[x3d-public] Specification review progress: PNG3, Tangent node, HAnim weekly progress
Michalis Kamburelis
michalis.kambi at gmail.com
Fri Jul 4 12:29:49 PDT 2025
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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