 | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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Gary Williams wrote in message ... (...) *a lightbulb appears above my head* Nevermind, I understand now. For some reason I was imagining inverting all three axes, but now I realize only two would need to be inverted, before the part is rotated 180 (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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Steve: (...) Because our clever rendering programs will notice that the first transformation matrix has negative determinant, and therefore will swap the CW and CCW checks. Play well, Jacob ---...--- -- E-mail: sparre@cats.nbi.dk -- -- Web...: (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: LeoCAD for Linux (Was: Compiling MPD Builder/Splitter for DOS/Win?)
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Leonardo: (...) I do have X installed _on_my_Linux_machine_, but I haven't managed to get the Macs here in Paris to run a X server (yet). Play well, Jacob ---...--- -- E-mail: sparre@cats.nbi.dk -- -- Web...: <URL:(URL) -- ---...--- (25 years ago, 1-Oct-99, to lugnet.cad, lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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(...) Why not simply: (...) Assuming the primitives are all defined so their faces are turned outward. I would see allowing both CW and CCW as a convenience for parts authors. There's no real difference between one way and the other. CW has a slight (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: LeoCAD for Linux (Was: Compiling MPD Builder/Splitter for DOS/Win?)
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(...) I'll add that to my page. I don't know (almost) anything about writing linux applications, so I don't know which options to use when compiling. (...) The MS Windows version works correctly (without creating a window) but the Linux version (...) (25 years ago, 1-Oct-99, to lugnet.cad, lugnet.cad.dev)
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| | Re: Hidden surface removal, and vertex order in part/primitive DAT files
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(...) I guess we could at least decide to use CCW to determine the normal of a face, unless there's someone who prefers to use CW ? Leonardo (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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(...) If we know that a face is CW, why not change it to CCW ? The most difficult task is to discover the orientation of a face, but once we have that information anyone can change the order of the points and fix the face. (...) This can be done (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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Lars C. Hassing wrote in message <938787015.279086@ns.cci.dk>... (...) of (...) we will (...) Hold on. Why not just have a button in the CAD program to turn the part inside-out by automatically manipulating the orientation matrix in the parent dat (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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Steve Bliss wrote in message <37f4ab7d.64002272@l...et.com>... (...) Doh'! You're right. (...) I'm having a difficult time picturing in my mind how an asymmetrical part can have its orientation matrix in the parent dat file mirrored and rotated (to (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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Jacob Sparre Andersen <sparre@sys-323.risoe.dk> wrote in message news:FIxHC0.E2v@lugnet.com... (...) I'm not so sure about this anymore. I think the ideal would be a program that could change the part files so that they are completely CCW. Using (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) [DAT]
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Lars: (...) [...] (...) This would demand a lot of work before people could start using programs that use this fact. (...) Right. (...) Just check the determinant of the rotation matrix (but you know that I suppose). (...) I would rather use some (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) [DAT]
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Leonardo Zide wrote in message <37F383E1.CA6B8962@c...com.br>... (...) I agree with John Van in that we need three keywords: CCW, CW, UNKNOWN. As the rendering program is going to keep track of the number of mirrorings of the transformations (or (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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(...) It wouldn't matter if they were closed-volume or not--they could still be turned inside out accidently. And an inside-out closed-volume primitive wouldn't do anybody any good. (...) Why? Steve (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: Hidden surface removal, and vertex order in part/primitive DAT files
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(...) I'm willing to change my parts, if the standard changes. Assuming parts which are *not* C(C)W need to be flagged at all. (...) I agree completely. Steve (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | New Group Idea
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We should have a lugnet.cad.dat.clones group, now that someone over on RTL is doing megablocks parts. bThe group would be expressly for posting clone lego parts, official sets and MOC's. -- Jonathan Wilson wilsonj@xoommail.com (URL) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: Hidden surface removal, and vertex order in part/primitive DAT files
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Michael Lachmann: (...) I think we agreed to use 0 CW and 0 CCW lines in the beginning of the files to indicate (C)CW compliancy, but you should have a look at what Steve actually has written in his parts. (...) It would be very nice if you (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: Hidden surface removal, and vertex order in part/primitive DAT files
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You mentioned that some parts have a "0 CW-Compliant" tag. Could we do something to make this a standard? Because than I could read this tag in MLCad and make the drawing faster!!!!! Tell me what you think! Mike (...) John VanZwieten wrote in (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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(...) MAX2DAT isn't really meant to be a comprehensive part authoring tool... it's easy to build simple objects (like a 2x2 tile or 1x1 round plate) directly in LEdit with primatives... but objects like complex technic pieces, wheels, etc often have (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | Re: Hidden surface removal, and vertex order in part/primitive DAT files
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Gary Williams wrote in message ... (...) Okay, I made a bad assumption there, since a group of polygons may terminate flush against another polygon, without touching its edges. But still I think a performance improvement could be realized by using (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | Re: Hidden surface removal, and vertex order in part/primitive DAT files
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Jean-Pierre PARIS wrote in message <37F3B871.74AE196F@w...doo.fr>... (...) My algorithm doesn't require the vertices to exactly match; I was intending to pass one ray per polygon through the dat object, not an arbitrarily large number. And only if (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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