[x3d-public] filling in field default values

[John Carlson]

Thanks Andreas, it seems like your XML would be useful as a post-processor
for the XML generated from X3DJSONLD.  Or, in particular, taking X3D JSON
and converting to STL.   I don’t see a need for such post-processing in
JSONParser for X3DOM and X_ITE, because I hand off DOM structures to DOM
parsers (which I hope add defaults).  But adding defaults for STL may be
quite necessary, for which I would have to convert to XML first, and then
back to JSON.   Do you have a pure X3D JSON version?   Thanks!

I thought that X3DTidy does what you suggest?  Not sure!

On Sun, Sep 5, 2021 at 6:30 AM Andreas Plesch <andreasplesch at gmail.com>
wrote:

> For X3D importers it is necessary to have knowledge about default values
> for any field. This knowledge could be built into an importer.
> Alternatively, it is possible to augment an X3D document with explicit
> values for all fields. Then any importer can just iterate over the given
> fields and see what it can do with them.
>
> Here is an attempt to do this using X3DUOM, with JS on an online notebook:
>
> https://observablehq.com/@andreasplesch/x3d-defaults
>
> It works by recursively visiting all XML scene child nodes, looking up the
> X3DUOM definition of it's fields and then adding fields with default values
> which are not already present. It is pretty straightforward and seems to
> work well enough. It spits out a new js DOM, and new XML as text.
>
> SF/MFNode fields are ignored. Thinking about it, it may be beneficial to
> have a NULL value XML representation for such fields:
>
> <Appearance>
>   <Material USE='NULL' />
> </Appearance>
>
> would be equivalent to
>
> <Appearance/>
>
> (abusing the USE parameter for lack of a better idea; perhaps an XML
> comment could also work).
>
> This way an importer would have to know less about Material as a field
> value of Appearance. It still would need to know that this means no diffuse
> and specular, and full emissive='1 1 1'. So perhaps the defaults processing
> should also already do this. I do not think that there are too many other
> NULL value defaults with some actual meaning ?
>
> Is there anything else to be aware of ?
>
> Now that I went through this exercise, it should be pretty straightforward
> to do the reverse, eg. remove all field attributes which have default
> values, for optimization.
>
> Thanks for reading, Andreas
>
> --
> Andreas Plesch
> Waltham, MA 02453
> ---on the phone---
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