<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">All quaternions must be normalized to be a legal rotation, so the length of the quaternion must always be one.<div><br></div><div>Holger<br id="lineBreakAtBeginningOfMessage"><div>
<div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div dir="auto" style="text-align: start; text-indent: 0px; overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; -webkit-text-stroke-width: 0px;">--</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; -webkit-text-stroke-width: 0px;">Holger Seelig</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; -webkit-text-stroke-width: 0px;">Leipzig, Germany</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; -webkit-text-stroke-width: 0px;"><br></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; -webkit-text-stroke-width: 0px;">holger.seelig@yahoo.de</div><div>https://create3000.github.io/x_ite/</div></div></div></div></div></div></div>
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<div><br><blockquote type="cite"><div>Am 14.02.2025 um 15:38 schrieb Joe D Williams via x3d-public <x3d-public@web3d.org>:</div><br class="Apple-interchange-newline"><div><div style="font-family: Arial; font-size: 12pt;"><div style="margin: 0.1rem 0px; line-height: 1;">> <span style="font-family: "Times New Roman"; font-size: medium; white-space: normal; float: none; display: inline;">So, sensibly, a zero rotation around any axis corresponds to the "zero unit Quaternion" (0, 0, 0, 1 XYZW), </span> </div><p style="margin: 0.1rem 0; line-height: 1.0;"> </p><div style="margin: 0.1rem 0px; line-height: 1;">Right. Not sure but 0 0 0 0 for unit quaternion might not be legal. I think the values must compute to1 to be legal?</div><div style="margin: 0.1rem 0px; line-height: 1;">Thanks,</div><div style="margin: 0.1rem 0px; line-height: 1;">Joe</div><p style="margin: 0.1rem 0; line-height: 1.0;"> </p><p style="margin: 0.1rem 0; line-height: 1.0;"> </p>
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<div class="elnk-inline-message-container" style="border-left: 1px solid #aaa; box-sizing: border-box; padding: 10px 0 10px 15px; margin: 0;"><p>-----Original Message-----<br>From: Andreas Plesch <andreasplesch@gmail.com><br>Sent: Feb 10, 2025 12:37 PM<br>To: Joe D Williams <joedwil@earthlink.net><br>Cc: Extensible 3D (X3D) Graphics public discussion <x3d-public@web3d.org><br>Subject: Re: [x3d-public] SFRotation default value spec. inconsistency</p><p style="margin: 0.1rem 0; line-height: 1.0;"> </p>
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<div><a href="https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#_node_rotation">https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html#_node_rotation</a></div>
<div>has indeed (0, 0, 0, 1 XYZW) as a default value.</div>
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<div>This is difficult to interpret as a rotation around an axis since the corresponding axis would be at first glance (0 0 0).</div>
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<div>x3dom converts quaternion (0, 0, 0, 1 XYZW) to (axis),angle (0,0,0),0 as does <a href="https://www.andre-gaschler.com/rotationconverter/">https://www.andre-gaschler.com/rotationconverter/</a> .</div>
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<div>On the other hand both SFRotation (0 0 1 0) and SFRotation (0 1 0 0) are also represented by quaternion (0, 0, 0, 1 XYZW).</div>
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<div>So, sensibly, a zero rotation around any axis corresponds to the "zero unit Quaternion" (0, 0, 0, 1 XYZW), making it a useful default value for quaternions. But that does not help with choosing a default axis for the SFRotation value.</div>
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<div>This will rarely matter. A use case may be when a SFRotation is initialized to the X3D default in a Proto but then only the angle is modified by a Proto script with the assumption that the axis is (0 0 1).</div>
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<div>-Andreas</div>
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<div class="gmail_attr" dir="ltr">On Mon, Feb 10, 2025 at 12:57 PM Joe D Williams <<a href="mailto:joedwil@earthlink.net">joedwil@earthlink.net</a>> wrote:</div>
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<div style="font-family: arial, sans-serif; font-size: 12pt;"><div style="margin: 0.1rem 0px; line-height: 1;">not zerp, zero</div>
