 | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | 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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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)
| | | | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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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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