RealityKit: ARKit + Motion Capture for robot character replication

Programming
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My Goal:
I am trying to create a 3D model similar to the robot shown in Apple’s Motion Capture example at WWDC 2019, which can be used with ARKit 3.0 motion capture to mimic my motions.

Questions:

  • What software did Apple use to create the robot.usdz file?
  • How can I convert formats like .glb/.gltf/.obj/.dae to .usdz using Apple’s Python-based tool while maintaining the scene graph?
  • How can I edit the scene graph of a .usdz file in Xcode and save the changes to the same .usdz file?
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Answers:

  • Apple used Autodesk Maya to create the robot.usdz file.
  • To convert formats like .glb/.gltf/.obj/.dae to .usdz, you can use the usd_from_gltf.py script provided by Apple, which is available on GitHub. The script converts the input file to a USDZ file while maintaining the scene graph.
  • To edit the scene graph of a .usdz file in Xcode and save the changes to the same .usdz file, you can use the USDZ tools provided by Apple, which can be installed from the Xcode menu: Xcode > Open Developer Tool > More Developer Tools. Once installed, you can use the usdzconvert command-line tool to extract the USD file from the USDZ package, edit it using any text editor or 3D modeling software that supports USD, and then use the usdzconvert tool again to create a new USDZ package with the modified scene graph.