/*
 * metallic.sl
 *
 * Lawson Wade
 *
 * A surface shader that simulates a shiny metal surface
 * using either a texture map (environmental mapping), or,
 * if no texture map is specified, a noisy index into
 * a color spline.
 */


#include "rmannotes.sl"
#include "colors.sl"


surface
metallic(
	 string texturemap = "";
	 float  Ka = 1,
                Ks = 1,
                Kr = 1,
                roughness = 0.1;
	 )
{
  point  Nf, V;
  point  R;
  color  surface_color, surface_opac;
  color  layer_color;
  float  ss, tt;
  float  phi, theta;
  float  d;
  

  Nf = faceforward(normalize(N), I);
  V = normalize(I);
  R = reflect(V, Nf);


  if (texturemap != "")
    {
      /* index into texturemap */

      R = transform("world", point "world" (0, 0, 0) + R);
      layer_color = Kr * color environment(texturemap, R);
    }
  else
  {
     R = transform("world", point "world" (0, 0, 0) + R);
     R = normalize(R);
     
     phi = acos(R . point "world" (0, 1, 0));
     theta = atan(zcomp(R), xcomp(R));
     
     phi = phi / PI;
     theta = mod(theta + 2 * PI, 2 * PI) / (2 * PI);

      d = noise(phi * 13.2173, theta * 7.9351);
      d = clamp(d, 0, 1);
      layer_color = spline(phi, Red, Red, White, White, Blue, Blue);
/*
			   Tan2,
			   Tan2,
			   Tan2,
			   Tan2,
			   Tan2,
			   Black,
			   Black,
			   Black,
			   Tan2,
			   Red3,
			   Yellow2,
			   AntiqueWhite3,
			   Black,
			   Black,
			   Black,
			   Red3,
			   Black,
			   Blue,
			   OrangeRed2,
			   Tan2,
			   White,
			   Black,
			   Black,
			   Red3,
			   Black,
			   Black,
			   AntiqueWhite3,
			   Red3,
			   White,
			   Black,
			   Black,
			   Black,
			   Black);
*/
    }


  surface_opac = Os;
  surface_color = Cs * (Ka * ambient()
			+ Ks * specular(Nf, -V, roughness)
			+ layer_color);

  Oi = surface_opac;
  Ci = surface_opac * surface_color;
}