Shape Keys/Blendshapes disappearing during animation on FBX import

[Ratlz]

Hello! I’m currently working on some animations for my game and now going through the “exciting” process of importing some of them. However, I have been having some issues with this, as it always seems I tend to have when importing any animations.

This time, parts of my mesh controlled by shape keys/blendshapes seem to disappear during the animation.

I initially thought this was because of the drivers I had created, but it seems that some blend shapes work just fine on import.

Here is what I’m working with, the various wires/tubes have corrective blendshapes, it works fine in Blender

I am using Blender 4.1 btw, and Unity 2021.3.10f1

Now, once I import to unity, it looks like this:

Fine! Right? That is, until I play the animation:

The knuckles pull back and suddenly the wires disappear completely.

I have checked the mesh renderer properties to see if the blendshape is even being animated, and yes, it is, but for some reason it still disappears.

Things I have tried so far:

Unselecting “apply modifiers” in the export settings and deleting any existing modifiers

Almost every combination of export settings I can think of

Enabling “import blendshape normals” in the fbx import settings (before I do this, the entire mesh disappears during blendshape value changes)

Keying the blendshapes manually in Unity, now this last solutions WORKS, BUT I do not really want to go through that tedious process. Also, for some reason, I have to delete all existing blendshape keys and rekey for it to work

Plenty of research on this topic, I’m not sure if I’m searching incorrectly but I haven’t found many similar issues

Things I have not tried:

Baking the blendshapes, I’m not sure how but I could maybe find out how, it would just be probably more tedious because then I’d have to combine that animation in Unity

[AndressMartin]

I am having the same problem and I also tried every solution you mentioned, except for baking the blendshapes. Indeed re-keying the blendshapes works, but it’s not practical. Have you found a solution for this?

[eilos_reddrex]

I hate to necromance this several months later, but I was having a similar issue where my model was disappearing when certain blendshapes were effectuated. I was able to fix this for myself by ensuring that there were no effected vertices in the blendshape that weren’t in its assigned vertex group.

I believe, in my case, because I was using proportional editing to update my model blends, I modified vertices that weren’t in the assigned vertex group. Expanding my vertex group to include the entire impacted area seems to have fixed it for me. Hope this helps.