Attach to component => crash

Hello everyone,

I’ve run into one really strange (and tedious) bug lately.
I’m currently using a heavily modified version of the TopDown template, and I’m trying to attach an actor (not much more than a static mesh and some variables) to the socket of a skeletal mesh - in other words: The pawn I use as a player character shall take a sword in his hand.

But whenever I do that, the same error happens again and again, and right now I’ve completely run out of ideas of why it does that and how to fix it: At first the game runs fine after I have attached the sword to my char’s hand (which it does absolutely right; no problem here). But a few seconds after begin to I walk around with the sword in my hand, I experience a crash.
That means: Not only does the editor crash, but my entire system does - I have no other options but to restart my computer. No bug or error report, it just freezes.

I’d really appreciate some help here, because I’ve no idea that to do now.
Thanks in advance!

Meanwhile I found out that this problem has it’s roots most likely in the AI Controller which I use to control my Player Character.

New Info: Nope, it’s most likely NOT the AI.
ATM it just seems to be the character movement, that doesn’t work with an actor attached to my pawn for… reasons.
Is there any physics or movement calculation in the UE that is known to cause random crashes? Anything concerning the “Attach actor to component” node, skeletal or static meshes, basically anything that can cause such a problem?
I’m grasping for straws right now…

Hello Datarecovery09,

I have a few questions for you that will help narrow down what issue it is that you are experiencing.

  1. Can you reproduce this issue in a clean project?
  2. If so, could you provide a detailed list of steps to reproduce this issue on our end?
  3. Could you provide screen shots of any blueprints that may be involved with this issue?
  4. Could you submitted the complete call stack that is given when your project crashes (Including machine ID)?

Hello,

thanks for the fast response!

I did what you suggested and recreated the problem with a clean project.

1.: I opened a new TopDownTemplate; UE 4.9.2
2.: Added a socket on the TopDownCharacter.
3.: I opened the TopDownController and created a new function that takes in an actor and, via the “Attach actor to component” node, attaches it to the aforementioned socket on the mesh of the TopDownCharacter.
4.: I imported a sword mesh & textures, then set it up as an actor.
=> Blueprint: On BeginPlay, it enables the input on the actor. On the press on a button, it casts to the TopDownController and calls the function I’ve created, with itself as the actor to attach.
As far as I can see this worked absolutely fine…

5.: … until I tried to change the mesh of the TopDownCharacter to a custom mesh (which, in my original project, had functioning animations etc.). I created a socket on it’s skeleton and set the animation controller to “None”; so it’s sliding around in t-pose.^^ Now with my own mesh as the TopDownCharacter, the crashes returned instantly: Press “O” to attach sword to hand => complete system crashes down in a matter of seconds.

Right now I can’t even give you screenshots of the blueprints because I can’t reopen the project again - the crashes seem to have completely broken it. Tomorrow I’ll try to recreate the whole thing again, reopen a new project, provoke the crash and hope that it doesn’t fry my blueprints.^^

As about the call stacks: If you mean the error log that pops up after the engine “normally” crashes (which it does now and then…^^) - I don’t get one. The whole system just crashes and I have to hit the reset button on my pc. Or are there any other logs that I just don’t know about right now?

Thank you very much!

Hello Datarecovery09,

I tried running through your steps to reproduce this issue. However, I was unable to do so. Would it be possible for you to supply the project that is having the crash?

Hello Datarecovery09,

We have not heard back from you in a few days, so we are marking this post as Resolved for tracking purposes. If you are still experiencing the issue you reported, please respond to this message with additional information and we will offer further assistance.

Thank you.

Hello,

Sorry that I didn’t respond in time; I wasn’t at home for the last three days.
I’ve opened up another project and recreated the issue, this time on UE 4.8, and while doing that I was able to gather additional information:

1.: I was wrong about the reason being my Character mesh/blueprint/skeleton/whatever. The crash also happens with Epic’s standard character and sometimes even when I just try to rotate a mesh in the viewport (strange enough: as now only while I rotate it, not while moving or scaling it…).
2.: More important: I encountered the exact same crash - everything freezes, mouse responds for a few additional seconds, then even the cursor freezes - while trying out WildStar (MMO, no free to play). There the problem was my graphics card, which is a R9 285 (pretty much the same card as the R9 380). Both of these cards, however, tend to cause some very specific crashes in certain situations. In WildStar I was able to solve the problem by setting the render mode to DX9, so I tried to force the UE4 to use OpenGL via adding “-OpenGL” to the target of the link (sorry for my English, it’s not my first language…^^). This didn’t work at all, since the starter won’t even… well, start with the “-OpenGL” entry added to it; it crashes instantly and tells me this: “No minidump found for this crash.”

Conclusion: I think it’s the bugged driver of the R9 285/380; nonetheless I’ve linked a dummy project to this post. Just run it in Viewport, press “O” (which attaches the sword to the characters hand) and run around for a few seconds; that’s what gives me the problem everytime.

Link: http://www.file-upload/download-10970556/Reference_48.7z.html

Thank you very much!

I was unable to download this project due to our firewall settings. Would it be possible for you to upload this project via dropbox or google drive?

Just uploaded it to google drive.

Link: https://drive.google.com/file/d/0Bx4368z9Q6hFMlZkaTJoSXdBUlE/view?pli=1

After doing a bit more digging I found that this is a known issue (UE-21389) and that it has been submitted to the developers for further consideration. I have provided a link to the original issue and you can navigate to that thread for future updates on this issue.

Link: Engine Crashes with video drivers crash and reset - Platform & Builds - Epic Developer Community Forums

Make it a great day

Thank you very much!
I’ll just wait for new drivers and/or an update to the Engine.

Hello again!

Just in case someone with the same problem as me finds this:
Seems like I found some kind of a (little bit glitchy^^) workaround via using the argument “-OpenGL” on the UE4Editor.exe, version UE4.10. When starting the engine, it will give you an error report as if it has crashed. Just ignore that - the engine should load up just fine, despite the crash report. You should have now forced it to use OpenGL in favor of DX11. The crash shouldn’t occur now.

Btw, it gave me an additional 5 fps. Just saying.^^

Thank you very much! :slight_smile: