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Ai relationship.png

ai_relationship is a point entity available in all Source games. It sets a relationship type between two parties. These parties can be an NPC, an NPC class, or the player(s). Any object descending from CBaseCombatCharacter can have relationships, most notably NPCs and players.


Name Description
Hate (D_HT) Considers the target an enemy. Most NPCs will attack if possible, although NPCs that cannot attack may flee instead.
Fear (D_FR) Tries to avoid/flee from the target. Behavior varies across NPCs. Most NPCs will just run to cover out of the target's sight while NPCs with ranged weapons may run away while shooting at the feared enemy.
Bug.png Bug: The trace code used by melee damage doesn't detect D_FR entities and therefore NPCs can't use melee attacks against them. (they may try, but they won't do any damage)
Code Fix: This can be fixed by going to CTraceFilterMelee::ShouldHitEntity() and replacing pBCC->IRelationType( pEntity ) == D_HT with pBCC->IRelationType( pEntity ) <= D_FR, which correctly accounts for both D_HT and D_FR.
Like (D_LI) Considers the target a friend. NPCs will never intentionally attack these targets and NPCs with bits_CAP_FRIENDLY_DMG_IMMUNE (e.g. citizens) will not take any damage from NPCs or players that have this disposition towards them.
Note.png Note: Only the disposition of the NPC that deals the damage is considered by bits_CAP_FRIENDLY_DMG_IMMUNE. If a citizen friendly to the player (citizen D_LI to the player) is attacked by a player that doesn't consider them friendly (player not D_LI to the citizen), they will take damage and may not retaliate without additional programming.
Code:bits_CAP_FRIENDLY_DMG_IMMUNE can be added to a NPC with AddCapabilities and is usually appended in an NPC's Spawn() function, although it can be toggled at any time.
Neutral (D_NU) Considers a target neutral. NPCs usually won't consider these targets at all, or at least not care about them as enemies or as allies. This is used for fauna like crows.
Tip.png Tip: Making a npc_citizen neutral to the player (but not the other way around) is used to prevent them from joining the player's squad.
Error (D_ER) This "error" disposition is used internally to determine if something went wrong in a relationship. Should not be used. NPC behavior mostly equivalent to neutral.[confirm]

Not available in <Half-Life: Source> <Counter-Strike: Source> <Day of Defeat: Source> <Left 4 Dead> <Left 4 Dead 2> <Counter-Strike: Global Offensive>.

Note.png Note: While ai_relationship does not exist in <Half-Life: Source> Half-Life: Source, the SetRelationship input works.

In code, it is represented by class CAI_Relationship, defined in ai_relationship.cpp.


  • 1: Notify subject of target's location
  • 2: Notify target of subject's location


Subject(s) (subject) <target_name_or_class>
The targetname or classname of the NPCs whose disposition will change.
Subject Class (subjectclass) <classname> (in all games since <Alien Swarm>)
As above, for classnames only.
Target(s) (target) <target_name_or_class>
The targetname or class name of the NPCs about whom the subject(s) will change their disposition towards.
Tip.png Tip: Use !player for the player.
Target Class (targetclass) <classname> (in all games since <Alien Swarm>)
As above, for classnames only.
Disposition (disposition) <choices>
The way the subject(s) should feel about the target(s)
  1. Hate
  2. Fear
  3. Like
  4. Neutral
Radius for subject (radius) <float>
Only NPCs within this distance of the entity will have their dispositions changed.
Disposition Priority (rank) <integer>
How much the subject(s) should Like/Hate/Fear the target(s). Higher priority = stronger feeling.
Start Active (StartActive) <boolean>
Apply this relationship as soon as the entity spawns?
Reciprocal (Reciprocal) <boolean>
Make the new disposition apply to the targets as well as the subjects.


Classname (classname) <string>
The classname defines the type of entity. Classnames can be changed using AddOutput, which will influence how the engine deals with the entity in certain circumstances.
Name (targetname) <string>
The name that other entities refer to this entity by.
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.
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. Every entity can be parented, even point entities. Entities which are parented will be forced to transition to the next map, such as from a trigger_transition. Some entities which aren't intended to be parented may not function correctly. phys_constraint can be used as a workaround to parenting.
Origin (X Y Z) (origin) <coordinates>
The position of this entity's center in the world. Rotating entities typically rotate around their origin.
Pitch Yaw Roll (X Y Z) (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.
Note.png Note: This works on brush entities, although Hammer doesn't show the new angles.
Flags (spawnflags) <integer>
Toggles features of an entity, its specific number is determined by the combination of flags added.
Response Contexts (ResponseContext) <string>
Pre-defined response system contexts for this entity. Format is key:value,key:value,.... Contexts may be filtered.
Effects (effects) <integer> !FGD
Combination of effect flags to use.
Local Time (ltime) <float> !FGD
The local time of the entity, independent of the global clock. Used mainly for physics calculations.
Next Think (nextthink) <float> !FGD
Amount of time before the entity thinks again.
Hammer ID (hammerid) <integer> !FGD
The entity's Hammer ID. Mainly used by plugins and debugging commands, such as ent_keyvalue. Can be manually assigned with the "hammerid" or "id" keyvalue. Entities spawned at run-time are not assigned any Hammer ID.
Disable for Xbox 360 (disableX360) <boolean> (in all games since <Left 4 Dead 2>) !FGD
If Yes, disables this entity on the Xbox 360 version of Source.
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. Try to avoid expensive operations in this function, as it may cause performance problems.
Lag Compensation (LagCompensate) <boolean> (in all games since <Left 4 Dead 2>) !FGD
Set to Yes to lag compensate this entity. Should be used very sparingly!
Is Automatic-Aim Target (is_autoaim_target) <boolean> (in all games since <Counter-Strike: Global Offensive>) !FGD
If set to 1, this entity will slow down aiming movement for consoles and joystick controllers when the entity is under the crosshairs.


Applies relationship changes. This will change all subject entities' relationships to all target entities.
Note.png Note: Once you fire ApplyRelationship, the entity is on until you send a RevertRelationship or RevertToDefaultRelationship input. During the time any entities that spawn who match the subject or target names will be affected.
Warning.png Warning: Unpredictable results may occur when two ai_relationship entities refer to the same set or subset of target or subject entities. This situation should be avoided.
Reverts relationship changes to what the relationship of the first one was at the time the ApplyRelationship input was called (or when this ai_relationship was spawned if Start Active is set).
Reverts relationship changes to the entities' default relationships, completely returning control of affected relationships to the code.


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.
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.
AddOutput <string>
Evaluates a keyvalue/output on this entity.
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.
DispatchEffect <string> (removed in <Left 4 Dead>) !FGD
Dispatches a special effect from the entity's origin. Removed and replaced entirely by the particle system since <Left 4 Dead>.
DispatchResponse <string> !FGD
Dispatches a response to the entity. See Response and Concept.
AddContext <string>
Adds to the entity's list of response contexts. Format is <key>:<value>.
RemoveContext <string>
Remove a context from this entity's list. The name should match the key of an existing context.
ClearContext <string>
Removes all contexts from this entity's list.
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.

See also