/*Wooksang's body shading for spin-body object*/ 

#include "rmannotes.sl" 
surface
spin_body(
	       float Ks = 0.3, Kd=1, Ka = 0.1,Km=0.4,roughness=0.1;
	       color first  = color (1,1,1);
	       color second = color (0,0,0);
	       color specularcolor = color (1,1,1);)
	       
{
  /*basic setting*/

  color surface_color, layer_color; 
  float surface_opac, layer_opac; 
  float r,freq=5;    
  vector V;
  normal Nf;
  point PP,newP;

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

/* background layer (layer 0) */
  surface_color = first;  
  surface_opac = 1;                  

/* become solid */
  PP = transform("shader", P);

/*calculate distance through x axis*/
/*  r = distance (point (xcomp(PP),0,0),point(0,0,0));*/
  r=xcomp(PP)+ycomp(PP);
  layer_color = second;
  r=repeat(r,1);
  layer_opac = step(0.25,r)-step(0.75,r);
  surface_color = blend(surface_color, layer_color, layer_opac); 
   

/* bump map */
  newP = calculatenormal(P+Km*layer_opac+normalize(N));
  Nf = faceforward(normalize(newP),I);

/* output */
  Ci=surface_color*(Ka*ambient()+Kd*diffuse(Nf))+specularcolor*Ks*specular(Nf,V,roughness);
}