The damage effect tag determines the results of damage application in a wide range of use cases, including but not limited to: projectile impacts, detonations, melee attacks, falling, and vehicle collisions. They can be part of an effect.

A damage effect is not strictly about applying shield and health damage to units; these tags can have an area of effect, impart acceleration on additional objects like items and projectiles too, and cause screen effects like colour flashes and shaking.


When damage to shields exceeds the currently shield vitality, damage carries over to health. When this occurs, the damage multiplier of the shields still carries over to the health damage. This even occurs if the current shield vitality is 0. The result is that the initial carryover health damage may be higher than expected with weapons like the plasma rifle, which have a 2x shield multiplier. Subsequent shots will impact the body and use its material type modifiers instead.

Impact damage formula

When applying a damage_effect as a projectile impact, the game may take projectile fields into account as well. When air or water damage ranges are set, the projectile's travel distance will scale damage between damage lower bound and a random selection between upper bounds. If air damage range is not set, it always uses the random high bound.

Firstly, the game randomly picks a value between the two upper bounds (will always be the same if both values are the same). Up to the projectile minimum air damage range, 100% unmodified damage is applied. However, past the minimum and up to the maximum damage ranges, damage linearly scales to the lower bound. Past this distance, the projectile disappears (but does not detonate).

In pseudocode, and assuming within max range:

//falloff is 0 to 1 based on travel distance between air damage ranges
let falloff = max(0,
  (travel_distance - air_damage_min) /
  (air_damage_max - air_damage_min)

//given a random_value between 0 and 1, interpolate between the two high bounds
let upper_bound_delta = upper_bound_2 - upper_bound_1;
let random_upper_bound = upper_bound_1 + random_value * upper_bound_delta;

//interpolate between lower and random upper bound
let raw_damage = (
  falloff * lower_bound +
  (1.0 - falloff) * random_upper_bound
//finally, damage is scaled by the multiplier for the impacted material
let damage_done = material_damage_multiplier * raw_damage;

Or, more visually:

Diagram of damage falloff for the shotgun

Related script functions and globals

The following are related functions that you can use in your scenario scripts and/or debug globals that you can enter into the developer console for troubleshooting.


(ai_print_damage_modifiers [boolean])

When an encounter is selected, damage modifiers are logged at the bottom of the screen.

(cheat_reflexive_damage_effects [boolean])

Any damage_effect applied to other characters, even dead ones, will appear on the player's screen regardless of who applied the damage. For example, if an Elite shoots a flood infection form, the player will see their screen flash blue and damage direction indicators appear. The player takes no actual damage. This can be helpful for testing visual effects.

(debug_damage [boolean])

When enabled, looking at any collideable object and pressing Space will display the object's body and shield vitalities on the HUD.

(debug_damage_taken [boolean])

Logs damage to the player as messages at the bottom of the screen. Includes body and shield vitality and the damage source.

Structure and fields

Field Type Comments
radius Bounds
  • Unit: world units

The minimum radius determines the sphere in which damage is 100% of damage upper bound. Damage fades linearly to damage lower bound at the maximum radius. Outside the maximum radius, 0 damage is dealt. The aoe core radius field does not affect this calculation.

Field Type Comments
min float
max float
cutoff scale float
  • Min: 0
  • Max: 1
flags bitfield
Flag Mask Comments
do not scale damage by distance 0x1
type enum
Option Value Comments
none 0x0
lighten 0x1
darken 0x2
max 0x3
min 0x4
invert 0x5
tint 0x6
priority enum
Option Value Comments
low 0x0
medium 0x1
high 0x2
duration float
  • Unit: seconds
fade function enum
Option Value Comments
linear 0x0
early 0x1
very early 0x2
late 0x3
very late 0x4
cosine 0x5
maximum intensity float
  • Min: 0
  • Max: 1
  • Default: 1
color ColorARGB
Field Type Comments
alpha float
red float
green float
blue float
low frequency vibrate frequency float
  • Min: 0
  • Max: 1
low frequency vibrate duration float
  • Unit: seconds
low frequency vibrate fade function enum?
high frequency vibrate frequency float
  • Min: 0
  • Max: 1
high frequency vibrate duration float
  • Unit: seconds
high frequency vibrate fade function enum?
temporary camera impulse duration float
  • Unit: seconds
temporary camera impulse fade function enum?
temporary camera impulse rotation float
temporary camera impulse pushback float
  • Unit: world units
jitter Bounds?
  • Unit: world units
permanent camera impulse angle float
camera shaking duration float
  • Unit: seconds

Controls how long camera shaking lasts. In H1CE and H1CE, short camera shakes (0.05) get skipped occasionally at high FPS since this feature is still tied to frame rate. This is fixed and interpolated by Chimera and by H1A natively.

