First motion after MotionDispatcher.Clear() completes in one frame

[NeonHazeGameStudio]

First motion after MotionDispatcher.Clear() completes in one frame

Summary

A motion scheduled immediately after MotionDispatcher.Clear() can complete in a single frame, even when its duration is set to 2.0 seconds.

This was reproduced with:

• MotionScheduler.UpdateIgnoreTimeScale
• MotionScheduler.Update
• MotionScheduler.UpdateRealtime

Environment

• Unity: 2021.3.45f2
• Render pipeline: URP
• LitMotion package: com.annulusgames.lit-motion
• LitMotion version: 2.0.2

Expected behavior

After calling MotionDispatcher.Clear(), a newly scheduled motion with duration 2.0 should animate for approximately 2 seconds.

Actual behavior

The first motion scheduled immediately after MotionDispatcher.Clear() completes in 1 frame.

Observed failing results immediately after MotionDispatcher.Clear():

• MotionScheduler.UpdateIgnoreTimeScale
  • Result: fail
  • Elapsed: 0.015s
  • Frames: 1
• MotionScheduler.Update
  • Result: fail
  • Elapsed: 0.003s
  • Frames: 1
• MotionScheduler.UpdateRealtime
  • Result: fail
  • Elapsed: 0.004s
  • Frames: 1

Observed passing results after waiting two player-loop yields following MotionDispatcher.Clear():

• MotionScheduler.UpdateIgnoreTimeScale
  • Result: pass
  • Elapsed: 2.001s
  • Frames: 413
• MotionScheduler.Update
  • Result: pass
  • Elapsed: 2.004s
  • Frames: 451
• MotionScheduler.UpdateRealtime
  • Result: pass
  • Elapsed: 2.004s
  • Frames: 451

Reproduction outline

1. Run a normal 2-second motion and confirm it takes approximately 2 seconds.
2. Call MotionDispatcher.Clear().
3. Immediately schedule another 2-second motion.
4. Measure elapsed realtime and frame count until the motion completes.
5. Repeat with these schedulers:
   • MotionScheduler.UpdateIgnoreTimeScale
   • MotionScheduler.Update
   • MotionScheduler.UpdateRealtime
6. Repeat the same test after waiting two player-loop yields after MotionDispatcher.Clear().

Notes

• This does not appear to be specific to one scheduler, because all tested schedulers failed when used immediately after MotionDispatcher.Clear().
• Waiting two player-loop yields after MotionDispatcher.Clear() makes the same schedulers behave correctly.
• I found the closed UpdateRunner.Reset fix, but this issue still reproduces in LitMotion 2.0.2.