CubicBezier.cs

using System;
using Dalamud.Interface.Animation;

namespace EngageTimer.UI.CustomEasing
{
    public class CubicBezier : Easing
    {
        private readonly double _p0;
        private readonly double _p1;
        private readonly double _p2;
        private readonly double _p3;

        public CubicBezier(TimeSpan duration, double p0, double p1, double p2, double p3) : base(duration)
        {
            _p0 = p0;
            _p1 = p1;
            _p2 = p2;
            _p3 = p3;
        }

        public override void Update()
        {
            this.Value = Math.Clamp(Math.Pow(1 - Progress, 2) * _p0
                                    + 3 * Math.Pow(1 - Progress, 2) * Progress * _p1
                                    + 3 * (1 - Progress) * Math.Pow(Progress, 2) * _p2
                                    + Math.Pow(Progress, 3) * _p3, 0d, 1d);
        }
    }
}