[x3d-public] X3D 4.0 specification problem: ClassicVRML Encoding, clause 5 Encoding of fields

John Carlson yottzumm at gmail.com
Tue Dec 24 07:56:49 PST 2024 

On Tue, Dec 24, 2024 at 9:36 AM John Carlson <yottzumm at gmail.com> wrote:

>
>
> Question:  is an MF field value with just brackets valid?
>


I found that this is valid in the grammar.

Thanks,

>
> John
>
>
> On Tue, Dec 24, 2024 at 3:36 AM Michalis Kamburelis via x3d-public <
> x3d-public at web3d.org> wrote:
>
>> Hi,
>>
>> I looked at
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19776-2v4.0-WD1/Part02/EncodingOfFields.html
>> --- looks like a great improvement, thank you! The new prose with new
>> examples is indeed more immediately obvious. It's also a good idea to
>> use real nodes / fields for the examples, not only artificial fooXxx
>> (as before), this makes things even more clear.
>>
>> One minor thing I noticed: in "5.1.2 Description" there's a typo,
>> "around ingle-valued field types". You missed "s" in "single-valued"
>> :)
>>
>> John also has good points (kudos for noticing):
>>
>> - SFVec2d example in 5.17 is wrong (" inputOutput SFVec2d field20 [
>> 0.0 0.0 ]"), it should *not* use [ ].
>>
>> - SFVec4d in 5.21 is also indeed wrong, "inputOutput SFVec4d field24a
>> [ 1.000000000001 42 666.35357878 32.6 ]" -> should have no brackets.
>>
>> Regards,
>> Michalis
>>
>> wt., 24 gru 2024 o 02:18 Brutzman, Donald (Don) (CIV)
>>
>> <brutzman at nps.edu> napisał(a):
>> >
>> > It took several days of effort but this clause is now fixed up.  Review
>> and comments welcome.
>> >
>> > Mantis 1484: ClassicVRML Encoding of Fields clause does not include
>> proper SFVec examples
>> > https://mantis.web3d.org/view.php?id=1484
>> >
>> > X3D encodings Part 2: Classic VRML encoding, 5 Encoding of fields
>> >
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19776-2v4.0-WD1/Part02/EncodingOfFields.html
>> >
>> > Happy holidays with X3D and VRML!  🙂
>> >
>> >
>> > 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
>> >
>> >
>> >
>> >
>> > ________________________________
>> > From: x3d-public <x3d-public-bounces at web3d.org> on behalf of Brutzman,
>> Donald (Don) (CIV) via x3d-public <x3d-public at web3d.org>
>> > Sent: Thursday, December 19, 2024 10:43 AM
>> > To: Michalis Kamburelis <michalis.kambi at gmail.com>
>> > Cc: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>; Extensible 3D
>> (X3D) Graphics public discussion <x3d-public at web3d.org>;
>> khyoo at chungbuk.ac.kr <khyoo at chungbuk.ac.kr>; Myeong Won Lee <
>> myeongwonlee at gmail.com>
>> > Subject: Re: [x3d-public] X3D 4.0 specification problem: ClassicVRML
>> Encoding, clause 5 Encoding of fields
>> >
>> > [changed subject line to reflect changed focus]
>> >
>> > Thanks again for your patient explanations Michalis, totally helpful.
>> We have finally zoomed in on the real problem.
>> >
>> > It is surprising (and maybe a little disappointing) that we have had
>> such egregious and misleading omissions in the ClassicVRML field
>> descriptions clause, unreported for so many years (since VRML97
>> apparently).  That was the cause of my mistaken thinking that encoding of
>> values were similar.  Nevertheless, it is a nice holiday present that we
>> have finally identified this source of confusion so that it might finally
>> get fixed.
