"Duncan Adamson" <dja### [at] docicacuk> wrote in message
news:3bb4754e$1@news.povray.org...
> Hang a rope from two points <0,1,0> and <1,1,0>
> The shape it makes is a caterary
>
> Rotate this shape around the x axis to get a catenoid

>(formula radius =
> (1/a)cosh(ax))

Is this the formula for a caterary or a catenoid? I'm looking for the formula
for a caterary.

Regards,

- Nekar

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caternary is of the form

y = (1/a)(cosh(a*x))
where a is a constant

note: this is equivalent to
y = (1/a)((e^(a*x) + e^(-a*x))/2)
where a is a constant
where e is the standard mathematical constant 2.817.....

Duncan

"Nekar Xenos" <j-p### [at] citywalkcoza> wrote in message
news:3bb481e2@news.povray.org...
>
> "Duncan Adamson" <dja### [at] docicacuk> wrote in message
> news:3bb4754e$1@news.povray.org...
> > Hang a rope from two points <0,1,0> and <1,1,0>
> > The shape it makes is a caterary
> >
> > Rotate this shape around the x axis to get a catenoid
>
> >(formula radius =
> > (1/a)cosh(ax))
>
> Is this the formula for a caterary or a catenoid? I'm looking for the
formula
> for a caterary.
>
> Regards,
>
> - Nekar
>
>
>

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Here is a very well rounded list of physical constants
http://www.alcyone.com/max/reference/physics/constants.html

Duncan Adamson wrote:

> caternary is of the form
>
> y = (1/a)(cosh(a*x))
> where a is a constant
>
> note: this is equivalent to
> y = (1/a)((e^(a*x) + e^(-a*x))/2)
> where a is a constant
> where e is the standard mathematical constant 2.817.....
>
> Duncan
>
> "Nekar Xenos" <j-p### [at] citywalkcoza> wrote in message
> news:3bb481e2@news.povray.org...
> >
> > "Duncan Adamson" <dja### [at] docicacuk> wrote in message
> > news:3bb4754e$1@news.povray.org...
> > > Hang a rope from two points <0,1,0> and <1,1,0>
> > > The shape it makes is a caterary
> > >
> > > Rotate this shape around the x axis to get a catenoid
> >
> > >(formula radius =
> > > (1/a)cosh(ax))
> >
> > Is this the formula for a caterary or a catenoid? I'm looking for the
> formula
> > for a caterary.
> >
> > Regards,
> >
> > - Nekar
> >
> >
> >

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Ahh, a rope from two points... I ass-u-me d one!


Duncan Adamson wrote:
> Hang a rope from two points <0,1,0> and <1,1,0>
> The shape it makes is a caterary
> 
> Rotate this shape around the x axis to get a catenoid (formula radius =
> (1/a)cosh(ax))
> 
> My catenoid has been rotated to stand on its end.
> 
> Duncan
> 
> "Is" <mee### [at] yahoocom> wrote in message news:3BB### [at] yahoocom...
> 
>>Your ropes hang that way?
>>
>>
>>Duncan Adamson wrote:
>>
>>>OK, I am sold on iso-surfaces.  A long time project of mine has been to
>>>create a catenoid (minimal surface object created by rotating a catenary
>>>(shape a hanging rope makes)).
>>>
>>>Functions are fantastic.  Here it is:
>>>
>>>
>>>
>>>
>>>
>>>catenoid.jpg
>>>
>>>Content-Type:
>>>
>>>image/jpeg
>>>Content-Encoding:
>>>
>>>x-uuencode
>>>
>>>
>>>
>>
> 
>

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Q: How do you make a catenoid?

A: Pull its tail.

I can't remember where I heard that one, probably somewhere on the net.  I
agree with you on isosurfaces, they're fantastic!

    ~Kevin Wampler~

Duncan Adamson wrote:

> OK, I am sold on iso-surfaces.  A long time project of mine has been to
> create a catenoid (minimal surface object created by rotating a catenary
> (shape a hanging rope makes)).
>
> Functions are fantastic.  Here it is:
>
>  [Image]

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I'll have to remember that one! But only for people who know what a catenoid
is - Explaining this joke would ruin any chance of getting a laugh (or
groan).


"Kevin Wampler" <kev### [at] tapestrytucsonazus> wrote in message
news:3BB4A2A6.72B562AE@tapestry.tucson.az.us...
> Q: How do you make a catenoid?
>
> A: Pull its tail.
>
> I can't remember where I heard that one, probably somewhere on the net.  I
> agree with you on isosurfaces, they're fantastic!
>
>     ~Kevin Wampler~
>
> Duncan Adamson wrote:
>
> > OK, I am sold on iso-surfaces.  A long time project of mine has been to
> > create a catenoid (minimal surface object created by rotating a catenary
> > (shape a hanging rope makes)).
> >
> > Functions are fantastic.  Here it is:
> >
> >  [Image]
>

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On Fri, 28 Sep 2001 14:01:09 +0100, "Duncan Adamson"
<dja### [at] docicacuk> wrote:

>Hang a rope from two points <0,1,0> and <1,1,0>
>The shape it makes is a caterary

Isn't it a parabola?


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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"Peter Popov" <pet### [at] vipbg> wrote in message
news:2d0brtk13k51jdgk4h98hajm1d5gh0db4g@4ax.com...
> On Fri, 28 Sep 2001 14:01:09 +0100, "Duncan Adamson"
> <dja### [at] docicacuk> wrote:
>
> >Hang a rope from two points <0,1,0> and <1,1,0>
> >The shape it makes is a caterary
>
> Isn't it a parabola?

Nope. IIRC a caterary is almost parallel at the start and end points.

- Nekar

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in news:2d0brtk13k51jdgk4h98hajm1d5gh0db4g@4ax.com Peter Popov wrote:

>>The shape it makes is a caterary
> 
> Isn't it a parabola?
> 
> 

http://www-groups.dcs.st-and.ac.uk/~history/Curves/Catenary.html

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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Peter Popov wrote:
> 
> On Fri, 28 Sep 2001 14:01:09 +0100, "Duncan Adamson"
> <dja### [at] docicacuk> wrote:
> 
> >Hang a rope from two points <0,1,0> and <1,1,0>
> >The shape it makes is a caterary
> 
> Isn't it a parabola?

IIRC, actually, the curve you get when you roll a parabola along an axis
and trace the focus.  Very similar to a parabola but not a parabola.

-- 
David Fontaine  <dav### [at] faricynet>  ICQ 55354965
My raytracing gallery:  http://davidf.faricy.net/

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