Function feather

Main.cpp:74–82

  y = ny;
}
void feather(double& x, double& y, double cx, double cy) {
  std::complex<double> z(x, y);
  std::complex<double> z2(x*x, y*y);
  std::complex<double> c(cx, cy);
  std::complex<double> one(1.0, 0.0);
  z = z*z*z/(one + z2) + c;
  x = z.real();
  y = z.imag();
}
void sfx(double& x, double& y, double cx, double cy) {
  std::complex<double> z(x, y);
  std::complex<double> c2(cx*cx, cy*cy);