#include "rmannotes.sl"

displacement woven_disp(float freq = 30, Km = 0.02)
{
  float surface_mag, layer_mag;
  float ss, tt;
  float fuzz = 0.05;
  float row, col;
  point Ndiff;

  /* background layer */

  surface_mag = 0;

  /* repeat layers */

  ss = repeat(s, freq);
  tt = repeat(t, freq);
  col = whichtile(s, freq);
  row = whichtile(t, freq);

  if (even(row) && odd(col) || even(col) && odd(row)) {

  /* layer 1 */

  layer_mag = spline(ss, 0.025, 0.025, 1, 0.25, 0.025);
  surface_mag = max(surface_mag, layer_mag) + layer_mag;

  /* layer 2 */

  layer_mag = spline(tt, 0.025, 0.025, 1, 0.025, 0.025);
  surface_mag = max(surface_mag, layer_mag) + layer_mag;
}
else{

  /* layer 2 */

  layer_mag = spline(tt, 0.025, 0.025, 1, 0.025, 0.025);
  surface_mag = max(surface_mag, layer_mag) + layer_mag;

  /* layer 1 */

  layer_mag = spline(ss, 0.025, 0.025, 1, 0.025, 0.025);
  surface_mag = max(surface_mag, layer_mag) + layer_mag;
}
  /* displace and account for smooth shading */

  Ndiff = normalize(N) - normalize(Ng);
  P += Km * surface_mag * normalize(N);
  N = normalize(calculatenormal(P)) + Ndiff;
}