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7 Replies Last post: Jan 22, 2009 9:47 AM by (Robert_A_WIlliams)  
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(Robert_A_WIlliams)
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Jan 19, 2009
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Jan 19, 2009 1:39 PM

Creating a Catenary Curve Assistance

Does anybody know how I can create a catenary curve (St. Louis Arch would be an example) in Illustrator. I suspect that it has to be done via scripting, but I'm no math wiz?

Thanks!
Bob
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(Stanley_Hoffman)
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1. Jan 19, 2009 9:41 PM in response to: (Robert_A_WIlliams)
Re: Creating a Catenary Curve Assistance
Robert, i'm not sure i got your question, could u make some examples of that catenary curve in pictures?
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(Robert_A_WIlliams)
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2. Jan 19, 2009 9:58 PM in response to: (Robert_A_WIlliams)
Re: Creating a Catenary Curve Assistance
A catenary curve is the theoretical shape of a hanging flexible chain or cable when supported at its ends and acted upon by a uniform gravitational force (its own weight) and in equilibrium. The curve has a U shape that is similar in appearance to the parabola, though it is a different curve.

The formula is y=a*cosh(x/a)

An example, can be found in the Wikipedia article for Catenary (http://en.wikipedia.org/wiki/Catenary).

The Saint Louis Arch is a cantenary curve.

I'm wanting to be able to change the curve I get by changing the values in the script, which I why I figured that was the only way I would be able to do it.
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storm371 User
storm371
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3. Jan 20, 2009 10:32 AM in response to: (Robert_A_WIlliams)
Re: Creating a Catenary Curve Assistance
Are you on a Mac or PC, Robert?
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(Robert_A_WIlliams)
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4. Jan 20, 2009 1:29 PM in response to: (Robert_A_WIlliams)
Re: Creating a Catenary Curve Assistance
I'm using a PC and Illustrator CS3.
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(Stanley_Hoffman)
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5. Jan 21, 2009 9:42 PM in response to: (Robert_A_WIlliams)
Re: Creating a Catenary Curve Assistance
Robert, I made a conclusion how would I make it. It's not hard to find a free tools in internet that draw a formular graphs, so u could make a graph u need using that tools, then "print screen" & "trace". That's it.
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storm371 User
storm371
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6. Jan 22, 2009 7:45 AM in response to: (Robert_A_WIlliams)
Re: Creating a Catenary Curve Assistance
Robert:

Aww I'm a Mac / Applescript guy. (I should probably know more Javascript but I have other languages I need to learn) 8^)

I do have a question though if I made a curve of three points with the center one being the apex - would just adjusting the y-coordinate of the start and end points up or down achieve the result?
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(Robert_A_WIlliams)
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7. Jan 22, 2009 9:47 AM in response to: (Robert_A_WIlliams)
Re: Creating a Catenary Curve Assistance
No I don't believe it would, the result would probably be more akin to a hyperbola, instead of a caternary, which are two different curves. That is how I would do it freehand though, by adjusting the curve to match the caternary of a known example.

Like this example:


Just looking for something more mathematically accurate.
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