Crash because of NaN, dynamic shadows related?

First info, I’m on 4.8.2.

For some reason that I have not been able to accurately pinpoint, I have a crash that happens seemingly at random: it’s not always after the same amount of time, not at the same place, not at the same part of the game flow. It’s seems to be occuring within the rendering thread and is basically complaining about a NaN matrix.

I would like to have at least a hint of what is going on, as far as I know, I don’t see any artifact or glitch in the scene as simply replacing the NaN matrix for the Identity matrix seems to correctly “bypass” the issue. Nevertheless, I would like to understand what is going on, and if you have any idea what can cause this or how to proceed to get a better idea of what is going on, please let me know!

Some of the logs seem to be pointing at an emitter from a particle system, but before recently, I did not have any issue with said particle system. I am currently thinking it could be a mixture of dynamic shadows and some types of emitters that do not play well together…but that’s just a guess…

Here is a part of the crash error log, attached is the complete log. Please note that the logs are not always the same, sometimes it gives different but similar output.
link text

Thanks in advance for the help!


LogUnrealMath:Error: FMatrix::InverseFast(), trying to invert a NIL matrix, this results in NaNs! Use Inverse() instead.
LogOutputDevice: === Handled error: ===
Ensure condition failed: false [File:c:\users\mdube\perforce\prodperforce\jotunn\engine_4.8_base\engine\source\runtime\core\public\math\UnrealMatrix.h] [Line: 266]
FMatrix::InverseFast(), trying to invert a NIL matrix, this results in NaNs! Use Inverse() instead.
UE4Editor-Core.dll!FWindowsPlatformStackWalk::StackWalkAndDump() {0x00007ffab34eb036} + 0 bytes 

Hey -

There is not really enough information for me to investigate/reproduce the crash on my end. You mentioned that the crash happens after a set amount of time, does that mean that after pressing PIE the crash is guaranteed after a little bit without input? Would it be possible for you to send me a copy of the project where the crash is occurring? You can do so by uploading the project and sending me a link to download it from. If you would rather do this privately you can send me a private message on the forums with the link rather than posting here.


It’s not really possible for me to get the whole project to you, I’ll try to isolate the issue in a single map and send it your way when I have some time. Like I said, the crash is pretty random, I really dont know what could be happening and don’t know the specifics of how to reproduce, I was just hoping for some “oh I saw that before it’s because of X” but I guess that cannot be that easy :stuck_out_tongue:

Thanks anyway, and i’ll update this issue as soon as possible…

Hey -

Were you able to find any additional information about the crash? For now I am marking this post as resolved for tracking purposes however you can reopen this by adding a comment. If you do encounter this crash again, please provide the callstack and the log files from the crash for more information.