Multiple objects animation (no armature) failed to convert about gltf2usd

[enzyme69]

Kind of related, but I tested a couple of BVH mocap armature into Blender and then trying to export and getting all kind of weird USDZ animation...

The issue seems like the Armature is all just a separate bones, and seems like Apple usdzconvert and GLTF2USD also cannot handle such hierarchy...

BLEND Blender 2.80
BVHRunner_005.blend.zip

Wondering if this is something that can be fixed?

[enzyme69]

As GLTF this works:
ManyAnim.zip

But when converted to USDZ, it failed...

[enzyme69]

It's just 2 box object animated for 10 frames.

I provide the blend, usda, gltf, fbx --- none of them works... only 1 object animating ><
boxanim.zip

[enzyme69]

This one actually works... parented all objects into an empty called ROOT. It's weird. I think I've done something similar in the past (?) with eyeballs animation.

this_work_parented_ROOT.zip

[enzyme69]

I tried with my Torus, with root parent... still does not work. It does not make sense...

Archive.zip

[enzyme69]

My feeling is that somewhat "only 1 animation" possible under 1 action take. Sometimes with the right "hack" multiple objects can work.

I tested with Sketchfab and very often only 1 animated object works... unless ...

[enzyme69]

My quick solution so far is to bring all those animated objects into SKETCHFAB, and then redownloading the gltf...

https://sketchfab.com/3d-models/hundred-torus-procedural-animation-fd8c3e9676944d9c8faf973d47898f39

It's weird but works. Someone at Apple, working on usdzconvert need to investigate this.

[enzyme69]

Twitter Thread:
https://twitter.com/jimmygunawanapp/status/1156732937565429767?s=20

I am still wondering what Sketchfab did when converting BLEND into GLTF that works with the converter...! BIG MYSTERY.

[enzyme69]

From Ash, one solution is to export as DAE, import back into Blender, export as GLTF. Then it works. Strange?

[enzyme69]

The answer might lie in "keyframing" everything, every channel properties and attributes of the objects, so they are all "identical" ...