Model fails to load in AR QuickLook from Safari when using auto USDZ and fixed scaling (iOS 15.4)

[milesgreen]

Description

When using auto USDZ generation in conjunction with fixed scaling, the model fails to load when opening to AR QuickLook from Safari. QuickLook opens, but all you see is a loading spinner that never resolves.

Previously, this was slightly broken in that the fixed scaling parameter was ignored, but the generated USDZ blob would at least load. Unfortunately, recent changes have now fully broken it.

The bug has been filed with webkit and it looks like a fix is being worked on:
https://bugs.webkit.org/show_bug.cgi?id=226265

Live Demo

https://modelviewer-auto-usdz.glitch.me/
On iPhone iOS 15.4 Safari, visit demo link. Select a model. View in AR. USDZ is being auto generated. QuickLook should open and display generated model. Exit AR. Now tick the Fixed Scale checkbox to set modelViewer.arScale="fixed". View in AR again. QuickLook opens but model never completes loading.

Version

• model-viewer: v1.10.1

Browser Affected

• Chrome
• Edge
• Firefox
• IE
• Safari 15.4

OS

• Android
• iOS 15.4
• Linux
• MacOS
• Windows

AR

• WebXR
• SceneViewer
• QuickLook

[elalish]

Thanks, I saw this in an earlier comment too and can repro. Considering Safari is busy fixing their bug, should we react to this? I don't love the idea of disabling a feature, just to reenable it once they fix their bug. What's their roll-out schedule like?

[milesgreen]

No insight as to schedule for fix, but Apple seems to be averaging iOS updates once a month at the moment. Hopefully, not too long.
Safari iOS has never respected the fixed scaling flag when auto generating USDZ (#2405). So if fixed scaling were to be removed for now, just in the instance of auto USDZ generation, it wouldn't change prior behaviour.
That said, reintroducing it once fixed leaves you with the question of whether to version check for compatibility 🙁

[maciekglowka]

Hi, I think the bug has been patched already - https://bugs.webkit.org/show_bug.cgi?id=236069
Not sure about rollout though (and browser version segmentation :/)

I think it is also possible that fragment will be now passed correctly to QuickLook and it will fix the scale as well - but we will see.

[milesgreen]

This issue still exists in iOS 15.5 beta (19F5047e)
Hopefully the fix gets rolled into 15.5 before final release.

[milesgreen]

This looks to be resolved in iOS 15.5 beta 4 (19F5070b).

[maciekglowka]

Great! Thanks for checking.
I see also on the bugzilla that QuickLook even respects no-scaling :)

[elalish]

I'm going to go ahead and close this since I'm here now and it looks like this will roll out. Feel free to ping this thread to reopen if the problem turns out not to be fixed.

[milesgreen]

Confirmed fixed in public release of iOS 15.5

[maciekglowka]

Great, now we need to hope that every iOS user updates soon enough :)