POV-Ray : Newsgroups : povray.advanced-users : What is the equation for a helix? Server Time
2 Nov 2024 11:23:18 EDT (-0400)
  What is the equation for a helix? (Message 1 to 5 of 5)  
From: David Fontaine
Subject: What is the equation for a helix?
Date: 17 Dec 1999 18:56:46
Message: <385ACC3F.AD113882@isd.net>
Identical to one formed by a sphere_sweep? (ie circular cross-section)

--
David   http://thunder.prohosting.com/~davidf  (ICQ 55354965)
"The paper holds their folded faces to the floor" -Pink Floyd


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From: Chris Huff
Subject: Re: What is the equation for a helix?
Date: 17 Dec 1999 23:08:38
Message: <chrishuff_99-C99CF6.23091117121999@news.povray.org>
In article <385ACC3F.AD113882@isd.net>, lfo### [at] isdnet wrote:

> Identical to one formed by a sphere_sweep? (ie circular cross-section)

Well, this one looks like a sphere sweep, the documentation covers the 
parameters:
   function "helix1", <1, 5, 0.2, 1, 1, 1, 0>
This function is a bit different, it will always create circular 
surfaces when sliced with a plane perpendicular to the axis of the 
helix. I think. It doesn't act like a sphere_sweep, though, more like a 
circle_sweep. I broke it up to make it more modular.
#declare cylFunc = function {sqrt((x-1)^2 + z^2)-y}

function {cylFunc(x+sin(5*y), 0.5, z+cos(5*y))}

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/


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From: David Fontaine
Subject: Re: What is the equation for a helix?
Date: 18 Dec 1999 16:07:24
Message: <385BF5FB.5C386956@isd.net>
> Well, this one looks like a sphere sweep, the documentation covers the
> parameters:
>    function "helix1", <1, 5, 0.2, 1, 1, 1, 0>

I wanted the actual function so I could modify it :-)


> This function is a bit different, it will always create circular
> surfaces when sliced with a plane perpendicular to the axis of the
> helix. I think. It doesn't act like a sphere_sweep, though, more like a
> circle_sweep. I broke it up to make it more modular.
> #declare cylFunc = function {sqrt((x-1)^2 + z^2)-y}
>
> function {cylFunc(x+sin(5*y), 0.5, z+cos(5*y))}

Um, yes, it is a circular cross-section, but it's too flat. I want something
that's identical to a sphere_sweep. Do you know where I could find the
function used by the built-in "helix1"?
Also this creates some nasty black spots on the surface. Do you get them as
well?

--
David   http://thunder.prohosting.com/~davidf  (ICQ 55354965)
"The paper holds their folded faces to the floor" -Pink Floyd


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From: Chris Huff
Subject: Re: What is the equation for a helix?
Date: 18 Dec 1999 16:14:31
Message: <chrishuff_99-93D292.16150718121999@news.povray.org>
In article <385BF5FB.5C386956@isd.net>, lfo### [at] isdnet wrote:

> I wanted the actual function so I could modify it :-)

> Um, yes, it is a circular cross-section, but it's too flat. I want 
> something that's identical to a sphere_sweep. Do you know where I
> could find the function used by the built-in "helix1"?

It is probably somewhere in the source code, I will look it up later. As 
it is, you can modify the parameters to it.

> Also this creates some nasty black spots on the surface. Do you get them 
> as well?

I would guess that increasing max_gradient would help.

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/


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From: Chris Huff
Subject: Re: What is the equation for a helix?
Date: 18 Dec 1999 16:37:29
Message: <chrishuff_99-050518.16380518121999@news.povray.org>
In article <chrishuff_99-93D292.16150718121999@news.povray.org>, Chris 
Huff <chr### [at] yahoocom> wrote:

> It is probably somewhere in the source code, I will look it up later.

Well, I found the function, but the equation used isn't documented. I 
will try to come up with one that works the way you want it, it might be 
helpful if I knew in what ways you wanted to modify the helix. Anyone 
with more math knowledge want to try?

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/


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