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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoPlainText>Andreas, thanks for sharing on x3d public mailing list. Agreed that this is an extremely powerful rendering technique - high "wow factor" for sure. <o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Perhaps of note is that the X3D working group spent a few years pursuing Constructive Solid Geometry (CSG) with little to show for it, since such approaches can be computationally intensive and not well suited to real-time rendering on diverse devices.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><ul style='margin-top:0in' type=disc><li class=MsoPlainText style='mso-list:l0 level1 lfo1'>Wikipedia: Constructive solid geometry (CSG)<o:p></o:p></li><li class=MsoPlainText style='mso-list:l0 level1 lfo1'>https://en.wikipedia.org/wiki/Constructive_solid_geometry<o:p></o:p></li></ul><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Avoiding the need for any geometry modification whatsoever when creating visual "holes" - totally sidestepping CSG modeling - seems quite novel.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Wondering if this differencing (see-through) technique is possible today using glTF 2.0 models? If a supporting X3D4 player might load it as glTF, then that might be a fast path to usage. <sub><o:p></o:p></sub></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Looking ahead, when ready, this seems like the nodes you are using in X3DOM (or some version thereof) might be strong candidates for inclusion in a future X3D 4.1 specification.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Meanwhile (as you also recently discussed) we might experiment with extensions to X3D 4.0, perhaps through metadata for forwards/backwards compatibility and validation. (Wish list: the ImageAtlas node never made the cut for X3D 4.0 and seems like a candidate for broader implementation as well.) The X in X3D is Extensibility...<o:p></o:p></p><p class=MsoPlainText><br>Congratulations on what seems to be a major achievement! 8)<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>all the best, Don<o:p></o:p></p><p class=MsoPlainText>-- <o:p></o:p></p><p class=MsoPlainText>Don Brutzman Naval Postgraduate School, Code USW/Br brutzman@nps.edu<o:p></o:p></p><p class=MsoPlainText>Watkins 270, MOVES Institute, Monterey CA 93943-5000 USA +1.831.656.2149<o:p></o:p></p><p class=MsoPlainText>X3D graphics, virtual worlds, navy robotics https://faculty.nps.edu/brutzman<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>-----Original Message-----<br>From: x3d-public <x3d-public-bounces@web3d.org> On Behalf Of Andreas Plesch<br>Sent: Sunday, July 2, 2023 9:20 AM<br>To: X3D Graphics public mailing list <x3d-public@web3d.org><br>Subject: [x3d-public] visual shape differencing with x3d</p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Let me share that we found that it is possible to simulate differencing of shapes in x3dom to a useful degree. This allows for transparent cutouts or holes:<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>https://andreasplesch.github.io/Library/Viewer/index.html?url=https://gist.githubusercontent.com/andreasplesch/415d151abee114858c79c20c8c4b49e0/raw/4c70463321df267b28298462af76b869adbfdfdb/BoxWithHoles183.x3d<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>The idea is to draw first transparent shapes which define the holes, including to the depth buffer. Then standard drawing of the solid shape will be hidden where the holes 'obscure' it (although the holes are actually transparent).<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>To do that requires two changes to default rendering of transparent shapes. For best rendering normally transparent shapes are rendered last and do not write to the depth buffer. Here they are drawn first and do write to the depth buffer.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>In x3dom this is implemented by allowing explicit definition of the sort (rendering) order of shapes (with a sortKey field), and by allowing direct access to the gl depthmask function with a Depthmode node.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>An easy way to generate cutouts or holes which is otherwise only possible with external CSG tools is a powerful use case for these lower-level x3d extensions. Perhaps other browsers have similar features or are inspired to consider those.<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>Andreas<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>--<o:p></o:p></p><p class=MsoPlainText>Andreas Plesch<o:p></o:p></p><p class=MsoPlainText>Waltham, MA 02453<o:p></o:p></p><p class=MsoPlainText><o:p> </o:p></p><p class=MsoPlainText>_______________________________________________<o:p></o:p></p><p class=MsoPlainText>x3d-public mailing list<o:p></o:p></p><p class=MsoPlainText><a href="mailto:x3d-public@web3d.org"><span style='color:windowtext;text-decoration:none'>x3d-public@web3d.org</span></a><o:p></o:p></p><p class=MsoPlainText><a href="http://web3d.org/mailman/listinfo/x3d-public_web3d.org"><span style='color:windowtext;text-decoration:none'>http://web3d.org/mailman/listinfo/x3d-public_web3d.org</span></a><o:p></o:p></p></div></body></html>