npc_antlion

npc_antlion is a point entity available in Half-Life 2, Half-Life 2: Episode One, Half-Life 2: Episode Two, and Half-Life 2: Deathmatch. It is a weak NPC that can burrow, and "fly" by jumping. The player can command them, provided that the antlion_allied global state is set and weapon_bugbait is equipped, otherwise they are hostile. In order for the player to be able to use the weapon_bugbait to call the antlions back, the "Follow target" key value on a npc_antlion_template_maker must be set to "!player". Their most common role in level design is that of cannon fodder. Antlions are blind, and navigate entirely by sound and smell. They can navigate by jumping and use the HULL_MEDIUM hull for navigation; this can sometimes make them hard to use.

Episode Two's acid-spitting Antlion Workers can be spawned by setting the "Worker Type" flag.

Tip:To repel Antlions from a chosen place, use prop_thumper or ai_sound.

Tip:Use npc_antlion_template_maker to efficiently monitor and respawn antlions on a continuous basis.

Note:Some keyvalues, spawnflags, effect flags, inputs, or outputs might not affect an NPC, based on the functionality and coding of the NPC.

Dedicated Console Variables

sk_antlion_health <int>

Antlion spawn health. Default: 30

sk_antlion_jump_damage <int>

Default: 5

sk_antlion_swipe_damage <int>

Default: 5

sk_antlion_air_attack_dmg <int>

Default: 10

g_debug_antlion <int>

Debug visualization.

Keyvalues

Start Burrowed ([todo internal name (i)]) <boolean>

If you want your antlion to start under the ground and dig up when you want.

Alert Radius ([todo internal name (i)]) <float>

Keep in mind that Antlions rely on sound, not sight.

Distance until eluded ([todo internal name (i)]) <integer>

Only available when "Burrow When Eluded" is flagged

Ignore Bugbait ([todo internal name (i)]) <boolean>

Useful for scripted sequences, in which player interference is undesirable.

Suppress unburrow effects ([todo internal name (i)]) <boolean>

Do not draw dust effects when unburrowing.

([todo internal name (i)]) <skin> !FGD

Affects regular Antlions' carapace colour. Same as a prop entity's Skin KV.

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BaseNPC keyvalues Expand

CBaseCombatCharacter: Relationship (Relationship) <string> !FGD <string|targetname or classname> <string|disposition> <int|rank> Changes whether this entity likes or dislikes certain other things. Used like the ai_relationship entity, with this entity as the subject. Values for disposition are: D_HT: Hate D_FR: Fear D_LI: Like D_NU: Neutral Physics Impact Damage Scale (physdamagescale) <float> Multiplier for damage amount when this entity is hit by a physics object. With a value of 0 the entity will take no damage from physics. CAI_BaseNPC: Target Path Corner (target) <targetname> The path_corner that this NPC will move to after spawning. Squad Name (squadname) <string> NPCs that are in the same squad (i.e., have matching squad names) will share information about enemies and will take turns attacking and covering each other. Hint Group (hintgroup) <string> Hint groups are used by NPCs to restrict their hint-node searching to a subset of the map's hint nodes. Only hint nodes with matching hint group names will be considered by this NPC. Hint Limit Nav (hintlimiting) <boolean> Limits NPC to using specified hint group for navigation requests. Does not limit local navigation. Sleep State (sleepstate) <choices> Holds the NPC in stasis until specified condition. See also Wake Radius and Wake Squad. 0: None 1: Waiting for threat 2: Waiting for PVS 3: Waiting for input, ignore PVS 4: Auto PVS 5: Auto PVS after PVS Wake Radius (wakeradius) <float> Auto-wake if player comes within this distance. Wake Squad (wakesquad) <boolean> Wake all of the NPCs squadmates if the NPC is woken. Enemy Filter (enemyfilter) <targetname> Filter entity to test targets against. Ignore unseen enemies (ignoreunseenenemies) <boolean> Prefers visible enemies, regardless of distance or relationship priority. DamageFilter: Damage Filter (damagefilter) <targetname> Name of the filter_damage_type entity that controls which entities can damage us.

Flags

ExpandBaseNPC flags 

Wait Till Seen : [1]

Prevents this NPC from seeing (or being seen) until it enters a player's viewcone.

Gag : [2]

Won't make IDLE sounds until it's angry.

Fall to ground (unchecked means teleport to ground) : [4]
Drop Healthkit : [8]

Causes this NPC to drop an item_healthvial upon dying.

Efficient : [16]

Don't acquire enemies or avoid obstacles

Wait For Script : [128]

Forces this NPC to "wait" in an idle state until it finishes playing a scripted_sequence.

Long Visibility/Shoot : [256]

By default, increases a NPC's sight range to 6,000 units and allows it to attack from anywhere within that distance.

Fade Corpse : [512]
Think outside PVS : [1024]

Allows this NPC to run its regular AI outside of any player's PVS.

Template NPC : [2048]

Marks this NPC as a template for entities like npc_template_maker. The NPC will not spawn on its own. This is not needed for point_template.

Do Alternate collision for this NPC (player avoidance) : [4096]

Note:This flag is disabled in episodic for player companions, because the StartScripting input does this.

Don't drop weapons : [8192]
Ignore player push : [16384] (in all games since )

Entity won't give way to player.

Burrow when eluded : [65535]
Use Ground Checks : [131072]
Worker Type : [262144] (in all games since )

Set this flag to spawn acid-spitting Antlion Workers instead of regular antlions.

