Hi Gail.

You have chosen a quite difficult "thing" to model,
but I like your idea.

Below is my suggestion for such an iso-surface.
Try to play around with the different constants.

-- 
Best regards,

Tor Olav

mailto:tor### [at] hotmailcom
http://hjem.sol.no/t-o-k/tokpicts.html
http://www.crosswinds.net/~tok


Gail Shaw wrote:
> 
> I decided I needed some atmospheric effects for my
> irtc entry (which I will post once it's more than a few cylinders
> and cones)
> 
> This is supposed to be the aurora borealis.  It's an isosurface
> containing media with a function used in the density.
> 
> For those who live far enough north to see the real thing, does
> it look right?
> 
> For the iso experts, is there any way I can randomly vary the
> distance between the peaks of a sine wave?
> 
> Comments? suggestions?


// ===== 1 ======= 3 ======= 3 ======= 4 ======= 5 ======= 6 ======= 7 =

#version unofficial MegaPov 0.6;
#include "colors.inc"

// ===== 1 ======= 3 ======= 3 ======= 4 ======= 5 ======= 6 ======= 7 =

$ SinX = function { 0.5*sin(x) }

$ Noise =
function {
   1.0*noise3d(x, 0, 2 + z/7)
  +0.2*noise3d(x*1.7, 0, z/4)
}

$ NoisySin = function { SinX(5*Noise(x, y, z), 0, 0) }

$ SheetY = function { y^2 - 0.04 } 

$ WavySheetY = function { SheetY(0, y + NoisySin(x, y, z), 0) }

$ Iso =
isosurface {
  function { WavySheetY(x, y, z) }
  max_gradient 5
  method 2
  contained_by { box { -5*<1, 1, 1>, 5*<1, 1, 1>} }
}

object {
  Iso
  pigment { color White }
  no_shadow
}

// ===== 1 ======= 3 ======= 3 ======= 4 ======= 5 ======= 6 ======= 7 =

background { color Blue/3 }

light_source { <-3, 3, -2>*100 color White }

camera {
  location <1, 1, -2>*5
  look_at <-1, -1, 0>
}

// ===== 1 ======= 3 ======= 3 ======= 4 ======= 5 ======= 6 ======= 7 =

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