Client RPC — call a function on a specific client from the server

Custom Event → Replicates = 'Run On Owning Client'. Only executes on the client that owns this actor. Use for player-specific UI updates, messages, sounds.

Multiplayer: Server RPC for damage, Multicast RPC for effects

Pattern for shooting in multiplayer: ON CLIENT: InputAction Shoot → ServerRPC_Shoot (Custom Event, Run On Server, Reliable). ServerRPC_Shoot (runs on SERVER): LineTraceByChannel → Branch(hit) → ApplyDamage → MulticastRPC_PlayEffect(ImpactPoint). MulticastRPC_PlayEffect (Custom Event, Multicast, Unreliable): SpawnNiagaraSystemAtLocation(NS_BulletImpact, ImpactPoint). Key rules: - Server RPC: Custom Event → Replicates='Run On Server', Reliable=true. - Multicast: Custom Event → Replicates='Multicast', Reliable=false (VFX can be dropped). - Client RPC: Custom Event → Replicates='Run On Owning Client'. - Never directly modify replicated vars on clients — always go through Server RPC.

Server RPC — call a function on the server from a client

Create a Custom Event → check 'Replicates' in Details → set to 'Run On Server', 'Reliable'. Call from client → executes on server. Reliable = guaranteed delivery (use for important events). Unreliable = may drop (use for frequent updates like position).

CreateDynamicMaterialInstance — create runtime modifiable material

UPrimitiveComponent method. Store result in variable and reuse. Create once in BeginPlay.

ApplyDamage — deal damage to a target actor

UGameplayStatics::ApplyDamage. Triggers EventAnyDamage on target.

EnhancedInputAction — Enhanced Input system action event

K2Node_EnhancedInputAction. ActionValue type depends on InputAction (Bool, Float, Axis2D, Axis3D). Triggers: Started, Ongoing, Triggered, Completed, Canceled.

CreateDynamicMaterialInstance — create a runtime-editable material copy

Must call this before SetScalarParameterValue/SetVectorParameterValue. Store the result in a variable for reuse.

Health and damage system with ApplyDamage and EventAnyDamage

Dealing damage: Event → ApplyDamage(TargetActor, BaseDamage, InstigatorController, DamageCauser, DamageTypeClass). Receiving: EventAnyDamage → Damage output → Subtract_FloatFloat(CurrentHealth, Damage) → FClamp(Result, 0, MaxHealth) → SET CurrentHealth → Branch(CurrentHealth <= 0) → True: DestroyActor. Initialize CurrentHealth=MaxHealth in BeginPlay.

EventAnyDamage — receive any type of damage

string

string