I was trying to figure out how to warp a cylinder into a sphere sweep
helix, but it didn't work.  It squished the thing for some reason.  My
thought was to turn the x dimension of the cylinder into the radius, and
the y dimension into the angle, but everything needs to be done
backwards.  I was trying to use a rectangular to polar conversion
formula, because of things needing to be backwards.  

I would appreciate it if someone could tell how to do it right.  I would
also like to know how to do the same thing using parametic surfaces, and
what it was that I was doing wrong.  

I think this is the code I was using.  

#include "colors.inc"
#include "finish.inc"
light_source {<3,4,-5>*100 rgb 2}
camera {location <12,0,-14> look_at 0 }

#version unofficial MegaPov 0.7;

#declare Cyl= function{((x-3)^2+y^2)^.5 -1}
//plane{y,-2 pigment{White}}
#declare Cyl2 =  function {Cyl(x,z*cos(pi/3) - y*sin(pi/3),
  y*cos(pi/3) + z*sin(pi/3))}
#declare Cir = function{(x*cos(y)+x*sin(y))}
#declare Cir2 = function{Cyl2(sqr(x^2+y^2),atan2(x,y),z)}

isosurface{
   function {Cir2(x,y,z)}
    contained_by{box{-2*pi,2*pi}}
    method 2
    eval
    pigment{Green}
    finish{Shiny}
   }

-- 
Dan Johnson 

http://www.geocities.com/zapob

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