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Tags: unreal, blueprints, event-graph, nodes, casting, interfaces, animation, state-machine, game-engine Last updated: 2026-06-27

Unreal Engine (Blueprints) Cheatsheet

Quick Reference

Concept	Key Node / Pattern
Events	`Event BeginPlay` / `Event Tick` / `Event ActorBeginOverlap`
Execution flow	White exec pins (▶) — sequential control flow
Data flow	Coloured data pins — values passed between nodes
Branching	`Branch` (bool) / `Switch on Int` / `Switch on String`
Casting	`Cast To <Type>` — convert reference to child type
Interfaces	`BPI_` prefix + `Event <Message>` — cross-class communication
Timelines	`Timeline` node — keyframed float/vector/colour curves
Animation	`State Machine` inside AnimBP — `State Alias` / `Blend Space`

Event Graph Basics

Event BeginPlay  → runs once on game start
Event Tick       → runs every frame (enable in Class Defaults)
Event EndPlay    → runs when actor is destroyed/level unloads

Branch & Flow Control

Event Tick
   │
   ▼
Branch ──True──▶ Print String "Active"
   │
False
   │
   ▼ (nothing)

Sequence Node

Event BeginPlay
   │
   ▼
Sequence ──Then 0──▶ Spawn Actor
         ├─Then 1──▶ Set Timer
         └─Then 2──▶ Play Sound

Casting

// C++ equivalent for reference
if (APlayerCharacter* PC = Cast<APlayerCharacter>(OtherActor)) {
    PC->TakeDamage(10);
}

Blueprint pattern:

OnActorBeginOverlap (Other Actor)
   │
   ▼
Cast To PlayerCharacter ──Success──▶ [Ref] ▶ Take Damage
   │
Cast Failed

Interfaces

Creating a Blueprint Interface:

Content Browser → Right-click → Blueprints → Blueprint Interface
Name: BPI_Interactable
Add function: Interact (no implementation in interface)

Calling an Interface:

OnActorBeginOverlap (Other Actor)
   │
   ▼
Does Implement Interface (BPI_Interactable)
   │
   ▼ True
Interact (Message) — Target: Other Actor

Interface vs Casting: Interfaces give loose coupling across unrelated classes. Casting requires knowing the exact class at compile time.

Animation Blueprint

AnimBP → AnimGraph → Add State Machine

State Machine:
  Idle ──(Speed > 0)──▶ Walk
  Walk ──(Speed == 0)──▶ Idle
  Any State ──(IsJumping)──▶ Jump
  Jump ──(OnLand)──▶ Idle

Transition Rules

Transition: Idle → Walk
Get Speed (float from Character Movement)
Float > Float ──True──▶ Can Transition

Blend Space 1D

Axis: Speed (0 → 600)
Place Idle at 0, Walk at 300, Run at 600
Sample in AnimBP: Blendspace Player (Speed)

State Alias

Use State Alias nodes to reference states by name. E.g. Alias GroundLocomotion → Idle / Walk / Run blendspace.

Timelines

Event BeginPlay
   │
   ▼
Timeline ──Update──▶ Set Actor Location (Lerp from A to B)
         ├─Finished──▶ Destroy Actor
         └─Play from Start

Curve Types

Float track: Smooth float value (0→1 over time)
Vector track: Colour or position interpolation
Event track: Trigger events at specific keyframes

Variables & Access

Exposure	Flag	Notes
Instance Editable	`Editable` (eye icon)	Shows in Details panel per-instance
Expose on Spawn	`Expose on Spawn`	Shows as pin on Spawn Actor node
Private	Uncheck both	Only accessible inside this Blueprint

Common Types

Boolean       → Branch
Integer       → Switch on Int
Float         → Math Expression, Lerp
Vector        → Location, Scale
Rotator       → Rotation
Transform     → Location + Rotation + Scale
Object Ref    → Cast To
Gameplay Tag  → Has Tag, Switch on Gameplay Tag

Tips

Event Tick is expensive — disable it when not needed. Prefer timers or timelines.
Use Function Libraries for stateless utility code shared across Blueprints.
Macros collapse repeated node graphs into a single reusable node.
Event Dispatcher = Blueprint version of C# events/delegates — bind listeners for decoupled communication.
Right-click a node → "Add to Code" to navigate to its C++ implementation.
Use Print String liberally during debugging — it's your console.log().
Collapse to Function tidies a selection into a reusable, callable function node.