Implementing a Time Reversal Effect in Unreal Engine

Introduction

A few days ago, I shared a video showcasing a time reversal effect I implemented in a prototype I’m collaborating on. This effect allows objects to return to their initial position, as if they’re in rewind! This is an exciting achievement and I wanted to share more details about how it works, the optimizations I’ve made, and the challenges I’ve encountered.

How It Works

This effect is implemented in a component. You can add this component to any actor you want and the component is the one that stores the owner’s transform. On each tick, the game stores the object’s transform only when it changes. This means we’re continuously tracking each object’s position, rotation, and scale in the game. When the time reversal effect is triggered, we go through this record in reverse, applying the transform to each object and creating a ‘rewind’ effect.

Optimizations

To optimize this process, I’ve implemented several strategies. Firstly, I only store the transform when it changes. This reduces the amount of data we need to store, especially for objects that are stationary for long periods of time. Additionally, I delete positions as they are traversed during time reversal. This frees up memory that we no longer need. Lastly, I use interpolation to smooth out the time reversal effect. This creates a more fluid animation and reduces the amount of data we need to store.

Pros and Cons

This effect has its pros and cons. On one hand, it creates a unique and visually impressive game mechanic. Players can interact with the game world in new and interesting ways, and there are many possibilities for puzzles and challenges based on this mechanic. However, this effect can be memory-intensive if not handled properly. We’re storing a large amount of data and need to ensure we’re managing that memory efficiently.

Additional Technical Details

Each component stores a reference to the Player Character at Begin Play and binds with an event dispatcher to trigger the effect. This means every object in the game is constantly listening to the Player Character and is ready to trigger the time reversal effect when needed.

Conclusion

Although there’s still much to do and situations to handle with this time reversal effect, I’m excited about the progress we’ve made so far. I hope that sharing this journey might help someone out there in their own game development adventures. Remember, every step forward is progress!