[x3d-public] Specification review progress: PNG3, Tangent node, HAnim weekly progress
John Carlson
yottzumm at gmail.com
Fri Jul 4 23:06:45 PDT 2025
I think Don may be aiming for: How does the Tangent node affect the
effective rendering of objects, or, how do tangents interact with lighting,
normals geometry and colors to change the color of geometry? I don't
know if current equations include tangents or not.
Sorry for butting my nose in.
John
On Fri, Jul 4, 2025 at 9:41 PM Michalis Kamburelis via x3d-public <
x3d-public at web3d.org> wrote:
> Great, thanks for applying.
>
> Note that you can remove now the sentence near the end,
>
> """Each element in the vector array provides a unit XYZ vector
> defining a tangent direction on the surface, together with a W component
> whose sign value (-1 or +1) indicates the handedness of the tangent
> base."""
>
> The beginning of my prose also contains this, I just split that 1 sentence
> into 2 sentences with a bit more information.
>
> As for:
> - " Still need an overview description for node itself"
> - " If one starts with Tangent node and then goes to X3D lighting
> equations, where would they find it?"
>
> -> hm, I am not clear what more do you think is necessary here, but I am
> happy to work on what we have and add what you think is needed. The
> "overview" for me is my sentence
>
> """Tangent vectors, if provided using this node, determine the tangent
> space in which the normalmaps (specified in the normalTexture fields of
> various material nodes) are specified."""
>
> -- maybe you want to move this sentence earlier, to make it clearer that
> this is an overview?
>
> I'll try to join Web3d call next Friday too, so maybe we can finalize this
> together during the call :)
>
> Thanks and regards,
> Michalis
>
> pt., 4 lip 2025 o 23:29 Don Brutzman <don.brutzman at gmail.com> napisał(a):
>
>> Thanks for review.
>>
>>
>> 1. Agreed, corrected.
>> 2. Added prose. Still need an overview description for node itself.
>> Have pushed resulting update online for ongoing review.
>> 3. Adjusted as an editors' note for now... we do need to mention this
>> point, hopefully clearly
>> 4. Very good. All changes committed to github and updated at
>> * 11.4.13 Tangent
>>
>>
>> - *
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent
>>
>>
>>
>> 5. Sorry but we do seem to need more... If one starts with Tangent
>> node and then goes to X3D lighting equations, where would they find it?
>>
>>
>> - *
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/lighting.html
>>
>>
>> v/r Don
>> ------------------------------
>> *From:* Michalis Kamburelis <michalis.kambi at gmail.com>
>> *Sent:* Friday, July 4, 2025 12:29 PM
>> *To:* Extensible 3D (X3D) Graphics public discussion <
>> x3d-public at web3d.org>
>> *Cc:* Richard Puk <puk at igraphics.com>; Don Brutzman <
>> don.brutzman at gmail.com>
>> *Subject:* Re: [x3d-public] Specification review progress: PNG3, Tangent
>> node, HAnim weekly progress
>>
>> Thanks for pursuing Tangent node in X3D! Comments for the node prose (
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent
>> , section "11.4.13 Tangent" ):
>>
>> 1. I guess it was just a copy-paste mistake that node declaration in
>> section "11.4.13 Tangent" says """TriangleFanSet :
>> X3DComposedGeometryNode""" :)
>>
>> You most likely wanted to say there """Tangent : X3DTangentNode""".
>>
>> 2. For the """TODO node definition and description.""" -- I wrote a
>> proposed prose, and placed it in
>> https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D .
>> See section "Prose for spec", from "Each element in the vector array
>> provides a unit XYZ vector defining a tangent direction on the
>> surface."....
>>
>> I welcome proposals to make it shorter :) I also welcome
>> double-checking what I wrote!
>>
>> 3. I would remove from spec the sentence """NOTE The Tangent node
>> functionality has no relation to Normal node functionality.""". The tangent
>> node is different, but sometimes related to normals, as my prose linked
>> above also explains. So this sentence could be a bit confusing, at least it
>> is to me. Maybe we don't need this sentence, or the intention behind it
>> should be phrased differently?
>>
>> 4. The sentence """NOTE See the GLTF specification for further technical
>> details.""" is good, keep it, that is indeed (one of the) design goals here.
