Bug 238022

Summary:	WebGl incorrect rendering on 15.4 using Playcanvas
Product:	WebKit	Reporter:	Martin <mvaligursky>
Component:	WebGL	Assignee:	Nobody <webkit-unassigned>
Status:	RESOLVED FIXED
Severity:	Major	CC:	avpeery, dino, djg, gman, kbr, kkinnunen, kpiddington, webkit-bug-importer
Priority:	P2	Keywords:	InRadar
Version:	Safari 15
Hardware:	All
OS:	iOS 15
Bug Depends on:	238196
Bug Blocks:

Description Martin 2022-03-17 07:18:54 PDT

WebGl rendering on 15.4 has some major problems using Playcanvas engine. This has not been the case on 15.3.

Repro steps:   https://playcanvas.github.io/#/graphics/area-picker

also these additional examples (available on the same url) have similar problems, some don't render at all:
- all anim blend trees + few more anim ones
- area picker
- clustered area lights
- grab pass
- post effects

tested on iphone XR 15.4 and also on Safari 15.4 Mac OS. Both WebGl1 and WebGl2.

A possible workaround seems to be disabling of antialiasing (which means passing { antialias: false } to canvas.getContext as an option when initializing WebGl.
Most of these examples do some form of rendering to texture and then using the results, but other examples using rendering to texture seems fine.

our tracking ticket: https://github.com/playcanvas/engine/issues/4136

Possibly related to:
https://bugs.webkit.org/show_bug.cgi?id=237906
https://bugs.webkit.org/show_bug.cgi?id=237006

Comment 1 Anna from Mapbox 2022-03-17 08:20:08 PDT

We had an issue with webGL rendering with the 15.4 upgrade (on iOS as well), and have also found disabling antialiasing to resolve the rendering problem. 
https://bugs.webkit.org/show_bug.cgi?id=237918

Comment 2 Radar WebKit Bug Importer 2022-03-18 16:17:02 PDT

<rdar://problem/90509311>

Comment 3 Kenneth Russell 2022-03-19 21:38:41 PDT

Can confirm that on an M1 MacBook Pro with Safari Technology Preview Release 141 (Safari 15.4, WebKit 17614.1.3.8), this example doesn't render correctly with "WebGL on Metal" enabled. It does render correctly with it disabled.

It renders correctly on Chrome Canary 102.0.4952.2 (Official Build) canary (arm64) with --use-angle=metal, so this bug has been fixed in top-of-tree ANGLE.

Comment 4 Kimmo Kinnunen 2022-03-22 02:41:30 PDT

Thanks for the report.
I think this is part of the 15.4 msaa regression, linked to in the depends on -section.

Comment 5 Dean Jackson 2022-03-28 17:43:18 PDT

Fixed in the ANGLE roll https://bugs.webkit.org/show_bug.cgi?id=238171