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From: Tom Melly
Subject: Isosurface functions
Date: 24 Sep 2002 10:47:20
Message: <3d907af8$1@news.povray.org>
Help please.

Can anyone suggest functions for:

A pipe (i.e. a cylinder with a hole running through it and a configurable
wall-thickness).

A brain-like effect.

Also, with a function like:
(f_hex_x(x,y,z,1) - 2/3)*-1
how would I go about wrapping this around a sphere? (if such a thing can be
done).

--
#macro A(V,B,C,R)#while(B-256)#if(V-128/B>=0)sphere{0,.5translate<C-4R-1,9>
pigment{rgb<1-C/8R/2C/8>}}#local V=V-128/B;#end#local B=B*2;#local C=C+1;#
end#end A(234,1,0,2)A(85,1,0,1)A(81,1,0,0)light_source{-5 1}//Tom Melly


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From: Christoph Hormann
Subject: Re: Isosurface functions
Date: 24 Sep 2002 11:04:06
Message: <3D907EE6.6D9AB5C4@gmx.de>
Tom Melly wrote:
> 
> Help please.
> 
> Can anyone suggest functions for:
> 
> A pipe (i.e. a cylinder with a hole running through it and a configurable
> wall-thickness).

http://www-public.tu-bs.de:8080/~y0013390/pov/ic/docu02.html#Cylinder_Hole

> 
> A brain-like effect.

Pardon?

> 
> Also, with a function like:
> (f_hex_x(x,y,z,1) - 2/3)*-1
> how would I go about wrapping this around a sphere? (if such a thing can be
> done).

Sure, the keyword is spherical coordinates, have a look at the f_r(),
f_ph() and f_th() functions in functions.inc.  For a start try something
like:

#declare f_1=function { (f_hex_x(x,y,z,1) - 2/3)*-1 } 

isosurface {                                         
  function { f_1(y, f_th(x, y, z)*5, 0) } 
  contained_by {box {<-5,-5,-5>,<5,5,5>}}    
  pigment { color NeonBlue } 
  finish { specular 0.3 } 
}

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______


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From: Tom Melly
Subject: Re: Isosurface functions
Date: 24 Sep 2002 11:19:07
Message: <3d90826b@news.povray.org>
"Christoph Hormann" <chr### [at] gmxde> wrote in message
news:3D907EE6.6D9AB5C4@gmx.de...
>
>
> > A brain-like effect.
>
> Pardon?
>

Your restraint is commendable ;) - an iso-surface that looks like the surface of
a brain?

As for the rest - many thanks...


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From: Christoph Hormann
Subject: Re: Isosurface functions
Date: 24 Sep 2002 11:25:39
Message: <3D9083F2.F8FC175B@gmx.de>
Tom Melly wrote:
> 
> > > A brain-like effect.
> >
> > Pardon?
> >
> 
> Your restraint is commendable ;) - an iso-surface that looks like the surface of
> a brain?

You could try the crackle pattern with non standard form vectors and maybe
other patterns.  But if you really want something looking like a human
brain i suggest taking some real data for it.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______


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From: Tom Melly
Subject: Re: Isosurface functions
Date: 24 Sep 2002 11:30:01
Message: <3d9084f9$1@news.povray.org>
"Christoph Hormann" <chr### [at] gmxde> wrote in message
news:3D9083F2.F8FC175B@gmx.de...

> other patterns.  But if you really want something looking like a human
> brain i suggest taking some real data for it.
>

Well, it's a brain-coral I'm aiming for, but I don't require realism, just the
effect.


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From: Sir Charles W  Shults III
Subject: Re: Isosurface functions
Date: 24 Sep 2002 12:10:25
Message: <3d908e71$1@news.povray.org>
Maybe you could try sphere sweeps controlled by a macro.  I suspect that
something like a "maze-drawing" algorithm combined with the sweeps would give a
nice "brainy" look.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip


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From: Tom Melly
Subject: Re: Isosurface functions
Date: 24 Sep 2002 12:21:19
Message: <3d9090ff$1@news.povray.org>
"Sir Charles W. Shults III" <aic### [at] cflrrcom> wrote in message
news:3d908e71$1@news.povray.org...
>     Maybe you could try sphere sweeps controlled by a macro.  I suspect that
> something like a "maze-drawing" algorithm combined with the sweeps would give
a
> nice "brainy" look.
>

The thought had occured - as to an iso-surface solution, I remain (probably
stupidly) convinced that there must be some way of randomly deforming surfaces
where the randomness remains consistent (to generate something like a maze,
although not necessarily with a "solution").

Take a function like:

  #declare Bed_func = function(x,y,z){
    y +
    5 +
    (sin(x*5 - sin(z + f_noise3d(x,0,z))*1)/20) -
    (sin((x+z)*1 -
    sin(z + f_noise3d(x,0,z))*1)/30)
  }

But have less regularity in the sin waves, both in frequency and amplitude (if
I've got the terminology right), but without any wave crossing or intersecting
with another.


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From: Jim Charter
Subject: Re: Isosurface functions
Date: 24 Sep 2002 19:04:08
Message: <3D90EFB0.9010406@aol.com>
Maybe a couple of interfering radial patterns with a scallop_wave and 
some turbulence?


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From: Mark Wagner
Subject: Re: Isosurface functions
Date: 24 Sep 2002 23:13:33
Message: <pan.2002.09.25.03.12.40.741776.211@gte.net>
On Tue, 24 Sep 2002 12:21:19 -0400, Tom Melly quoth:

> "Sir Charles W. Shults III" <aic### [at] cflrrcom> wrote in message
> news:3d908e71$1@news.povray.org...
>>     Maybe you could try sphere sweeps controlled by a macro.  I suspect
>>     that
>> something like a "maze-drawing" algorithm combined with the sweeps
>> would give
> a
>> nice "brainy" look.
>>
>>
> The thought had occured - as to an iso-surface solution, I remain
> (probably stupidly) convinced that there must be some way of randomly
> deforming surfaces where the randomness remains consistent (to generate
> something like a maze, although not necessarily with a "solution").

Someone came up with a crackle-based pattern that forms a square maze
about a year ago.  If you could apply a suitable wavy distortion to that
pattern, you'd probably get what you are looking for.

-- 
Mark


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From: Christopher James Huff
Subject: Re: Isosurface functions
Date: 25 Sep 2002 12:31:27
Message: <chrishuff-370EA5.12285325092002@netplex.aussie.org>
In article <3d90826b@news.povray.org>, "Tom Melly" <tom### [at] tomandlucouk> 
wrote:

> Your restraint is commendable ;) - an iso-surface that looks like the surface 
> of a brain?

Try messing around with functions using abs(). This:

function {pow(abs(f_noise(x, y, z)*2 - 1), 0.5)}

should be a good start. The noise function is usually "rounded" on each 
"side" of 0.5, this adjusts the range to make the lower half negative 
and then "folds" the negative part back to positive, making a bumpy, 
creased effect. The pow() function adjusts the falloff. Watch out for 
grid artifacts though

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/


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