next path_track on the path.
Bug.png Bug: Due to poor coding, the Reverse and StartBackward may not function correctly if the New Train Speed property in the involved path_track entities is set to 0. The train may fail to reverse, jamming in place or moving in the wrong direction. To solve this issue, some or all of the path_tracks must have their New Train Speed variable set to a non-zero value.
Bug.png Bug: Trains stop short at a distance from their targets, regardless of speed. The higher the speed, the larger will be the distance it stops away from the path. At low speeds, this is negligible.
Warning.png Warning: The trains should not be parented. Instead, logic_measure_movement should be used to replicate the parenting, as it will not cause crashes or mismatches.

In code, it is represented by theCFuncTrackTrainclass, defined in thetrains.cppfile.



First Stop Target (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) (startspeed) <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) (speed) <integer>
The speed that the train will move at after it spawns, 0 = stopped.
Change Velocity (velocitytype) <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 (orientationtype) <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 (wheels) <integer>
Used for turning and stopping.
Tip.png Tip: Increase the value for smoother turns.
Height above track (height) <integer>
The height above the track that this train moves.
Bank Angle on Turns (bank) <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 (dmg) <integer>
The amount of damage this train does to entities that block it.
Minimum Light Level (_minlight) <string>
The minimum level of ambient light that hits this brush.
Move Sound (MoveSound) <sound>
A sound that is played (and looped) while the train is moving.
Move Ping Sound (MovePingSound) <sound>
A sound that is played more frequently as the train speeds up.
Start Sound (StartSound) <sound>
A sound played when the train starts moving.
Stop Sound (StopSound) <sound>
A sound played when the train stops moving.
Volume (10 = loudest) (volume) <integer>
Volume of the sound when the train is moving.
Min pitch (1-255, > 100 = higher) (MoveSoundMinPitch) <integer>
The sound pitch value that the train will approach as it comes to a stop.
Max pitch (1-255, > 100 = higher) (MoveSoundMaxPitch) <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 (MoveSoundMinTime) <float>
Minimum interval at which to play the move ping sound.
Max move sound interval (MoveSoundMaxTime) <float>
Maximum interval at which to play the move ping sound.


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.


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.


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.


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.

Distance between wheels is the distance in Hammer Units between the front axle and rear axle of your train. The rear axle moves the train and stays on the track. The front axle turns as it approaches path_tracks and does not stay on the track.



  • 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.png 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 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.


Fired when the train starts moving in either direction.
Fires continuously every tick when the train is currently moving to its next destination.
Warning.png Warning: In the default FGD, this is incorrectly listed as "OnNext", AND its description is completely wrong in the default FGD! (Fires when this train picks a new point to move towards (and just after OnStart))


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.