multi-draw broken after the recent update to Safari. (Safari 15.4 (17613.1.17.1.6))

[Philip Taylor]

Hello, after the recent update to Safari 15.4 (17613.1.17.1.6), our multi-draw code started throwing exceptions on all multi-draw calls. (multiDrawElementsWEBGL)

WebGL: INVALID_OPERATION: multiDrawElementsWEBGL: countsOffset out of bounds

We haven't been able to address the issue, and have since disabled multiDraw on Safari, but this is now causing a performance regression that we would like to avoid.

Can I be guided by an expert in this area to find a solution? There is a possibility that we are doing something wrong on our side, but so far we can't get to the bottom of it.

Thanks
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Philip TAYLOR

CTO, Zea Inc.

Montréal, Québec

M: +1.514.582.4325

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[David Smith]

Try turning off antialiasing. This fixed a number of issues for me.

David A. Smith

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[Ken Russell]

Hi Philip,

Unfortunately a bug was introduced in Safari's validation for WEBGL_multi_draw along with what looks like a security bug fix.

I've posted a patch to WebKit fixing it in https://bugs.webkit.org/show_bug.cgi?id=238239 . Unfortunately it will probably take some time for this to propagate out.

Sorry that a regression like this made it past automated testing of any browser. There are safeguards in place to prevent this sort of thing from happening, but it looks like there are some gaps in WebGL conformance testing in WebKit.

In the interim - I'd encourage you and other developers to test your products regularly with pre-release versions of browsers like Chrome Canary / Dev, Firefox Nightly, Microsoft Edge Canary Channel, and Safari Technology Preview, and file any bugs against browsers as soon as you see them.

Thanks,

-Ken

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[Philip Taylor]

Thanks a lot for this feedback Ken. 

We will try to make an effort to implement testing of the beta browsers going forward so we can catch these issues earlier.

Phil

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Philip TAYLOR

CTO, Zea Inc.

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