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Entity Tween

GitHub release (latest SemVer) Unity

Entity compatible tween library for Unity ECS/DOTS and Project Tiny (DOTS Runtime).

Table of Contents

Demonstration

Link to the larger gif

Configuration

Hardware

Features

Dependencies

Optional

Installation

Entity Tween is a Unity package. You can install it from the git URL in Unity package manager.

Or, you can edit Packages/manifest.json manually, adding git URL as a dependency:

"dependencies": {
    "com.timespawn.entitytween": "https://github.com/NagaChiang/entity-tween.git"
}

To specify particular branch or tag, you can add it after the URL:

"dependencies": {
    "com.timespawn.entitytween": "https://github.com/NagaChiang/entity-tween.git#develop"
}

"dependencies": {
    "com.timespawn.entitytween": "https://github.com/NagaChiang/entity-tween.git#v0.1.0"
}

To update existing Entity Tween package to the latest, remove the dependency on com.timespawn.entitytween in Packages/packages-lock.json then refresh:

"dependencies": {
    "com.timespawn.entitytween": {
      "version": "https://github.com/NagaChiang/entity-tween.git",
      "depth": 0,
      "source": "git",
      "dependencies": {},
      "hash": "d3341cf672c26d1f0fe6e09d3bf7978c8cf22df7"
    }
}

For more information, please visit Unity documentation.

Examples

The main entry point of the library is the Tween class. All functionality have overloads to support EntityManager, EntityCommandBuffer and EntityCommandBuffer.ParallelWriter.

Move the entity

float3 start = new float3(0.0f, 0.0f, 0.0f);
float3 end = new float3(1.0f, 1.0f, 1.0f);
float duration = 5.0f;
bool isPingPong = false;
int loopCount = 1;

Tween.Move(entityManager, entity, start, end, duration, EaseDesc.SmoothStep, isPingPong, loopCount);
Tween.Move(commandBuffer, entity, start, end, duration, EaseDesc.SmoothStep, isPingPong, loopCount);
Tween.Move(parallelWriter, sortKey, entity, start, end, duration, EaseDesc.SmoothStep, isPingPong, loopCount);

Stop the entity

Tween.Stop(entityManager, entity);

Loop infinitely

When loopCount is 0, it means loop the tween infinitely. It's recommended to use Tween.Infinite in case it changes in the future.

Tween.Move(entityManager, entity, start, end, duration, EaseDesc.SmoothStep, isPingPong, Tween.Infinite);

Check if the entity is tweening

Any entity with component TweenState is tweening; that is, to know if the entity is tweening, check if the entity has any TweenState component in any way.

if (EntityManager.HasComponent<TweenState>(entity))
{
    Debug.Log("It's tweening!");
}

Known Issues

Compatibility with Unity 2021

According to the forum thread, Entities package is not compatible with Unity 2021 until the end of 2021.

You must stay on Unity 2020 LTS and on Entities 0.17 for now. Future releases of Entities will not be compatible with Unity 2021 until the end of the year at the earliest. Upgrading to 2021.1 and using current or future Entities packages will not work and is not expected to work.

Workflow

Command

When starting a tween by calling Tween's functions (e.g. Tween.Move()), it creates a tween command component of its kind (e.g. TweenTranslationCommand) containing the tweening data on the target entity.

If starting multiple tweens with the same type consequently, the command component will be overridden by the last one, which means only the last tween will be successfully triggered.

Generation

TweenGenerateSystem is an abstract generic system, which will take the commands of its kind, then append a TweenState with an unique tween ID to the DynamicBuffer of the target entity. Also, it creates another component with the same tween ID, storing the start and end information of the tween.

Making TweenState an IBufferElementData allows multiple active tweens on the same entity at the same time, while the other part of the tween data, e.g. TweenTranslation, is an IComponentData, which ensures that there must be only one tween of the certain type.

For example, TweenTranslationGenerateSystem, which inherits TweenGenerateSystem, will take TweenTranslationCommand then create TweenState and TweenTranslation on the target entity.

Easing

TweenEaseSystem iterates all TweenState components and update the elapsed time of the tween, then calculate the progress by Ease.CalculatePercentage() for later use.

Applying

For every type of tweens, there is a system responsible for applying the value to the target component.

For example, TweenTranslationSystem takes TweenState and TweenTranslation and interpolate the value depending on the eased percentage, then apply it to Translation.

Checking State

TweenStateSystem iterates all TweenState components checking if they're about to be looped, ping-ponged or destroyed. The tween will loop infinitely when its TweenState.LoopCount == 0; however, if it just ticked to 0 from 1, the system will mark it as pending destroy with TweenDestroyCommand;

Destroying

TweenDestroySystem is also an abstract generic system for each type of tween to implement, which destroys TweenState marked by TweenStateSystem earlier and its corresponding tween data component.

For example, TweenTranslationDestroySystem will be responsible for destroying TweenState and TweenTranslation.

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