IK Retargeter Causing UEFN To Crash

Summary

When attempting to open IK Retargeter, UEFN will crash to desktop. This occurs predominantly with existing IK Rig assets, but has also occurred inconsistently with newly created ones.

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

Stability

Steps to Reproduce

When double clicking on an IK Retargeting Rig, UEFN will crash. This occurs in several different projects and when the Retargeter contains any number of different meshes. This also occurs, although less consistently, when you create a new IK Retarget from scratch.

Expected Result

When attempting to open the viewport for a Retargeter, you should not have UEFN crash.

Observed Result

When attempting to double click the asset inside the Content Browser, UEFN crashes.

Platform(s)

PC

Hi @TheJackBlade ,

Please try the example in the Documentation first of all

Transfer Character Animations in Unreal Editor for Fortnite | Unreal Editor for Fortnite Documentation | Epic Developer Community

The assets created in UE5 often do not works and need to be developed in Fortnite version

This is happening to me too. At first it crashed when I simply created the retargeter, but after multiple attempts at reopening the project I can get the retargeter to create and even add the skeletal meshes to it, but it crashes constantly and is unusable.

It’s super unstable and already made one of my projects essentially corrupted b/c it crashes as soon as the level loads in after adding the retargeter.

Same issue. Nothing to do with migrated from UE5. We’ve been working on retargetting for a NPC for weeks in a project and now we cannot open the Rig or retarget without the editor crashing. This is since the recent update. This is an editor bug!

Getting someone to take a look.

1 Like

FORT-867959 has been created and its status is ‘Unconfirmed’. This is now in a queue to be reproduced and confirmed.

Please install a page file over 32GB, as you can see my memory usage is over 20GB whilst opening the IK Retargeter.

see this post
hi you may need to add a 64GB pagefile.sys, which I documented in
Install a bigger pagefile.sys
Then everything works without crashing.

34.00 needs more virtual Memory for most of the Feature examples and now with the latest UE5.6 updates, which UEFN is based on .

Tried The video
Mixamo to Fortnite Using IK Rig Retargeting
and with this 32GB there are not no crashes.

Check that in Windows 11 your project does NOT have OneDrive in its path, often UEFN will crash.

There is a warning message on new project creation but no checks on older projects

Thank you @Jimbohalo10

Folks, if you install a bigger pagefile, and this is still happening, please send me your UEFN logs.

How to get your Fortnite logs

This doesn’t appear to work. I set the page file sizes to 64GB for both of my drives and still getting the crash when working with the retargeter.

hi @thejerenator ,
Well, we all need the logs as in the picture below please

Sure thing, how do I send them?

Hi @thejerenator
You can pick the current log as broken as one text, or better still use Windows compression, or use WinRAR and select zip of logs directory or leave it as ,Rar and drag fro Windows file explorer to zip/rar to the post.

If you need confidentiality, then send by PM to @Flak .
If you send the logs in an open post, more devs can look into the crash.

Ok, here you go:

Logs.zip (5.2 MB)

1 Like

Maybe related - the model in the retargeter has 113 bones - is it possible I’m exceeding a bone count limit for UEFN?

EDIT: I tried removing bones, reskinning the model to have 74 bones, deleted the previous 113 bone version from the project, recreated the IK Rig for it, and the retarget works to set up, but closing and reopening the retargeter also crashes so seems like not the root of the issue.

hi @thejerenator ,

Looking at the most recent UEFN Log

Please can you Verify your Installation using this post

[2025.03.03-18.53.14:331][675]LogAssetEditorSubsystem: Opening Asset editor for IKRetargeter /DinosaurGame01/Dinos/RTG_Raptor.RTG_Raptor
[2025.03.03-18.53.14:332][675]LogChaosDD: Not creating Chaos Debug Draw Scene for world World_1

So the
Opening Asset editor for IKRetargeter
ON
/DinosaurGame01/Dinos/RTG_Raptor.RTG_Raptor



[2025.03.03-18.53.14:374][675]LogActorComponent: RegisterComponentWithWorld: (/Engine/Transient.World_1:PersistentLevel.AnimationEditorPreviewActor_0.DebugSkelMeshComponent_0) Already registered. Aborting.
[2025.03.03-18.53.14:407][675]LogSkeletalMesh: Display: Waiting for skinned assets to be ready 0/1 (dino_Raptor) ...

The Crash error starts here, this is difficult because protected parts of UEFN do NOT have the symbols table links available, but as highlighted above the problem is a crash in
Opening Asset editor for IKRetargeter

[2025.03.03-18.53.14:785][675]LogWindows: Error: === Critical error: ===
[2025.03.03-18.53.14:785][675]LogWindows: Error:
[2025.03.03-18.53.14:785][675]LogWindows: Error: Fatal error!
[2025.03.03-18.53.14:785][675]LogWindows: Error:
[2025.03.03-18.53.14:785][675]LogWindows: Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION writing address 0x0000000000000118
[2025.03.03-18.53.14:785][675]LogWindows: Error:
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff89bf59d96 ntdll.dll!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff792dd2e34 UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff78cec2f08 UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff788376da3 UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff7883752d2 UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff78838239f UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff788381638 UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff78838060c UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction
[2025.03.03-18.53.14:785][675]LogWindows: Error: [Callstack] 0x00007ff788377a77 UnrealEditorFortnite-Win64-Shipping.exe!UnknownFunction

The fix for this is targeted for a future update. Thank you for reporting!