Sniper
npc_sniper is a point entity available in 
Half-Life 2, 
Half-Life 2: Episode One, 
Half-Life 2: Episode Two, 
Half-Life 2: Deathmatch, and 
Black Mesa.
In Half-Life 2 games, this is a Combine soldier with an overwatch sniper rifle which uses blue laser sight, making it capable of extreme accuracy at extreme range.
In Black Mesa, this is a HECU marine with a sniper rifle which uses red laser sight.
The npc_sniper does not actually have its own model - rather, it uses a Combine soldier (or HECU marine in Black Mesa) model in-game (if its Hidden flag is not set) playing its idle animation, with the rifle's laser coming from the center of the hull. Only explosions and burning damage can hurt the sniper.
The sniper doesn't turn on his sight until after he sees the player or an NPC within an acceptable range and angle, and will turn it off again after he is done. He will prioritize the player over any other target. If he loses track of the player, he will get frustrated and shoot three rounds at the area where the player was last seen, often targeting smaller prop_physics (like soda cans, melons, melon chunks, cinderblocks, ...) but not large prop_physics (like soda machines). He will then resume to targeting any other visible targets.
Tip:The sniper will pay attention to info_snipertargets if ordered to (with the SweepTarget, SweepTargetHighestPriority or SweepGroupRandomly inputs).
AltNames: This entity is also tied to proto_sniper. 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.
- Patience Radius
(radius) <integer>
- Sniper will hold fire until the target is within this radius. After that, sniper will always attack, even if the target retreats outside of this radius.
- Initial Misses
(misses) <integer>
- How many times to miss a target on purpose before beginning to fire accurately.
- Beam Brightness (0 to 255)
(beambrightness) <integer>
- How bright the laser sight beam should be. (0 - 255)
- Shoot zombies in chest
(shootZombiesInChest) <boolean>
- If true, aim for chest instead of headcrab. Useful when at great distance and height.
- Bullet shield distance
(shielddistance) <float>
- !OBSOLETE
- Bullet shield radius
(shieldradius) <float>
- !OBSOLETE
- Paint interval
(PaintInterval) <integer>
- Sniper will keep a target painted for this many seconds before shooting. 'Faster Shooting' sniper flag multiplies this by 0.75.
- Paint interval variance
(PaintIntervalVariance) <integer>
- When shooting at NPCs, a random number between 0 and this is added to PaintInterval for every shot.
BaseNPC keyvalues
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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: HateD_FR: FearD_LI: LikeD_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.
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Flags
BaseNPC flags
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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.
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Hidden : [65536]
- The sniper will not have a model while alive. Should be checked.
Laser Viewcone : [131072]
No Corpse : [262144]
- The sniper leaves no corpse.
Start Disabled : [524288]
- The sniper starts disabled
Faster shooting : [1048576]
Confirm:Doesn't seem to do anything?No sweep away from target : [2097152]
- The sniper will not reset it's aim after firing
Todo: No sweep away from target was missing from this page for over 10 years, is it absent in some games? Existence confirmed in 
and
Inputs
EnableSniper- Enable Shooting.
DisableSniper- Disable Shooting.
SetDecoyRadius <integer>- Set Decoy Radius.
SweepTarget <targetname>- Makes the sniper sweep to an info_snipertarget specified in the parameter, with a behavior specified in the properties of the info_snipertarget.
Note:Using this input to set the sniper's target to anything enclosed or touching a Block LOS textured brush may cause the map to crash.
SweepTargetHighestPriority <targetname>- Same as SweepTarget, but the sniper will prioritize sweeping to this target above targeting anything else, including the player.
SweepGroupRandomly <string>- The sniper will take alternating shots at info_snipertargets belonging to a specific group (specified in its parameter) until interrupted by an NPC. (Group associations are declared in the Group Name property of these targets.)
StopSweeping- Stop any target sweeping operation started by entity I/O
ProtectTarget <targetname>- Protect the specified target. The sniper will attempt to shoot the enemy nearest the protect target at all times.
BaseNPC inputs
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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: HateD_FR: FearD_LI: LikeD_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.
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Outputs
OnShotFired- Sniper's current enemy.
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.
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See also
Class hierarchy
Bug:it's the only NPC that doesn't use server side ragdolls in 
Black Mesa 2012. [todo tested in?]