>> >
>> > X3D 3.3 ClassicVRML Encoding, clause 5 Encoding of fields
>> >
>> https://www.web3d.org/documents/specifications/19776-2/V3.3/Part02/EncodingOfFields.html
>> >
>> > Have checked X3dToClassicVRML.xslt and X3dToVRML97.xslt stylesheet
>> converters, X3DJSAIL export, and our many many X3D Example Archives
>> scenes.  They match what you are saying (thank goodness).
>> >
>> > I am adding this problem to the issue tracker.  Dick and I will work on
>> a revision for community review.
>> >
>> > Mantis 1484: ClassicVRML field reference does not include proper SFVec
>> examples
>> > https://mantis.web3d.org/view.php?id=1484
>> >
>> > Future revisions will appear in github and as follows.  Let's watch for
>> similar unintended errors in the specification, the ripples from spec
>> errors spread a wide wake.
>> >
>> > X3D 4.0 ClassicVRML Encoding, clause 5 Encoding of fields
>> >
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19776-2v4.0-WD1/Part02/EncodingOfFields.html
>> >
>> > Of course I also agree that fast efficient rigorous parsing holds
>> essential importance.  Your castle-model-viewer and castle-model-converter
>> continue to be essential in our sustained efforts to get ClassicVRML
>> exactly right.
>> >
>> > Castle Model Converter (formerly tovrmlx3d))
>> > https://castle-engine.io/castle-model-converter
>> >
>> > Looking forward to continuing relentless progress with ClassicVRML and
>> X3D!  🙂
>> >
>> >
>> > 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
>> >
>> >
>> >
>> >
>> > ________________________________
>> > From: Michalis Kamburelis <michalis.kambi at gmail.com>
>> > Sent: Wednesday, December 18, 2024 8:38 PM
>> > To: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
>> > Cc: Extensible 3D (X3D) Graphics public discussion <
>> x3d-public at web3d.org>; khyoo at chungbuk.ac.kr <khyoo at chungbuk.ac.kr>;
>> Myeong Won Lee <myeongwonlee at gmail.com>
>> > Subject: Re: [x3d-public] X3D 4.0 specification problem:
>> TextureProjectorparallel.fieldOfView
>> >
>> > NPS WARNING: *external sender* verify before acting.
>> >
>> >
>> > Hi Don,
>> >
>> > AD A -
>> >
>> > No, when writing the SFVec4f in X3D classic encoding, the square
>> > brackets "[ ... ]" cannot be used. I believe my understanding matches
>> > both the spec and all existing X3D implementations.
>> >
>> > 1. The example you noticed (on
>> >
>> https://www.web3d.org/documents/specifications/19776-2/V3.3/Part02/EncodingOfFields.html#SFVec4f
>> > ) ... shows MFVec4f, not SFVec4f .
>> >
>> >     It's indeed a bit misleading, as the spec section titled "5.20
>> > SFVec3f and MFVec3f" describes both MF- and SF- variants. And the
>> > example "fooVec3d [ 1.000000000001 42 666.35357878 32.6, 7 94
>> > 0.100000000007 143.998 ]" lacks any annotation. Adding there a
>> > description would help: "This is an example of MFVec4f in classic
>> > encoding, fooVec3d contains here two 4-dimensional vectors." .
>> >
>> > 2. On the same page, the text higher makes it clear that "square
>> > brackets" are used for multiple-value fields: """Multiple-valued
>> > fields are written as an ordered list of values enclosed in square
>> > brackets and separated by whitespace."""
>> >
>> > 3. The grammar on
>> >
>> https://www.web3d.org/documents/specifications/19776-2/V3.3/Part02/grammar.html
>> > confirms it:
>> >
>> > """
>> > mffloatValue ::=
>> >     sffloatValue |
>> >     [ ] |
>> >     [ sffloatValues ] ;
>> >
>> > ....
>> >
>> > sfvec4fValue ::=float float float float ;
>> > """"
>> >
>> > No square brackets for sfvec4fValue . (And that's good I think; square
>> > brackets are consistently used in X3D classic encoding for lists of
>> > values.)
