Scar Rewind System

What was fixed in version 3.0

Version 2.0 compiled without errors but crashed Unreal Engine 5.2 at runtime. Eight root causes were identified and resolved. Every fix is documented below for full transparency.

Quick start: Blueprint setup

The Scar Rewind System is fully Blueprint-native. Every feature is accessible through Blueprint nodes. No C++ is required at any stage.

1. 01Enable the plugin. Go to Edit > Plugins, search for Scar Rewind System, check Enabled, and click Restart Now. The plugin appears under the Gameplay category.
2. 02Add the component to your actor. Open any Blueprint Actor, click Add Component in the Components panel, and search Scar Rewind Component. Recording begins automatically when you press Play, with no extra setup.
3. 03Wire up input to start rewind. In the Event Graph, add your Input Action event, for example IA_Rewind. Drag the Scar Rewind Component reference in and connect the Started or Pressed exec pin to Start Rewind.
4. 04Wire up input to stop rewind. From the same input event, connect the Completed or Released exec pin to Stop Rewind on the component. That is the complete minimal setup.
5. 05Test in-editor. Press Play and enable Show Debug on the component to see a live status overlay above the Actor showing state, buffer fill and energy. Hold your rewind key to see the Actor travel back in time.

Creating your ghost Blueprint actor

The ghost trail spawns a Blueprint Actor you create and fully control. This gives you complete creative freedom: any mesh, material, particle effect or animation can serve as the ghost echo. The component handles spawn, position updates and destruction automatically.

1. 01Create a new Blueprint Actor. In the Content Browser right-click, choose Blueprint Class, then Actor. Name it something like BP_RewindGhost.
2. 02Add a Static Mesh Component and assign the same mesh your character or prop uses.
3. 03Apply a translucent material. Create a Material with Blend Mode set to Translucent and Lighting Model set to Unlit, set Opacity to around 0.35, and apply it to the mesh. You can also add a Niagara component for a particle-based echo.
4. 04Disable collision. Select the mesh component, and in Details > Collision set Collision Presets to NoCollision so the ghost does not block the player or other actors.
5. 05Optional: add effects. Niagara components, Timeline animations, audio, material animations, or any Blueprint logic. The ghost Blueprint can do anything a normal Blueprint Actor can do.
6. 06Assign it in the rewind component. Select the Actor with the Scar Rewind Component, and under Details > Scar Rewind System > Ghost Trail set Ghost Actor Class to BP_RewindGhost and enable Show Ghost Trail.
7. 07Set the linger duration. Under the same Ghost Trail category, set Ghost Trail Linger Duration to how many seconds the ghost should stay visible after rewind ends. The default is 1.5 seconds, and 0 destroys it immediately.

Component properties reference

All properties are editable from the Details panel in the Blueprint editor. No code is required to configure any of these settings.

Core

Energy system

Cooldown

Axis lock

Ghost trail

Post process

Priority and debug

Blueprint node reference

Every function listed here is available as a Blueprint node. Drag the Scar Rewind Component reference into the Event Graph and pull off a wire to search for any of these nodes.

Core nodes

Bookmark nodes

Bookmarks save a named moment in history. Restore Bookmark is an instant teleport: it does not play through the intervening history, it jumps directly to that moment.

Energy nodes

State query nodes

Events and delegates

All events are BlueprintAssignable. In the Blueprint editor, select the Scar Rewind Component in the Components panel, then look in the Details panel under Events and click the green plus button next to any event to add it directly to the graph.

Global world rewind

Global World Rewind rewinds every eligible movable Actor in the level simultaneously with a single Blueprint node. Enemies, projectiles, props and vehicles are all rewound together. Actors with a Scar Rewind Component use their own per-actor buffer, and all other eligible movable Actors use the global snapshot cache built by the subsystem.

How to access the subsystem in Blueprint

Right-click in any Blueprint Event Graph and search for Get World Subsystem. In the Class dropdown select Scar Rewind Subsystem. Pull off the return value wire to access all global rewind nodes.

