/* Pete Hriso  Assignment #6 d */
#include "rmannotes.sl"

displacement dissmoken( float offset = 0.25;
		       float amountofsmoke = 8 ;
		       float scale = 1;
		       float fadeaway = 2;
		       float Km = .1;
		       color black = color (0, 0, 0);)
{

  color paper, ink, smoke;
  float paper_opac, ink_opac; 

  float variable;           
  float limit;    
  float amplitude = 1;   
  float sum = 0;
 
  float magnitude;
  point PP, Nf, V;
  float pixelsize, twice;
  float turb;

  /* init */
  
  V = normalize(I);
  Nf = faceforward (normalize(N),V);
 
 
 /* transform P to shader */


  PP = scale * transform ("shader", P);
  limit = sqrt (area(PP));
  for(variable = 0; variable < amountofsmoke && amplitude > limit; variable += 1){ 
    sum += amplitude * snoise(PP);
	PP *= 2;
	amplitude *= 0.5;
    }
 
  /* raise by the power  */
  
  magnitude = clamp(sum+offset, 0, 1) * pow(abs(Nf . V), fadeaway);
  
  
  /* output */
  
  
  P += Km * magnitude * normalize(N);
  N = calculatenormal(P);
 
}