vertical method
Implementation
Widget vertical(double aniValue, int index, double page, Widget child) {
double indexAni = page - index;
double gauss = math.exp(-(math.pow((indexAni.abs() - 0.5), 2) / 0.08)); //<--caluclate Gaussian function
return Transform.translate(
offset: Offset(0, -parallax * gauss * indexAni.sign),
child: child,
);
}