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/* Perlin's "Bozo's Donut"
* Perlin, Ken, "An Image Synthesizer", SIGGRAPH '85
*/
surface
bozo(
float k = 4, /* noise amplification */
Ka = 1,
Kd = 0.5,
Ks = 0.5,
roughness = 0.1;
color specularcolor = 1
)
{
normal Nf = faceforward(normalize(N),I);
vector V = normalize(-I);
color cc;
float i;
cc = color noise(k*P) ;
/* map ranges of noise values into different colors */
for ( i=0.0; i<3.0; i+=1.0) {
if (comp(cc,i) < 0.3) setcomp(cc,i,0.3);
else
if (comp(cc,i) < 0.6) setcomp(cc,i,0.6);
else setcomp(cc,i,1.0);
}
/* specular reflection model */
Oi = Os;
Ci = Os * (Cs * (Ka * ambient() + cc * Kd * diffuse(Nf))
+ specularcolor * Ks * specular(Nf,V,roughness));
}
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