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How a character takes damage

Health, damage and hit reactions are one layer, and it is the same layer on the player, on the AI and on the practice dummy. Three components do the work, and only one of them ever removes a hit point.

Component What it owns
BP_VitalsSystem The vitals themselves: health, stamina, anything you add. The only thing in the project that subtracts.
BP_HitReactionManager The physical reaction. The body bends where it was hit, then recovers.
BP_FallDamageComponent Turns a fall into an amount of damage and sends it.

All three live in Content/TheLastTemplate/Blueprints/ActorComponents/.

BP_VitalsSystem holds a Vitals array, one row per vital, and each row points at a vital Data Asset. Two of those ship: DA_Vital_Health and DA_Vital_Stamina. See Change health and stamina, or add a new vital.

Damage arrives through Unreal's own damage events

You do not need a custom function to hurt something in this template. The standard nodes work:

  • Apply Damage and Apply Radial Damage land on Event Any Damage.
  • Apply Point Damage lands on Event Point Damage, the only path that knows which bone was hit.

Both paths end at the same call, Remove Vital Amount on BP_VitalsSystem.

The two paths are kept apart by a damage type, Content/TheLastTemplate/Blueprints/Misc/DamageTypes/DT_PointHit.

Event Point Damage does three things Event Any Damage does not:

  1. it scales the damage by the bone that was hit,
  2. it stores the bone, the direction and the location of the hit on the character,
  3. it hands the hit to BP_HitReactionManager.

Warning

When you call Apply Point Damage yourself, set Damage Type Class to DT_PointHit. With any other damage type both events fire and the character loses health twice, once at full value and once scaled by the bone. Nothing warns you.

Radial damage has no handler of its own. An explosion reaches a character through Event Any Damage, so its amount is subtracted as written, with no bone multiplier and no procedural reaction.

Where bone multipliers come from

Event Point Damage calls Get Bone Damage, in Content/TheLastTemplate/Blueprints/Functions/BFL_DamageLibrary. It takes the base damage and the bone name and returns the damage to apply.

Bone Multiplier
head, neck_01, neck_02 5
spine_03, spine_04, spine_05 2
thigh_l, thigh_r, calf_l, calf_r 0.8
clavicle_l, clavicle_r 0.7
upperarm_l, upperarm_r, lowerarm_l, lowerarm_r 0.5
Hand_L, Hand_R, foot_l, foot_lr, ball_l, ball_r 0.4
spine_01, spine_02, Pelvis 1
any bone that is not listed 1

Those are the Unreal mannequin's bone names. foot_r is not among them, so a hit on the right foot is not matched and takes plain damage. A skeleton that names its bones differently falls through the same way, everywhere including the head, so add its bone names to Get Bone Damage if you retarget the template onto one.

What one removal actually does

Remove Vital Amount takes a vital type and an amount, and in that order it:

  • multiplies the amount by Damage Taken Multiplier before subtracting from health. It ships at 1. This is the field the damage resistance skill writes, and you can write it yourself, see Add or change a skill.
  • subtracts, and clamps the vital at 0.
  • fires On Health Damage. Bind to that dispatcher for screen effects, audio or anything of your own.

When health reaches 0 the component pauses the vital drain, turns Invulnerable on, sets Is Dead, and fires On Death. What the body does after that belongs to the character class. See Fall damage, death and the ragdoll.

Invulnerability is one flag for the whole actor

BP_VitalsSystem carries a single Invulnerable boolean. Not one per vital, not one per body part. Two functions drive it: Set Invulnerable State and Toggle Invulnerable State.

While it is on the character cannot die. The component switches it on itself the moment a character dies, so a body cannot be killed a second time.

What already has the setup

  • BP_PlayerCharacter, BP_NPCCharacter and BP_ZombieCharacter carry all three components and both damage events.
  • BP_Dummy carries BP_VitalsSystem and BP_HitReactionManager and no fall damage. It is the ragdoll test target.
  • BP_TrainingDummy is not a Character and has no vitals at all. It is two meshes on a physics constraint with one field, Impulse Per Damage. It moves when you hit it and that is all it does.

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