>> >
>> > I do find the grammar very helpful to resolve such questions :) It's
>> > unambiguous, and implementations (using my own) follow it literally.
>> >
>> > So, I think my concern still stands. Changing
>> > OrthoViewport.fieldOfView type (MFFloat -> SFVec4f) would break
>> > parsing of all the models in X3D classic encoding (and VRML 2.0) that
>> > specify value of this field. They use right now square brackets [ .. ]
>> > (necessary for MFFloat with > 1 value), which are not allowed for
>> > SFVec4f.
>> >
>> > I honestly don't think there's a way to avoid it, except reverting
>> > this spec change. I cannot change in our implementation
>> > OrthoViewport.fieldOfView to SFVec4f -- I have users using classic
>> > encoding, and VRML 2.0 too, we cannot really break it. And maintaining
>> > exceptional treatment in the parser (to allow both MFFloat and
>> > SFVec4f) is not maintainable, we cannot have special rules like this
>> > (that depend on node and field name) at the parser level.
>> >
>> > I know that we could change the grammar (to allow [ ... ] in SFVec4f)
>> > but IMHO we should not change the grammar (which will complicate
>> > parsing) just to account this one single exceptional change to one
>> > field in one node.
>> >
>> > AD B - No, I didn't describe any special handling in our parser. And
>> > such exceptions during parsing would be really hard to maintain, I
>> > deliberately don't want them. Parser should not have any special rules
>> > for specific nodes or fields -- this makes parser code more obvious.
>> >
>> >    On the contrary -- we parse OrthoViewport.fieldOfView as MFFloat
>> > now. Only later (after parsing) we just look at the count of MFFloat.
>> > When it's less than 4, we treat the remaining numbers as if they were
>> > default. But this is nice "local" code near OrthoViewport.fieldOfView
>> > logic. It's *not* part of the parser.
>> >
>> > Regards,
>> > Michalis
>> >
>> > czw., 19 gru 2024 o 03:06 Brutzman, Donald (Don) (CIV)
>> > <brutzman at nps.edu> napisał(a):
>> > >
>> > > Thanks for looking at this Michalis.
>> > >
>> > > A. Sorry but I'm not clear about what you are saying...  Went to look
>> at the existing ClassicVRML encoding and it is showing [square brackets]
>> for SFVec4f:
>> > >
>> > > X3D Classic VRML encoding, clause 5 encoding of fields, 5.22 SFVec4f
>> and MFVec4f
>> > >
>> https://www.web3d.org/documents/specifications/19776-2/V3.3/Part02/EncodingOfFields.html#SFVec4f
>> > >
>> > > The SFVec4f field specifies a four-dimensional (4D) single-precision
>> vector. An MFVec4f field specifies zero or more 4D single-precision
>> vectors. SFVec4f's and MFVec4f's are encoded as four ISO C floating point
>> values (see ISO/IEC 9899) separated by whitespace.
>> > > EXAMPLE
>> > > fooVec3f [ 1 42 666 -43.8, 7 94 0 0.0001 ]
>> > >
>> > > ... And so am expecting your SFVec4f example would look the same,
>> with  [square brackets] around numeric values.  Please advise what you
>> think.
>> > >
>> > > OrthoViewpoint { fieldOfView [ -1 -1 1 1 ] }
>> > >
>> > >
>> > > B.  Depending on that, am next wondering... you describe how the
>> current MFFloat approach already requires additional special handling by
>> your parser if an incorrect number of values is encountered.  If there is a
>> difference regarding [square brackets] for SFVec4f then maybe a parser
>> adjustment for that might be possible too... Or, even if they are the same,
>> maybe just keeping your error-handling parser for v3.3 content the same
>> (also for backwards reliability) is a good idea also.
>> > >
>> > > C. We are currently working on ClassicVRML Encoding spec for v4.0
>> now, so if any problems are found then we can resolve them.
>> > >
>> > > D.  I found several problems with the Grammar... Dick and I also
>> discussed them yesterday.  When time permits, will post about that soon.
