OMI_ref

[robertlong]

Rendered

[mrmetaverse]

Practical and super interesting. Curious, could this afford us something like crafting?

[robertlong]

@humbletim stated that node refs should be able to specify a bounding box for the object to fit within. Kinda like <image width="w" height="h" />

[robertlong]

Yinch and Lyuma requested that nodes be able to load fallbacks for progressive loading.

We need to handle recursion. Either by allowing it with a max depth or disallowing it entirely.

So long as there's no actual cycles recursion should be allowed. Ex. nodes cannot reference themselves but a node can reference another object within it's own document.

[expenses]

Cool, I like this a lot! I've implemented something similar for https://github.com/expenses/mateversum. Here's an example: https://github.com/expenses/mateversum/blob/master/web/sponza_with_mirror.json

Some things that would be important to me:

• As well as a 3-dimensional translation field, I'd be great to have a scalar scale field and a rotation field of some kind. As these files would ideally be human-writable, I think that an euler rotation makes the most sense, with each field being a value in degrees. These can be transformed to quaternions after being loaded.
• I'm not sure if there's a way to specify this in gltf already, but it'd be nice to have a way to specify 'global' textures. Because I'm doing Image Based Lighting (IBL) I want to specify a diffuse cubemap, a specular cubemap and a GGX lookup table.

[madjin]

Noice, I made a quick example of a Sponza + mirror in Webaverse to compare with (https://github.com/madjin/sponza)

More docs on Webaverse scenes: https://docs.webaverse.com/docs/engineering/app/scene/scene-file-quickstart

{
  "objects": [
    {
      "type": "application/light",
      "content": {
        "lightType": "ambient",
        "args": [[255, 255, 255], 2]
      }
    },
    {
      "type": "application/light",
      "content": {
        "lightType": "directional",
        "args": [[255, 255, 255], 2],
        "position": [1, 2, 3]
      }
    },
    {
      "position": [
        0,
        0,
        0
      ],
      "start_url": "https://madjin.github.io/sponza/glTF/Sponza.glb"
    },
    {
      "position": [
        0,
        0,
        -2
      ],
      "start_url": "https://webaverse.github.io/mirror/"
    }
  ]
}

More about Webaverse here: https://github.com/webaverse

[humbletim]

here are a few links to existing "JSON scene dialects" found in the wild.

(hoping we can compare/contrast some of these at a next meeting to help determine which use cases fall in or out of scope of OMI_ref)

• plan2scene Example

• tangrams Example

• Yocto/GL Example

• Decentraland Examples:

  • avatar-assets
  • multiple scene composition
  • individual scene asset

• hifi Example

• KhronosGroup Example

• Smithsonian Voyager SVX Example

• metaverses.io Example

• OpenARCloud GeoPose Examples

• WallpaperEngine Example

• SceneJS Example

• AFRAME Example (HTML)

[robertlong]

Awesome list! Thanks @humbletim! Can people try to take a look over these by next meeting? We can also go over them then.

[madjin]

This topic reminds me of A's presentation at a recent M3 demo day: M3 Mixer: A on Metaverse Clipboard

Text is the most portable data format. A shows demo of a webxr editor where he spawns cubes, ctrl-c to copy, then ctrl-v to paste in another webxr app. Metaphor for lowest friction interop between programs being the clipboard.

View on sketchfab: https://sketchfab.com/3d-models/a-presentation-be95c13d41104bffa84f815c6d6d4d53

[gm3]

Great list of metadata examples! Will take a look, cheers!

[humbletim]

@robertlong mentioned discovering Khronos/gLXF (spec currently being drafted)

example of .glxf JSON file:

{
    "asset": {
        "version": 2.0,
        "experience": true
    },
    "assets": [
        {
            "name": "Soccer Player",
            "uri": "soccer_player.gltf",
            "scene": "player"
        },
        {
            "name": "Ball",
            "uri": "ball.gltf",
            "nodes": [ "ball" ],
            "transform": "none"
        }
    ],
    "nodes": [
        {
            "name": "Root Node",
            "children": [ 1, 2 ]
        },
        {
            "name": "Soccer Player Node",
            "asset": 0,
            "translation": [ 0, 0, 0 ]
        },
        {
            "name": "Soccer Ball Node",
            "asset": 1,
            "translation": [ -10, 0, 35 ]
        },
        {
            "name": "Ball Destination Node",
            "translation": [ 51, 0, 80 ]
        },
        {
            "name": "Ball Origin Node",
            "translation": [ -10, 0, 35 ]
        }
    ]
}

[humbletim]

another interesting example that supports referring to specific named nodes in an external resource.

• Iron Engine Scene.json Example

...
    "name": "Scene.json",
    "objects": [
        {
            "data_ref": "mesh_Cube.json/Cube",
            "dimensions": [
                2.0,
...

[robertlong]

I'm no longer working on this spec and it needs another champion to continue.