Subject:
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Re: 1-8sphe.dat tesselations compaire image
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Newsgroups:
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lugnet.cad
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Date:
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Wed, 4 Oct 2000 20:17:18 GMT
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Viewed:
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820 times
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In lugnet.cad, Travis Cobbs writes:
> It does look good, but it is actually a 32 tesselation, not a 48 (32
> segments around the equator of an entire sphere). I assume the 48 version
> could be generated using the same procedure and trisecting instead of
> bisecting, but I'm not sure how easy that is.
You're right, I haven't thought of that. Well, you get the general idea.
It would be 3 parallel bands of quads along the perimeter, and the rest
diveded proportionaly. Generating this is fairly easy in my cad program, and I
can use the wire-frame model also to obtain a list of sufficiend accurate
coordinates.
> Just out of curiosity, are the quads actually planar?
They are not -perfectly- planar, but the deriviation will be very small. In
fact, if you model a quad that is not parallel to either the X-, Y- or Z-axis
in dat format, it is almost never perfectly planar (as I've found out when I
made certain parts). With Lars C. Hassing I've discused what deviation would
still be acceptable: if the distance of the fourth point from the plane
defined by the other 3 points is smaller than 0.01 LDU we both think it's good
enough, and L3P can make a good conversion to POV with this limit. We're able
to check this treshold with one of the options of the L3P program.
And if so, how close are they to the surface of the sphere?
The coordinates would be right on, because my wire frame model uses arcs. I've
used a similar model to fix the low-res 1-8sphe.dat.
> It's probably even reasonable to do programatically, although I'm not sure off
> the top of my head to do the trisecting, and whether that would be easy.
Hmm, I think you would need discontinuities in the algorithm. Would a list of
the intermediate points derived from my wire-frame model do for you ?
Greetings, M. Moolhuysen.
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Message is in Reply To:
 | | Re: 1-8sphe.dat tesselations compaire image
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| "Manfred Moolhuysen" <moom@nospamchello.nl> wrote in message news:G1wK2M.6ry@lugnet.com... (...) closely, (...) primitive. (...) It does look good, but it is actually a 32 tesselation, not a 48 (32 segments around the equator of an entire sphere). (...) (24 years ago, 4-Oct-00, to lugnet.cad)
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