RESOLVED DUPLICATE of bug 237113 237230
REGRESSION (iOS 15.4 beta) - WebGL race condition between clearing depth buffer and switching framebuffers 
https://bugs.webkit.org/show_bug.cgi?id=237230
Summary REGRESSION (iOS 15.4 beta) - WebGL race condition between clearing depth buff...
Christoph Bartschat
Reported 2022-02-25 15:54:16 PST
This is a regression between iOS 15.3.1 and 15.4. As can be see in this demo: https://codepen.io/cmb8/pen/GROXmKp We should see two gears spinning normally, but instead we get visual artifacts that obscure the objects from getting properly rendered. This behavior is caused by calling: context.clear(context.DEPTH_BUFFER_BIT) then immediately calling: context.bindFramebuffer(...) If we add a finish() call between the two calls, the issue does not occur. This problem affects many 8th Wall projects that use three.js, like our sample project here: https://8thwall.8thwall.app/unitcube-threejs/ or more recently, this Super Bowl promotional tie-in from Kia: https://www.kiadogmentedreality.com Disabling "WebGL via Metal" in "Experimental WebKit Features" and relaunching Safari fixes the behavior. Video of expected behavior: https://www.youtube.com/watch?v=SAp_RXDD7_0 Video of unexpected behavior: https://www.youtube.com/watch?v=d8cr-LP40hs
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Add attachment proposed patch, testcase, etc.
Kenneth Russell
Comment 1 2022-02-25 15:56:10 PST
+Kyle and John in case they can help triage this. Wonder whether it was fixed in the most recent ANGLE roll.
Kimmo Kinnunen
Comment 2 2022-02-28 23:42:37 PST
Thanks for the report. I think this has the same root cause as bug 237113. In order to workaround, you can try if you can rework the rendering so that it does not need the `autoClear = false`. I.e. use `autoClear = true`. Leaving this in until fix for bug 237113 is testable.
Radar WebKit Bug Importer
Comment 3 2022-03-04 15:55:17 PST
<rdar://problem/89839163>
Christoph Bartschat
Comment 4 2022-03-30 10:29:06 PDT
Now that bug 237113 has been closed, do we have confirmation that the problem described here has also been fixed?
Brent Fulgham
Comment 5 2022-06-23 15:44:17 PDT
*** This bug has been marked as a duplicate of bug 237113 ***
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