Timeline - 自定义轨道

Playable轨道和自定义轨道的区别

1) Playable轨道中，自定义PlayableBehaviour的上一级只能是Playable。

自定义轨道中，上一级是我们自定义的Playable

2) 自定义轨道可以直接在轨道上绑定目标，Playable轨道中则不行，需要只能使用ExposedReference<CanvasGroup> _target的方式

自定义轨道来实现CanvasGroup补间动画

自定义轨道类

using UnityEngine;
using UnityEngine.Playables;
using UnityEngine.Timeline;

[TrackClipType(typeof(CanvasGroupClip))]
[TrackBindingType(typeof(CanvasGroup))] //用于直接在轨道上绑定对象
public class MyCanvasGroupTrack : TrackAsset
{
    public override Playable CreateTrackMixer(PlayableGraph graph, GameObject go, int inputCount)
    {
        return ScriptPlayable<CanvasGroupMixerBehaviour>.Create(graph, inputCount);
    }
}

自定义轨道需要有一个Mixer的Playable

using UnityEngine;
using UnityEngine.Playables;

public class CanvasGroupMixerBehaviour : PlayableBehaviour
{

    public override void ProcessFrame(Playable playable, FrameData info, object playerData)
    {
        if (!(playerData is CanvasGroup canvasGroup))
            return;

        float blendedValue = 0;
        float totalWeight = 0;

        var inputCount = playable.GetInputCount();
        for (var i = 0; i < inputCount; ++i)
        {
            var playableInput = (ScriptPlayable<CanvasGroupBehaviour>)playable.GetInput(i);
            var behaviour = playableInput.GetBehaviour();

            var inputWeight = playable.GetInputWeight(i);
            float progress = (float)(playableInput.GetTime() / playableInput.GetDuration());

            if (inputWeight == 0)
                continue;

            blendedValue += Mathf.Lerp(behaviour.startValue, behaviour.endValue, progress) * inputWeight;
            totalWeight += inputWeight;
        }

        //blendedValue += canvasGroup.alpha * (1 - totalWeight);
        canvasGroup.alpha = blendedValue;
        Debug.Log($"CanvasGroupMixerBehaviour: count: {inputCount}, alpha:{blendedValue}");
    }

}

轨道资源类（同Playable轨道）

using UnityEngine;
using UnityEngine.Playables;

[System.Serializable]
public class CanvasGroupClip : PlayableAsset
{
    public CanvasGroupBehaviour template = new CanvasGroupBehaviour();

    public override Playable CreatePlayable(PlayableGraph graph, GameObject go)
    {
        var playable = ScriptPlayable<CanvasGroupBehaviour>.Create(graph, template);
        return playable;
    }

}

轨道资源行为类

using UnityEngine;
using UnityEngine.Playables;

[System.Serializable]
public class CanvasGroupBehaviour : PlayableBehaviour
{
    [SerializeField]
    public float _startValue;
    [SerializeField]
    public float _endValue;

    public float startValue => _startValue;
    public float endValue => _endValue;

}

#

PlayableGraph的可视化图形：

其他

1) 如果我们注释掉TrackBindingType，会发现无法在轨道上直接绑定对象了