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Revision as of 10:20, 22 March 2012 by Nullptr (talk | contribs) (Added it to [[Category:Constraints] because it's a VPhysics constraint.)
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phys_spring is a point entity available in all Source games. It is a physically simulated spring. length is what's known as the "natural spring length". This is how long the spring would be if it was at rest (nothing hanging on it or attached). When you attach something to the spring, it will stretch longer than its natural length. The amount of stretch is determined by the spring constant constant. The larger the spring constant the less stretch in the spring.


Entity 1 <targetname>
First entity to attach.
Entity 2 <targetname>
Second entity to attach.
Spring Axis <vector>
Use the helper. Drag it out to match the virtual spring.
Spring Length <string>
How long the spring would be if it was at rest (nothing hanging on it or attached). 0 means the length of the brush.
Spring Constant <string>
Stiffness of the spring. The larger the number the less the spring will stretch.
Damping Constant <string>
How much energy the spring loses. The larger the number, the less bouncy the spring.
Relative Damping Constant <string>
The amount of energy the spring loses proportional to the relative velocity of the two objects the spring is attached to.
Break on Length <string>
If the spring's length ever exceeds this length, the spring breaks.


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.


  • 1 : Force only on stretch


SetSpringConstant <float>
Set the Spring Constant.
SetSpringLength <float>
Set the Spring Length.
SetSpringDamping <float>
Set the Spring Damping.


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.



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.