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ai_goal_follow

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Ai goal follow.png

ai_goal_follow is a point entity available in all Source Source games.

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January 2024

It makes the target NPCs follow another object or the player at a configurable distance. NPCs may react in some way if they can't path to their leader.

Note.pngNote:NPCs do not intelligently follow their leader. They will simply walk or run depending on distance directly towards it. If the followers happen to block a path, they will not move out of the way and the leading NPC will eventually give up trying to path. (Depends on Formation.)

This entity is not in Left 4 Dead Left 4 Dead 2.


In code, it is represented by theCAI_FollowGoalclass, defined in theai_behavior_follow.cppfile.

ConVars/Commands

Cvar/CommandParameters or default valueDescriptorEffect
ai_debug_follow00 disables, 1 enablesTells when an NPC is having trouble following their leader. Requires developer 1. Does not function. [confirm]
ai_follow_use_points10 disables, 1 enables
Blank image.pngTodo: Effect description.
ai_follow_use_points_when_moving10 disables, 1 enables
Blank image.pngTodo: Effect description.

Keyvalues

Target Entity (goal) <string>
The name of the entity that the NPCs should follow. If this value is blank, NPCs will follow the player, if they are friendly towards them.
Formation (Formation) <choices>
How close to the target the NPCs should follow.
  • 0: Close circle
  • 1: Medium Circle
  • 2: Wide circle
  • 3: Sidekick
  • 4: Vortigaunt
Blank image.pngTodo: What exactly do 3 and 4 do?

AI_GoalEntity:

Actor(s) to affect (actor) <target_name_or_class>
The targetname or classname of any NPCs that will be included in this goal. Wildcards are supported.
Search Type (SearchType) <choices>
What the Actor(s) to affect keyvalue targets by.
  • 0: Entity Name
  • 1: Classname
Start Active (StartActive) <boolean>
Set if goal should be active immediately.

Base:
Name (targetname) <string>
The name that other entities use to refer to this entity.
Parent (parentname) <targetname>
Maintain the same initial offset to this entity. An attachment point can also be used if separated by a comma at the end. (parentname [targetname],[attachment])
Tip.pngTip:Entities transition to the next map with their parents
Tip.pngTip:phys_constraint can be used as a workaround if parenting fails.
Origin (X Y Z) (origin) <coordinates>
The position of this entity's center in the world. Rotating entities typically rotate around their origin.
Note.pngNote:Hammer does not move the entities accordingly only in the editor.
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.pngNote:This works on brush entities, although Hammer doesn't show the new angles.
Classname (classname) <string> !FGD
Determines the characteristics of the entity before it spawns.
Tip.pngTip:Changing this on runtime still has use, like making matching an entry in S_PreserveEnts will persist the entity on new rounds!
Flags (spawnflags) <integer> !FGD
Toggles exclusive features of an entity, its specific number is determined by the combination of flags added.
Effects (effects) <integer> !FGD
Combination of effect flags to use.
Entity Scripts (vscripts) <scriptlist> (in all games since Left 4 Dead 2) (also in Team Fortress 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. Scripts executed on the worldspawn entity will be placed in root scope.
Think function (thinkfunction) <string> (in all games since Left 4 Dead 2) (also in Team Fortress 2)
Name of the function within this entity's script that'll be called automatically every 100 milliseconds, or a user-defined interval if the function returns a number. 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.

Inputs

OutsideTransition  (in all games since Half-Life 2: Episode One) !FGD
Usually this is automatically done by a trigger_transition when the map changes, but it can be done manually as well. It sends the entity into a "dormant" state where it is disabled even though the entity may still think it is active. This is done in the case that the player decides to go back to a previous map, where the entity will then become non-dormant again and ensure NPCs continue to follow. Only available for the HL2 Episodes and Portal.

AI_GoalEntity:

Activate
Make the goal active if it wasn't already. NPCs will begin taking orders.
Deactivate
Make goal inactive.
UpdateActors  !FGD
Tell the goal entity to re-check Actor(s) to affect in case any disappeared, or any new NPCs spawned.[confirm]

Base:
AddContext <string>
Adds to the entity's list of response contexts. See Context.
AddOutput <string>
Assigns a new keyvalue/output on this entity. For keyvalues, some rely on extra necessary code to be ran and won't work if its simply just changed through this input. There is a strict format that must be followed:
// Format of changing KeyValues: "AddOutput [key] [value]"
//// Raw text:
"OnUser1" "!self,AddOutput,targetname new_name"

// Format of adding an Output: "AddOutput {targetname}:{inputname}:{parameter}:{delay}:{max times to fire, -1 means infinite}"
//// Raw text:
"OnUser1" "!self,AddOutput,OnUser1:SetParent:!activator:0.0:-1"
// Arguments can be left blank, but the empty blank should still be contained.
//// Raw text:
"OnUser1" "!self,AddOutput,OnUser1:ClearParent::0.0:-1"
ClearContext
Removes all contexts from this entity's list.
ClearParent
Removes this entity from the the movement hierarchy, leaving it free to move independently.
FireUser1 to FireUser4
Fires the respectiveOnUseroutputs; see User Inputs and Outputs.
Kill
Removes this entity and any entities parented to it from the world.
KillHierarchy
Functions the same as Kill, although this entity and any entities parented to it are killed on the same frame, being marginally faster thanKillinput.
RemoveContext <string>
Remove a context from this entity's list. The name should match the key of an existing context.
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.
Use  !FGD
Same as a player invoking +use; no effect in most cases.
DispatchResponse <string> !FGD
Dispatches a response to the entity. See Response and Concept.
DispatchEffect <string> (removed since Left 4 Dead) !FGD
Dispatches a special effect from the entity's origin; See also List of Client Effects. Replaced by the particle system since Left 4 Dead.
RunScriptFile <script> (in all games since Left 4 Dead 2) (also in Team Fortress 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) (also in Team Fortress 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.
Icon-Bug.pngBug:In Hammer, using string arguments will corrupt the VMF file's structure, making the file unviewable for the next Hammer session.
Note.pngFix:Remove the string argument manually with a text editor.
Note.pngNote:Team Fortress 2 Backtick characters ` are replaced with quotation marks at runtime, allowing quotation marks to be used when normally not possible.
CallScriptFunction <string> (in all games since Left 4 Dead 2) (also in Team Fortress 2) !FGD
Calls a VScript function defined in the scope of the receiving entity.
TerminateScriptScope  (only in Team Fortress 2) !FGD
Destroys the script scope of the receving 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.

Outputs

Base:

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.