Alf Peake wrote:

>Maybe worth checking astro stuff?
>Adaptive optics where the image is distorted to remove atmospheric
>distortions. Perhaps the way images from multiple sites are combined.
>
>
>Alf
>
VISAR came from NASA where they were using it to look at sunspots I 
believe...
still, I understand that the commercial set up goes for about $20k, if 
you have any
idea of where to look for free software from astronomical places....

So far I've managed to straighten one of my test images, but it still 
seems a bit off
of true...

#version 3.5;
#include "colors.inc" 
#include "math.inc"
global_settings { assumed_gamma 1.0 }
// ----------------------------------------
camera {
  orthographic
  location  <1, 1, -2.0>
  look_at   <1, 1, 0>
}
background {rgb <0.5, 0.5, 0.5>}

// show the X and Y Axis
// cylinder {-200*x, 200*x, 0.01 pigment {checker Red White translate 
-0.5*y} finish {ambient 1}}
// cylinder {-200*y, 200*y, 0.01 pigment {checker Red White translate 
-0.5*x} finish {ambient 1}}

#declare xsize = 100;       // image size
#declare ysize = 100;

#declare AX = 18 /xsize;    // coords of rectangle in image to be 
straightened
#declare AY = 5  /ysize;
#declare BX = 84 /xsize;
#declare BY = 12 /ysize;
#declare CX = 6  /xsize;
#declare CY = 84 /ysize;
#declare DX = 94 /xsize; 
#declare DY = 96 /ysize; 

#declare fn_image = function {   // the input image
  pigment {
    image_map {
      png "testimg.png"
      once
    }
    scale <xsize, ysize, 1>      // pixel units
  }
}
#local SAB = (BY-AY)/(BX-AX);  // slope along AB = (BY-AY)/(BX-AX)
#local SCD = (DY-CY)/(DX-CX);  // slope along CD = (DY-CY)/(DX-CX)
#local SACr = (CX-AX)/(CY-AY); // slope along AC (rotated) = (CX-AX)/(CY-AY)
#local SBDr = (DX-BX)/(DY-BY); // slope along BD (rotated) = (DX-BX)/(DY-BY)
#local IA = 1-(AY - SAB*AX);   // intersect of AB with Y axis = AY - 
slope at A * AX
#local IC = 1-(CY - SCD*CX);   // intersect of CD with Y axis = CY - 
slope at C * CX  
#local IB = (CX - SACr*CY);    // intersect of AC with X axis = CX - 
slope at AC* CY
#local ID = (DX - SBDr*DY);    // intersect of BD with X axis = CX - 
slope at AC* CY
#local fn_I = function(v) { ((IA-IC)*v )}; // ((IA-IC)*v + IC)}; // (min 
- max)*v -max
#local fn_S = function(v) { (SAB-SCD)*v + SCD};
#local fn_Ib = function(u) { ((IB-ID)*u + ID)};
#local fn_Sb = function(u) { ((SACr-SBDr)*u + SBDr)};
#local fn_deformy = function(u,v) { (fn_S(v)*u + fn_I(v)) };  // u
#local fn_deformx = function(u,v) { (1-(fn_Sb(u)*v + fn_Ib(u))) };  // v

mesh2 {
  vertex_vectors {
    xsize*ysize,
#local ypix = 0;
#while (ypix != ysize)
  #local xpix = 0;
  #while (xpix != xsize)
    
<fn_deformx(xpix/xsize,ypix/ysize),fn_deformy(xpix/xsize,ypix/ysize),0>,   
    #local xpix = xpix +1;
  #end
  #local ypix = ypix +1;
#end
  }
  texture_list {
    xsize*ysize,
#local ypix = 0;
#while (ypix != ysize)
  #local xpix = 0;
  #while (xpix != xsize)
      texture {
        pigment {
          rgb <fn_image(xpix,ypix,0).x,
               fn_image(xpix,ypix,0).y,
               fn_image(xpix,ypix,0).z>
        }
        finish {ambient 1}     
      }
    #local xpix = xpix +1;
  #end
  #local ypix = ypix +1;
#end
  }
  face_indices {
    (xsize-1)*(ysize-1)*2,
#local ypix = 0;
#while (ypix != (ysize-1))
  #local xpix = 0;
  #while (xpix != (xsize-1))
    <ypix*xsize+xpix, ypix*xsize+xpix+1, (ypix+1)*xsize+xpix>,
     ypix*xsize+xpix, ypix*xsize+xpix+1, (ypix+1)*xsize+xpix,

    <ypix*xsize+xpix+1, (ypix+1)*xsize+xpix+1, (ypix+1)*xsize+xpix>,
     ypix*xsize+xpix+1, (ypix+1)*xsize+xpix+1, (ypix+1)*xsize+xpix,
          
    #local xpix = xpix +1;
  #end
  #local ypix = ypix +1;
#end
  }
  scale 2
}

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