ai_goal_follow

ai_goal_follow is a point entity available in all Source games except Left 4 Dead series.

class hierarchy
CAI_FollowGoal defined in ai_behavior_follow.cpp ↳CAI_GoalEntity ↳CBaseEntity

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.

NoteNPCs 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.)

ConVars/Commands

Cvar/Command	Parameters or default value	Descriptor	Effect
ai_debug_follow	0	0 disables, 1 enables	Tells when an NPC is having trouble following their leader. Requires developer 1. Does not function. [confirm]
ai_follow_use_points	1	0 disables, 1 enables	Todo: Effect description.
ai_follow_use_points_when_moving	1	0 disables, 1 enables	Todo: Effect description.

Keyvalues

Name (targetname) <string>

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

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 (mostly same as Medium Circle, but a bit looser range (120 to 160 units) and tries to keep LOS to the follow target. Used by Alyx for the majority of EP2)
• 4: Vortigaunt (mostly same as Sidekick, but operates more freely in combat (can chase enemies within a larger range from the follow target). Used by the Lone Vort in EP2)

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.

Inputs

OutsideTransition  (in all games since ) !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]