Animation Validation

The Core Difference: “DJ Mode”

In Maya or Blender, animation is like a reference you can peek at:

• You scrub the timeline → see the pose at that frame.
• You tweak a slider → your change applies immediately.
• Both work simultaneously, no conflict.

In RealityKit, animation is like a DJ who won’t give up the mic:

• The AnimationPlaybackController takes exclusive control of animated properties.
• While it’s active, your manual changes get overwritten every frame.
• You must stop the controller completely to edit manually.

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Scenario: Testing a Blend Shape

What you expect (Maya/Blender):

1. Scrub to frame 60.
2. See the blend shape at that frame.
3. Tweak the slider to test a different value.
4. Scrub to frame 80 to see another pose.

What happens in RealityKit:

1. Scrub to frame 60 → ✅ Works (if controller is paused).
2. See the blend shape → ✅ Works.
3. Tweak the slider → ❌ Controller overwrites your edit instantly.
4. You must stop the animation first → then slider works.
5. But now scrubbing doesn’t show preview → you lost the controller.

The Trade-off

Mode	Scrub Preview	Manual Sliders
Animation Paused	✅ See any frame	❌ Locked
Animation Stopped	❌ Shows base pose	✅ Full Control

You can’t have both at once. This is a RealityKit design decision, not a bug.

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Why RealityKit Works This Way

RealityKit is designed for runtime apps, not animation editing:

• Performance: The runtime assumes playback is authoritative.
• Blending: Multiple animations can layer (e.g., walk + facial expression).
• Continuous Time: There is no concept of “current frame”, only continuous seconds.

Practical Workaround in Preflight

We implemented a hybrid approach to mitigate this:

1. Pause: Controller stays alive, scrubbing shows preview.
2. Touch a slider: Automatically Stops controller, releases control.
3. Press Play: New controller starts, scrubbing works again.

It’s not seamless like Maya, but it gives you both features with one extra click.