>> > >
>> > > Have fun with X3D ClassicVRML Encoding!  🙂
>> > >
>> > >
>> > > 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
>> > >
>> > >
>> > >
>> > >
>> > > ________________________________
>> > > From: x3d-public <x3d-public-bounces at web3d.org> on behalf of
>> Michalis Kamburelis via x3d-public <x3d-public at web3d.org>
>> > > Sent: Wednesday, December 18, 2024 5:37 PM
>> > > To: Extensible 3D (X3D) Graphics public discussion <
>> x3d-public at web3d.org>
>> > > Cc: Michalis Kamburelis <michalis.kambi at gmail.com>;
>> khyoo at chungbuk.ac.kr <khyoo at chungbuk.ac.kr>; Myeong Won Lee <
>> myeongwonlee at gmail.com>
>> > > Subject: Re: [x3d-public] X3D 4.0 specification problem:
>> TextureProjectorparallel.fieldOfView
>> > >
>> > > The change of OrthoViewpoint.fieldOfView from MFFloat to SFVec4f
>> > > breaks compatibility (badly) for X3D classic encoding, from what I can
>> > > see.
>> > >
>> > > Previously (when OrthoViewpoint.fieldOfView is MFFloat, so in X3D <=
>> > > 4.0 and VRML 2.0) this was valid:
>> > >
>> > >     OrthoViewpoint { fieldOfView [ -1 -1 1 1 ] }
>> > >
>> > > And this was "undefined how it works (spec doesn't say what happens
>> > > for < 4 values), but at least parsing was OK" (CGE made some effort to
>> > > tolerate it):
>> > >
>> > >     OrthoViewpoint { fieldOfView [ -1 -1 ] }
>> > >
>> > > Now (when OrthoViewpoint.fieldOfView is SFVec4f) both above are
>> > > invalid, at parsing. One has to write this:
>> > >
>> > >     OrthoViewpoint { fieldOfView -1 -1 1 1 }
>> > >
>> > > ... but the new form is invalid if loaded into a browser that expects
>> > > OrthoViewpoint.fieldOfView to be old MFFloat.
>> > >
>> > > And, before anyone suggests this: It's not reasonable for X3D browsers
>> > > to define OrthoViewpoint.fieldOfView with one type for X3D >= 4.1, and
>> > > another type for older X3D versions. At least I cannot imagine
>> > > maintaining this exceptional behavior throughout the codebase :) We
>> > > need to have a one definition of OrthoViewpoint with one type for
>> > > fieldOfView, otherwise we cause a big complication (also for
>> > > developers using our API).
>> > >
>> > > So, I'm a bit baffled what to do. If I change
>> > > OrthoViewpoint.fieldOfView to SFVec4f, I *will* break some X3D models
>> > > for users and I will get bugreports about it. If I don't, I will not
>> > > be compatible with X3D 4.1. For now, I choose the latter.
>> > >
>> > > Regards,
>> > > Michalis
>> > >
>> > > czw., 19 gru 2024 o 01:42 John Carlson via x3d-public
>> > > <x3d-public at web3d.org> napisał(a):
>> > >
>> > >
>> > >
>> > > >
>> > > > I’m imagining there will be changes to C++ SAI.  Once new types are
>> in place I can attempt to test.  I suggest getting an X3DUOM out soon, so I
>> can regenerate my fieldTypes.js file, which affects all my serializers.
>> > > >
>> > > > No one is using my serializers that I know of, so this particular
>> change won’t probably affect anyone.  They would have to update, and I
>> don’t currently recommend that.
>> > > >
>> > > > Bug reports are welcome:
>> > > >
>> > > >
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fcoderextreme%2FX3DJSONLD%2Fissues&data=05%7C02%7Cbrutzman%40nps.edu%7C98ebb53e439741334cb708dd1fe70c37%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638701800556379299%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C80000%7C%7C%7C&sdata=sNGbCXeuSBEnFH2Mnp8RVNttmB%2FqDIKHhbv6YaxdOjE%3D&reserved=0
>> > > >
>> > > >
>> > > > AFAIK, this does not affect X3D JSON, since MFFloat and SFVec4f are
>> represented by arrays.
