Model disappears during staging & camera change on iOS 15.2 only (since v2.0.0)

[Stynson]

Description

After updating to v2.0.0 on iOS the model disappears during staging & camera change (rotation/zoom/pan etc.)
It reappears after the interaction finished. This includes user interactions and also programatically initiated ones.
The issue 100% reproducible with all modelviewer.dev examples too on iPhones (with iOS 15.2)

RPReplay_Final1664793004.MP4

Same issue happens with animated models too without user interaction:

RPReplay_Final1664794467.MP4

Reproduce:
Visit modelviewer.dev/examples with an iPhone running iOS 15 and rotate the models.

Expected behavior:
Model should be visible during the rotation.

Live Demo

visit this with iPhone running iOS 15.2:
https://modelviewer.dev/examples/stagingandcameras/

Version

• model-viewer: v2.0.0

Browser Affected

• Chrome
• Edge
• Firefox
• IE
• Safari

OS

• Android
• iOS, version: 15.2 ( it can't be reproduced with iOS 16.0 or iOS 15.4.1 )
• Linux
• MacOS
• Windows

[elalish]

Yeah, the iOS 15 rollout was a bit of a WebGL disaster. I'm not super excited to try to work around temporary WebKit bugs, but are you saying v1.12 was working properly on iOS 15.2? @grorg any idea what WebKit change this might have been related to?

[Stynson]

Indeed v1.12 works properly and v2.0 not that's the interesting part.

[westcode]

I can confirm we also started observing this exact issue after upgrading v1.12.1 to v2.0.2.

[elalish]

Considering iOS 15.2 didn't even make it onto this version share chart, I'm not going to prioritize fixing this, especially since I don't have an iOS 15.2 device to repro with. If any of you would like to debug and submit a PR, I'd be stoked though!

[Stynson]

Managed to debug it and opened a PR with the fix: #3941