<div dir="ltr">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.<div><br></div><div>Sorry for butting my nose in.<br><div><br></div><div>John</div></div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Fri, Jul 4, 2025 at 9:41 PM Michalis Kamburelis via x3d-public <<a href="mailto:x3d-public@web3d.org">x3d-public@web3d.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Great, thanks for applying.</div><div><br></div><div>Note that you can remove now the sentence near the end, </div><div><br></div><div>    """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.""" </div><div><br></div><div>The beginning of my prose also contains this, I just split that 1 sentence into 2 sentences with a bit more information. </div><div><br></div><div>As for:</div><div>- "
Still need an overview description for node itself"</div><div>- "
If one starts with Tangent node and then goes to X3D lighting equations, where would they find it?"</div><div><br></div><div>-> 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 </div><div><br></div><div>    """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."""</div><div><br></div><div>-- maybe you want to move this sentence earlier, to make it clearer that this is an overview?</div><div><br></div><div>I'll try to join Web3d call next Friday too, so maybe we can finalize this together during the call :)</div><div><br></div><div>Thanks and regards,</div><div>Michalis</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">pt., 4 lip 2025 o 23:29 Don Brutzman <<a href="mailto:don.brutzman@gmail.com" target="_blank">don.brutzman@gmail.com</a>> napisał(a):<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div>




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Thanks for review.</div>
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<div role="presentation">Agreed, corrected.</div>
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<div role="presentation">Added prose.  Still need an overview description for node itself.  Have pushed resulting update online for ongoing review.</div>
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<div role="presentation">Adjusted as an editors' note for now... we do need to mention this point, hopefully clearly</div>
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<div role="presentation">Very good.  All changes committed to github and updated at</div>
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<div role="presentation">* 11.4.13 Tangent</div>
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<div role="presentation">* <a id="m_-1817947643216787260m_3980620289549214466LPlnk428735" href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent" target="_blank">
https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent</a></div>
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<div role="presentation">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?</div>
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<div role="presentation">* <a id="m_-1817947643216787260m_3980620289549214466LPlnk470185" href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/lighting.html" target="_blank">
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v/r Don</div>
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<div id="m_-1817947643216787260m_3980620289549214466divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Michalis Kamburelis <<a href="mailto:michalis.kambi@gmail.com" target="_blank">michalis.kambi@gmail.com</a>><br>
<b>Sent:</b> Friday, July 4, 2025 12:29 PM<br>
<b>To:</b> Extensible 3D (X3D) Graphics public discussion <<a href="mailto:x3d-public@web3d.org" target="_blank">x3d-public@web3d.org</a>><br>
<b>Cc:</b> Richard Puk <<a href="mailto:puk@igraphics.com" target="_blank">puk@igraphics.com</a>>; Don Brutzman <<a href="mailto:don.brutzman@gmail.com" target="_blank">don.brutzman@gmail.com</a>><br>
<b>Subject:</b> Re: [x3d-public] Specification review progress: PNG3, Tangent node, HAnim weekly progress</font>
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<div dir="ltr">Thanks for pursuing Tangent node in X3D! Comments for the node prose (
<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent" target="_blank">
https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent</a> , section "11.4.13 Tangent" ):<br>
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1. I guess it was just a copy-paste mistake that node declaration in section "11.4.13 Tangent" says """TriangleFanSet : X3DComposedGeometryNode""" :)<br>
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   You most likely wanted to say there """Tangent :  X3DTangentNode""".<br>
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<div>2. For the """TODO node definition and description.""" -- I wrote a proposed prose, and placed it in <a href="https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D" target="_blank">https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D</a> .
 See section "Prose for spec", from "Each element in the vector array provides a unit XYZ vector defining a tangent direction on the surface.".... </div>
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<div>    I welcome proposals to make it shorter :) I also welcome double-checking what I wrote!</div>
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<div>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?</div>
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<div>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.</div>
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<div>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.</div>
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<div>Regards,</div>
<div>Michalis</div>
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<div dir="ltr">pt., 27 cze 2025 o 18:47 Don Brutzman via x3d-public <<a href="mailto:x3d-public@web3d.org" target="_blank">x3d-public@web3d.org</a>> napisał(a):<br>
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Dick and I held another weekly specification editors' meeting.</div>
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After a tumultuous week checking out for retirement, I finally have some things for us to review.</div>
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a. <b>PNG3</b></div>
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X3D Architecture draft v4.1, clause 18 Texturing component, 18.2.2 Texture map image formats</div>
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X3D Architecture draft v4.1, clause 18 Texturing component,18.4.2 MovieTexture</div>
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Normative references: W3C_PNG</div>
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Of note, PNG3 is now final:  🙂</div>
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<u><a href="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" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWAba839763-a782-8b92-ca38-6f250f3effae" style="color:rgb(64,7,162)" target="_blank">Portable
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W3C Recommendation, 24 June 2025</div>
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<a href="https://www.w3.org/TR/png-3/" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWAb9dc1b2f-ea14-eda3-63d1-0022116e08c1" target="_blank">https://www.w3.org/TR/png-3/</a></div>
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PNG Third Edition, Implementation Report (includes animated PNG image)</div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin-top:0px;margin-bottom:0px">
<a href="https://w3c.github.io/png/Implementation_Report_3e/" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA92442057-741a-1689-d949-00e7481eb30f" target="_blank">https://w3c.github.io/png/Implementation_Report_3e/</a></div>