>>
>> 5. As for question """How does Tangent node affect the 17.2.2 Lighting
>> model? Consistent rendering is necessary. """ -- I think we don't need to
>> say anything more, actually. The lighting spec already says """N =
>> normalized normal vector at this point on geometry. [...] It is modified by
>> the normalTexture providing normals in the tangent space (see
>> X3DOneSidedMaterialNode definition).""" and that's actually enough, I think.
>>
>> Regards,
>> Michalis
>>
>> pt., 27 cze 2025 o 18:47 Don Brutzman via x3d-public <
>> x3d-public at web3d.org> napisał(a):
>>
>> Dick and I held another weekly specification editors' meeting.
>>
>> After a tumultuous week checking out for retirement, I finally have some
>> things for us to review.
>>
>> a. *PNG3*
>>
>> - X3D Architecture draft v4.1, clause 18 Texturing component, 18.2.2
>> Texture map image formats
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#TextureMapImageFormats
>> - X3D Architecture draft v4.1, clause 18 Texturing component,18.4.2
>> MovieTexture
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#MovieTexture
>> - Normative references: W3C_PNG
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/references.html#W3C_PNG
>>
>>
>> Of note, PNG3 is now final: 🙂
>>
>>
>> - *Portable Network Graphics (PNG) Specification (Third Edition)
>> <https://www.bing.com/ck/a?!&&p=85f7cc4f26f850c116f5b9afcb2987d31a5a02381bf6cb7b802a97c05394ec22JmltdHM9MTc1MDk4MjQwMA&ptn=3&ver=2&hsh=4&fclid=0999e3c9-3acb-60ad-25bf-f62b3b486183&psq=w3.org+png+third+edition&u=a1aHR0cHM6Ly93d3cudzMub3JnL1RSL3BuZy0zLw&ntb=1>*
>> - W3C Recommendation, 24 June 2025
>> - https://www.w3.org/TR/png-3/
>>
>>
>>
>> - PNG Third Edition, Implementation Report (includes animated PNG
>> image)
>> - https://w3c.github.io/png/Implementation_Report_3e/
>> -
>> https://w3c.github.io/png/Implementation_Report_3e/img/APNG-Icos4D.png
>>
>>
>>
>> b. *Tangent node*
>>
>>
>> - Mantis 1496: add Tangent node to support advanced rendering
>> capabilities of glTF
>> - https://mantis.web3d.org/view.php?id=1496
>>
>>
>> with
>>
>> - Michalis Kamburelis: Tangent node in X3D
>> - https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D
>>
>>
>>
>> - Holger Seelig: Tangent node
>> - https://create3000.github.io/x_ite/components/rendering/tangent/
>>
>> - X3D Architecture draft v4.1, clause 11 Rendering component
>> - 11.3.2 X3DComposedGeometryNode
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DComposedGeometryNode
>> - 11.3.7 X3DTangentNode
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DTangentNode
>> - 11.4.13 Tangent
>> -
>> https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent
>> And related implementing nodes
>>
>>
>> Here is the preliminary draft for Tangent node. *Dear rendering
>> experts: more prose needed for draft specification that describes this
>> functionality!*
>> *11.4.13 Tangent*
>>
>> TriangleFanSet : X3DComposedGeometryNode {
>> SFNode [in,out] metadata NULL [X3DMetadataObject]
>> MFVec4f [in,out] vector []
>> }
>>
>> *TODO* node definition and description.
>> Each element in the *vector* array provides a unit XYZ vector defining a
>> tangent direction on the surface, together with a W component whose sign
>> value (-1 or +1) indicates the handedness of the tangent base.
>> NOTE The Tangent node functionality has no relation to Normal node
>> functionality.
>> NOTE See the GLTF <http://../references.html#GLTF> specification for
>> further technical details.
>> *TODO * How does Tangent node affect the 17.2.2 Lighting model
>> <http://lighting.html#LightingModel>? Consistent rendering is necessary.
>>
>> c. Discuss *HAnim progress* on weekly calls - encouraging! 🙂
>>
>> - Many diverse topics (such as single/double floating-point
>> precision, etc.) can go into the use-case modeling guidelines
>> - Iterative improvement is always best
>> - We will stay focused on refinements to HAnim 2.0, and identify
>> larger issues (such as Coveroid/Clothing) for the HAnim working group
>>
>>
>> d. *Schedule*
>>
>> - No call next Monday - am retiring!
>> - Next Wednesday call: final review for annual ISO meeting in
>> Alexandria VA the following week
>> - Next Friday call: also cancelled, July 4 Independence Day in USA.
>>
>>
>> Aloha! v/r Don
>>
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