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

Thu Mar 26 08:27:38 PDT 2020

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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>> >>> >>>>
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>> >>> >
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>>
>
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