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<div style="border-left: 1px solid #aaaaaa; box-sizing: border-box; padding: 10px 0px 10px 15px; margin: 0px;"><p>-----Original Message-----<br>From: Extensible 3D (X3D) Graphics public discussion <<a href="mailto:x3d-public@web3d.org" target="_blank" rel="noopener">x3d-public@web3d.org</a>><br>Sent: Feb 10, 2025 9:50 AM<br>To: Extensible 3D (X3D) Graphics public discussion <<a href="mailto:x3d-public@web3d.org" target="_blank" rel="noopener">x3d-public@web3d.org</a>>, X3D Graphics public mailing list <<a href="mailto:x3d-public@web3d.org" target="_blank" rel="noopener">x3d-public@web3d.org</a>><br>Cc: Joe D Williams <<a href="mailto:joedwil@earthlink.net" target="_blank" rel="noopener">joedwil@earthlink.net</a>>, Andreas Plesch <<a href="mailto:andreasplesch@gmail.com" target="_blank" rel="noopener">andreasplesch@gmail.com</a>><br>Subject: Re: [x3d-public] SFRotation default value spec. inconsistency</p><p style="margin: 0.1rem 0px; line-height: 1;"> </p>
<div style="font-family: arial, sans-serif; font-size: 12pt;"><div style="margin: 0.1rem 0px; line-height: 1;">I think the 0 0 1 0 should be used everywhere for default axis-angle. </div><div style="margin: 0.1rem 0px; line-height: 1;">I thinkI see 'zerp' unit quaternions (as in gltf as 0 0 0 1 XYZW) </div><div style="margin: 0.1rem 0px; line-height: 1;">Thanks,</div><div style="margin: 0.1rem 0px; line-height: 1;">Joe</div><p style="margin: 0.1rem 0px; line-height: 1;"> </p>
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<div style="border-left: 1px solid #aaaaaa; box-sizing: border-box; padding: 10px 0px 10px 15px; margin: 0px;"><p>-----Original Message-----<br>From: Extensible 3D (X3D) Graphics public discussion <<a href="mailto:x3d-public@web3d.org" target="_blank" rel="noopener">x3d-public@web3d.org</a>><br>Sent: Feb 10, 2025 8:44 AM<br>To: X3D Graphics public mailing list <<a href="mailto:x3d-public@web3d.org" target="_blank" rel="noopener">x3d-public@web3d.org</a>><br>Cc: Andreas Plesch <<a href="mailto:andreasplesch@gmail.com" target="_blank" rel="noopener">andreasplesch@gmail.com</a>><br>Subject: Re: [x3d-public] SFRotation default value spec. inconsistency</p><p style="margin: 0.1rem 0px; line-height: 1;"> </p>
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<div>The JS SAI spec. at <a href="https://www.web3d.org/documents/specifications/19777-1/V3.3/Part1/functions.html#FieldServices" target="_blank" rel="noopener">https://www.web3d.org/documents/specifications/19777-1/V3.3/Part1/functions.html#FieldServices</a></div>
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<div>does not list functions for SFColorRGBA, only SFColor. There may be an earlier report. -Andreas</div>
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<div class="gmail_attr" dir="ltr">On Mon, Feb 10, 2025 at 11:31 AM Andreas Plesch <<a href="mailto:andreasplesch@gmail.com" target="_blank" rel="noopener">andreasplesch@gmail.com</a>> wrote:</div>
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<div><a href="https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/fieldTypes.html#SFRotationAndMFRotation" target="_blank" rel="noopener">https://www.web3d.org/documents/specifications/19775-1/V4.0/Part01/fieldTypes.html#SFRotationAndMFRotation</a></div>
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<div>specifies that (0 0 1 0) is the value of an uninitialized SFRotation given as (x y z a).</div>
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<div>However, the JS SAI spec. in table 7.18 in <a href="https://www.web3d.org/documents/specifications/19777-1/V3.3/Part1/functions.html#SFRotationInstanceCreationFunction" target="_blank" rel="noopener">https://www.web3d.org/documents/specifications/19777-1/V3.3/Part1/functions.html#SFRotationInstanceCreationFunction</a></div>
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<div>effectively makes (0 1 0 0) the default value if no parameters are provided.</div>
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<div>The inconsistency does not have much of an impact since both are 0 rotations but I believe (0 1 0 0) - a 0 rotation around y - may have been intended as the default.</div>
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<div>-Andreas</div>
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<div>Andreas Plesch<br>Waltham, MA 02453</div>
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<div>Andreas Plesch<br>Waltham, MA 02453</div>
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<div>Andreas Plesch<br>Waltham, MA 02453</div>
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