Morph targets have 1 frame offset on FBX import

Hello, my team is encountering the issue reported here: Unreal Engine Issues and Bug Tracker (UE-248975). Morph targets have a 1 frame offset when importing an FBX with Interchange. This was working correctly in 5.4, so the issue seems to have been introduced in 5.5 (our current version).

We are hoping to fix the issue ourselves prior to the 5.6 release. Could you please point us towards specific files or classes in the Interchange plugin that are relevant for starting our investigation? Any guidance on where to start looking would accelerate the debugging process on our side.

Thank you in advance for your time and advice!

Steps to Reproduce
Follow the repro steps logged here: Unreal Engine Issues and Bug Tracker (UE-248975)

Hey,

Depending on how you’re setting up the keys for the morph targets, you can start in

FFbxScene::AddMorphTargetAnimationsor if you’ve attached them to the skeleton as attributes:

FbxScene.AddAnimationI would be curious as to how you’re exporting your scenes from your DCC. I did a little test where I exported your character, animated the morph targets, and then imported the newly created animation in and everything worked as expected. If we can pinpoint differences in the export process we might be able to also debug the issue on engine side easier. Would it be possible to provide a source FBX as well for the animation you’ve packaged with the scene?

Hi Dustin, thanks for the quick turnaround.

Our animator tried renaming the morph targets to match the asset name within Maya (rather than the filename itself) and it works as expected.

I’ll update the title of the ticket to reflect this is resolved and not a regression. We can mark this issue resolved.

Thanks for your help!