#version 3.7;
//------------------------------------------
// SDL for emulating the plotting of an isosurface based on a POV-Ray internal
function
// Bill Walker - September 2017
//------------------------------------------
global_settings {assumed_gamma 1}
#include "colors.inc"

light_source { <-1,8,2> color White}

camera {
 location <0, 10, -10>
 look_at  <0, 0, 0>
}

plane {y, -1 pigment { checker Grey, White }}

/*
isosurface{ function{f_spiral(
   x, // PARAM _X
   y, // PARAM _Y
   z, // PARAM _Z
   6, // PARAM (0) distance between windings,
   0.2, // PARAM (1) thickness,
   15, // PARAM (2) outer diameter of the spiral,
   0, // PARAM (3) not used,
   0, // PARAM (4) not used,
   0.5 // PARAM (5) spiral cross-sectional shape 0-round, 1-square, etc
   )}
   accuracy 0.01
   threshold 0 // default value
   max_gradient 21 // high value = more precision = more render time (ideal
value indicated in "messages")
   contained_by {sphere {<0,0,0>, 15}}
   texture {pigment {Red}}
   }
*/

//sphere {<0,0,0>, 15 pigment {rgbt <0.9, 0, 0, 0.4>}}

#macro F_SPIRAL (X, Y, Z, Spacing, Thickness, Dia, Unused1, Unused2, Shape)
     #declare r = sqrt (X*X + Z*Z); // Cartesian distance from origin to point
in x-z plane

     #if (X = 0 & Z = 0)    // Fudges that first awkward starting point by
nudging x from 0 to Epsilon
          #declare X = 0.000001;
     #end

 #declare Theta = atan2 (Z, X);    // calculates the angle around the y-axis of
the current point
 #declare r = r + Spacing * Theta/tau;   // calculates the radius of the current
point on the spiral surface
 #declare r2 = mod (r, Spacing) - (Spacing/2); // determines what layer of the
winding is being plotted

 //######################################################################################
 //  This whole block just determines how to plot the cross sectional shape of
the spiral
 //  Round, square, or somewhere in between
 #if (Shape = 1)
  #declare r2 = sqrt(r2*r2 + Y*Y);

     #elseif (Shape != 0)
          #declare temp = 2/Switch;
          #declare r2 = pow( (pow(abs(r2), temp) + pow(abs(Y), temp)), 1/temp);

     #else
          #declare r2 = max (abs(r2), abs(Y));
          #declare r = sqrt(X*X + Y*Y + Z*Z);

 #end
 //######################################################################################
     #declare VALUE = -min( Dia - r, Thickness - min(r2, r) );

     #declare D1 = sqrt(X*X + Y*Y + Z*Z);
     #declare D2 = sqrt(X*X + Y*Y + Z*Z + VALUE*VALUE);

     #if (abs (D1 - D2) < STEP)
      //If the value is close'nough (TM) [less than the granularity of my plot
(STEP)], plot a sphere
      sphere {<0, 0, 0>, 0.03 translate <X, Y, Z> rotate y*Theta}
     #end

#end // end macro F_SPIRAL

#declare _Spacing = 3;
#declare _Thickness = 0.1;
#declare _Dia = 4;
#declare _Unused1 = 1;
#declare _Unused2 = 0;
#declare _Shape = 1;

#declare STEP = 0.05;

union {
 #for (Y, -_Thickness, _Thickness, STEP)
  #for (X, -_Dia, _Dia, STEP)
   #for (Z, -_Dia, _Dia, STEP)
    // for every <X, Y, Z> point, return a value of the isosurface function
    F_SPIRAL (X, Y, Z, _Spacing, _Thickness, _Dia, _Unused1, _Unused2, _Shape)
   #end
  #end
 #end
 texture {pigment {rgb <0, 0, 0.5>} finish {specular 0.4} }
 no_shadow
}

Post a reply to this message

Attachments:
Download 'emulated_spiral_0.png' (245 KB)

Preview of image 'emulated_spiral_0.png'