[x3d-public] Using IMPORT / EXPORT to selectively include parts of glTF file in X3D, and multiply them as much as necessary

[GPU Group]

Looks good - I like it. -Doug
(PS the ExternProto was an analogy. The syntax looks like this:
Shape { url='library.gltf#name }
)

On Mon, Apr 4, 2022 at 8:23 PM Michalis Kamburelis <michalis.kambi at gmail.com>
wrote:

> ( No real avocados were hurt while generating screenshots for this email
> :) )
>
> I started to write an answer to Doug email "Other ways to use gltf >
> like ExternProto" and then I realized that I just pursue a different
> approach, so I may as well create a new thread. The goal is similar:
> how to get *part* of glTF scene into X3D file? But here I decided to
> do it using IMPORT / EXPORT + Inline, not ExternProto.
>
> I thought that IMPORT / EXPORT may be nice, as IMPORT / EXPORT have an
> explicit purpose "make something available to the outer scene".
>
> So I tried how far can I take it. And  implemented it in
> CGE/view3dscene, and made demos :) You can now use IMPORT / EXPORT to
> selectively take (and reuse as many times as you wish) parts of inner
> glTF models inside outer X3D file.
>
> 1. Older demo: I have already used this approach for animations in
> glTF in CGE/view3dsdcene, i.e. I export them from glTF and you can
> IMPORT and control them. See
>
> https://github.com/castle-engine/demo-models/tree/master/blender/skinned_animation
> , file skinned_anim_run_animations_from_x3d.x3dv does
>
> """
> DEF InlinedAnimations Inline {
>    url "skinned_anim.glb"
> }
> IMPORT InlinedAnimations.jump AS jump
> IMPORT InlinedAnimations.walk AS walk
> """
>
> and then it can start  animations jump, walk. They are just TimeSensor
> nodes in X3D. I can ROUTE events to them.
>
> 2. I have now extended this approach to glTF materials (X3D Appearance
> nodes) and transformation groups and cameras (X3D Viewpoint /
> OrthoViewpoint nodes). I can export anything named from glTF this way.
>
> See
> https://github.com/michaliskambi/x3d-tests/tree/master/gltf/avocado_and_exports
> and attached screenshot with scene that can reuse Avocado appearance,
> or transformation, or mesh.
>
> It looks like this:
>
> """
> Switch {
>   children DEF InlinedAvocado Inline {
>     url "glTF/Avocado.gltf"
>   }
> }
> IMPORT InlinedAvocado.Avocado_2 AS AvocadoMeshes
> IMPORT InlinedAvocado.CastleEncoded_2256_Avocado_d AS AvocadoAppearance
> IMPORT InlinedAvocado.Avocado AS AvocadoTransform
>
> Shape {
>   appearance USE AvocadoAppearance
>   geometry IndexedFaceSet { ... }
> }
> ...
> """
>
> 3. Why IMPORT / EXPORT? I felt this way there's less extra concepts.
>
>   A. Do not want to see original glTF? Then place "Inline" inside "Switch".
>
>   B. Writing "IMPORT" is simpler than ExternProto, no need to repeat
> the node declaration.
>
> 4. To make this work:
>
>   A. The browser must make sure to generate EXPORT for all named
> things when importing glTF file.
>
>   B. The browser must be more tolerant for USE clauses than spec.
>
>     X3D spec says (
>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/components/networking.html#IMPORTStatement
> ) """Nodes imported into an X3D scene using the IMPORT statement may
> not be instanced via the USE statement. """. I decided to ignore this
> limit now in CGE/view3dscene, you can reUSE nodes you get with IMPORT.
>
>     There seems to be no drawback from this. We only resolve USE
> looking at IMPORTed names if the name cannot be found in non-imported
> nodes. And it makes IMPORT / EXPORT much more powerful, also for
> X3D<->X3D interaction.
>
> 5. Note: I'm not really trying to make a case that "IMPORT / EXPORT is
> a better approach than ExternProto". They both seem reasonable
> approaches. I just decided to test IMPORT / EXPORT approach to the
> fullest, and I dabbled with it already in the demo with
> skinned_anim_run_animations_from_x3d.x3dv .
>
> Regards,
> Michalis
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