Representing Spatial Icons for WebApps

[raviramachandra]

As a part of immersive-web group, there is a proposal to use spatial / 3D favicons for immersive-web pages/apps. See explainer here: https://github.com/immersive-web/spatial-favicons/blob/master/explainer.md

WebApps manifest today has "icons" member in the manifest, but is restricted to "Image Resources" as per spec. Our initial idea was to "re-use" this member to spatial icons as well, except that the mime type will be a non-image mime type and the sizes will have additional dimension. But the WebApp manifest explicitly says: "Image Resources" and there is an associated algorithm to handle intelligent fetching on need basis.

There are couple of approaches:

1. Extend the "icons" member to include Non Image Resources.
2. Introduce a new "spatial-icon" member to avoid any confusion and let the "platform"/ User Agent make an appropriate decision on which resource to use.

We are open to other ideas and hoping to get some feedback from WebApp manifest spec authors.

[marcoscaceres]

I think 1 should be sufficient:

{
      "src": "icon/some-3d.format",
      "type": "application/some.3d.format"
}

The type can differentiate... the sizes don't matter.

[raviramachandra]

@marcoscaceres a followup question: Should we add some kind of Note that the "icons" array may contain non-image resources for Immersive Web usecases ?
"sizes" is an important requirement that immersive web community had brought up. Since 3D assets have order of magnitude higher file size, the "sizes" attribute would serve as a reference to the platform/UA to download an appropriate asset for the usecase.

This is how we intended to use that:

{
    "src": "asset/high-lod.glb",
    "type": "model/gltf-binary"
    "sizes": "60x60x60"
},
{
    "src": "asset/medium-lod.glb",
    "type": "model/gltf-binary",
    "sizes": "30x30x30"
}

[marcoscaceres]

ok, so we would need to modify sizes to support a third dimension. The sizes processing algorithm is deferred to HTML link rel icons sizes attribute... could HTML pages also use 3D icons?

[cwilso]

yes, HTML pages could use 3D icons too.

Also - Ravi, I seem to recall we discussed that "sizes" was really "detail level", and maybe an arbitrary XYZ bounds wasn't the right way to capture that?

[marcoscaceres]

We discussed this at TPAC. The starting point would be to file a bug with the HTML spec:

• https://github.com/whatwg/html/

You need to get HTML to support "XxYxZ", then Web Manifest will just work based on what HTML does.

[christianliebel]

You need to get HTML to support "XxYxZ", then Web Manifest will just work based on what HTML does.

Related definition: https://html.spec.whatwg.org/multipage/semantics.html#attr-link-sizes

[kenzkiran]

@marcoscaceres @christianliebel I will open an issue on HTML spec.
@cwilso Yes, sizes analogous to quality (or LOD). We can resolve that here:
immersive-web/spatial-favicons#5

[fallaciousreasoning]

The results of the discussion are here. As this is going to be discussed in the HTML spec, shall we close this?

[aarongustafson]

I feel like it’s ok to leave this for now and we can migrate it to the ImageResource repo so (once it lands in HTML) we can include an example spatial icon.

[aarongustafson]

Closing in favor of w3c/image-resource#27