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Engine hangs / freezes when looking at certain points

In one of my projects, in fullscreen PIE mode and standard in-editor navigation, looking at specific directions causes the editor to freeze until the mouse is moved to change direction. Fraps and UE4's frame rate monitor don't dip or otherwise show anything unusual has happened, and the engine is still receiving input even though it's frozen, as I can unfreeze it by changing my direction, or hovering my mouse over a UI element.

This seems to have nothing to do with performance and does not occur in standalone VR mode, only in the scenarios described above.

This happens in 4.10.1 and the 4.11 preview.

This is probably hard to comprehend as written, but I'm hoping it's a known bug in which case someone should know what I'm describing. If it's completely unheard of, I can provide a video.

EDIT: The issue doesn't occur in PIE if diagnostics are running such as Stat > Advanced > SceneRendering. It's as if there is just a deadzone in my scene where the frames don't update if I'm looking in that direction, but having stats running seems to force it to update. The issue still occurs in editor mode even if stats are running. In this case the stats console also freezes with the rest of the editor.

Product Version: UE 4.10
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asked Dec 29 '15 at 02:25 PM in Rendering

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avatar image mechanicalsnowman Jan 17 '16 at 12:22 PM

No one?

To add to this, using Open Broadcaster Software, when UnrealEngine4 freezes OBS actually records as if there are no issues. It seems like it could be a GPU issue then? Could I get some technical assistance? I'd be happy to troubleshoot and send diagnostics information if anyone could assist me.

avatar image Logan Bailey ♦♦ STAFF Jan 19 '16 at 06:57 PM

Hello mechanicalsnowman,

Would you provide your DxDiag(System Specs). Also if you would post a short video illustrating the freeze? I will be investigating any known issues with the editor freezing in Fullscreen PIE and standard in-editor navigation. With this information I should have a better idea as to why this freeze is happening.


avatar image mechanicalsnowman Jan 19 '16 at 08:19 PM

Thanks for the reply Logan, I've attached my DxDiag as a .zip, I've sent you the password on forums.unrealengine.com (sorry for the inconvenience).

I'll record something within a day or two.

link text

dxdiag.zip (7.5 kB)
avatar image mechanicalsnowman Jan 20 '16 at 06:46 AM

Hey Logan, I had the opportunity to take a video, and strangely enough the problem seems to be resolved across all my projects.

I didn't update UE4 or change anything in my projects since I last had the issue, so I'm beginning to think it's a problem with my machine.

If you could, please keep this marked as unresolved for a few more days and I'll come back to say if the issue is gone for good - it's been happening since start of Jan so I'd be surprised if it is fixed without me having done anything.

avatar image Logan Bailey ♦♦ STAFF Jan 21 '16 at 03:41 PM

Sure, no problem. Post again if the problem happens again.

avatar image mechanicalsnowman Jan 22 '16 at 08:08 AM

Thought it was resolved, but I jumped the gun. I've attached a video file showing the problem, it had to be recorded with a video camera because screen recording programs don't acknowledge the problem. (password is the same as for my DxDiag, sorry for passwording everything, let me know if there's any issues in viewing or opening stuff).

I've never seen anything like this, UE4 is on the left, OBS is on the right, streaming from the left monitor. Looking at 'problem areas' freezes UE4 completely, or at least, prevents it from updating to my screen for some reason.

Note that this is in no way performance or frame rate related. My frame rate is reported as 120FPS at all times, even during screen freezes, and using VR preview on the Rift has no issues at all.

I recently upgraded my graphics card to an R9 Fury X, I've been running and using UE4 almost daily for a year prior to this upgrade and have not seen this issue, so I can't help but assume its the fault of my graphics card, but why?

link text

test.zip (1.5 MB)
avatar image Tim Hobson ♦♦ STAFF Jan 26 '16 at 03:58 PM

Hi MechanicalSnowman,

I'm taking over this issue for Logan, Would you be able to send me the password on the forums. Once you have done that I can take a look and see if anything stands out that may be the issue.


avatar image mechanicalsnowman Jan 26 '16 at 04:22 PM

Thanks Tim, I've sent you a PM.

Some additional info if it helps - the hangs happen most often when looking at reflection capture actors, and pointlights which cast shadows, among probably other things. I'm open to testing specific things in a blank project if it would help.

The same behavior persists across all my projects, and all UE4 versions. Let me know if there's any other information that might help with diagnostics.

avatar image Tim Hobson ♦♦ STAFF Jan 28 '16 at 03:47 PM

Hey, I was able to see the DxDiag with that password, but that same password did not work on the video. Can you send me that password as well? Thank you!

avatar image mechanicalsnowman Jan 28 '16 at 04:06 PM

That is weird, sorry about that! The password should work on this, I noticed that there was a space at the end when I sent it to you on the forums, so if you copy+pasta make sure the space isn't included!

link text

test.rar (1.5 MB)
avatar image Tim Hobson ♦♦ STAFF Feb 02 '16 at 08:19 PM

I've tried to reproduce this on my end, but I'm not seeing anything really. This could be I'm just using template projects that haven't really been setup in any specific way, but you did mention this is multiple projects.

Looking at your DxDiag, your AMD GPU drivers are a couple of months old. Have you tried updating to the latest ones 15.30.1025.1001 that are available here: http://support.amd.com/en-us/download

This could be a likely cause, but at the moment I can't say for certain since I'm running on a Nvidia GTX-680.

If you're able to reproduce this in a simple test project I can do some comparisons in our Lab with multiple machine setups and on my machine to see if I'm seeing the same results.

If this is only happening in your personal projects, it may be worth doing some CPU/GPU profilling to see where the hiccups are happening when you're turning/moving the camera, but I'm not sure if this would help much since it's only happening in the editor and not when you are doing Standalone or recording with OBS as you mention.

avatar image mechanicalsnowman Feb 06 '16 at 01:46 PM

Thanks for trying.

I just updated to drivers 16.1.1, it doesn't fix the problem. I've found another interesting feature of the bug which might lead to some clues. It can't be captured by prntscrn or screen recording, so I Photoshopped a simulation of it.

When a UI window is on top of the game window in PIE, a border of 10 or so pixels around that window shows the game running behind it just fine. But in the rest of the window, it shows it as crashed.

![alt text][1] [1]: /storage/temp/77573-ue4freeze.jpg

At this point, this issue is so extreme and unusual, and with 0 other people reporting it, I don't have much hope for it being fixed in this forum. Profiling wouldn't help as UE4 is running fine, except it seems some video just doesn't get pushed to the monitor.

Print screen and screen recording don't show any issue, but just the pixels on the monitor are crashed.

Is there anyone at Epic that works with low-level graphics stuff that you could possibly consult? Any engineer who works with graphics drivers, things like that?

ue4freeze.jpg (238.2 kB)
avatar image mechanicalsnowman Mar 16 '16 at 06:46 AM

Any updates?

avatar image mechanicalsnowman Mar 25 '16 at 09:40 AM

Could I get any kind of response, even if it's to say this issue isn't being looked at by Epic, just so I can get some closure?

It's been 4 months nearly.

avatar image mechanicalsnowman Mar 28 '16 at 05:54 PM

this is a story all about how

avatar image mechanicalsnowman Mar 30 '16 at 01:16 PM

my life got flip turned upside down

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