Subject:
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Re: POV-Ray Chain Program
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 30 Jul 1999 23:44:20 GMT
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Viewed:
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678 times
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Adam Howard wrote:
> Hi All!
>
> I was surfing the web the other day and discovered a wonderful plug-in for
> POV-Ray that can create chains. Considering all the talk about hoses and a
> desire for the chain piece in Ldraw I thought it would be great if this
> programs ideas could be used to develop a similar program for ldraw. I sent
> an email to the author asking what math he used and how he went about
> programming it. He replied with the following email:
>
> "Hi - I forwarded this to me at work, because my internet connection was
> down
> at home...
> anyhow...
>
> If you downloaded the .inc, and you know POV the math
> is there for all to see;-)
>
> In short (and going from memory):
>
> I use the formula for a catenary (look for Andrews
> treasure trove of mathematics if you can't find it
> anywhere else, I don't have the URL handy).
>
> I curve fit the catenary formula given the two points,
> mapping one to 0,0 and the other to x,y. (After the
> chain is built I rotate it and translate it to the
> proper location.
>
> because there are an infinite number of curves that
> can pass through two points, I use a variable to set
> the "length" (through the droop) of the curve.
>
> I initially calculated the slope to map each link, but this
> really didn't work. In my final solution I determined
> the endpoint of the each link by iteratively solving (binomial
> search) the curve equation and comparing the distance between
> this point and the current point using an error variable so the
> loops didn't go too deep. Repeat for the next link.
>
> I initially planned to reverse this, so you could specify
> the length of the chain (number of links) and it would
> determine the missing value to scale the chain appropriately
> but doing it iteratively caused POV to break.
>
> If the source isn't clear enough, drop me a line back.
>
> -Rob"
>
> You can find his program at http://www.geocities.com/SoHo/7865/chain.htm
>
> I am not a good computer programmer. So I just wanted to throw this idea
> out and see if anyone else would like to work on a chain/hose/rope plug-in
> for ldraw.
>
> Thanks,
> Adam
cool idea.
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Message has 1 Reply:
 | | Re: POV-Ray Chain Program
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| In lugnet.cad.dev, Jonathan Wilson writes: Hi, I'll check out the math and look for a more LDraw-like approach. I had already some problems with the elastic parts, and now indeed need a chain for OMR 8844 (blue small helicopter). My first intention (...) (25 years ago, 2-Aug-99, to lugnet.cad.dev)
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Message is in Reply To:
| | POV-Ray Chain Program
|
| Hi All! I was surfing the web the other day and discovered a wonderful plug-in for POV-Ray that can create chains. Considering all the talk about hoses and a desire for the chain piece in Ldraw I thought it would be great if this programs ideas (...) (25 years ago, 30-Jul-99, to lugnet.cad.dev)
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