When importing from a USDStageActor into Unreal, via the USDStage GUI, if prims have single time-sampled attributes the transforms reset to origin ( the keyed or timesampled transform is lost ).
There may be an issue with USD prims with time-sampled attributes - or at least an issue of user expectations.
When importing from a USDStageActor into Unreal, via the USDStage GUI, if prims have single time-sampled attributes the transforms reset to origin ( the keyed or timesampled transform is lost ). The reason they are lost is there is not a Level Sequence generated when imported - as it appears that the USDStage's Level Sequence does not key any attributes when only one time sample exists on a prim. The xform is also not baked onto the imported asset, so there is no way to return the imported geo back to its proper location.
When you reference the same a USD file and layer an over a non-timesampled xform the transforms were maintained on import - on the sub-location on the asset.
There are three usd file examples:
A couple of things to note about these examples:
The usd files can be found in the following Box link. In that Box directory is a Problem_Description.boxnote for more information.
I recorded a video walking thru the example usda files and some observations I had.
The immediate issue to address is to handle the single timesample case better, maybe by keying it in the USDStage's Level Sequence, and then also generating a Level Sequence on import.
The next step would be adding an Import option to bake down xforms and/or keys to a single frame onto the imported assets.
Let me know if you have any questions, or want to discuss the import topic.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-151557 in the post.