/*Solid surface shader: luckystone
 * Final Assignment: shader with turbulence, solid texture.
 * Tom Suchan
 * This shader simulates a marble like stone with colored veins.*/
#include "rmannotes.sl"

surface luckystone(float Ka = 0.2, Kd = 0.4, Ks = 0.6, roughness = 0.1)
{
  color paper, ink;
  float paper_opac, ink_opac;
  float fuzz = 0.05;
  point Nf, V;
  point PP;
  float x, y, z;
  float noifreq = 5;
  float noiscale = 0.8;
  float noi, noi2;
  float pixelsize, twice;
  float scale, turb = 0;
  float turbfreq = 2;
  float H, L;
  float col;

/* layer one: create turbulance, paper */
  
  PP = transform("shader", P) * turbfreq;
  pixelsize = sqrt(area(PP));
  twice = pixelsize * 2;
  for(scale = 1; scale > twice; scale /= 2)
  turb += abs(noise(PP/scale) - 0.5) * scale;
  turb = turb * 2;

  paper = spline(turb, color(1,0,0), color(1,0,0), color(1,1,1), 
                 color(0,0,1), color(0,0,1));
  paper_opac = 1;

  Nf = faceforward(normalize(N), I);
  V = -normalize(I);

  /* transform P to shader space*/

  PP = transform("shader", P);
  PP += noise(PP) * 0.5;
  
  x = xcomp(P);
  y = ycomp(P);
  z = zcomp(P); 

  noi = noise(y * noifreq, x * noifreq);

  /* perturb y, set noise*/
  rotate2d(y, x, radians(45), .5, .5, y, x);
  col = whichtile(y, 3);
  y = repeat(y, 3);
  y  = y + snoise(noi + 3752) * noiscale;
  H = udn(noi * 4319, .2, .4);
  L =  udn(noi * 597, .4, .7);
  noi2 = noise(col * noifreq);
  
   /* veins, generate %, choose color */

  if(udn(noi2 * 452, 0, 1) > 0.3){
  
  if(even(col)){
  ink =  spline(turb, color(1,1,1), color(1,1,1), color(1,1,1), 
                 color(0,0,0), color(0,0,0));

  ink_opac = pulse(H, L, fuzz, y);
  }
  if(odd(col)){
   ink_opac = pulse(L, H, fuzz, y);
   ink =  spline(turb, color(0,0,0), color(1,0,0), color(1,0,0), 
                 color(0,0,0), color(0,0,0));
  }
 /* else{
    ink_opac = pulse(L, H, fuzz, y);
    ink =  spline(turb, color(0,0,0), color(0,0,0), color(0,0,0), 
                 color(0,0,1), color(0,0,1));
    }*/
  paper = mix(paper, ink, ink_opac);
 } 
  /* plastic illum */

  paper = paper * Ka * ambient() +
          paper * Kd * diffuse(Nf) +
          Ks * specular(Nf, V, roughness);

  /* output */

  Oi = paper_opac;
  Ci = paper_opac * paper;
}