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.

Note: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.)

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]