noise method
Implementation
double noise(double x, double y) {
final int X = x.floor() & 255;
final int Y = y.floor() & 255;
x -= x.floor();
y -= y.floor();
final double u = _fade(x);
final double v = _fade(y);
final int A = _p[X] + Y;
final int B = _p[X + 1] + Y;
return _lerp(
v,
_lerp(u, _grad(_p[A], x, y), _grad(_p[B], x - 1, y)),
_lerp(u, _grad(_p[A + 1], x, y - 1), _grad(_p[B + 1], x - 1, y - 1)),
);
}