[x3d-public] Specification review progress: PNG3, Tangent node, HAnim weekly progress

Fri Jul 4 14:29:42 PDT 2025

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

  1.
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<mailto: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
[X]

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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