<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">https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#Tangent</a> , section "11.4.13 Tangent" ):<br><br>1. I guess it was just a copy-paste mistake that node declaration in section "11.4.13 Tangent" says """TriangleFanSet : X3DComposedGeometryNode""" :)<br><br>   You most likely wanted to say there """Tangent :  X3DTangentNode""".<br><br><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">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><div><br></div><div>    I welcome proposals to make it shorter :) I also welcome double-checking what I wrote!</div><div><br></div><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><div><br></div><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><div><br></div><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><div><br></div><div>Regards,</div><div>Michalis</div></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">pt., 27 cze 2025 o 18:47 Don Brutzman via x3d-public <<a href="mailto:x3d-public@web3d.org">x3d-public@web3d.org</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 class="msg4038270252408106593">




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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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<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#TextureMapImageFormats" id="m_4038270252408106593OWA8b154c31-69f7-b93b-9e6c-3afdedf33beb" title="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#TextureMapImageFormats" style="margin:0px" target="_blank">https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#TextureMapImageFormats</a></div>
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X3D Architecture draft v4.1, clause 18 Texturing component,18.4.2 MovieTexture</div>
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<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#MovieTexture" id="m_4038270252408106593OWAcc9faabf-4baa-f6f6-5518-cad405fde740" title="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#MovieTexture" style="margin:0px" target="_blank">https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#MovieTexture</a></div>
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Normative references: W3C_PNG</div>
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<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/references.html#W3C_PNG" id="m_4038270252408106593OWAa25a3df1-f0f1-5fc4-0a49-133a11147246" target="_blank">https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/references.html#W3C_PNG</a></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_4038270252408106593OWAba839763-a782-8b92-ca38-6f250f3effae" style="color:rgb(64,7,162)" target="_blank">Portable
 Network Graphics (PNG) Specification (Third Edition)</a></u></div>
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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_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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<a href="https://w3c.github.io/png/Implementation_Report_3e/" id="m_4038270252408106593OWA92442057-741a-1689-d949-00e7481eb30f" target="_blank">https://w3c.github.io/png/Implementation_Report_3e/</a></div>
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b. <b>Tangent node</b></div>
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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_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>
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with</div>
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Michalis Kamburelis: Tangent node in X3D</div>
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<a href="https://github.com/michaliskambi/x3d-tests/wiki/Tangent-node-in-X3D" id="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>
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Holger Seelig: Tangent node</div>
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<a href="https://create3000.github.io/x_ite/components/rendering/tangent/" id="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>
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X3D Architecture draft v4.1, clause 11 Rendering component</div>
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11.3.2 X3DComposedGeometryNode</div>
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<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DComposedGeometryNode" id="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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11.3.7 X3DTangentNode</div>
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<a href="https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/rendering.html#X3DTangentNode" id="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_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>
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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>
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<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_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_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>
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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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Next Friday call: also cancelled, July 4 Independence Day in USA.</div>
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Aloha! v/r Don</div>
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