Subject:
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Re: Symmetries other than 16 and 48?
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sat, 24 May 2003 16:51:47 GMT
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Viewed:
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3267 times
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"Steve Bliss" <steve.bliss@earthlink.net> wrote in message
news:8ljscv8fn458bfvbui9d7m3ajimc2fofvm@4ax.com...
> In lugnet.cad.dev, Lance Hopenwasser wrote:
>
> > What is the general way of handling parts/primitives that have rotational
> > symmetries other than 16 and 48? I am currently looking at reworking • 73071
> > (the old Technic Differential), which has a rotational symmetry of 28, • and
> > 3649 (Technic Gear 40 Tooth), which (obviously) has a rotational symmetry • of
> > 40.
>
> For parts with unusual symmetries, I would suggest either (or both):
>
> 1. Make a subfile in parts\s with 1 segment of the part, then use that
> subfile as many times as you need.
That makes a lot of sense, especially for segments that would not be
used by other parts.
> 2. Find a higher-level symmetry that is common with 16 or 48 (greatest
> common factor?), and use that. For example, a part with 40-symmetry
> meshes with 16-symmetry at a level of 8-symmetry. So every 5 teeth in
> the gear go with every 2 segments of a ring/cylinder/etc.
I guess that would mean coding 5 teeth individually and reusing it 8
times. Certainly better than coding 40, but somehow not 100% ideal to
me. On the other hand, I fully acknowledge that practicality sometimes
does have to take precedence over the ideal.
> > Ideally, I would like to create rings, cylinders, etc. that match the
> > natural symmetry so that I can create a single tooth primitive that could • be
> > repeated easily with appropriate seams
>
> That would be a good approach to use in creating your part file. But
> the files you build to create the part might need to be reorganized
> before the part is submitted to the library. I typically work with 5-20
> subfiles in the making of a part (actually, I use less now, because I
> usually use the MPD format). Most often, I inline these down to just 1
> or 2 files before submitting.
I will probably need some help in determining the best organization
(subfiles vs. inline). I am starting with 73071, and when I get it done,
I will post what I have to the newsgroup to get suggestions about the
best organization before submitting it to the library.
> > (call me obsessive, but I hate overlapping polygons).
>
> Me too! I use them, but I don't like 'being sloppy'. In the long run,
> overlapping polygons are practically unavoidable. If you code your
> parts so that your polygons match up cleanly with LDraw's polygonal
> 'curved' primitives, POV-Ray renderings of your part will either have
> gaps or overlapped polygons.
I guess this is where the POV-Ray meta statements could be really useful.
I need to look into that and see how complicated it is. From what I have
seen, it is an intriguing concept -- allowing for nice looking pieces both
in traditional LDraw-based programs and more advanced rendering
programs.
> > Could we create directories for these other
> > primitives just like the 48 series? It seems to me that this should fit • in
> > well with the current structure, but I confess I don't know how hardcoded
> > the directory structure is.
>
> It's not that the directory structure is hard-coded, it's a matter of
> what makes sense for the library, what adds value. The real power of
> primitives is their reusability. I'm afraid if we started making more
> subdirectories of ldraw\p, with different segment-counts of curved
> primitives, we'd end up with more confusion, and the primitive library
> would be harder to use.
I totally understand. That could become extremely confusing.
> In no way do I want to discourage you from working on these files. I
> know 73071 in particular is a mess, and I'd love for it to get cleaned
> up. I'm just trying to respond to your questions, answering as I see
> things.
Don't worry, you're quite the opposite from discouraging. Knowing what
the standards are makes it easier to design the part in a way that is
compatible
with current work, which is very important to me. I would hate to do all
this work and have it be useless.
Thanks,
--Lance--
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Message is in Reply To:
 | | Re: Symmetries other than 16 and 48?
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| (...) For parts with unusual symmetries, I would suggest either (or both): 1. Make a subfile in parts\s with 1 segment of the part, then use that subfile as many times as you need. 2. Find a higher-level symmetry that is common with 16 or 48 (...) (23 years ago, 23-May-03, to lugnet.cad.dev)
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