>> > > >
>> > > > If you recommend tweaking X3DUOM before your release, I can see
>> what I can do, but it’s not currently a priority for me.  Reading the X_ITE
>> component into Blender is higher priority.
>> > > >
>> > > > Someone speaking up can change the priority.
>> > > >
>> > > > John
>> > > >
>> > > > On Wed, Dec 18, 2024 at 6:00 PM Brutzman, Donald (Don) (CIV) via
>> x3d-public <x3d-public at web3d.org> wrote:
>> > > >>
>> > > >> During a specification editors' meeting yesterday, Dick and I made
>> another step forward.
>> > > >>
>> > > >> Mantis 1398: OrthoViewpoint fieldOfView type needs to be SFVec4f,
>> not MFFloat
>> > > >> https://mantis.web3d.org/view.php?id=1398
>> > > >>
>> > > >> namely
>> > > >>
>> > > >> If specialty methods for homogeneous transformations (or other
>> operations) are needed by SAI implementations, they can receive specialized
>> definitions to match.
>> > > >> It is important to remember that (a) no nodes currently use
>> homogenous coordinates, and (b) ClipPlane definition of a half-plane is
>> different than the two parallel-projection extents.
>> > > >> A graceful approach not requiring implementation changes might be
>> adding prose to Clause 5 field definitions noting alternate usages may
>> occur. For example, appended to the fist sentence, "or other usage of a
>> 4-tuple."
>> > > >>
>> > > >> We applied that change in draft X3D 4.1 Architecture, also
>> committed into git and pushed online.
>> > > >>
>> > > >> 5.3.20 SFVec4d and MFVec4d
>> > > >>
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/fieldTypes.html#SFVec4dAndMFVec4d
>> > > >> 5.3.21 SFVec4f and MFVec4f
>> > > >>
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/fieldTypes.html#SFVec4fAndMFVec4f
>> > > >>
>> > > >> ==========================
>> > > >> 5.3.20 SFVec4d and MFVec4d
>> > > >> The SFVec4d field or event specifies a three-dimensional (3D)
>> homogeneous vector, or other usage of a 4-tuple. An MFVec4d field or event
>> specifies zero or more SFVec4d values. 3D homogeneous vectors. SFVec4d's
>> and MFVec4d's are represented as a 4-tuple of double-precision floating
>> point values (see 5.3.4 SFDouble and MFDouble). The allowable form for a
>> double-precision floating point number is defined in the specific encoding.
>> > > >> The default value of an uninitialized SFVec4d field is (0 0 0 1).
>> The default value of an MFVec4d field is the empty list.
>> > > >> 5.3.21 SFVec4f and MFVec4f
>> > > >> The SFVec4f field or event specifies a three-dimensional (3D)
>> homogeneous vector, or other usage of a 4-tuple. An MFVec4f field or event
>> specifies zero or more SFVec4f values. 3D homogeneous vectors. SFVec4f's
>> and MFVec4f's are represented as a 4-tuple of single-precision floating
>> point values (see 5.3.5 SFFloat and MFFloat). The allowable form for a
>> single-precision floating point number is defined in the specific encoding.
>> > > >> The default value of an uninitialized SFVec4f field is (0 0 0 1).
>> The default value of an MFVec4f field is the empty list.
>> > > >> ==========================
>> > > >>
>> > > >> If anyone can think of any reason not to restrict validation of
>> OrthoViewpoint fieldOfView to SFVec4f, instead of an MFFloat array of
>> length 4, please speak up.  Am hoping to apply this change next to
>> validation tools next, improving quality assurance and author confidence
>> that a model is valid.  Avoiding run-time errors and maintaining
>> consistency, with no harm to existing X3D models or implementations, is
>> important.
