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.
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.
Itâs 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. Weâve 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!
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.
Maybe related - the model in the retargeter has 113 bones - is it possible Iâm 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.
[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
[2025.03.03-18.53.14:407][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
Iâve just tried using the IK Retargeter, and ran into the exact same issue as described above.
Build Version: 5.6.0-42223143+++Fortnite+Release-35.00
Iâve tried cleaning the cache, re-installing, creating a new project but it crashes everytime as soon as I try to open a newly created IK Retargeter asset.
[2025.05.14-23.59.09:931][595]LogAssetEditorSubsystem: Opening Asset editor for IKRetargeter /Synty_TEST/RTG_NewRetargeter.RTG_NewRetargeter
[2025.05.14-23.59.09:932][595]LogChaosDD: Not creating Chaos Debug Draw Scene for world World_3
[2025.05.14-23.59.09:935][595]LogStreaming: Display: FlushAsyncLoading(2372): 1 QueuedPackages, 0 AsyncPackages
Not sure if this is related but while troubleshooting I also found that reloading the FN Asset âMedium Base Skeletonâ which is located in: /All/Fortnite/Characters/PlayerBasics crashes the Engine as well.
My IK Retargeter from before 34.10 is still crashing, and my new IK Retargeters are no longer working. Is there any current work around or fix to get a custom skeletal mesh on an IK Rig for a guard?
@Flak
Do we have any updated information on a fix for this? 34.10 has come and gone and this is still an issue keeping us from using UEFNâs custom NPC guard system for several projects.
This process creates new animation assets for your target character from the source. You cannot assign animations that are on your source character to your target character without following this process.
As you go through this tutorial, you will practice the retargeting workflows with a Fortnite character using the FN_Mannequin asset inside the Animation Starter template in Unreal Editor for Fortnite (UEFN).
Open UEFN and create a new project, ensuring that you select the Animation Starter template from the Feature Examplessection.
My PC does have a 32GB page file manually added, which mentioned in past post How to add a 32gb pagefile
my virtual memory usage is 21.7 GB of 38GB just idle using the UEFN Example jumps to 34GB when opening the IK editor and adding a virtual bone
Update
With the release of 5.6.0 at the State of Unreal on 3rd June please visit the new Methuman features at
The further update to UE5.6 is relevant to UEFN IK Retargeted, which uses a different version of MetaHuman. Therefore, UE4/5 Standard Engine Metahuman engine projects will crash.
They will pass UEFN Validity Checking but WILL crash UEFN as different data is being sent into IK Editor unchecked
