[x3d-public] url MFString handling

[Andreas Plesch]

Are there suggestions on how to handle back-up "#viewpoint" style urls
for Anchor in case Viewpoints with matching def names do not exist ?

https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/networking.html#Anchor

paragraph nine explains that in this case:

"In this case, if the node derived from X3DViewpointNode is not found,
no action occurs on activation."

This seems to mean that back-up #viewpoint urls should not be tried so
that no action can occur. Would that make the most sense ?

I actually cannot think of a use case for back-up #viewpoint urls, so
that case may be intentionally left ill defined and open to browser
implementations.

Any feedback welcome,

Andreas

On Tue, Apr 19, 2022 at 9:34 PM Andreas Plesch <andreasplesch at gmail.com> wrote:
>
> x3dom currently lacks support for back-up urls to use if the first
> urls do not work. I am trying to add support and wonder how to deal
> with corner cases.
>
> The spirit of the spec. here is pretty clear:
> https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/networking.html#X3DUrlObject
>
> says that a url which cannot be located or if the retrieved data
> cannot be interpreted should be skipped. Subsequent urls are then used
> as back-ups.
>
> Currently, x3dom checks if an inline x3d url can be parsed as xml and
> if so if it has a Scene element.
>
> The first corner case happens if there is a X3D element but it does
> not contain a Scene element. This could be interpreted to mean an
> empty X3D document with an empty Scene, or that it perhaps should be
> skipped as not interpretable. I would probably favor skipping as this
> would normally happen by mistake.
>
> The second corner case is a Scene element without content. Should such
> X3D be considered interpretable ?  I think x3dom is currently set up
> to parse it without error resulting in an empty Scene, probably with
> default NavigationInfo and Viewpoint. So this could be considered
> interpretable and not be skipped.
>
> https://www.web3d.org/x3d/content/examples/X3dSceneAuthoringHints.html#urls
>
> says a result needs to be "legal". But legal is by definition what is
> provided in the spec., eg. comes down to being interpretable.
>
> The tooltip at https://www.web3d.org/x3d/content/X3dTooltips.html#Inline.url
>
> does not seem to further clarify.
>
> Any feedback appreciated,
>
> Andreas
>
> --
> Andreas Plesch
> Waltham, MA 02453



-- 
Andreas Plesch
Waltham, MA 02453