Shortly after I tried that Omniverse method, Cameron White posted a native Houdini solution. Again not guaranteed to work in all cases, but fixes this particular thing.
My understanding is the drag-n-drop in Omniverse is doing 2 things, getting the skeleton configured for animation (which Sketchfab should be doing), and then binding the animation (which Sketchfab should also be doing). Houdini can do this but there's a few more steps involved (ideally you'd just put these nodes on a shelf or make an HDA, so you don't have to do all these steps every time):
First, prep the skeleton for animation:
- In lops, create a file (or sublayer) node, load in the original sketchfab usdz
- Append a confgure primitive lop
- Set the primitive path, you can drag and drop it from the scene graph tree, or ctrl-click on the selector to bring up a floating outliner. Point it to the skeleton, which is at /scene/SkinnedMeshes/Sketchfab_model/root/GLTF_SceneRootNode/RootNode_0_0/skeletal_3_3/GLTF_created_0/GLTF_created_0_rootJoint/shark_root_4_4/skin0/skeleton
- Enable 'Apply API Schema', set it to SkelBindingAPI
Next, bind the animation to the skeleton:
- Append a edit properties lop
- Click edit properties
- In the filter at the bottom of the first column, search for animationSource
- The column will find skel:AnimationSource in Schemas/SkelBindingAPI. Select it, click the arrow between the columns to add it, click accept
- Set the primitives path to the same skeleton you set earlier
- Set the skel:AnimationSource value to the 'swimming' skelAnimation prim. Easiest to drag and drop it from the scene graph tree, the path should be /scene/SkinnedMeshes/Sketchfab_model/root/GLTF_SceneRootNode/RootNode_0_0/skeletal_3_3/GLTF_created_0/GLTF_created_0_rootJoint/shark_root_4_4/skin0/swimming
The shark should now play its animation. To get this over to sops, you use the same usd character import sop, but this time point to lops instead of a usd on disk:
- In sops, create a usd character animation sop
- Set the lop path (in my case /obj/lopnet1/editproperties2 )
- That will bring in the mesh and animated skeleton
- Append a joint deform which will move the mesh using the joints.