[x3d-public] Extensibility > proto extends builtin > how declare/detect type

[John Carlson]

My perhaps misunderstanding is that only abstract nodes can be extended.

I think OO inheritance has been deprecated except for interfaces, and
wrapping (delegating) ends up being a better choice for most cases.

Doug, are you considering extending of concrete nodes?

On Sun, Nov 9, 2025 at 8:23 AM GPU Group via x3d-public <
x3d-public at web3d.org> wrote:

> Builtin - nodes defined in x3d specs
> Q. how to declare / detect what builtin node type a ProtoDeclare extends?
> Thanks,
> -Doug Sanden
> Normally if we want to change parameters on a builtin node, we tinker
> directly with the builtin node in the scene with routes and scripts.
> In theory builtin nodes are extensible -- a ProtoDeclare can wrap a
> builtin, IS all the fields, and add some spice with a Script node inside
> the proto that updates some fields on each frame. But how is the x3d
> browser code supposed to detect what builtin node type is being extended?
> For example, Shape.appearance.material can take different types of
> material nodes: UnlitMaterial, Material, PhysicalMaterial. In browser
> application code there's different handling of each type:
> if mat.type == UNLIT then
> ...
> else if mat.type == MATERIAL then
> ...
> else if mat.type == PHYSICAL then
> ...
> endif
> But a ProtoInstance has a ProtoDeclare type which doesn't give a hint as
> to which builtin type the ProtoDeclare is extending.
> Q1. How is the code supposed to detect which builtin type to process?
> Q2. If a ProtoDeclare extends a previous ProtoDeclare, which extends a
> builtin type, and assuming single-inheritance chain from builtin, how can
> browser code detect the original bultin being extnded?
>
> _______________________________________________
> x3d-public mailing list
> x3d-public at web3d.org
> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://web3d.org/pipermail/x3d-public_web3d.org/attachments/20251109/79757667/attachment.html>