[x3d-public] Finding more than one use of a DEF in VRML

Thu Mar 26 14:06:05 PDT 2020

Maybe I am missing it, but how does an ID correspond to a DFF? 
My mem is going and maybe rtfm again, but correspond(s) is not the right word.  
It must be a unique string and is independent of an ID, or am I missing new stuffs.

➢ Finding more than one use of a DEF in VRML

There are these uses: 
designate a node that is part of the scenegraph, 
USE the DEF to insert node in the scenegraph,
be anchor target,. 
Same as XML or classic or any other x3d
Joe

Sent from Mail for Windows 10

From: John Carlson
Sent: Thursday, March 26, 2020 8:51 AM
To: Michalis Kamburelis
Cc: X3D Graphics public mailing list
Subject: Re: [x3d-public] Finding more than one use of a DEF in VRML

Doing a bit more searching:

https://www.web3d.org/x3d/content/X3dTooltips.html#ID 

 "ID is a NMTOKEN that is unique within the scene, corresponding to the DEF attribute in X3D."

On Thu, Mar 26, 2020 at 10:34 AM John Carlson <yottzumm at gmail.com> wrote:
I feel like an idiot.  I even read the specifications on this one and didn't get very far.

On Thu, Mar 26, 2020 at 10:27 AM John Carlson <yottzumm at gmail.com> wrote:
Now I understand why I got all the blank stares when I suggested using a symbol table for DEFs. To me, a DEF is like a var in ECMAScript.  I guess DEF is more like id attribute in HTML5: double references are "allowed", for some reason.

Very confusing for someone coming from a standard programming language like Java.

Now i understand what you guys mean when you say ID/IDREF (at least the first half).

John

On Thu, Mar 26, 2020 at 10:21 AM John Carlson <yottzumm at gmail.com> wrote:
Gotcha. 

On Thu, Mar 26, 2020 at 9:50 AM Michalis Kamburelis <michalis.kambi at gmail.com> wrote:
There isn't a "name" field general for all nodes. Some specific nodes
have "name" field, but it's specific to these nodes and their needs
(MetadataXxx, CADPart, CADLayer, HAnimHumanoid, HAnimJoint,
X3DVertexAttributeNode etc.). And it has special interpretation (e.g.
for X3DVertexAttributeNode this "name" is a shader per-vertex
attribute name).

So when X3D specification (link you posted,
https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/concepts.html#DEFL_USESemantics
) talks about """Node names""" -> it means that names assigned using
DEF. Not names assigned using name="xxx"...

Confusing, I know.

It's an unfortunate collision of terms, the "name of X3D node" can
indeed be interpreted in various ways, depending on context. When
someone talks of a general X3D node, then they surely mean "name
assigned using DEF".

