USDZExporter: Make including anchoring properties optional.

[vincentfretin]

Description

Quicklook actually supports anchoring a model on wall or floor (placing a fridge for example) when you don't include the anchoring and planeAnchoring properties in the generated usdz.
There was no way to do that with the options, you could only chose between horizontal and vertical. I propose here to be able to give {ar: undefined} in the options so we don't include those two properties when generating the usdz
Also when those properties are not present, the model is actually not auto rotated by 90 degrees compared to using alignment: 'vertical', see discussion in google/model-viewer#3989 (comment)
I have a branch of model-viewer 3.5.0 based on three r163 where I tested this change https://github.com/vincentfretin/model-viewer/tree/ios-placement-wall

[Mugen87]

There is already the quickLookCompatible property. Could it also be an option to do this:

const alignment = options.quickLookCompatible === false ? `
		token preliminary:anchoring:type = "${options.ar.anchoring.type}"
		token preliminary:planeAnchoring:alignment = "${options.ar.planeAnchoring.alignment}"
	` : '';

If there are use cases where you want to use the anchoring and planeAnchoring properties, maybe a new boolean is easier to understand than ar: undefined. Something like quickLookAutoAnchoring with false as the default value?

[vincentfretin]

I don't think we can use the existing quickLookCompatible here. You may want quickLookCompatible=true for the material fix but still want the anchoring to be floor (alignment horizontal) only.
Another flag quickLookAutoAnchoring may be better indeed, but that one is not a good name imo, it's not really specific to QuickLook here, as far as I know those properties are read for Reality Composer, and probably other softwares that can load usdz. "Auto" in the name is confusing, not sure what that does. I propose includeAnchoringProperties as a better name. What do you think?

[Mugen87]

includeAnchoringProperties sounds good.

[vincentfretin]

Ok, I'll make the changes tomorrow. With includeAnchoringProperties: true as the default in options.

[vincentfretin]

Ok that's done. I also retested my model-viewer build with it.

[vincentfretin]

@Methuselah96 you seems to be the guy doing the latest updates on @types/three.
I did the changes to USDZExporter.d.ts for this PR and #28049 in vincentfretin/DefinitelyTyped@7204ae9 and tested it inside the model-viewer repo, my editor doesn't give typescript error so I think the changes are ok. I'm not sure how to proceed just to be sure this changes are included in @types/three 0.165.0. There may be other changes needed to the types elsewhere for 0.165.0 I am not aware of.

[Methuselah96]

@vincentfretin You can create a PR at https://github.com/three-types/three-ts-types. That's where the maintenance of @types/three happens and for each monthly release we just flush the changes to DefinitelyTyped, so no need to worry about other changes for 0.165.0 since those can be handled separately.

[mrdoob]

Should we set this to false by default?

[vincentfretin]

I think for most models, you want it to be anchored to the floor. Having a model snap to the wall may be confusing if it was not intended, so having it true by default make sense to me. Having the model snap to the wall should be explicitly stated in my opinion. For model-viewer tag, default is ar-placement="floor", and you can change it to ar-placement="wall" (working currently for Android WebXR). For iOS using a-placement="wall" will set includeAnchoringProperties=false in a future PR I'll do once r165 is released.

[mrdoob]

Sounds good 👍