I recently ran into this problem and found that it was caused by the new UE5 Skeleton Compatibility feature. In this case, you need to delete all the Skeleton Compatibility Settings, create UE4 and UE5 rig files and target them one by one, then restore your UE5 skeleton configuration.
Making new retargeter worked for me at least, worth trying.
So dumb, but turning off bone debug in 5.1 worked for me.
I have tried this exact workflow many times with no possible solution. That is, if you want hands and feet to work properly. My solution was to do the following:
Download Mixamo animation
Convert mixamo animation with Blender plugin
Convert these now inside of UE5 with the UNAMedia converter found on the marketplace (not free)
Import into your ue project using the metahuman skeleton.
This has worked perfectly for me after about 3 months of daily trial and error. There are some things you will have to figure out on your own but this workflow has allowed me to convert every single mixamo animation to metahuman with flawless results. I have went on to implement hand and feet IK with beautiful results. Good luck.
I hope this can help someone. (UE5.1)
I wasn’t using Metahuman but having the same problem.
It was fine before editing bones for matching initial pose between source and target.
but when I edit a single bone and export animation, it crashed.
Here is the solution:
Don’t edit target skeleton, edit Source Skeleton!
it works magically for me. Checked by restarting editor several times.
Same here. UE 5.3
This- or at least a variant of it- is happening in UE 5.4. It’s happening on any retargeted animation.
Retargeting the animation works, but when I go to open the animation sequence, I get a crash. I tried creating a new skeleton from the existing one and retargeting again- same issue.
I’m getting the same issue as @Godwhacker
Retargetting works fine, exporting is fine, but as soon as I open an exported animation after retargeting, crash…every time.
I get this from the crash log:
Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 758]
Array index out of bounds: 68 into an array of size 68
From what I can tell, it’s referencing the number of bones in the skeleton in the IK Retargeter asset…
The
The source skeleton has 87 bones, 70 with labels
The target skeleton has 85 bones, 70 with labels
so…the point is, I really don’t know what’s going on, but it’s annoying.
Yeah, I agree, from what I can pick apart the out of bounds array has to do with number of bones possibly to be retargeted being at a mismatched count. I genuinely do not know either, but maybe.
I figured it out…
I added 2 bones to the target skeleton, and no crash or error…
So yeah, the number of bones between the source and target has to match exactly regardless of where the rigs come from
I’m still getting an error on the project file when starting up the project: “The UnrealEditor.target file does not exist. Would you like to build the editor?”
If I select yes, it then tells me could not be compiled. Try rebuilding from source manually.
I don’t know what to do about that now that I know what happens.
Oh shoot! I’m sorry, I think I just bumped the post when I saw it was unsolved.
No, you’re good…it still kind of isn’t resolved because you have to add bones to one or the other, so Epic needs to fix that…and fix the issue with what I put in my edited post.
1 Like
Same issue in 5.4 with the same log:
Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 758]
It’s definitely still happening in 5.4. I now have a load of animations that are essentially poisoned- if I open them, I get a crash. I retargeted from a skeleton with a lot of bones to one with far fewer, so just adding bones until the number in the array is large enough isn’t really feasible.