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Animation.md

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Animation

Provides components / systems / authorings / data structures to simulate sprite animation. It just shifts UVs over time which looks like different sprite rendered. While it just UV shifting animation sprite sequence should be a solid texture sheet.

How it works

All animation data lives in provided ScriptableObjects (mentioned below). In baking phase it bakes all immutable animation data into blob (see SpriteAnimationAuthoring). Then in runtime it changes UVAtlas component value over time to perform flipbook animation.

SpriteAnimatedRendererAuthoring

Inherited from SpriteRenderAuthoring it also bakes all needed animation data provided as SpriteAnimationSet. If you want to implement your own authoring you can still use static methods provided by this class to perform same baking.

Prepare assets

To work with animation part you need to create SpriteAnimationSet and bunch of SpriteAnimation. You can create them like most of ScriptableObjects by calling context menu in project and selecting Create/NSprites/Animation Set / Create/Nsprites/Animation (sprite sequence).

SpriteAnimation

A ScriptableObject containing sprite sequence (as solid sprite sheet) where each sprite has duration of how long it stays before switch to next frame. This class also requires additional data like frame count resolution.

SpriteAnimationSet

A ScriptableObject containing set of SpriteAnimations with string names (which used as IDs)

SpriteAnimationBlobData

A struct blob to contain runtime immutable animation data. Contains int ID which corresponds to animation name with help of Animator.StringToHash, atlas UVs of sprite sheet, it's frame resolution, BlobArray<float> of frame durations and sum of all frames duration.

Change animation during runtime

Using AnimatorAspect

You can use this aspect to change animation by it's ID in a simple way.

// this example is from Age-of-Sprites project https://github.com/Antoshidza/Age-of-Sprites/blob/main/Assets/Sources/Rome/Systems/MovableAnimationControlSystem.cs
[BurstCompile]
private partial struct ChangeAnimationJob : IJobEntity
{
    public int SetToAnimationID;
    public double Time;

    private void Execute(ref AnimatorAspect animator)
    {
        animator.SetAnimation(SetToAnimationID, Time);
    }
}

Manually

Basically to change animation we should set AnimationIndex to another index and reset AnimationTimer and FrameIndex and also calculate proper UVAtlas of 1st frame of animation you choosed. Though the short way is to just change AnimationIndex, set FrameIndex to last frame index in choosed animation and set AnimationTimer to current Time.ElapsedTime which will trigger SpriteUVAnimationSystem to calculate next frame which should be the 1st frame of choosed animation.

You can inspect example of doing this by looking at AnimatorAspect source code.

Components

Type Description
AnimationSetLink Provides link to BlobArray<SpriteAnimationBlobData>
AnimationIndex Currently playing animation from AnimationSetLink
FrameIndex Currently displayed frame from sprite sheet texture
AnimationTimer Timer which has value of global time + frame duration. When timer excided (timer value equals current global time) frame index increases