>> > > >>
>> > > >> Have fun with high-quality X3D!  🙂
>> > > >>
>> > > >>
>> > > >> 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
>> > > >>
>> > > >>
>> > > >>
>> > > >>
>> > > >> ________________________________
>> > > >> From: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>
>> > > >> Sent: Friday, December 13, 2024 1:14 PM
>> > > >> To: Holger Seelig <holger.seelig at yahoo.de>; X3D <
>> x3d-public at web3d.org>
>> > > >> Cc: khyoo at chungbuk.ac.kr <khyoo at chungbuk.ac.kr>; Myeong Won Lee <
>> myeongwonlee at gmail.com>
>> > > >> Subject: Re: [x3d-public] X3D 4.0 specification problem:
>> TextureProjectorparallel.fieldOfView
>> > > >>
>> > > >> Excellent question, thanks for asking Holger.
>> > > >>
>> > > >> This issue has been carefully tracked and regularly revisited
>> since July 2022.
>> > > >>
>> > > >> Mantis 1398: OrthoViewpoint fieldOfView type needs to be SFVec4f,
>> not MFFloat
>> > > >> https://mantis.web3d.org/view.php?id=1398
>> > > >> Mantis 1468: must SFVec4f/SFVec4d fields be homogeneous?
>> > > >> https://mantis.web3d.org/view.php?id=1468
>> > > >>
>> > > >> The X3D Working Group was unable to reach consensus on this issue
>> prior to conclusion of version 4.0, unfortunately.  Dick Puk and I took a
>> close look at this recently too. Here is a synopsis of the Mantis issues.
>> > > >>
>> > > >> I advocate use of SFVec4f for all parallel fieldOfView values
>> because it is the strictest appropriate datatype that can validate content.
>> Retaining the legacy MFFloat type definition for fieldOfView allows 3d
>> models (produced by humans or tools) to define arrays of illegal length,
>> making failures mysterious.  Conceptual consistency is important too.
>> > > >>
>> > > >> Reviewing the Mantis issues, additional concerns included:
>> > > >>
>> > > >> Incompatibility with prior X3D implementations.  Since a 4-tuple
>> content value is a valid MFFloat array, I'm not seeing any backwards
>> incompatibility if a prior X3D 3.3 implementation encounters the four
>> values of a SFVec4f array.  There are no representation problems since
>> value syntax is compatible for our various encodings as well.
>> > > >>
>> > > >> SFVec4f fields are actually not homogenous coordinates.  The spec
>> uses the word "homogenous" when referring to
>> > > >>
>> > > >>  X3D4 Architecture, Clause 5 Field type reference, 5.3.20 SFVec4d
>> and MFVec4d
>> > > >>
>> https://www.web3d.org/specifications/X3Dv4/ISO-IEC19775-1v4-IS/Part01/fieldTypes.html#SFVec4dAndMFVec4d
>> > > >> "The SFVec4f field or event specifies a three-dimensional (3D)
>> homogeneous vector." (and similarly for SFVec4d, SFVec4f and MFVec4f).
>> > > >> However none of these fields are mathematically homogeneous, see
>> > > >>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FHomogeneous_coordinates&data=05%7C02%7Cbrutzman%40nps.edu%7C98ebb53e439741334cb708dd1fe70c37%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638701800556398488%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C80000%7C%7C%7C&sdata=%2F3CZD9IDEdkAZaIJ9BWi4dKFk0mblQfkBstpx0lEsg0%3D&reserved=0
>> > > >>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FHomogeneous_coordinates%23%2Fmedia%2FFile%3ARationalBezier2D.svg&data=05%7C02%7Cbrutzman%40nps.edu%7C98ebb53e439741334cb708dd1fe70c37%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638701800556410503%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C80000%7C%7C%7C&sdata=Q%2BWMcMy2W%2FYzedb2wd7Efsgd28M1of%2FFy3pO2GKRTF4%3D&reserved=0
>> > > >> Of related note is that ClipPlane 4-tuple "plane" field is also
>> SFVec4f.
