 | | CW/CCW, vertex sequence, co-planar, convex, (115kB) —Lars C. Hassing
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| | | Here are 50 messages regarding the above subjects. The first from January 1998 where Leonardo Zide suggested CW/CCW. I support the CW/CCW idea (isn't it annoying knowing almost 50% of all faces are drawn to waste), though it will cost a considerable (...) (25 years ago, 29-Sep-99, to lugnet.cad.dev)
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| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Leonardo Zide
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| | | | | (...) I miss that kind of discussion, those were very interesting subjects. Also, where's Jeff Findley ? (...) I've already thought about a ray intersection algorithm but I've never tried to implement it, I might try do it now. Some problems that I (...) (25 years ago, 29-Sep-99, to lugnet.cad.dev)
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| | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —John VanZwieten
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| | | | | | | Leonardo Zide <leonardo@centroin.com.br> wrote in message news:37F24ACE.49636F....com.br... (...) What if when a ray intersected 3 surfaces, it made the first CCW, the last CW, and left the middle surface unmarked. If you traced enough rays from (...) (25 years ago, 29-Sep-99, to lugnet.cad.dev)
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| | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Lars C. Hassing
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| | | | | | | | John VanZwieten wrote in message ... (...) Me too! (...) "enough rays" - exactly what stroke me too when I read Leonardo's posting! With the fast computers nowadays we could shoot millions of rays at the part from all possible viewing angles (this (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —John VanZwieten
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| | | | | | | | | (...) CW, (...) as (...) What I was concerned about are situations where a single quad is used as the outside of a section of a part and the inside of a section of a part. A theoritical example would be a minifig head. You could use a single 4- (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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| | | | | | | | | | John VanZwieten wrote in message ... (...) the (...) in (...) What if the part that referenced such a primitive had a '0 invert' comment on the line before the primitive reference, if that instance of the primitive was intended to appear inside-out? (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —John VanZwieten
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| | | | | | | | | | Gary Williams <graywolf@pcpros.net> wrote in message news:FIvo77.F2B@lugnet.com... (...) In the case I'm talking about, 1 primitive is used in 1 instance to be both an outer face and an inner face. In this case, you'd have to fix it manually by (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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| | | | | | | | | | John VanZwieten wrote in message ... (...) primitive (...) the (...) ray (...) A hypothetical batch dat fixer program could examine the primitives first and flag the ones that were not closed volumes, since those would be the only ones that would (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Steve Bliss
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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: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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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) —Gary Williams
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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) —Steve Bliss
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| | | | | | | | | | (...) OIC now. I think. If an asymmetrical part is mirrored, it keeps the same shape, but is turned inside out. To get it right-side-out again, it must be re-mirrored. In other words, there's no way to produce left- and right-handed pairs of (...) (25 years ago, 3-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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| | | | | | | | | | Steve Bliss wrote in message <37f4edd7.8510607@lu...et.com>... (...) are (...) rotated (...) thinking. (...) Possibly. I'm not to great when it comes to expressing myself. I think if an even number of mirror operations are performed on a part, its (...) (25 years ago, 3-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Bram Lambrecht
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| | | | | | | | | | (...) I mirror sub-parts often in my models (for hoses, wings, etc.). Would this require an INVERT? --Bram Bram Lambrecht / o o \ BramL@juno.com ---...---oooo-----(_...o---...--- WWW: (URL) (25 years ago, 3-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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| | | | | | | | | | Bram Lambrecht wrote in message <19991003.083644.509...no.com>... (...) No. Our software will detect mirror operations and correct for them. -Gary (25 years ago, 3-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Steve Bliss
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| | | | | | | | | | (...) I've been thinking the exact opposite -- mirroring should be a valid method for turning subfiles inside-out, and the software doesn't need to do anything special to deal with it (except to notice the inversion, and pass that info on to the (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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| | | | | | | | | | Steve Bliss wrote in message <37f8c86b.239282689@...et.com>... (...) But more often than not, when mirroring an element or subassembly, it's not the intent of the author to turn it inside out. Typical model builders shouldn't concern themselves (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Steve Bliss
