# include "rmannotes.sl"

displacement alienground(float Km = 0.2,
                         patternfreq = .1)
{
  float surf_mag;
  float lay_mag;
  float dist;
  float  i;
  point c;
  point PP;

  float pattern = 3;
  float dphase = 0.03;

  PP = transform("shader", P);

  surf_mag = 0;
  dist = 0;
 
  for (i = 0; i < pattern; i += 1) 
   {
    c = (udn(i * 132  + 0.5, 0.3, .8),
              0,
              udn(i * 892 + 0.5, -.3, -0.2));
    dist = distance(PP, c);
    dist = udn(noise(PP * 0.4) * 9, -0.35, -0.25);
    lay_mag = sin(dist * 2 * PI * patternfreq + dphase * sqrt(patternfreq)) 
      / patternfreq ; 
    surf_mag += lay_mag * patternfreq;
   }

  PP = P + -Km *surf_mag * normalize(N);
  N = calculatenormal(PP);

}