[Webkit-unassigned] [Bug 230216] New: METAL z-fighting with low camera near range

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=230216

            Bug ID: 230216
           Summary: METAL z-fighting with low camera near range
           Product: WebKit
           Version: Safari Technology Preview
          Hardware: All
                OS: All
            Status: NEW
          Severity: Major
          Priority: P2
         Component: WebGL
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: remi at barney-studios.com
                CC: dino at apple.com, kbr at google.com, kkinnunen at apple.com

Hi,

I'm currently working on a ThreeJS viewer and got a big z-fighting problem using iOS 15 beta and Safari Technology Preview on MacOS. To make this as clear as possible, I created a minimalist example: https://demos.barney-technologies.com/webkit_metal_zfighting/example/index.html

On older webkit versions it works well, but on the preview version we got this kind of z-fighting: https://imgur.com/a/vPtIMMi

We tried disabling WebGL2, but it doesn't change anything. This only disappears when disabling METAL.



The problem is mostly visible when using a small camera FOV (here 13), and a low camera near (here 0.01). The more you get away from the model, the more it appears. Using a basic (noop) ThreeJS shader causes the bug to be really more visible. Only thing we could do is increase the near range but it doesn't suit all of our use cases.


Is this normal? Is it something you've already see? I feel that it might break a lot of projects already online. :/

A ThreeJS contributor recommended posting the issue here. If it helps, here is the ThreeJS-specific thread: https://discourse.threejs.org/t/rendering-bug-with-metal-ios-macos/29812

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