/*
 * duck_bill_color(): color surface for duck bill pattern
 *
 *  M. Geroch
 *  TV Digital Lighting HW 5
 * Spring, 1996
*/


#include "/usr/local/accad/shaders/rmannotes.sl" 


surface 
duck_bill_color(float Ka=0.4, Kd=0.4, 
		Ks = 1.0, roughness=0.1; 
		color specularcolor=1; )
{
  float D, finder;
  color layer_color, layer_opac, surface_color, surface_opac;
  color trim_color = color "rgb" (0.2, 0.2, 0.1);
  color find_color = color "rgb" (0.0, 0.0, 1.0);
  float fuzz = 0.005;
  point Nf, V;

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

  surface_color = Cs;
  surface_opac = Os;

  /* edge lines around bill */ 
  D = 1 - smoothstep(0.02-fuzz, 0.02, s) 
      + pulse(0.48, 0.52, fuzz, s)
	+ smoothstep(0.98-fuzz, 0.98, s);

  surface_color = blend(surface_color, trim_color, D);

  /* center_ridge of top of bill */
  D = 0.7 * pulse(0.24, 0.26, fuzz, s);
  surface_color = blend(surface_color, trim_color, D);

 /* air holes */ 
  D = 1 - smoothstep(0.02-fuzz, 0.02, 
		     sqrt(pow((s-0.17), 2) + pow((t-0.61),2)));
  surface_color = blend(surface_color, trim_color, D);

  D = 1 - smoothstep(0.02-fuzz, 0.02, 
		     sqrt(pow((s-0.33), 2) + pow((t-0.61),2)));
  surface_color = blend(surface_color, trim_color, D);



  Oi = surface_opac;
  Ci = Oi * ( surface_color * (Ka*ambient() + Kd*diffuse(Nf)) + 
                specularcolor * Ks * specular(Nf,V,roughness) );

}