>> > > >>
>> https://www.web3d.org/specifications/X3Dv4/ISO-IEC19775-1v4-IS/Part01/components/rendering.html#ClipPlane
>> > > >>
>> > > >> All review welcome, hopefully I have correctly synopsized all
>> concerns.
>> > > >>
>> > > >> I think it would be beneficial to resolve this issue by reaching
>> consensus and applying remedies as follow.
>> > > >>
>> > > >> Omitting the over-strict word "homogenous" from the four SF/MF Vec
>> 4f/4d definitions in future X3D 4.1 prose,
>> > > >> Updating future X3D 4.1 prose to use SFVec4f for
>> TextureProjectorParallel fieldOfView,
>> > > >> Using SFVec4f in X3D 4.0 DTD, Schema, X3DUOM validation and X3D
>> Tooltips, since that type strictly confirms fieldOfView correctness with no
>> backwards compatibility problems.
>> > > >>
>> > > >> Is consensus now possible?  Thanks for all careful consideration.
>> > > >>
>> > > >> 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
>> > > >>
>> > > >>
>> > > >>
>> > > >>
>> > > >> ________________________________
>> > > >> From: Holger Seelig <holger.seelig at yahoo.de>
>> > > >> Sent: Friday, December 13, 2024 11:29 AM
>> > > >> To: X3D <x3d-public at web3d.org>
>> > > >> Cc: Brutzman, Donald (Don) (CIV) <brutzman at nps.edu>;
>> khyoo at chungbuk.ac.kr <khyoo at chungbuk.ac.kr>; Myeong Won Lee <
>> myeongwonlee at gmail.com>
>> > > >> Subject: Re: [x3d-public] X3D 4.0 specification problem: upVector
>> field for TextureProjector, TextureProjectorParallel
>> > > >>
>> > > >> I just realised that TextureProjectorparallel.fieldOfView is of
>> type SFVec4f, but OrthoViewpoint.fieldOfView is of type MFFloat.
>> > > >>
>> > > >> Which of the two is better?
>> > > >>
>> > > >> OrthoViewpoint is definitely older.
>> > > >>
>> > > >> I think of SFVec4f as a mathematical 4d vector.
>> > > >>
>> > > >>
>> https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/components/textureProjection.html#TextureProjectorParallel
>> > > >>
>> https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/components/navigation.html#OrthoViewpoint
>> > > >>
>> > > >> Best regards,
>> > > >> Holger
>> > > >>
>> > > >> --
>> > > >> Holger Seelig
>> > > >> Leipzig, Germany
>> > > >>
>> > > >> holger.seelig at yahoo.de
>> > > >>
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcreate3000.github.io%2Fx_ite%2F&data=05%7C02%7Cbrutzman%40nps.edu%7C98ebb53e439741334cb708dd1fe70c37%7C6d936231a51740ea9199f7578963378e%7C0%7C0%7C638701800556422280%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C80000%7C%7C%7C&sdata=EyAy636i6iNSYFBrRDdqg178Wi93D3sVzQJQ%2FqGIxDc%3D&reserved=0
>> > > >>
>> > > >> Am 08.12.2024 um 05:21 schrieb Brutzman, Donald (Don) (CIV) via
>> x3d-public <x3d-public at web3d.org>:
>> > > >>
>> > > >> However
>> > > >>
>> > > >>
>> > > >> _______________________________________________
>> > > >> x3d-public mailing list
>> > > >> x3d-public at web3d.org
>> > > >> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>> > > >
>> > > > _______________________________________________
>> > > > x3d-public mailing list
>> > > > x3d-public at web3d.org
>> > > > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>> > >
>> > > _______________________________________________
>> > > x3d-public mailing list
>> > > x3d-public at web3d.org
>> > > http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>
>> _______________________________________________
>> x3d-public mailing list
>> x3d-public at web3d.org
>> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>
>
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