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| | | | | | | | | | | (...) True. But mirroring is an advanced technique. Well, maybe intermediate-level. Anyway, it's not for beginners. (...) True. Allowing mirroring/inversion for parts authors allows them to use a single set of primitives, while keeping part-files (...) (25 years ago, 5-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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| | | | | | | | | | | | Steve Bliss wrote in message <37f9f5c6.74291430@l...et.com>... (...) not (...) inversion. (...) For WizardCAD I was intending to change the behavior of the mirror functions depending on what type of file the user opened the file as. If they open a (...) (25 years ago, 5-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Lars C. Hassing
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| | | | | | | | | | Gary Williams wrote in message ... (...) I agree with Gary that mirroring should not turn subfiles inside-out. The rendering program should correct (C)CW-ness by looking at the transformation. Part authors should use the INVERT for explicitly (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Leonardo Zide
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| | | | | | | | (...) When you draw a part with a pattern transparently, I guess it's not a good idea to remove the backfaces or you might not see the pattern from some angles. (...) About that discussion, IMO it would be better to have *everything* CCW instead of (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Lars C. Hassing
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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) —Jacob Sparre Andersen
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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) —John VanZwieten
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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) —Leonardo Zide
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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) —Jeff Boen
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| | | | | | | | | | | | (...) why can't you simply mod your proggy to handle the conversion automatically?? i mean.. if your proggy is smart enough to detect uninified normals and then allows the user to press a key to mod the CW/CCW property of the face, why can't you (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Leonardo Zide
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| | | | | | | | | | | | (...) Because the program doesn't work that way, it just turns backface culling on and draws everything in green, then switch to "frontface culling" (does it exist ?) and draws everything red. I've been busy finishing my first game project (not Lego (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Steve Bliss
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| | | | | | | | | | (...) That would be nice, but it's unrealistic. (...) No, they shouldn't. Just because the part XYZ is CW, a program can't assume that the primitive ABC is also CW. (...) I like this. I don't like it for use on primitives, but DOUBLE-SIDED could (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Jacob Sparre Andersen
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| | | | | | | | | | [ I got a bit too much good French red wine, so maybe I shouldn't try to answer now, but ... ] Steve: (...) Right. (...) Shouldn't all elements of transparent parts be drawn? (...) Yes. (I start to suspect that wine has a good influence on my (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Gary Williams
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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) —Steve Bliss
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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: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Jacob Sparre Andersen
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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: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Steve Bliss
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| | | | | | | | (...) Jacob: (...) Why? Having a negative determinate *should* turn subfiles inside-out. IMO. That's a useful function. Having programs checking determinates is not useful, and wastes rendering time. Steve (25 years ago, 3-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Jacob Sparre Andersen
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| | | | | | | | Steve: (...) Hmm??? Yes you're right (again :-). Play well, Jacob ---...--- -- E-mail: sparre@cats.nbi.dk -- -- Web...: <URL:(URL) -- ---...--- (25 years ago, 3-Oct-99, to lugnet.cad.dev)
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| | | | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Steve Bliss
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| | | | | | | | Jacob: (...) Steve: (...) Jacob: (...) It happens every once in awhile. Actually, which approach *would* be better? Examining the transformation matrix to determine the state of inversion, and adjusting the CW/CCW setting to correct for it, would (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
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| | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Jeff Boen
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| | | | | | There are commands in 3DS and 3DSMAX to "unify" normals (normals are what we're discussing... the vector that points perpendicular to a face, indicating which side is "out", which side is shaded or rendered)... i would assume there is documentation (...) (25 years ago, 29-Sep-99, to lugnet.cad.dev)
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| | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Steve Bliss
