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</o:shapelayout></xml><![endif]--></head><body lang=DE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Thx to all of you for your great help.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Considering this reasons, i will stick with the homogeneous way.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>.philipp<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Von:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Keith Victor [mailto:keithrvictor@gmail.com] <br><b>Gesendet:</b> Dienstag, 27. August 2013 06:58<br><b>An:</b> Philipp Serfling<br><b>Cc:</b> x3d-public@web3d.org<br><b>Betreff:</b> Re: [X3D-Public] reason / benefits of homogeneous coordinates in NURBS?<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><div><div><div><div><div><div><p class=MsoNormal style='margin-bottom:12.0pt'>Hello Philipp:<o:p></o:p></p></div><p class=MsoNormal style='margin-bottom:12.0pt'>Yes, I feel your pain.<o:p></o:p></p></div><p class=MsoNormal>I implemented X3D NURBS in Vivaty Player/Vivaty Studio many years ago, and recall running into that problem.<o:p></o:p></p></div><p class=MsoNormal>The spec clearly says that fourth parameter is "weight", and references the NURBS book, that tells you exactly how to implement it. The Spec and the NURBS book do NOT refer to "weight" as being "w", the forth homogenous coordinate. weight is weight. It does however, start with the letter "w". <o:p></o:p></p></div><p class=MsoNormal><br>But, Contact and others used the "weight" as "w", the fourth homogenous coordinate. Since that is the gold standard, the bug propagates. <o:p></o:p></p></div><div><p class=MsoNormal><br>FWIW, Vivaty used the proper interpretation of the NURBS weight field :)<o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal>So, to answer your question, IMHO, the only benefit of choosing the Homogenous coordinate interpretation is that it is consistent with the other X3D players. Consistent with the spec... not so much.<o:p></o:p></p><div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Keith Victor<o:p></o:p></p></div><p class=MsoNormal>Apple<o:p></o:p></p><div><p class=MsoNormal><span style='font-size:7.5pt'>(these are my opinions, and not those of my employer)</span><o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><o:p> </o:p></p><div><div><div><div><p class=MsoNormal style='margin-bottom:12.0pt'><br><br><o:p></o:p></p></div></div></div></div></div></div><div><p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p><div><p class=MsoNormal>On Mon, Aug 26, 2013 at 12:04 AM, Philipp Serfling <<a href="mailto:Philipp.Serfling@t-systems-mms.com" target="_blank">Philipp.Serfling@t-systems-mms.com</a>> wrote:<o:p></o:p></p><p class=MsoNormal>Hi,<br>i´m sorry to bother you again with my problems, but if anyone know some<br>resources or reasons for my problem written underneath, i would be very<br>thankful.<br><br>thx<br>.philipp<br><br><br>-----Ursprüngliche Nachricht-----<br>Von: Philipp Serfling [mailto:<a href="mailto:Philipp.Serfling@t-systems-mms.com">Philipp.Serfling@t-systems-mms.com</a>]<br>Gesendet: Mittwoch, 14. August 2013 15:09<br>An: '<a href="mailto:x3d-public@web3d.org">x3d-public@web3d.org</a>'<br>Betreff: reason / benefits of homogeneous coordinates in NURBS?<br><br>hello,<br><br>I´ve noticed that in x3d the control points of a nurbs surface are<br>represented in homogeneous coordinates<br>see:<br><a href="http://castle-engine.sourceforge.net/x3d_implementation_nurbs.php#section_ho" target="_blank">http://castle-engine.sourceforge.net/x3d_implementation_nurbs.php#section_ho</a><br>mogeneous_coordinates<br><br>Is there any benefit in doing it that way compared to the "normal /<br>intuitive way" (also explained in the link) ?<br><br>I´m asking for two reasons:<br><br>1. White_dune, Instant Reality & BSContact Player are using the homogeneous<br>way.<br> But Octaga Player uses the "normal" way.<br><br>2. I´m currently implementing NURBS Curves and PatchSurfaces in X3DOM and<br>i´m not sure if i should implement the homogeneous<br> or the "normal way". Currently i´m developing both, but the homogeneous<br>way is unintuitive and more complex and i really don´t see any advance.<br><br>thx for your help<br>.philipp<br><br><br>_______________________________________________<br>X3D-Public mailing list<br><a href="mailto:X3D-Public@web3d.org">X3D-Public@web3d.org</a><br><a href="http://web3d.org/mailman/listinfo/x3d-public_web3d.org" target="_blank">http://web3d.org/mailman/listinfo/x3d-public_web3d.org</a><o:p></o:p></p></div><p class=MsoNormal><o:p> </o:p></p></div></div></div></body></html>