/* Marla Mayerson*/
/* This shader is based on a turbulent model and simulates a cloudy planet*/
/*surface like the moon*/
#include "rmannotes.sl"

surface cloudy(float turbfreq = 2;
	     color topc = color (1, 0, 0);
		 color bottomc = color (0, 0, 1);
		 float Ka = 0.5, Kd = 0.5;
		 float Ks =0.5, roughness = 0.16; color specularcolor = 1)

{
  color paper, ink;
  float paper_opac, ink_opac;
  float ss, tt;
  point Nf, V;
  point PP;

  float pixelsize, twice;
  float scale, turb;

  paper = 0;
  paper_opac =1;

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

 
  ss = s;
  tt = t;
  ink = mix(topc, bottomc, t) + mix(topc, bottomc, s);
  ink_opac = 1;
  paper = mix(paper, ink, ink_opac);
  
  paper = paper * Ka * ambient() +
  paper * Kd * diffuse(Nf) +
  specularcolor * Ks * specular(Nf, V, roughness);



  PP = transform("shader", P) * turbfreq;

  pixelsize = sqrt(area(PP));
  twice = pixelsize * 2;

  turb = 0;
  for (scale = 1; scale > twice; scale /= 2)
    turb += abs(noise(PP / scale) - 0.5) * scale;
  turb = turb * 2;

  Ci =turb;
  Oi = paper * paper_opac;
  
}