/* 
 * Beach ball procedural texture for mapping onto a sphere
 *
 * Mark Fontana
 * Digital Lighting, SP 96
 *
 */

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

surface beachball_color(float Ks = 0.4, Kd = 0.6, Ka = 0.1, roughness= 0.1;
                        color specularcolor = 1,
                              color1 = color (1, 0, 0),
                              color2 = color (0, 1, 0),
                              color3 = color (0, 0, 1),
                              color4 = color (1, 1, 0))
{
  point Nf = faceforward(normalize(N), I);
  point V = -normalize(I);
  color surface_color, layer_color;
  color layer_opac, stripe_opac;
  float ss, fuzz = 0.0001;

  surface_color = color (1, 0, 1);  /* purple top and bottom caps */
  Os = t;

  ss = repeat(s,3);
  stripe_opac = pulse(0.07, 0.93, fuzz, t);      /* stripe layers */

  layer_color = color1;
  layer_opac = stripe_opac*pulse(0.0, 0.25, fuzz, ss);
  surface_color = blend(surface_color, layer_color, layer_opac);

  layer_color = color2;
  layer_opac = stripe_opac*pulse(0.25, 0.50, fuzz, ss);
  surface_color = blend(surface_color, layer_color, layer_opac);

  layer_color = color3;
  layer_opac = stripe_opac*pulse(0.50, 0.75, fuzz, ss);
  surface_color = blend(surface_color, layer_color, layer_opac);

  layer_color = color4;
  layer_opac = stripe_opac*pulse(0.75, 1.0, fuzz, ss);
  surface_color = blend(surface_color, layer_color, layer_opac);

  /* output */

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

  Oi = Os;
  Ci = Os * surface_color;
}