ECS-Tween

⚠ DEPRECATED ⚠

This repository was used for educational purposes, and is now long left abandonned.
Luckily, a more complete solution is out there, check out PlasticTween !

A very simple Unity tweening engine using pure ECS that works with GameObjects!

This is still very early stage, and it only supports position and rotation tweening, and few easing types. Rotation and Position can be used simulatinously.

Example

float time = 10f; // 10 seconds
Tween.Position(gameObject, targetPosition, time, EasingType.ExpIn);
Tween.Position(gameObject, fromPosition, toPosition, time, EasingType.Linear);
Tween.MovePosition(gameObject, translateVector, time);
Tween.Rotation(gameObject, Random.rotation,  Random.rotation, time, EasingType.ExpIn);

How does it work?

The idea behind this is to harvest ECS architecture to execute thousands of tweens efficiently. Great thing about tweening is that we're always working with data, which makes this kind of project perfect for ECS. The only part that's not entierly parallelized is when final interpolated transform needs to be copied to the GameObject once all jobs are complete during one frame.

An entity in our case would be a tweening instance. This doesn't cost us in performance and allows us to remove all component data related to the tween in one go.

By using one of the tweening functions, we link an Entity to GameObject ( using AddToEntityManager ) and then include the following ComponentData types:

TweenLifetime: Contains Start Time, and Lifetime ( tween time )
TweenTime: Represents normalized time, calculated using current time and TweenLifetime values
TweenPosition: contains current position and target position to interpolate

The following ComponentData types are required to update GameObject's transform.

Position: Required for CopyTransformToGameObject
CopyTransformToGameObject: Required to update GameObject's transform from Position

The flow

1. TweenNormalizedTime System

We first normalize time from using TweenTime and TweenLifetime, this is handled by this system. TweenTime is the final normalized result.

2. TweenEasingExpIn System ( only used for ExpIn easing )

When TweenEasingExpIn is present, we transform TweenTime value after TweenNormalizedTimeSystem has been executed. This transforms Linear time into ExpIn time value. ( same for TweenEasingExpOutSystem )

3. TweenPosition System / TweenRotation System

Interpolates position/rotation using TweenTime and TweenPosition and sets Position/Rotation.

4. TweenComplete System

Marks entities as complete ( TweenComplete ) that are past their lifetime ( TweenLifetime )

5. TweenRemove System

Handles removal of entities ( not GameObjects ) that are marked as complete ( TweenComplete ) Reason why this and previous systems are separate is because we would like to be able to have callbacks before an entity is removed.

6. TweenUpdateTransform System

Takes Position, Rotation and applies them to the GameObject.

Groups

Groups are necessary to keep the correct update order, because we can't interpolate when time needs to be "eased" first. Same thing for copying Entity transform to GameObject, we have to first interpolate it before we apply it to our GameObjects.

1. TweenTimeUpdate Group

Main time normalization job

2. TweenEasingUpdate Group

Includes all easing calculation jobs

3. TweenInterpolation Group

All lerping/slerping of positions and rotations

Contribute

I'd love to hear you out on improving this system, any contribution is welcome.

Xerios/ECS-Tween