npc_headcrab

GoldSrc

Half-Life: Source

Source Engine

Source 2

edit

Class hierarchy
CHeadcrab ↳CBaseHeadcrab ↳CAI_BaseNPC ↳CBaseCombatCharacter ↳CBaseFlex ↳CBaseAnimatingOverlay ↳CBaseAnimating ↳CBaseEntity
npc_headcrab.cpp

npc_headcrab is a point entity available in Half-Life 2 series and Black Mesa. These are the classic, slow-moving headcrabs. They attack by jumping at the player's head and inflict a nominal amount of damage. Almost any weapon can dispatch them easily.

Commonly found attached to a zombie host body, they will detach if that host is sufficiently damaged below the head.

There are several other headcrab variants and associated zombie types.

See also env_headcrabcanister which is a mortar shell containing a payload of headcrabs. The mortar shell inflicts damage within a radius of where it lands and releases headcrabs after impact. Triggers and entity options offer control over impact damage and when the headcrabs are released, among other options.

Placement Tip:Classic headcrabs can be paired with their fast-moving or poisonous relatives to make it more interesting.

Placement Tip:Avoid the cliche of placing headcrabs in vents; they would likely be more of an annoyance than an improvement on gameplay.

Bug:If a headcrab is burrowed, using inputs or command that would kill it like sethealth 0 or npc_kill npc_headcrab does not work. They get ignored and the headcrab's health doesn't change.  (tested in: Half-Life 2)

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

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

BaseHeadcrab:

Start burrowed (startburrowed) <boolean>

Should this npc start burrowed? Will unburrow via input or if an enemy gets near.

BaseNPC keyvalues

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

Start hidden : [65536]
Start hanging from ceiling : [131072]

BaseNPC 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.

Inputs

Burrow  !FGD

Burrow. If no burrow points within 512 units, does nothing.

BurrowImmediate  !FGD

Burrow immediate.

Unburrow  !FGD

Unburrow.

StartHangingFromCeiling

Start hanging from ceiling.

DropFromCeiling

Drop if hanging from ceiling.

BaseNPC 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

BaseNPC Outputs

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.

Dedicated Console Variables

Only in Black Mesa 2012. Requires this texture to display properly as the texture has been removed.

Cvar/Command	Parameters or default value	Descriptor	Effect
sk_headcrab_health		int	A headcrab's spawn health.
sk_headcrab_melee_dmg		int	Melee damage.
g_debug_headcrab		bool	Toggle headcrab debugging.
sk_headcrab_min_jump_dist		int	Headcrab min jump distance. Only in Black Mesa 2012.
sk_headcrab_max_jump_dist		int	Headcrab max jump distance. Only in Black Mesa 2012.
sv_headcrab_can_latch_on_player		bool	Toggles headcrab's ability to attach player's head (if player catches it with head).

See also

• env_headcrabcanister