Unity deletes empty tracks from timelines in __internalAwake

Is there any way for it to not do this? I'm working on automation tools that generate timelines and tracks for other disciplines to populate. Making them have to manually re-add the tracks is a drag.

 

Interesting. I have a class AttackTimeline that extends TimelineAsset, and then a custom editor that allows us to create a list of animation clips and create a timeline for each of them. The creation loop in the editor looks like this:

Code (CSharp):

1. // Create new attack timelines for anything that does not already have one
2. foreach (AnimationAttackBinding aab in aabs)
3. {
4.     if (aab.Timeline == null)
5.     {
6.         string path = AssetDatabase.GetAssetPath(aab.Clip);
7.         string filename = aab.Clip.name + NEW_ATTACK_SUFFIX;
8.         string newPath = path.Replace(Path.GetFileName(path), filename);
9.         newPath = AssetDatabase.GenerateUniqueAssetPath(newPath);
10.  
11.         Debug.LogFormat("Creating new AttackTimeline: {0}", filename);
12.  
13.         AttackTimeline newTimeline = CreateInstance<AttackTimeline>();
14.         newTimeline.Initialize(aab.Clip, Director, Animator);  // Sets up the animation track and attack track
15.         AssetDatabase.CreateAsset(newTimeline, newPath);
16.         AssetDatabase.SaveAssets();
17.         aab.Timeline = AssetDatabase.LoadAssetAtPath<AttackTimeline>(newPath);
18.     }
19. }

The AttackTimeline's initialisation function looks like this:

Code (CSharp):

1. public void Initialize(AnimationClip clip, PlayableDirector director, Animator animator)
2. {
3.     AnimationTrack animTrack = CreateTrack<AnimationTrack>(null, "Animation Track");
4.     animTrack.CreateClip(clip);
5.     CreateTrack<AttackTrack>(null, "Attack Track");
6.     CreateTrack<CritPointTrack>(null, "Crit Spawns");
7.     CreateTrack<MotionControlTrack>(null, "Motion Control");
8.  
9.     AnimationTriggerName = AnimationAttackBinding.GetTriggerName(clip);
10.     AnimationTriggerHash = Animator.StringToHash(AnimationTriggerName);
11.  
12.     director.SetGenericBinding(animTrack, animator.gameObject);
13. }

After doing this, the new timelines look as expected and work until the editor is restarted. I am beginning to think that I might need to call SaveAssets before calling Initialize. I will try that.

 

So, after deferring the initialize until after reloading the asset the tracks remain as expected. Here's what I changed in the loop:

Code (CSharp):

1. AttackTimeline newTimeline = CreateInstance<AttackTimeline>();
2. AssetDatabase.CreateAsset(newTimeline, newPath);
3. AssetDatabase.SaveAssets();
4. aab.Timeline = AssetDatabase.LoadAssetAtPath<AttackTimeline>(newPath);
5. newTimeline.Initialize(aab.Clip, Director, Animator);  // Sets up the animation track and attack track
6. EditorUtility.SetDirty(newTimeline);

It's weird that I have to do this... it feels like a bug? I don't know, maybe that's how the Unity assets are supposed to work? (I'm in 2018.1.0f1)