Parenting: "Cannot move/rename ancestral prim"

I am a TOTAL foreigner to Omniverse Create, but NOT to 3D animation. I have 30 years professional experience as an animator, not programming/coding. This means tech has steadily advanced past the simple realms of dedicated packages like Lightwave, Blender, Maya, etc. USD, with meshes attached to xform nodes, is new to me, but understandable as a UI construct.

With that, I’ve imported/converted an FBX model to USD in Create. No problem. The model was natively created in Lightwave, and it’s layer (mesh) structure and naming was preserved in the xform/mesh nodes, as well as material/shader names and BASIC shader params. The model was exported directly out of LW’s Modeler app to FBX. The Lightwave Object file format (LWO) supports hierarchical parent/child structure, however, such is NOT preserved in the USD. All xforms/meshes exist under a root (world?) xform node having the same name as the REFERENCED USD file.

I MUST rebuild the parent/child hierarchy of the native LW object in Create 2022.2.2, but cannot, because drag-dropping one xform/mesh onto another xform/mesh results in “Cannot move/rename ancestral prim.” Pardon my ignorance at such a basic fundamental operation, but Huh? Why?

As I further fumble around in Create (for lack of instructions/tutorials for babies), I converted all Referenced xform/meshes to Payloads, with no change in parenting ability.

Can an “ancestral” prim (whatever that means… top level? original? first node below root?) be CHANGED to “non-ancestral” (or whatever) so that these xform/meshes can be arbitrarily moved around to rebuild the native LW object’s parent/child tree from whence the USD came from? How?

No, I do NOT need Physics for this project. All objects will be static for a VR walk around-type UX.

Thanks for any assistance/explanations, etc.

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Really?! It’s been almost a week and NO ONE has anything to say? I’m languishing here. I even tried exporting an FBX Scene from Lightwave Layout (2019.1.5) with all 73 layers/meshes properly parented and oriented into their required static positions/orientations (single keyframe animation nonetheless), yet NONE of the parent hierarchy and translations were recognized when converted to USD and added as a new reference in the world scene I’m creating.

SOMEONE has to have an answer and/or workaround!

Hi @DeanScott

Maybe this old post can help shed some light on the problem:


Thank you for the help. I’ll use this next time. While I was waiting, I discovered that UV Maps were not being “preserved” in the FBX export of the LWO. When an albedo image map was applied to the USD converted mesh/layer with a known uv map, the image did not displayed until “Use project UV” was enabled, which, obviously, wasn’t the droid I was looking for.

I have since created models that are fully “setup” with all parts translated and oriented into position, tripled all n-gons, and exported as OBJ, which DID preserve uv maps (export settings set to create one uvmap for the entire model and flatten all layers into one mesh).

So, when and if I need to animate discrete meshes (object layers) in Create, I will export as an “unflattened” OBJ and do the USD Convert and Save Flattened in Create per your guidance above.

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