[x3d-public] X3D minutes16 July 2020: Inline refresh, https, description; X3DUrlObject: glTF support

[Michalis Kamburelis]

I looked at the new prose that requires support for glTF in Inline in X3D.
Comments:

1. What is the goal of level 4 of the "Lighting" component,
https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD2/Part01/components/lighting.html
? As far as I can see, level 3 of this component already includes
everything -- all nodes (3 light nodes with all fields supported). I don't
know what is different between level 3 and 4.

2. Level 4 of the "Networking" component (bottom of
https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-WD2/Part01/components/networking.html
) now says this:

    """
    Support for .gltf (model/gltf+json) and .bin (application/octet-stream).
    Requires support for Shape component level 2 and Lighting component
level 4.
    """

    My notes:

    - The .bin extension (and MIME type) is not standardized, and it is
also outside of scope for this X3D prose, IMHO. "Inline" node in X3D will
*not* refer to .bin files. The glTF contents refer to .bin files. IOW, the
support for external binary files (with whatever extension) is implicit in
"supporting glTF".

    - If you wanted to include the "packed" glTF files, then you probably
wanted to instead mention .glb ("model/gltf-binary" MIME type). Possibly
you mistakenly confused the .glb and .bin files.

    - This clause is too imprecise, IMHO. What exactly glTF features do we
require to be supported? As you saw in my document on
https://github.com/michaliskambi/x3d-tests/wiki/Converting-glTF-to-X3D , we
have straightforward way to convert many things from glTF to X3D nodes, but
not 100% of glTF. There are lots of details that still need to be filled to
express 100% of glTF in X3D. Even some things I mention on my wiki are
right now just extensions of CGE or X3DOM, which are not (yet?) in X3D
spec. This is a work in progress, and I suppose it will happen across
multiple implementations.

My proposal:

AD 1 - Remove level 4 of the "Lighting" component. It doesn't seem needed.

AD 2 - Change the level 4 of the "Networking" component text, to require
this:

    """
    Support for glTF models in Inline nodes, with .gltf (model/gltf+json)
and .glb (model/gltf-binary) formats.
    Minimum required glTF support:
    - glTF transformation hierarchy (glTF "nodes", which correspond to X3D
"Transform" nodes),
    - glTF meshes,
    - glTF standard physical materials (correspond to X3D PhysicalMaterial
nodes, requires "Shape" component level 2 support)
    - glTF unlit (KHR_materials_unlit) materials (correspond to X3D
UnlitMaterial nodes)
    - loading of external binary data referenced from .gltf files (e.g. for
vertex coordinates)
    """

Regards,
Michalis



sob., 1 sie 2020 o 20:22 Don Brutzman <brutzman at nps.edu> napisał(a):

> Discussed briefly with Dick and Michalis.  Also added requirement for
> corresponding level 4 in Lighting component.
>
> On 8/1/2020 8:05 AM, Don Brutzman wrote:
> > Important gap: we don't specifically call out glTF under Inline node in
> Networking component.
> >
> > Existing prose:
> > ===============
> > 9.4.2 Inline
> > [...]
> > The run-time system can support any number of 3D model resource types as
> long as those follow the abstract model definition (see 2.[RFC2077]),
> provide a registered content type (e.g. model/x3d-xml, model/gltf-bin,
> model/stl, etc.), and can be determined with some form of content
> negotiation (see 2.[RFC2616]). The run-time system must support at least
> one X3D type (e.g. model/x3d-xml) but can also support and negotiate any
> number of X3D encodings and (optionally) non-X3D representation formats.
> > ===============
> >
> > Recommended additions:
> >
> > "Support for loading glTF assets also requires support for Shape
> component level 3."
> >
> > Support levels:
> >
> >      4
> >      Model support
> >      Support for .gltf (model/gltf+json) and .bin
> (application/octet-stream)
> >
> > Normative references
> >
> > * GLTF
> > * GL Transmission Format (glTF) Specification, The Khronos Group,
> Version 2.0, 2017.
> >    https://github.com/KhronosGroup/glTF/tree/master/specification/2.0
> >
> > Related reference section for glTF MIME information:
> >
> > [1] glTF File Extensions and MIME Types
> >
> https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#file-extensions-and-mime-types
> >
> > All review and potential improvement of this important section is
> welcome.
> >
> > all the best, Don
>
> all the best, Don
> --
> Don Brutzman  Naval Postgraduate School, Code USW/Br
> brutzman at nps.edu
> Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
> X3D graphics, virtual worlds, navy robotics
> http://faculty.nps.edu/brutzman
>
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