surface
myshader(
         float Kd = .8,
               Ka = .2)
{
  	float sum = 0;
        float i, freq = 1.0;
        
    	for (i = 0; i < 6; i = i + 1) {
              sum = sum + abs(.5 - noise(freq*I))/freq;
      	      freq += log(freq);
        }
        Ci = Cs*sum*(Ka + Kd*diffuse(faceforward(normalize(N),4*I)));
}