[x3d-public] conversion of glTF metadata to X3D metadata; . versus _ in names

Mon Oct 9 08:40:03 PDT 2023

Seems like an authoring-style preference but it actually has an interoperability consideration.

If these names might be used as DEF identifiers, then it turns out to be important to avoid using a dot (.) notation scheme.  That is because, when converted to equivalent ClassicVRML or VRML97, that character will thwart proper execution of ROUTE statement which use it.

X3D-Edit has option of appending Script nodes as part of a tracing feature, appending debug labels to DEF names for predictability while avoiding other name collisions.  Originally those were using "." to create new names, now using "_" as the connecting character.

Have recently added warnings to X3D-Edit when “.” gets used.  Continuing, will further update X3D Tooltips, X3D Schematron QA, and X3D Tidy cleanups too.  Will further update our collected hints on these issues.

*       X3D Scene Authoring Hints: Naming Conventions
*       https://www.web3d.org/x3d/content/examples/X3dSceneAuthoringHints.html#NamingConventions

I think this consideration only applies to DEF names, not seeing any problem with Metadata node name fields.

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 https://faculty.nps.edu/brutzman

-----Original Message-----
From: x3d-public <x3d-public-bounces at web3d.org> On Behalf Of Andreas Plesch
Sent: Monday, October 9, 2023 7:48 AM
To: Holger Seelig <holger.seelig at yahoo.de>
Cc: X3D <x3d-public at web3d.org>
Subject: Re: [x3d-public] conversion of glTF metadata to X3D metadata

Hi Holger,

Thank you for your feedback. I did not think too much about the name for the Metadata node which holds the scene.extras json value.

To me "scene.extras" is more of a programming convention whereas the value of a name string should be more abstract, or descriptive in a linguistic sense. So a dot would mean a full stop which would not make a lot of sense. But I can see that this is a rather aesthetic consideration, and that a direct json path style name has its own benefits by following very closely the glTF source..

Let us know what you think,

Cheers, Andreas

On Mon, Oct 9, 2023 at 7:25 AM Holger Seelig <holger.seelig at yahoo.de<mailto:holger.seelig at yahoo.de>> wrote:

>

> In X_ITE I also create a WorldInfo, but parse only the toplevel metadata so far.

>

> I like the way you described it, but why do you translate 'scene.extras' to 'scene_extras'? I would leave it as it is.

>

> Holger

>

> --

> Holger Seelig

> Leipzig, Germany

>

> holger.seelig at yahoo.de<mailto:holger.seelig at yahoo.de>

> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcrea

> te3000.github.io%2Fx_ite%2F&data=05%7C01%7Cbrutzman%40nps.edu%7Ccf4f0e

> 97804a4fcea0bf08dbc8d6f0b9%7C6d936231a51740ea9199f7578963378e%7C0%7C0%

> 7C638324597718881372%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQI

> joiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=EBmxnT

> 5bwmCp5%2BnWcoTZT3ttFfXIWF8lNjsRGR0%2FupM%3D&reserved=0

>

> Am 09.10.2023 um 00:14 schrieb Andreas Plesch <andreasplesch at gmail.com<mailto:andreasplesch at gmail.com>>:

>

> glTF can contain rich metadata, on the toplevel and very targeted at

> any sublevel.

>

> At any level, there is an "extras" property which can contain any

> value including objects with arbitrary key:value pairs.

>

> At the toplevel, there is an asset object which has a set of defined

> keys such as "copyright" (as well as its own "extras" property).

>

> In addition to this unstructured metadata for core glTF, there is a

> metadata extension for more structured metadata, extensible through

> namespaces:

>

> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith

> ub.com%2FKhronosGroup%2FglTF%2Fblob%2Fmain%2Fextensions%2F2.0%2FKhrono

> s%2FKHR_xmp_json_ld%2FREADME.md&data=05%7C01%7Cbrutzman%40nps.edu%7Ccf

> 4f0e97804a4fcea0bf08dbc8d6f0b9%7C6d936231a51740ea9199f7578963378e%7C0%

> 7C0%7C638324597718881372%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiL

> CJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=IX

> 8lXkW3K1nuBhZaurJlA6Qz0Db%2BYqjj6bicwxDg4%2FM%3D&reserved=0

>

> There are many ways to map glTF metadata to X3D metadata. How should

> we manage this ? It may make sense to coordinate systematic behaviour.

>

> x3dom uses the WorldInfo node for toplevel metadata:

> - asset object properties go into the info field as key:value string pairs.

> - asset.extras go into a WorldInfo MetadataSet "asset_extras"

> - scene.extras  go into a WorldInfo MetadataSet "scene_extras"

>

> In addition, "extras" at lower levels go into MetadataSets of

> corresponding nodes, using the json value types for Metadata types.

>

> How do other browsers translate "extras" ?

>

> x3dom should also support the KHR_xmp_json_ld extension, by staying

> very close and literal to the glTF data.

>

> One feature of the extension is that sets (packets) of metadata are

> defined once at the toplevel, and then referenced (instantiated) from

> any other level. This seems to map well into DEF/USE. A large

> "KHR_XMP_GLTF" root MetadataSet would contain all metadata and just

> referenced by USE from Shapes/Material etc. I think this could work

> well. I think json property names can become Metadata name values, and

> json value types can be mapped into Metadata types.

>

> If there have been thoughts or attempts to implement the glTF metadata

> extension, any ideas or feedback would be great. Would it be useful to

> start to think about a xml Metadata schema which follows the glTF

> extension requirements and recommendations ? This may not be feasible

> due to the extensible nature of the extension..

>

> Cheers, Andreas

>

> --

> Andreas Plesch

> Waltham, MA 02453

>

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--

Andreas Plesch

Waltham, MA 02453

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