Host a single "canonical" annotation JSON file

[JulieWinchester]

Acceptance criteria:

• Create a single complete stand-alone JSON file encoding demo annotations to be used by each demo

[JulieWinchester]

Based on the notes from https://github.com/IIIF/3d/issues/22, here are my suggestions:

• A top-level object with property annotations, value is array of nodes, as used by Voyager JSON.
• Node is object with properties id, normal, position, and value, most or all of which are included in all demo JSON files.
• Node id is integer ID value, as used by Model Viewer and X3D demos.
• Node position coordinates specified relative to model origin, aligning with how they are specified (in practice) in Aleph, Model Viewer, and X3D demos.
• Node normal coordinates should be unit-length vector. What coordinates specify is implementation-specific, but usually determines annotation visibility and/or placement of annotation label.
• Node coordinates must be specified as array of three numeric values, as used by Voyager and X3D demos.
• Node value provides node label title. value and title are both used for this in current demos, value is used by Model Viewer and X3D.
• Node color and scale are excluded.

Suggested example JSON:

{
  "annotations": [
    {
      "id": 0,
      "normal": [ 0.294, 0.114, 0.949 ],
      "position": [ 0.017, 1.806, 0.341 ],
      "value": "visor"
    },
    {
      "id": 1,
      "normal": [ 0.472, 0.059, 0.880 ],
      "position": [ 0.518, 0.956, 0.122 ],
      "value": "glove"
    }
  ]
}

[gjcope]

Per 4/19 meeting - Will we include annotation tag offset in the proposed spec? Would that happen through magnitude of normal vector or in another way?

[JulieWinchester]

This example JSON is now hosted on IIIF 3D repo: https://github.com/IIIF/3d/blob/main/demo/json/label-annotation-issue-17.json

[edsilv]

That's the model-viewer demo updated to use the above annotation json format: https://codesandbox.io/s/model-viewer-annotations-demo-3k5tqo?file=/index.html