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<a href="https://w3c.github.io/png/Implementation_Report_3e/img/APNG-Icos4D.png" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA9cab3b06-f697-2707-7fae-2268561ded0d" target="_blank">https://w3c.github.io/png/Implementation_Report_3e/img/APNG-Icos4D.png</a></div>
<div role="presentation" style="width:100%;display:inline-block"><img style="max-width: 100%;"></div>
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b. <b>Tangent node</b></div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
Mantis 1496: add Tangent node to support advanced rendering capabilities of glTF</div>
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<a href="https://mantis.web3d.org/view.php?id=1496" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA8833a777-c33d-3514-736c-3cb9f72ecba3" title="https://mantis.web3d.org/view.php?id=1496" style="margin:0px" target="_blank">https://mantis.web3d.org/view.php?id=1496</a></div>
</li></ul>
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with</div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
Michalis Kamburelis: Tangent node in X3D</div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px;color:rgb(51,122,183)">
<a href="https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA0fb85db0-782f-c5c4-df98-d0caa5fd2fdb" title="https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D" rel="noopener" style="color:rgb(51,122,183);margin:0px;text-align:left" target="_blank">https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D</a></div>
</li></ul>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
Holger Seelig: Tangent node</div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
<a href="https://create3000.github.io/x_ite/components/rendering/tangent/" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA33399d69-f0ca-aae8-80cc-e4568b552920" title="https://create3000.github.io/x_ite/components/rendering/tangent/" style="margin:0px" target="_blank">https://create3000.github.io/x_ite/components/rendering/tangent/</a></div>
<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
X3D Architecture draft v4.1, clause 11 Rendering component</div>
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11.3.2 X3DComposedGeometryNode</div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DComposedGeometryNode" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWAe0026356-f3cd-748c-a876-918dd29c0575" title="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DComposedGeometryNode" style="margin:0px" target="_blank">https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DComposedGeometryNode</a></div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
11.3.7 X3DTangentNode</div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DTangentNode" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA84e76067-de9f-ce4b-43b5-43ceaba7f485" title="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DTangentNode" style="margin:0px" target="_blank">https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DTangentNode</a></div>
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11.4.13 Tangent</div>
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<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWAeef0a269-f1d4-49bd-055f-e51d2d0ea589" title="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent" style="margin:0px" target="_blank">https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent</a></div>
<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin:0px">
And related implementing nodes</div>
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Here is the preliminary draft for Tangent node.  <span style="color:rgb(200,38,19)">
<b><i>Dear rendering experts:  more prose needed for draft specification that describes this functionality!</i></b></span></div>
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<span style="background-color:rgb(255,255,0)"><b>11.4.13 Tangent</b></span></div>
<pre style="margin-left:25px"><div style="text-align:left;text-indent:0px;font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)"><span style="background-color:rgb(255,255,0)">TriangleFanSet : X3DComposedGeometryNode {
  SFNode  [in,out] metadata NULL [X3DMetadataObject]
  MFVec4f [in,out] vector   []
}
</span></div></pre>
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<span style="color:rgb(200,38,19);background-color:rgb(255,255,0)"><b>TODO</b> </span>
<span style="color:rgb(0,0,0);background-color:rgb(255,255,0)">node definition and description.</span></div>
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<span style="background-color:rgb(255,255,0)">Each element in the <i>vector</i> 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.</span></div>
<div style="text-align:left;text-indent:0px;margin-top:18px;margin-bottom:18px;font-family:Aptos,Aptos_EmbeddedFont,Aptos_MSFontService,Calibri,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0)">
<span style="background-color:rgb(255,255,0)">NOTE  The Tangent node functionality has no relation to Normal node functionality.</span></div>
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<span style="background-color:rgb(255,255,0)">NOTE  See the <a href="http://../references.html#GLTF" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA3c1640ba-7e25-aa28-0374-f69691877d04" target="_blank">
GLTF</a> specification for further technical details.</span></div>
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<span style="color:rgb(200,38,19);background-color:rgb(128,255,255)"><b>TODO </b>
</span><span style="color:rgb(0,0,0);background-color:rgb(128,255,255)">How does Tangent node affect the
<a href="http://lighting.html#LightingModel" id="m_-1817947643216787260m_3980620289549214466x_m_4038270252408106593OWA696d616d-833d-7a3e-bcb6-8702a6146ca5" target="_blank">
17.2.2 Lighting model</a>? Consistent rendering is necessary.</span></div>
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c. Discuss <b>HAnim progress</b> on weekly calls - encouraging!  🙂</div>
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Many diverse topics (such as single/double floating-point precision, etc.) can go into the use-case modeling guidelines</div>
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Iterative improvement is always best</div>
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We will stay focused on refinements to HAnim 2.0, and identify larger issues (such as Coveroid/Clothing) for the HAnim working group  </div>
</li></ul>
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d. <b>Schedule</b></div>
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No call next Monday - am retiring! </div>
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Next Wednesday call: final review for annual ISO meeting in Alexandria VA the following week</div>
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<div role="presentation" style="direction:ltr;text-indent:0px;line-height:normal;margin-top:0px;margin-bottom:0px">
Next Friday call: also cancelled, July 4 Independence Day in USA.</div>
</li></ul>
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Aloha! v/r Don</div>
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_______________________________________________<br>
x3d-public mailing list<br>
<a href="mailto:x3d-public@web3d.org" target="_blank">x3d-public@web3d.org</a><br>
<a href="http://web3d.org/mailman/listinfo/x3d-public_web3d.org" rel="noreferrer" target="_blank">http://web3d.org/mailman/listinfo/x3d-public_web3d.org</a><br>
</div>
</blockquote>
</div>
</div>
</div>

</div></blockquote></div>
_______________________________________________<br>
x3d-public mailing list<br>
<a href="mailto:x3d-public@web3d.org" target="_blank">x3d-public@web3d.org</a><br>
<a href="http://web3d.org/mailman/listinfo/x3d-public_web3d.org" rel="noreferrer" target="_blank">http://web3d.org/mailman/listinfo/x3d-public_web3d.org</a><br>
</blockquote></div>