[x3d-public] coord = NULL ?

[Andreas Plesch]

Thanks for your response, Don.

Good point on the warning. I think it is clear enough that NULL for
coord should not lead to browser errors.

NULL as default value often means semantically in the spec. that no
value is provided. As thinking aid, here is a sentence
"If no value is provided for coord, there is no geometric rendering."
To make clear that this does not mean that the node is inert "but all
events are processed." may be augmented.

But I am not sure if either addition would be really necessary. I just
came across that while trying to translate IndexedTriangleSet to
BabylonJS.

A small oversight:

In https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/components/rendering.html#IndexedTriangleSet,
second paragraph, second sentence "Descriptions of the color, coord,
normal, and texCoord fields are provided in the Color, ColorRGBA,
Coordinate, Normal, and TextureCoordinate nodes, respectively." the
word "Coordinate" is currently not linked to

https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/components/rendering.html#Coordinate

as it is in all other node descriptions.

all the best , Andreas

On Mon, Nov 8, 2021 at 12:02 AM Brutzman, Donald (Don) (CIV)
<brutzman at nps.edu> wrote:
>
> Good question, thanks Andreas.
>
> In general the architecture specification tries to remain silent about reporting errors and warnings.  We're not opposed to them!  However detection and handling of such conditions can reduce performance and sometimes be problematic to comply with, so we avoid that.
>
> Your comments seem sensible to me.  I'd certainly not expect to see any geometric rendering of a Shape if no coordinates were provided by the author.  I will check X3D Schematron to confirm whether we have warnings about that model condition.  Perhaps it should be noted in X3D Tooltips and X3D Scene Authoring Hints as well.
>
> BTW recommend using version "CD1" to see continuing editorial corrections by Dick Puk and I following recent CD ballot submission to ISO.
>
> * https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD1/Part01/components/rendering.html#X3DComposedGeometryNode
>
> 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: Sunday, November 7, 2021 7:59 PM
> To: X3D Graphics public mailing list <x3d-public at web3d.org>
> Subject: [x3d-public] coord = NULL ?
>
> X3DComposedGeometry based nodes have a coord field which is NULL by default:
>
> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4-CD/Part01/components/rendering.html#X3DComposedGeometryNode
>
> But the spec. language does not spell out what a browser should do with a NULL value for the coord field, in contrast to other fields like color or normal.
>
> It may seem nonsensical to have a geometry node with null coordinates and therefore deemed outside the scope of the spec. But as it is an in,out field, coord may be updated, and an initial NULL may have then use cases. So a NULL value should at least generate no fatal error, and probably no warning. Are there other aspects to consider ? Should there be a difference between a NULL coord field, and a default Coordinate node with an empty array for its point field ? It seems not.
>
> It seems self-evident that there should not be any rendering activity, and that routing through other fields should still occur while coord is NULL.
>
> It may be fine to leave behaviour to browsers with the expectation to do something sensible.
>
> Andreas
> --
> Andreas Plesch
> Waltham, MA 02453
>
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-- 
Andreas Plesch
Waltham, MA 02453