[x3d-public] Wishlist for view3dscene

Fri Feb 10 11:31:34 PST 2023

I’m not sure why I wrote the last sentence.  Withdrawn.

On Fri, Feb 10, 2023 at 1:19 PM John Carlson <yottzumm at gmail.com> wrote:

>  There should be an option to convert binary vertex and index data to
> ASCII, if only during authoring.
>
> Remember that Joe/designers like to tweak.
>
> I find that converting JSON through JavaScript massively increases
> precision, but i haven’t looked at why yet.  Maybe JSON/JavaScript
> numerical libraries should be responsible for keeping precise, accurate
> numbers, perhaps by storing alternate encodings for I/O and computation.
>
> One can always convert to EXI and back, to serve ASCII purposes.
>
> John
>
> On Fri, Feb 10, 2023 at 12:36 PM Michalis Kamburelis <
> michalis.kambi at gmail.com> wrote:
>
>> We use optional scientific notation (with exponent) when writing
>> numbers in CGE/view3dscene. To be precise, we use a formatting option
>> that outputs either a scientific or decimal notation, whichever is
>> shorter. The scientific notation is not that much shorter to win
>> usually.
>>
>> As for round-trips: you must have maximum precision to have reliable
>> round-trips, I believe :) Otherwise you will always discover use-cases
>> when you loose some digits, and they will be important for someone.
>>
>> glTF does what is obvious, and I'd say X3D should follow, this is
>> something I'd like to work on for X3D 4.1 (
>> https://github.com/michaliskambi/x3d-tests/wiki/Binary-meshes ).
>> Namely, the floats in per-vertex data are always stored as binary.
>> Only the floats like material parameters are stored as text in JSON.
>>
>> X3D binary encoding is one solution here, but it is not wide-spread,
>> e.g. I hope zero hope that Blender exporter would output X3D binary
>> encoding someday (there's too many other critical issues in Blender
>> X3D exporter). And X3D binary encoding doesn't make data interleaved,
>> so it doesn't solve the issue of effectively delivering it to GPU.
>>
>> "keep numbers and arrays as strings" -- no, this really wouldn't help
>> with anything. The X3D browser has to parse the text to numbers at
>> some point, to process the points, upload them to GPU etc. Right now
>> the bottleneck of reading real-life X3D is always, in my experience,
>> "your code effectively has to make million of text-to-float
>> conversions". I believe this is a bottleneck regardless of the
>> programming language, 1000 * 1000 calls to text-to-float is always
>> going to be much slower than reading binary data (where you say "this
>> is my pointer to 1000 * 1000 * 4 bytes, just copy there the contents
>> of this file").
>>
>> Regards,
>> Michalis
>>
>> pt., 10 lut 2023 o 18:57 John Carlson <yottzumm at gmail.com> napisał(a):
>> >
>> > Not sure how feasible this is with Pascal, etc.   Perhaps consider
>> scientific or engineering notation with exponents.
>> >
>> > In most cases i see, extending precision significantly increases file
>> size, and makes it harder to do round trips.
>> >
>> > I don’t know if there’s a JavaScript or Python solution for this.
>> >
>> > Perhaps we should not implement number types in our synthesized
>> programs, and keep numbers and arrays as strings.   Then we have to ask
>> what is done in glTF.
>> >
>> > John
>> >
>> > On Fri, Feb 10, 2023 at 7:13 AM Michalis Kamburelis <
>> michalis.kambi at gmail.com> wrote:
>> >>
>> >> Thanks, and sorry for a delay in answering!
>> >>
>> >> The "description" field has been added to texture nodes and few more,
>> >> as you can see in another thread on x3d-public :)
>> >>
>> >> As for digits precision when saving: it's not so easy, in general it's
>> >> (one of) the problems that come from X3D using text representation for
>> >> floats in per-vertex data. Namely, if we cut the saved numbers to 4
>> >> decimal places, I'm 90% sure that I will get a valid bugreport from
>> >> someone:
>> >>
>> >> """
>> >> Hey, my stuff no longer works! My models (in glTF, X3D, whatever) have
>> >> vertexes at coordinates like Z = 0.00001, 0.00002, 0.00003. And now,
>> >> after processing and saving to X3D using your tools, they are all
>> >> equal zero, resulting in bugs (things start to fight in Z buffer).
>> >> """
>> >>
>> >> Surely we could add a configuration option for it, but it feels
>> >> counter-productive, when my recommendation to everyone would be still
>> >> "use the maximum precision, to be safe". I would add a feature that I
>> >> explicitly say should not be used.
>> >>
>> >> In the end, the longer text representation for numbers only hurts the
>> >> file size. And I don't believe we can really fix it by outputting less
>> >> digits. The right solution is storing per-vertex data in a binary
>> >> blob, when each float is binary 4 bytes, so it's
>> >>
>> >> - efficient storage
>> >> - efficient reading by X3D implementation to a "float[] array", no
>> >> need for text parsing.
>> >>
>> >> Regards,
>> >> Michalis
>> >>
>> >>
>> >>
>> >>
>> >> śr., 28 gru 2022 o 21:00 Brutzman, Donald (Don) (CIV)
>> >> <brutzman at nps.edu> napisał(a):
>> >> >
>> >> > Hi Michalis. Joe and I are really enjoying the many excellent
>> features of view3dscene.
>> >> >
>> >> >
>> >> >
>> >> > Here are some suggested refinements and improvements.
>> >> >
>> >> >
>> >> >
>> >> > View3dscene converter: round off significant digits, rather than 10+
>> decimal places.  (For example, suggested values in HAnim spec go to 4
>> decimal places.
>> >> >
>> >> >
>> >> >
>> >> > View3dscene: note that we have added ‘description’ field to many
>> nodes in X3D4, including ImageTexture.
>> >> >
>> >> > 1 warnings:
>> >> > X3D: Unknown X3D field name (unhandled X3D XML attribute)
>> "description" in node "ImageTexture"
>> >> > Scene URL: "C:\x3d-code\www.web3d.org
>> \x3d\content\examples\HumanoidAnimation\Skin\JoeSkeletonSkinSiteSaluteWalk.x3d".
>> >> > Use "File->View Warnings" menu to view these warnings again.
>> >> >
>> >> >
>> >> >
>> >> > Coming soon: import test of three models in HAnim Motion
>> specification.
>> >> >
>> >> >
>> https://www.web3d.org/documents/specifications/19774/V2.0/MotionDataAnimation/MotionDataAnimation.html
>> >> >
>> >> >
>> >> >
>> >> > Again thanks for great work.
>> >> >
>> >> >
>> >> >
>> >> > 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
>> >> >
>> >> >
>> >>
>> >> _______________________________________________
>> >> x3d-public mailing list
>> >> x3d-public at web3d.org
>> >> http://web3d.org/mailman/listinfo/x3d-public_web3d.org
>>
>
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