quick look configuration how to write a usdz with?

Based on what I read in https://developer.apple.com/documentation/RealityKit/validating-usd-files, the APIs that Apple provides don't (currently?) provide any support for writing out USD files, and specifically for variants - the tooling of the various renderers allows you to select between variants, but it expects the variants to already be defined within the USD file.

There is a Entity.write(to: URL) capability that is new this year, but it creates a proprietary .reality format that isn't a stock USD(a/z) file. Based on my digging, the .reality file is a possibly a super-set of USD, because when it was created, the analog to capabilities needed in RealityKit didn't exist in the USD spec. Which may be (I suspect) still the case today.

i have to process your answer trying to understand it

thank you very much for your explanation... now i have to truly understand it... 😄

I recommend following the tutorial on Pixar's website to learn more about variants and how to author them using the USD API https://openusd.org/docs/Authoring-Variants.html

Additionally, you can also author variants inside 3D applications like Maya and Houdini, but I recommend first starting with the API tutorial above. If you don't have the USD API, you can get it for Python by running pip3 install usd-core. Note that you will need Python installed for this to work.

To convert a USDA file to USDZ, you can use the usdzip command, that is provided as part of macOS 15.

To create the USDZ file, you would run

usdzip output.usdz -a input.usda This will create a file called output.usdz

For example, if I save this text from the Pixar tutorial as input.usda, and run the command above, I will be get back a USDZ file that can be used by the configurator.

#usda 1.0
(
    defaultPrim = "hello"
)

def Xform "hello" (
    variants = {
        string shadingVariant = "green"
    }
    prepend variantSets = "shadingVariant"
)
{
    custom double3 xformOp:translate = (4, 5, 6)
    uniform token[] xformOpOrder = ["xformOp:translate"]

    def Sphere "world"
    {
        float3[] extent = [(-2, -2, -2), (2, 2, 2)]
        color3f[] primvars:displayColor
        double radius = 2
    }

    variantSet "shadingVariant" = {
        "blue" {
            over "world"
            {
                color3f[] primvars:displayColor = [(0, 0, 1)]
            }
        }

        "green" {
            over "world"
            {
                color3f[] primvars:displayColor = [(0, 1, 0)]
            }
        }

        "red" {
            over "world"
            {
                color3f[] primvars:displayColor = [(1, 0, 0)]
            }
        }
    }
}