 | | Part Authors: opinions sought on T-Junctions
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If you are a part author, I'd appreciate it if you read this post. I know it's long, but it needs to be in order to correctly describe the issue. When looking at one one of the parts in the inaugural Part of the Month contest in LDView (on my work (...) (18 years ago, 4-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) I try to minimise file size whenever possible myself and have nothing against T juctions. While the gaps can be annoying I feel that they are a fault of the rendering program rather than the parts. (18 years ago, 4-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) It's possible that by setting up meshes POVray can largely avoid the problem as it rotates points and then joins them. My opinion is that Part Authors should stick to keeping the polygon count down rather than jumping through hoops to try to (...) (18 years ago, 4-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) in all the parts I've made so far there is just one with a t-junction: (URL) (if I remember correctly it's where the two red quads are surrounded by the white border) but it is forgiveable I think, as it was one of the first parts I've ever (...) (18 years ago, 4-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) This is a really old issue. I think the previous consensus was that (URL) T-Junctions are bad.> Look at the bottom of the message for the comments on T-Junctions. Actually this is such an old issue, I could swear there was an ASCII art (...) (18 years ago, 4-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) It's not really constrained to high zoom. If you have a 1% chance of any given pixel along any given T-junction boundary edge resulting in a hole, then you'll have the roughly the same number of holes at any zoom level, since in general the (...) (18 years ago, 5-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) There are T-junctions there, but the ones that produce the most visible dots are between the white stripe and the moon. Both of those colors are light, so the dark background showing through is much higher contrast, which makes the dots much (...) (18 years ago, 5-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) Much as I'd like to agree on this, I don't think the fact that nobody posted back then disagreeing with my statement really counts as consensus. I pointed out the problem, but didn't ask for opinions on whether parts should be modeled that (...) (18 years ago, 5-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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--snip-- (...) Just to be clear it's not the render time I'm worried about... it's the authoring time. Tim (18 years ago, 5-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) Heh, I think I found the (URL) ASCII art>. I coulda sworn it made it into a FAQ somewhere though. Oh well. Have fun, Don (18 years ago, 5-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) T-junctions are a quality issue in part files. I don't think they should be strictly forbidden (that is, having T-junctions is not a reason to hold a part file from official release). Generally, I wouldn't even say that a part with T-junctions (...) (18 years ago, 5-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) Sounds reasonable to me. Any chance a T-junctions FAQ could be created on the parts tracker reference page, and the above could make it into a policy statement in the parts review FAQ? Most of my original post here could be used as the FAQ, (...) (18 years ago, 5-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) I'd really appreciate it if you didn't blame it on the rendering programs. There's really nothing that they can do to fix the problem. I can understand why you might feel that they are at fault, but it really isn't true. As such, you might (...) (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) Arguably it's probably the algorithms and/or numerical proccessing that are at fault. Certainly when you design scientific code algorithms they should usually be created in such a way that it minimises numerical error. Of course I don't expect (...) (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) Well... Technically it is true. The rendering program ought to be able to scan all the points in each part and look for intersections with every edge in the part. Then break up the offensive T-joins automagically and render it perfectly. (...) (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) OK, I stand corrected. Technically a program can fix things a load time. However, you might be surprised at how long it takes. It's "only" O(n^2), but each iteration is slow. You have to search the current line segment against all other line (...) (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) Well actually what txt2dat does is a slightly different problem - it has a few simple closed loops and has to triangulate the complex polygons bounded by them (it uses the excellent (URL) triangle library> to do that). Renderers on the other (...) (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) There is, however, such a thing as an impractical problem ;) ROSCO (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) blah, blah, blah, snip Oops, I was trying to be all ironical in a geeky math sorta way. But apparently I failed. Guess I shoulda used more winkies... Do people still use winkies? Or have they gone obsolete like ASCII art? Anyhow, sorry about (...) (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) No there's not. I'm a physicist... not an engineer ;) Tim (18 years ago, 6-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions [DAT]
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Something else to consider is that T junctions will often appear in model files themselves between two parts as shown in this simple example. 0 Model exported from LeoCAD 0 Original name: 1 4 20.00 -24.00 30.00 1.00 0.00 0.00 0.00 1.00 0.00 0.00 (...) (18 years ago, 7-Mar-07, to lugnet.cad.dat.parts, FTX)
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| | Re: Part Authors: opinions sought on T-Junctions
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(...) Yes, that's true, but in such cases there are generally lines separating the polygons (parts), and people expect to see those in the render. The problem we're talking about here is artifacts showing up on the faces of individual parts where (...) (18 years ago, 7-Mar-07, to lugnet.cad.dat.parts, FTX)
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