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From: Jeff Daniels
Subject: how does the "one over f" fractal noise function work?
Date: 7 Feb 2000 01:44:38
Message: <389E6A1E.FAFFD004@erols.com>
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I want to put objects in 3-D space according to the same "1/f fractal
noise" pattern that's used in granite textures. But I don't know the
math behind 1/f fractal noise, and I can't find anywhere on the net that
discusses it without assuming that I already understand it completely.
Can someone explain to me how, given an x,y,z point, I would use a 1/f
fractal noise function to compute the [ size | color | orientation ] of
the object at that point?
Post a reply to this message
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Jeff Daniels wrote:
>
> I want to put objects in 3-D space according to the same "1/f fractal
> noise" pattern that's used in granite textures. But I don't know the
> math behind 1/f fractal noise, and I can't find anywhere on the net that
> discusses it without assuming that I already understand it completely.
> Can someone explain to me how, given an x,y,z point, I would use a 1/f
> fractal noise function to compute the [ size | color | orientation ] of
> the object at that point?
You will find a very comprehensive discussion on noise patterns at
Hugo Elias' site and he uses POV-Ray as an example of how it is
implemented -
http://freespace.virgin.net/hugo.elias/models/m_perlin.htm
--
Ken Tyler - 1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
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From: Jeff Daniels
Subject: Re: how does the "one over f" fractal noise function work?
Date: 7 Feb 2000 02:27:06
Message: <389E7406.9A836E81@erols.com>
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Oh, man! This is *exactly* what I've been looking for.
Gotta love this internet thing; I hope it catches on!
Ken wrote:
> Jeff Daniels wrote:
> >
> > I want to put objects in 3-D space according to the same "1/f fractal
> > noise" pattern that's used in granite textures. But I don't know the
> > math behind 1/f fractal noise, and I can't find anywhere on the net that
> > discusses it without assuming that I already understand it completely.
> > Can someone explain to me how, given an x,y,z point, I would use a 1/f
> > fractal noise function to compute the [ size | color | orientation ] of
> > the object at that point?
>
> You will find a very comprehensive discussion on noise patterns at
> Hugo Elias' site and he uses POV-Ray as an example of how it is
> implemented -
>
> http://freespace.virgin.net/hugo.elias/models/m_perlin.htm
>
> --
> Ken Tyler - 1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
> http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/
--
http://www.etour.com/default.asp?associd=aff3787
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In article <389E6A1E.FAFFD004@erols.com>, Jeff Daniels
<jef### [at] erols com> wrote:
> I want to put objects in 3-D space according to the same "1/f fractal
> noise" pattern that's used in granite textures. But I don't know the
> math behind 1/f fractal noise, and I can't find anywhere on the net that
> discusses it without assuming that I already understand it completely.
> Can someone explain to me how, given an x,y,z point, I would use a 1/f
> fractal noise function to compute the [ size | color | orientation ] of
> the object at that point?
If you use MegaPOV 0.4, you can use the noise3d() function to build your
own fractal noise function or you can use the eval_pattern() function to
get the value of any pattern at each point. Using eval_pattern has the
advantages of being simpler(just use eval_pattern(granite, POINT)) and
it makes it easy to use other patterns.
An alternative that would work in the official version would be to make
the noise function in POV script. As Ken already suggested, the Hugo
Elias web page is a good source of information on this.
--
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/
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