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| | | | | | | (...) It wouldn't be impossible to fix primitive usage so that primitives such as 4-4cyli.dat are always applied as infinitely thin 1-sided objects. Would that solve the problem? (...) I don't think re-engineering the library is impossible. (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Leonardo Zide
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| | | | | | (...) I was curious, how do you add a stud to a part if you're using MAX2DAT ? Can it be done in 3DS or you have to edit the part later ? I thought that we've agreed that the new parts would have to pass L3P tests for coincident verts and bow-ties, (...) (25 years ago, 30-Sep-99, to lugnet.cad.dev)
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| | | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB) —Jeff Boen
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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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| | | | | (canceled) —Gary Williams
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| | | | | | | (canceled) —Gary Williams
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| | | | | Re: CW/CCW, vertex sequence, co-planar, convex —John VanZwieten
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| | | | It seems to me that there are two major "camps" in the CW/CCW debate. A. Face-by-Face Method This method suggests that CW-ness be ultimately evaluated on a face-by-face basis. Each quad in a primitive or part would hold a value of CW,CCW, or (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Gary Williams
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| | | | John VanZwieten wrote in message ... (...) Actually, I count three ideas. (...) messy. (...) when (...) the (...) to (...) only (...) have (...) in (...) CW (...) slightly (...) for (...) The third option, which I believe would be best, is similar (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Lars C. Hassing
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| | | | Gary Williams wrote in message ... (...) Well, inside/outside-ness also counts. It doesn't make sense to certify a part before ALL its subfiles have defined what is inside/outside. Until then you cannot determine whether or not you need any INVERTS. (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Jacob Sparre Andersen
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| | | | | Lars mentions the problem of "uncertified" parts using "certified" primitives. Is it so much of a problem? <much thinking> I can't find any other easy solution than using different names for the "certified" versions of the _primitives_. That way we (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Lars C. Hassing
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| | | | | | Jacob Sparre Andersen wrote in message ... (...) Certified primitives are harmless when used by old uncertified parts, so there's no need to create special certified versions. And in stead of fixing parts to reference the new names, you might just (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Steve Bliss
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| | | | (...) Checking the order of points in a file should not depend on checking the inversion or subfiles for the file. That's why we've been talking about the 0 FACE UNKNOWN -- so parts of files can be fixed, even if the entire file can't be addressed. (...) (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Lars C. Hassing
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| | | | (...) Yes, you can of course settle for checking only the tris/quads of a file and put UNKNOWN around subfile references. But then you would miss the most important speed boost coming from the primitives, which are responsible for the majority of (...) (25 years ago, 9-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Steve Bliss
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| | | | (...) Understood and agreed. (...) Also, the primitive files will (generally) require less work than most part-files. [About introducing processing-by-file-type] (...) Yes, if they didn't have a 0 CLIPPING ON directive. That's why I said a good (...) (25 years ago, 11-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Lars C. Hassing
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| | | | (...) Yes, this works for *new* models/submodels. Will you really require all existing models to go through a new good editing program, before they could benefit from backface-culling? I don't think that is necessary. Once an old model references a (...) (25 years ago, 11-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Steve Bliss
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| | | | (...) Sure. But I also feel that it would make sense for rendering programs to give the user control, so that clipping can be set to default to off, or default to on, or to be totally disabled. (...) If a certified part-file can turn clipping on, (...) (25 years ago, 13-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Lars C. Hassing
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| | | | Steve Bliss wrote... (...) Yes, rendering programs should have these reasonable options. But I think it is safe to start clipping from opaque certified parts. (...) Parts are objects with obvious orientation. You are not in doubt what is (...) (25 years ago, 14-Oct-99, to lugnet.cad.dev)
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| | | | | | Re: CW/CCW, vertex sequence, co-planar, convex —Steve Bliss
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| | | | (...) Disagree. Being able to turn clipping on and off separately from specifying the direction of winding is a functional difference, not 'syntax sugar'. (...) OK. Steve (25 years ago, 15-Oct-99, to lugnet.cad.dev)
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