[x3d-public] conversion of glTF metadata to X3D metadata
Andreas Plesch
andreasplesch at gmail.com
Mon Oct 9 20:05:55 PDT 2023
Thanks for the outlook and structure. Keeping the discussion super
informal as a mailing list thread is where we are and possibly remain
for a while.
I am not sure if establishing a dedicated github repo
'glTF-X3D-Metadata-mapping' would be an appropriate next step as
participation then would require a Github account but it seems like
the most convenient way to have a place for discussion, examples,
drafts. Could be worthwhile even if with low traffic. Would
Web3DConsortium want to create such a repository?
Bidirectional mapping seems possible but the focus would be on the
glTF to X3D direction. Hopefully, the reverse direction would emerge
from that. For example, the discussion so far indicates that META
header statements would potentially not be translated to glTF extras.
A related question is if a glTF inline should expose the glTF metadata
to the enclosing scene in some way. A scene may want to display
copyright or license information from glTF metadata, for example. With
X3D inlines it is possible to export and import Metadata nodes but
that is not an option with glTF inlines. Of course it is possible for
an author to add Metadata to the Inline explicitly. Some automatic
exposure would be essential, however, if the Inline url may be changed
by SAI.
So one option may be to automatically export a WorldInfo node derived
from the glTF. Perhaps all glTF nodes after translation to X3D should
be exported by default, with some predictable or discoverable naming
scheme ? And perhaps also be imported by default ?
Regards,
-Andreas
On Mon, Oct 9, 2023 at 6:40 PM Brutzman, Donald (Don) (CIV)
<brutzman at nps.edu> wrote:
>
> Great to learn of all this potential consistency and interoperability!
>
>
>
> I think it is very appropriate for X3D Working Group to collect bidirectional mapping rules between X3D and glTF metadata.
>
>
>
> This can be super informal at first,
> We can collect and publish examples,
> We can write corresponding metadata-conversion validation rules and integrate those test diagnostics in our tool suite,
> This can become a Web3D Consortium Recommend Practice,
> This will be of definite interest to Metaverse Standards Forum (MSF) 3D Web Interoperability Group,
> This might eventually be part of X3D 4.1 specifications.
>
>
>
> 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 10:49 AM
> To: Michalis Kamburelis <michalis.kambi at gmail.com>
> Cc: X3D <x3d-public at web3d.org>
> Subject: Re: [x3d-public] conversion of glTF metadata to X3D metadata
>
>
>
> Thanks, Michalis. x3dom does pretty much the same mapping of extras to metadata, with minor differences:
>
>
>
> The name of the MetadataSet is "extras" except for "scene_extras" and "asset_extras" for WorldInfo MetadataSets.
>
>
>
> Numbers become MetadataFloat rather than MetadataDouble.
>
> MetadataDouble is more appropriate for the json number type, I believe, but MetadataFloat seems more commonly used in X3D since 32bit suffices in most cases.
>
>
>
> Here is the full conversion:
>
> https://github.com/x3dom/x3dom/blob/master/src/util/glTF/glTF2Loader.js#L149
>
>
>
> Does CGE convert the asset object as well ?
>
>
>
> I am also looking for examples of uses of the glTF metadata xmp extension but could not find much so far. I suspect Adobe may have such examples.
>
>
>
> Best, Andreas
>
>
>
> On Mon, Oct 9, 2023 at 1:20 PM Michalis Kamburelis <michalis.kambi at gmail.com> wrote:
>
> >
>
> > In CGE/view3dscene we convert glTF "extras" to X3D Metadata.
>
> >
>
> > Our practical use-case for it is that Blender allows to define "custom
>
> > properties" on various objects (Blender meshes, objects, cameras...)
>
> > and the Blender->glTF exporter puts these "Blender custom properties"
>
> > in "glTF extras". Being able to read these things in Castle Game
>
> > Engine allows authors to define some things in Blender that can be
>
> > game-specific and that are attached to particular objects, e.g.
>
> >
>
> > - "this is a monster spawn point",
>
> > - "this is a destructible wall with 123 hit points",
>
> > - "this is lava",
>
> > - "walking on this floor hurts the player, taking 4 hit points per
>
> > second",
>
> > - "this is a water volume, if player is inside this then it should be
>
> > treated as underwater".
>
> >
>
> > So we convert glTF extras tro X3D Metadata, and give CGE users easy
>
> > way to access this metadata, and everyone is happy, no matter what
>
> > tool and format they use -- they get possibilities :) See
>
> > https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcastle-engine.io%2Fblender%23_custom_properties&data=05%7C01%7Cbrutzman%40nps.edu%7C7b4de2dc055541b84b2108dbc8f0399f%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638324706343579427%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Xpv5MHdNU54VlqbxMSsjnyQ4jB2g92%2Fxyu%2B%2FsvPZzLk%3D&reserved=0 .
