Resolved Calling PlayableBehaviour functions with no clips present?

Hi everyone!
I have noticed that a timeline does not call PlayableBehaviour's functions (like ProcessFrame() or OnGraphStop()) when there are no TimelineClips present on track, probably for performance reasons.

We could use this behavior to perform "return to default" operations on left out data from previously played timelines (that can be skipped). Technically we could use "OnGraphStart()" or "OnGraphStop" functions to clean things up, but it tends to disrupt the editing process (cleaning up animations when stopping on a clip etc.).

For example:
MixerBehaviour code:

Code (CSharp):

1. using UnityEngine;
2. using UnityEngine.Playables;
3.  
4. public class ExamplePlayerMixerBehaviour : PlayableBehaviour
5. {
6.     public override void ProcessFrame(Playable playable, FrameData info, object playerData)
7.     {
8.         Debug.Log($"Clips on track: {playable.GetInputCount()}");
9.     }
10. }

Output screenshot:


As you can see, there is no "Clips on track: 0" debug log present from "Example Track 0" track. Is it the expected behaviour? Can we override it somehow? Thank you in advance!

 

By default, if there's no clip and no marker on the track, the MixerPlayabe won't be created. You can override

TrackAsset.CanCreateTrackMixer()

to always return true (or to any condition) to preserve the MixerPlayable.

 

That is exactly what we needed, thanks a lot!