Inputs

Unburrow, Burrow

Burrow from or into the ground.

BurrowAway

Burrow and remove yourself.

FightToPosition <targetname>

Try to reach the given entity.

StopFightToPosition

Stop trying to reach an entity.

EnableJump, DisableJump

Allow/disallow jumping unless absolutely needed for navigation.

IgnoreBugbait, HearBugbait

Whether to respond to weapon_bugbait.

JumpAtTarget <targetname> !FGD

The antlion will attempt to jump through or at the target.

ExpandBaseNPC inputs 

CAI_BaseNPC:

ActivateSpeedModifier  !FGD

DisableSpeedModifier  !FGD

Break

Smash into pieces. If this is not possible, disappear.

BecomeRagdoll  (in all games since )

Remove itself and instantly become a ragdoll with zero force (just go limp). OnDeath, etc. outputs will NOT be fired.

ForceInteractionWithNPC <string> <string>  (in all games since )

Force the NPC to use a dynamic interaction with another NPC. Syntax is <targetname> <dynamic interaction>.

ForgetEntity <targetname>

Clears out the NPC's knowledge of a named entity.

UpdateEnemyMemory  (in all games since )

Update (or create) this NPC's memory of of the given entity.

GagEnable

GagDisable

Gagged NPCs won't speak (or moan, caw, etc.) unless made to be a choreographed scene.

HolsterWeapon  (in all games since )

UnholsterWeapon  (in all games since )

Force the NPC to holster or unholster their weapon. Ignored if the NPC is scripting or if the NPC doesn't use weapons.

HolsterAndDestroyWeapon  (in all games since )

Same as HolsterWeapon, except the weapon is destroyed once it has been concealed.

IgnoreDangerSounds <float>

Ignore danger sounds for the specified number of seconds.

InsideTransition  !FGD

OutsideTransition  !FGD

SetBodyGroup <integer>

HACK: Sets this NPC's body group (from 0–n).

SetEnemyFilter <string>

SetHealth <integer>

Set the NPC's health.

SetMaxLookDistance <float> (only in )

Sets the maximum look distance for the NPC. Defaults are 2048 and 6000 for long range NPCs.

SetRelationship <string|targetname or classname> <string|disposition> <int|rank>

Changes whether this NPC likes or dislikes certain others. Used like the ai_relationship entity, with this NPC as the subject.

Values for disposition are:

• D_HT: Hate
• D_FR: Fear
• D_LI: Like
• D_NU: Neutral

SetSquad <string>

Change the name of this NPC's squad. Leaving the parameter blank will remove the NPC from any existing squad.

StartScripting

StopScripting

Enter/exit scripting state, where NPCs ignore a variety of stimulus that would make them break out of their scripts. They ignore danger sounds, ignore +Use, don't idle speak or respond to other NPCs' idle speech, and so on.

Wake

Wakes up the NPC if it is sleeping.

CBaseCombatCharacter:

KilledNPC  !FGD

Tells the entity it killed something. Despite the name, this can include a player. This input will be automatically sent by the victim when they die.

physdamagescale <float>

Scales damage energy when this character is hit by a physics object. With a value of 0 the NPC will take no damage from physics.

DamageFilter:

SetDamageFilter <string>

Sets the entity to use as damage filter. Pass in an empty string (no parameter) to clear the damage filter.

Outputs

OnReachedFightGoal

Fires when the antlion reaches his specified fight-to location.

OnUnBurrowed

Fires when the antlion unburrows.

BaseNPC Outputs Expand

OnDamaged Fired when this NPC takes damage (!activator is the damage inflictor). OnDamagedByPlayer Fired when this NPC is hurt by a player (!activator is the attacker or vehicle driver [if friendly fire]). OnDamagedByPlayerSquad Fired when this NPC is hurt by a player OR by one of the player's squadmates (!activator is the attacker or vehicle driver [if friendly fire]). OnDeath Fired when this NPC is killed (!activator is the killer). OnDenyCommanderUse Fired when this NPC has refused to join the player's squad. OnForcedInteractionAborted Fired when the NPC aborts a forced interaction for some reason (target NPC died, couldn't be pathed to, etc.). OnForcedInteractionStarted Fired when the NPC starts a forced interaction. OnForcedInteractionFinished "NPCs in actbusies can no longer perform dynamic interactions." Todo: What does this mean? OnHalfHealth Fired when this NPC reaches half of its maximum health. OnHearCombat Fired when this NPC hears combat sounds. OnHearPlayer Fired when this NPC hears the player. OnHearWorld Fired when this NPC hears a sound (other than combat or the player). OnFoundEnemy <targetname> Fired when this NPC establishes line of sight to its enemy. OnLostEnemy Fired when this NPC loses its enemy. Usually due to the enemy being killed/removed, or because this NPC has selected a newer, more dangerous enemy. OnLostEnemyLOS Fired when this NPC loses line of sight to its enemy. OnFoundPlayer <targetname> Fired when this NPC establishes line of sight to its enemy, and that enemy is a player. OnLostPlayer Fired when this NPC loses its enemy, and that enemy was a player. Usually due to the enemy being killed/removed, or because this NPC has selected a newer, more dangerous enemy. OnLostPlayerLOS Fired when this NPC loses line of sight to its enemy, and that enemy is a player. OnSleep Fired when this NPC enters a sleep state. OnWake Fired when this NPC comes out of a sleep state.

See also

• Mapping with Antlions
• npc_antlion_template_maker
• npc_antlionguard