Why is the file size of a .reality file so much larger than .usdz?

Question

I am using Apple's new Reality Composer application to attach an image anchor to my .USDZ.

My USDZ file is +/- 5MB when imported to Reality Composer and the reference image is 100KB. When I export my .reality file from Reality Composer, the file size explodes to 17MB.

Answer 1

I suppose file size does definitely depend on file format's architecture.

Sometimes the size of .reality file is greater than .usdz, sometimes it's less (however, .reality files have a much faster uploading time than .usdz).

If you manually rename a scene.reality file to scene.zip file and then unzip it on your Desktop (you can do the same trick with scene.usdz and scene.rcproject files), you must see a folder, named assets, containing several binary .arz files. These files describe Reality Composer's scene: its entities, animation, dynamics, anchor types, etc.

Thus, the total number of .arz files defines the size of scene.reality container in MB.

Also, you can find there an assetMap.json file which might look like that:

{
  "scenes" : [
    {
      "sceneIdentifier" : "EDD9ED29-977B-4C2E-A20A-8B073090B950",
            "sceneName" : "Scene",
             "fileName" : "Scene2.compiledscene"
    }
  ]
}