3D Selector for model parts

[tomcrane]

(decisions and suggestions from IIIF/3d#11 (comment))

If the entirety of a 3D model is to be painted into a Scene, the painting annotation body is just the content resource:

"body": {
    "id": "https://example.org/iiif/my-model.someFormat",
    "type": "Model",
    "format": "application/something"
}

If only part of the model is required, a SpecificResource with a Selector is required.

From the Napoli workshop, the proposal is a WktSelector:

https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry

"body": {
    "type": "SpecificResource",
    "source": [
        {
            "id": "https://example.org/iiif/my-model.someFormat",
            "type": "Model",
            "format": "application/something"
        }
    ],
    "selector": [
        {
            "type": "WktSelector",
            "value": "POLYGONZ(( 0 0 0, 1 0 0, 0 1 0, 0 0 1 ))"
        }
    ]
}

Note that the value uses POLYGONZ not POLYGON: https://gis.stackexchange.com/a/206631

It is up to the client to determine how it extracts the part from the whole.

Note that a full example of a SpecificResource may also have one or more transforms (as #xx) if only part of the model is required.

[JulieWinchester]

Personally, I think it is likely that this is impractical for many viewer implementers to achieve on a geometry level (e.g., creating a crop or subset of geometry based on a 3D polygon selector).

At the Basel working meeting on October 26 2023, there was general support for either considering selecting parts of models to be out of scope or at least to put this on the back-burner until 3D spec work has progressed significantly further.

However, this style of selector will probably still be very important for allowing text label annotations to target a 3D polygonal region, even if it is not used for selecting parts of 3D models to annotate into a Scene.

[tomcrane]

Suggest that this issue should be split - the original issue likely deferred, and a new issue created for targeting specific 3D regions of a scene.

[tomcrane]

Split into #2269, propose defer this original issue for now.

[azaroth42]

+1 to defer