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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Fri, 23 May 2003 17:01:22 GMT
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Viewed:
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932 times
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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.
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.
> 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.
> (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.
> 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.
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.
Steve
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Message has 1 Reply:
 | | Re: Symmetries other than 16 and 48?
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| "Steve Bliss" <steve.bliss@earthlink.net> wrote in message news:8ljscv8fn458bfv...4ax.com... (...) 73071 (...) and (...) of (...) That makes a lot of sense, especially for segments that would not be used by other parts. (...) I guess that would (...) (21 years ago, 24-May-03, to lugnet.cad.dev)
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Message is in Reply To:
| | Symmetries other than 16 and 48?
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| 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 (...) (21 years ago, 22-May-03, to lugnet.cad.dev)
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