camera shaking falloff function enum?
camera shaking random translation float
  • Unit: world units
camera shaking random rotation float
camera shaking wobble function enum
Option Value Comments
one 0x0
zero 0x1
cosine 0x2
cosine variable period 0x3
diagonal wave 0x4
diagonal wave variable period 0x5
slide 0x6
slide variable period 0x7
noise 0x8
jitter 0x9
wander 0xA
spark 0xB
camera shaking wobble period float
  • Unit: seconds
  • Default: 1
camera shaking wobble weight float
sound TagDependency: sound
breaking effect forward velocity float
  • Unit: world units per second
breaking effect forward radius float
  • Unit: world units
breaking effect forward exponent float
breaking effect outward velocity float
  • Unit: world units per second
breaking effect outward radius float
  • Unit: world units
breaking effect outward exponent float
damage side effect enum
Option Value Comments
none 0x0
harmless 0x1
lethal to the unsuspecting 0x2
emp 0x3

Completely depletes target units' energy shields, no matter their amount.

damage category enum
Option Value Comments
none 0x0
falling 0x1
bullet 0x2
grenade 0x3
high explosive 0x4
sniper 0x5
melee 0x6
flame 0x7
mounted weapon 0x8
vehicle 0x9
plasma 0xA
needle 0xB
shotgun 0xC
damage flags bitfield
Flag Mask Comments
does not hurt owner 0x1
can cause headshots 0x2

If enabled, any headshot against an unshielded enemy will kill it regardless of the amount of damage inflicted. Even a 1-damage pistol still instantly kills a Hunter because of this flag. It is an instant kill even if the shield threshold is met with a headshot (after shields have been reduced to 0 by the damage effect but health is full). For example, even though the pistol deals 25 damage and players have 75 shield vitality, if the final shot is a headshot the player dies. Although there is also a can cause multiplayer headshots flag, it has a separate meaning and this flag applies to both SP and MP. A model's headshot area is determined by its head region.

pings resistant units 0x4
does not hurt friends 0x8
does not ping units 0x10
detonates explosives 0x20

If enabled, causes the effect to trigger the explosion of dropped grenades within its radius, used for explosion chaining. This only applies to maps loaded in singleplayer mode. Note that the item receiving damage (e.g. the grenade equipment) must also have its destroyed by explosions flag enabled. If the grenade has been placed within the scenario in Sapien, the does accelerate flag will also need to be checked in the properties window.

only hurts shields 0x40
causes flaming death 0x80
damage indicators always point down 0x100
skips shields 0x200
only hurts one infection form 0x400
can cause multiplayer headshots 0x800

Applies a 2x damage multiplier to headshots in multiplayer (based on how the map was loaded, not scenario type). This multiplier stacks with material modifiers below, so for example a cyborg armor modifier of 2 with this flag enabled results in a 4x headshot damage modifier. A model's headshot area is determined by its head region.

infection form pop 0x1000
damage aoe core radius float
  • Unit: world units

Objects within this radius will be damaged regardless of obstructions in the BSP. Outside this radius, there must be a line of sight between the effect and target. Contrary to the Guerilla tooltip, this field does not determine if the damage has an area of effect; see radius.

damage lower bound float

Sets the minimum amount of damage done when this effect is applied in a scaled way. For example, projectiles can have min and max damage ranges for air and water.

damage upper bound Bounds?

Maximum damage will be randomly chosen from this range.

damage vehicle passthrough penalty float
damage active camouflage damage float
damage stun float
  • Min: 0
  • Max: 1
damage maximum stun float
  • Min: 0
  • Max: 1
damage stun time float
  • Unit: seconds
damage instantaneous acceleration float

Controls how much moveable objects are accelerated by this effect. This is scaled by the acceleration scale field of object.

dirt float
sand float
stone float
snow float
wood float
metal hollow float
metal thin float
metal thick float
rubber float
glass float
force field float
grunt float
hunter armor float
hunter skin float
elite float
jackal float
jackal energy shield float
engineer skin float
engineer force field float
flood combat form float
flood carrier form float
cyborg armor float

Also labeled as simply cyborg in Guerilla. Used to modify damage on all body parts of the cyborg (spartan) biped.

cyborg energy shield float

Damage modifier for the "cyborg energy shield" material type. See the shield material type field of the unit's model_collision_geometry tag.

human armor float
human skin float
sentinel float
monitor float
plastic float
water float
leaves float
elite energy shield float

Damage modifier for the "elite energy shield" material type. See the shield material type field of the unit's model_collision_geometry tag. Note that this field receives a hard-coded singleplayer adjustment at map compile time for the pistol's damage effect.

ice float
hunter shield float


Thanks to the following individuals for their research or contributions to this topic:

  • Conscars (Checking multiplayer headshot flag and radii behaviour)
  • gbMichelle (Reverse engineering the damage formula)
  • Kavawuvi (Invader tag definitions)
  • King Feraligatr (Testing EMP effect on shields)
  • Mortis (Explaining headshot damage and bleedthrough)
  • MosesOfEgypt (Tag structure research)