Global rewind settings (on the subsystem)

To exclude any specific Actor from global rewind, add the tag ScarIgnoreGlobal in its Details panel under Tags. Actors with Mobility set to Static are always excluded automatically because they cannot move.

Pickup exclusion from global rewind

Global rewind does not affect pickups. Rewinding the world while the player has already collected an item would cause confusing behaviour, for example a weapon disappearing from the player hand or a health pack reappearing and then vanishing again as the timeline moves. The system provides two automatic methods to keep pickups out of the global rewind.

Method 1: tag the pickup actor (recommended)

Add the tag ScarIsPickup to any Actor Tags array in the Details panel. The global rewind system skips this Actor entirely, whether or not it has been picked up. Use this for weapons, health packs, ammo, keys, collectibles, and any other item the player can interact with.

1. 01Select the pickup Actor in the level, or open its Blueprint.
2. 02In Details, scroll to Tags.
3. 03Click the plus button and type: ScarIsPickup
4. 04That is all. The Actor is now permanently excluded from global rewind.

Method 2: ownership detection (automatic)

When a player picks up an item, most inventory and equipment systems set the item Owner to the Pawn that collected it. The global rewind system detects this automatically: any Actor whose Owner is a Pawn subclass is skipped during global rewind. That means already-collected items are excluded without any extra tags or configuration.

Summary of all exclusion rules

Batch operations via subsystem

The Scar Rewind Subsystem lets you control every registered Scar Rewind Component in the level at once. All components register automatically at Begin Play, so you do not need to manage this manually. Access it via Get World Subsystem > Scar Rewind Subsystem.

Game design recipes

Ready-made configurations for common rewind gameplay patterns. All settings are applied in the Details panel of the Scar Rewind Component or via Blueprint nodes. No code is required.

Death rewind

The player dies. Call Start Global Rewind with Duration 3.0 to rewind 3 seconds. The ghost trail with a 2-second linger shows the player where they were, post process desaturation signals the timeline reversal, and the energy system prevents abuse.

Use Rewind Energy .............. On
Show Ghost Trail ............... On (assign your ghost Blueprint)
Ghost Trail Linger Duration .... 2.0
Use Post Process Effect ........ On, Desaturation 0.8

// From your death event:
Start Global Rewind (3.0)

Puzzle environment reset

// Add Scar Rewind Component to every puzzle Actor
On mistake:  Rewind All Actors      // subsystem
On success:  Clear All Buffers      // prevents rewinding past the clean state

Bullet time sequence

Post Process Chromatic Aberration ... 3.0
Post Process Desaturation ........... 1.0

Set Global Time Dilation (0.2)
Start Global Rewind (2.0)   // replays the last 2 seconds in slow motion

Checkpoint restore

// At each safe zone trigger:
Save Bookmark ("Checkpoint")

// From your death or respawn event:
Restore Bookmark ("Checkpoint")   // instant, no intervening history

Resource-limited rewind

A stamina-gated rewind. The player gets 4 seconds per use, takes 20 seconds to fully recharge, and must wait 2 seconds between uses.

Use Rewind Energy ....... On
Max Rewind Energy ....... 100
Energy Drain Rate ....... 25
Energy Recharge Rate .... 5
Rewind Cooldown ......... 2.0

// Bind On Energy Changed -> Progress Bar Set Percent

2D platformer side-scroller lock

Lock Location Y ... On   // locks the depth axis
Lock Rotation ..... On   // keeps the sprite facing correctly

Collectible-safe world rewind

// Add tag ScarIsPickup to every collectible Actor
Start Global Rewind
// Picked-up items (Owner is Pawn) and tagged items are excluded automatically

Performance notes

The Scar Rewind System is built with performance as a first priority. Here is what you get out of the box and what to watch for in large scenes.

File reference

All plugin source files are in your project Plugins/ScarRewindSystem/ folder. You do not need to edit any of these files to use the plugin. This reference is for developers who want to extend the system.