Regards,
Michalis

czw., 26 mar 2020 o 15:25 John Carlson <yottzumm at gmail.com> napisał(a):
>
> Maybe I'm confused.  Are node names
>
> name="node name"
>
> or
>
> DEF="node name"
>
> I've been using "DEF value" for "DEF keyword" I think.
>
> I think if the DEF keyword is not unique with in a scope, my ProtoExpander will blow big chunks, but I'll have to check.
>
> There were many discussions on the mailing list about this, and maybe I didn't understand because I wasn't phrasing the question properly.
>
> In some cases in the wrl previously reported, the DEF keyword is not unique in the source file, but I didn't check for the source (that is, I didn't inspect the source file very much), there could be additional scope stuff like a PROTO.
>
> John
>
> On Thu, Mar 26, 2020 at 7:25 AM Michalis Kamburelis <michalis.kambi at gmail.com> wrote:
>>
>> I have to correct myself -- I see x3d 3.3 specification says """Node names shall be unique in the context within which the associated DEF keyword occurs."""
>>
>> All right, that's good. Looks like this rule was improved at some x3d version. That's good, it is a better idea to have all names unique (e.g. for easy EXPORT).
>>
>> It still remains a question why did my converter generate repeated DEF. It should not, if source VRML didn't repeat them. I'll look into it -- please send input to reproduce it:)
>>
>> Regards,
>> Michalis
>>
>> W dniu czw., 26.03.2020 o 12:09 Michalis Kamburelis <michalis.kambi at gmail.com> napisał(a):
>>>
>>> As I mentioned in the other thread, multiple DEF with the same name
>>> are just allowed by the X3D specification. Last one "wins" (obscuring
>>> the others with the same name). Maybe they should be disallowed or
>>> discouraged, it's another discussion. But right now they are allowed
>>> and proper VRML / X3D reader should understand them.
>>>
>>> As to why my exporter created them -- I need to see the relevant input
>>> file to answer it. There should be a good reason for it :)
>>>
>>> Regards,
>>> Michalis
>>>
>>> czw., 26 mar 2020 o 06:30 John Carlson <yottzumm at gmail.com> napisał(a):
>>> >
>>> > DEF/USE is how multiparent nodes are achieved, but all DEF and USE with the same value are the same node, except for a few special cases.
>>> >
>>> > This is what one reason why HTML DOM is a poor choice...the nodes have only one parent.
>>> >
>>> > Or I’m still battling windmills?
>>> >
>>> > John
>>> >
>>> > On Wed, Mar 25, 2020 at 10:16 PM GPU Group <gpugroup at gmail.com> wrote:
>>> >>
>>> >> double defining:
>>> >> - this stymied me too, until I realized the DEF/USE are just for the parser, and its the sequence that counts although different for different browsers.
>>> >> - if you redef 3 times, then USE, what will you get?
>>> >> - that depends on the web3d browser, with some sticking to the first DEF, some the last DEF.
>>> >>
>>> >> On Wed, Mar 25, 2020 at 9:01 PM John Carlson <yottzumm at gmail.com> wrote:
>>> >>>
>>> >>> If one DEF specified a shape and another DEF with the same value with a different shape, wouldn't the 2 browsers show different shapes if they picked different DEFs?
>>> >>>
>>> >>> I don't think double DEFs should be allowed within the same namespace.
>>> >>>
>>> >>> John
>>> >>>
>>> >>> On Wed, Mar 25, 2020 at 9:12 PM GPU Group <gpugroup at gmail.com> wrote:
>>> >>>>
>>> >>>> Chisel? "it was simply put in the public domain by Trapezium when they folded many years ago. They didn¹t specify any license" - Louka
>>> >>>> http://dug9.users.sourceforge.net/web3d/temp/chisel-src.zip
>>> >>>> But I suspect double-deffing isn't illegal. I think I've been through it, and different browsers honored the first or last definition.
>>> >>>> -Doug
>>> >>>>
>>> >>>> On Wed, Mar 25, 2020 at 7:43 PM John Carlson <yottzumm at gmail.com> wrote:
>>> >>>>>
>>> >>>>> That is, more than one DEF with the same value.
>>> >>>>>
>>> >>>>> I realize that separate PROTOs may have the same DEF due to namespaces.   Unfortunately writing a Unix script to find this takes massive brain power.
>>> >>>>>
>>> >>>>> John
>>> >>>>>
>>> >>>>> On Wed, Mar 25, 2020 at 8:37 PM John Carlson <yottzumm at gmail.com> wrote:
>>> >>>>>>
>>> >>>>>> I’m not particular looking for a vrml parser unless it catches double use of a DEF.
>>> >>>>>>
>>> >>>>>> Thanks,
>>> >>>>>>
>>> >>>>>> John
>>> >>>>>>
>>> >>>>>> I’m thinking my next project might be a VRML validator if there isn’t one handy?  Anyone?
>>> >>>>>>
>>> >>>>>> I know I can translate VRML to XML.
>>> >>>>>>
>>> >>>>>> John
>>> >>>>>>
>>> >>>>>> On Wed, Mar 25, 2020 at 3:38 PM John Carlson <yottzumm at gmail.com> wrote:
>>> >>>>>>>
>>> >>>>>>> Say, where is a VRML Validator? !!!!
>>> >>>>>>>
>>> >>>>>>> On Wed, Mar 25, 2020 at 3:33 PM John Carlson <yottzumm at gmail.com> wrote:
>>> >>>>>>>>
>>> >>>>>>>> I will download X3D-Edit and do some validation on the files, or go to the validation site @ savage
>>> >>>>>
>>> >>>>> _______________________________________________
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>>> >>>>> x3d-public at web3d.org
>>> >>>>> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>> >>>>
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>>> >
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