Subject:
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Re: Equation of a sphere?
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Tue, 15 Apr 2003 17:33:32 GMT
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Viewed:
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399 times
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In lugnet.off-topic.geek, Dave Schuler writes:
> Quite a while back I asked for help in computing the equation of a circle
> from three known points, and I received very useful (and ultimately
> successful) assistance from several people. In addition, my searches led me
> to a piece of software that handled the calculations for me, making my job
> that much easier.
>
> So here's my next question: I now have four non-coplaner points and I need
> to derive the sphere that they describe. I'm not having particular luck in
> running through the equations because I get bogged-down in my liberal arts
> math ignorance. Does someone know of a program that will compute the
> equation of a sphere from four points?
>
> Thanks muchly.
>
> Dave!
A quick search reveals:
http://astronomy.swin.edu.au/~pbourke/geometry/spherefrom4/
Which reveals that:
(x - A)^2 + (y - B)^2 + (z - C)^2 = R
Where A,B,C = the x,y,z coordinates that the circle is centered around, and
R is the radius you're looking for. Theoretically (tho I haven't tried), you
could plug your 4 points into the above generic equation, and then solve for
A,B,C, and R. Of course maybe this leads to some gross degree polynomial
that's difficult to solve, but I dunno.
The web page I cited seems to want you to solve it using matrices, which I
totally forget.
DaveE
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Message is in Reply To:
 | | Equation of a sphere?
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| Quite a while back I asked for help in computing the equation of a circle from three known points, and I received very useful (and ultimately successful) assistance from several people. In addition, my searches led me to a piece of software that (...) (21 years ago, 15-Apr-03, to lugnet.off-topic.geek)
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