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UE4 4.20 Crashes Mac with Metal 2

Before I post a bug report, I'd like to know if any other Mac developers have experienced this. When we moved to 4.20, we began to hang our computers when loading or playing levels in the editor. This was a very hard hang (or crash, it happens both ways). It turned out both levels we had problems with happened to have a lot of objects or had complex lighting builds. By switching to Metal 1.2 shaders, the hangs and crashes stopped. We could also stop them by removing a number of objects in the world.

One other factor of note was that OS X wasn't hanging when it would just hang, you could ssh in, but the User Interface was gone.

It would reboot the computer sometimes and that would allow us to see the system log. It appears that 4.20 with Metal 2.0 was trigging some bug in the video drivers. We had this happen with two Mac Pros, 32G, dual 700 video cards (the trashcan style macs). The machines would also both show the symptom of the fans spinning up (if you know the trashcans, they don't tend to get the fans going often). I don't think this is a UE4 bug as much as 4.20 just using the Metal 2.0 shaders.

I am curious if anyone else has experienced this.

Product Version: UE 4.20
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asked Sep 30 '18 at 06:38 PM in Bug Reports

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avatar image Jeff A ♦♦ STAFF Oct 01 '18 at 01:18 PM


We've recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.



avatar image eagletree Oct 01 '18 at 02:26 PM

Thank you, I did just submit it, but I was also hoping that someone else may have run across it too. It possibly is something that should be submitted to Apple, but Epic needs to do that though, since I wouldn't know how we are triggering the video driver problem with Metal 2. It's pretty tough to crash a Mac, in fact this is the only thing I've had happen in many years that would do this (aside from hardware issues), I would think Apple would want to know since Metal is still wet behind the ears, but probably not from me since I could tell them no details.

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