>
> >
>
> > To turn glTF (most typical) key-map into X3D Metadata, we wrap it into
>
> > X3D MetadataSet called "ContainerForAllMetadataValues" .
>
> >
>
> > glTF extras like this:
>
> >
>
> > """
>
> > "meshes" : [
>
> > {
>
> > "extras" : {
>
> > "mesh_custom_property" : 1,
>
> > "mesh_property_2" : "some string"
>
> > },
>
> > "name" : "Cube",
>
> > """
>
> >
>
> > -> are converted into X3D metadata like this:
>
> >
>
> > """
>
> > metadata MetadataSet {
>
> > name "ContainerForAllMetadataValues"
>
> > value [
>
> > MetadataDouble {
>
> > name "mesh_custom_property"
>
> > value 1
>
> > }
>
> > MetadataString {
>
> > name "mesh_property_2"
>
> > value "some string"
>
> > }
>
> > ]
>
> > }
>
> > children Shape {
>
> > """
>
> >
>
> > See
>
> > https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
>
> > ub.com%2Fcastle-engine%2Fdemo-models%2Ftree%2Fmaster%2Fblender%2Fcusto
>
> > m_properties&data=05%7C01%7Cbrutzman%40nps.edu%7C7b4de2dc055541b84b210
>
> > 8dbc8f0399f%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C6383247063437
>
> > 35644%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJB
>
> > TiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=kNU3YJFvT%2Br2iMl2ybY
>
> > 272DG4yvy2BNW79fHW3cLjpU%3D&reserved=0
>
> > https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgith
>
> > ub.com%2Fcastle-engine%2Fdemo-models%2Ftree%2Fmaster%2Fblender%2Fcusto
>
> > m_properties_2&data=05%7C01%7Cbrutzman%40nps.edu%7C7b4de2dc055541b84b2
>
> > 108dbc8f0399f%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C63832470634
>
> > 3735644%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLC
>
> > JBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=%2BBwXTwnSh81onXJMz
>
> > aOMktrWiJ9HZz%2B1hYoMtx9s1zY%3D&reserved=0
>
> > for more examples, including both glTF, resulting X3D, and also source
>
> > Blender files.
>
> >
>
> > Regards,
>
> > Michalis
>
> >
>
> > pon., 9 paź 2023 o 16:49 Andreas Plesch <andreasplesch at gmail.com> napisał(a):
>
> > >
>
> > > 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> 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
>
> > > > https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2F
>
> > > > create3000.github.io%2Fx_ite%2F&data=05%7C01%7Cbrutzman%40nps.edu%
>
> > > > 7C7b4de2dc055541b84b2108dbc8f0399f%7C6d936231a51740ea9199f75789633
>
> > > > 78e%7C0%7C0%7C638324706343735644%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiM
>
> > > > C4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7
>
> > > > C%7C%7C&sdata=CIAucgq0iTAEa5jfliJ6ZJiRVKhxrqXn0DsUb9lRJf4%3D&reser
>
> > > > ved=0
>
> > > >
>
> > > > Am 09.10.2023 um 00:14 schrieb Andreas Plesch <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%2F
>
> > > > github.com%2FKhronosGroup%2FglTF%2Fblob%2Fmain%2Fextensions%2F2.0%
>
> > > > 2FKhronos%2FKHR_xmp_json_ld%2FREADME.md&data=05%7C01%7Cbrutzman%40
>
> > > > nps.edu%7C7b4de2dc055541b84b2108dbc8f0399f%7C6d936231a51740ea9199f
>
> > > > 7578963378e%7C0%7C0%7C638324706343735644%7CUnknown%7CTWFpbGZsb3d8e
>
> > > > yJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%
>
> > > > 7C3000%7C%7C%7C&sdata=hbpLcxJiMrjkkdvJgqwCCmZ%2FygW0hVDEsLk34ipndm
>
> > > > Y%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
>
> > > >
>
> > > > _______________________________________________
>
> > > > x3d-public mailing list
>
> > > > x3d-public at web3d.org
>
> > > > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
> > > >
>
> > > >
>
> > >
>
> > >
>
> > > --
>
> > > Andreas Plesch
>
> > > Waltham, MA 02453
>
> > >
>
> > > _______________________________________________
>
> > > x3d-public mailing list
>
> > > x3d-public at web3d.org
>
> > > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
>
>
>
>
>
>
> --
>
> Andreas Plesch
>
> Waltham, MA 02453
>
>
>
> _______________________________________________
>
> x3d-public mailing list
>
> x3d-public at web3d.org
>
> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
--
Andreas Plesch
Waltham, MA 02453
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