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


displacement wfallsd(float km = 0.5, freq = 20)
{
  point NN, Nf;
  point V = -normalize(I);
  float magnitude;
  point PP;
  float width, cutoff, fade, turb, turb2, maxfreq = 25, f;
  uniform point down = (0,-1,0);

  PP = transform("shader", P) * freq;

  width = filterwidth_point(PP);
  cutoff = clamp(0.5 / width, 0, maxfreq);

  turb = 0;
  for (f = 1; f < 0.2 * cutoff; f *= 2) 
    turb += abs(snoise(PP * f)) / f;

  fade = clamp(2 * (cutoff - f) / cutoff, 0, 1);
  turb += fade * abs(snoise(PP * f)) / f;

  turb2 = 0;
  for (f = 1; f < 0.2 * cutoff; f *= 2) 
    turb2 += abs(snoise(N.PP * f)) / f;
  fade = clamp(2 * (cutoff - f) / cutoff, 0, 1);
  turb2 += fade * abs(snoise(PP * f)) / f;

  magnitude = pow(turb1, 4);
  NN = normalize(N);

  P += km * magnitude * normalize(Ng);     
  P += down*turb*turb2*2;
  N = calculatenormal(P);

 
}