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{{wrongtitle|title=phys_lengthconstraint}}
{{tabs|main=source|source=1|source2=1|phys_lengthconstraint}}
[[Category:Entities]]
{{LanguageBar}}
==Entity Description==
{{CD|CPhysLength|file1=physconstraint.cpp|CPhysConstraint}}
'''Entity Name:''' phys_lengthconstraint
{{this is a|point entity|name=phys_lengthconstraint}} It is a [[:Category:Constraints|constraint]] that restricts the maximum (and optionally minimum) distance two objects are allowed to be from each other. It is most often used to simulate [[move_rope|rope]], though it does not support the "stiffening" of rope attachment points that can be observed in reality; an object can rotate a full 360° in fact, clipping right through any rope that may be attached.
This is a physical [[constraint]] between two physically simulated objects. If one object is not specified then the respective end of the [[constraint]] will be anchored to the [[world]].


This is imporantant to note:
{{Important|The constraint is calculated not from the origin/mass centre of the attached entities, but from the entity's own origin and the location of its Hammer [[Hammer_View_Menu#Show_Helpers|helper]] (attachpoint). Be sure to place them appropriately or the game will crash!}}
* Object 1 is [[anchored]] to the centerpoint of the [[phys_lengthconstraint]].
* Object 2 is [[anchored]] to the origin of the [[phys_lengthconstraint]].
* Objects will rotate around their ends with this entity. If you dont want them to rotate around their ends use a different [[constraint]].


[[Category:Entities]]
The constraint can be made rigid with its [[#Flags|second spawnflag]]. It then behaves much like a [[phys_ballsocket]], except that the objects can freely rotate around their ''own'' centres.
----
===See Also===


[[List of entities]]
{{Official vmf example|sdk_phys_lengthconstraint.vmf}}
 
{{tip|To suspend a standard wooden crate and allow the player to break its constraint by pulling, use a force limit of 1350.}}
 
== Keyvalues ==
{{KV Targetname}}
{{KV|Additional Length|intn=addlength|float|Elasticity of the constraint. It is allowed to stretch this many units over or under its maximum and minimum length. The constraint will try to spring back to its preferred length.}}
{{KV|Minimum Length|intn=minlength|float|Minimum distance between origin and attachpoint. Irrelevant if the constraint is rigid. Default is 0.}}
{{KV|Attached object 2 point|intn=attachpoint|vecline|The second end of the constraint (the other is the origin). The second attached entity will be [[phys_constraint|rigidly constrained]] to this location, and the first to the origin.}}
{{KV TwoObjectPhysics}}
 
== Flags ==
{{Fl TwoObjectPhysics|Keep Rigid}}
 
== Inputs ==
{{I TwoObjectPhysics}}
 
== Outputs ==
{{O TwoObjectPhysics}}
 
[[Category:Constraints|L]]

Latest revision as of 06:34, 29 April 2025

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C++ Class hierarchy
CPhysLength
↳CPhysConstraint
↳CLogicalEntity
↳CServerOnlyEntity
↳CBaseEntity
C++ physconstraint.cpp

phys_lengthconstraint is a point entity available in all Source Source games. It is a constraint that restricts the maximum (and optionally minimum) distance two objects are allowed to be from each other. It is most often used to simulate rope, though it does not support the "stiffening" of rope attachment points that can be observed in reality; an object can rotate a full 360° in fact, clipping right through any rope that may be attached.

Icon-Important.pngImportant:The constraint is calculated not from the origin/mass centre of the attached entities, but from the entity's own origin and the location of its Hammer helper (attachpoint). Be sure to place them appropriately or the game will crash!

The constraint can be made rigid with its second spawnflag. It then behaves much like a phys_ballsocket, except that the objects can freely rotate around their own centres.

PlacementTip.pngExample:See steamapps/common/sourcesdk_content/hl2/mapsrc/sdk_phys_lengthconstraint.vmf for example use (comes with Source SDK installation [confirm])
Tip.pngTip:To suspend a standard wooden crate and allow the player to break its constraint by pulling, use a force limit of 1350.

Keyvalues

Name (targetname) <string>[ Edit ]
The name that other entities refer to this entity by, via Inputs/Outputs or other keyvalues (e.g. parentname or target).
Also displayed in Hammer's 2D views and Entity Report.
See also:  Generic Keyvalues, Inputs and Outputs available to all entities

Additional Length (addlength) <float>
Elasticity of the constraint. It is allowed to stretch this many units over or under its maximum and minimum length. The constraint will try to spring back to its preferred length.
Minimum Length (minlength) <float>
Minimum distance between origin and attachpoint. Irrelevant if the constraint is rigid. Default is 0.
Attached object 2 point (attachpoint) <vector>
The second end of the constraint (the other is the origin). The second attached entity will be rigidly constrained to this location, and the first to the origin.

TwoObjectPhysics:

Entity 1 (attach1) <targetname>
Entity 2 (attach2) <targetname>
The entities to constrain. Leave one or the other field blank to constrain to the world.
Note.pngNote:Only one entity will be constrained, even if several share the given targetname.
Constraint System Manager (constraintsystem) <targetname>
A phys_constraintsystem that this constraint should be a part of. This avoids the "jiggling" caused by constraints applied to the same set of entities fighting with each other.
Force Limit to Break (forcelimit) <float>
Impact force required to break the constraint, in pounds. 0 means infinite. A way of calculating this is to set it to the weight of an object that would break the constraint if it were resting on its objects.
Torque Limit to Break (torquelimit) <float>
Torque required to break the constraint, in pounds*inches. 0 means infinite. A way of calculating this is to multiply any reference mass by the resting distance (from the center of mass of the object) needed to break the constraint.
Play Sound on Break (breaksound) <string>
A sound played when the constraint is broken.
Follow teleport distance (teleportfollowdistance) <float>
If one constrained object teleports more than this many units away, the other will teleport with it.


Flags

No Collision until break : [1]
Keep Rigid : [2]
Start inactive : [4]
Change mass to keep stable attachment to world : [8]
Do not connect entities until turned on : [16]

Inputs

TwoObjectPhysics:
Break
Force the constraint to break.
TurnOn
Enable the constraint; do this if the constrained objects don't exist when it spawns. Note that broken constraints cannot be turned back on as they have been deleted.
TurnOff
Disable the constraint.

Outputs

TwoObjectPhysics:
OnBreak
Fired when the constraint breaks.
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