protected override double EaseInCore(double normalizedTime)
{
double bounces = Math.Max(0.0, (double)Bounces);
double bounciness = Bounciness;
//Anything less than one will cause a DivideByZeroException
if (bounciness < 1.0 || DoubleUtils.IsOne(bounciness))
{
// Just a bit more than one to get (almost) the same effect without dividing by zero
bounciness = 1.001;
}
double bouncinessCompliment = 1.0 - bounciness;
double power = Math.Pow(bounciness, bounces);
//Get the number of units, where the first bounce has a width of 1 unit, using a geometric series plus half a unit
//for the final bounce
double totalUnits = (1.0 - power) / bouncinessCompliment + power * 0.5;
//The unit we are currently in
double currentUnit = normalizedTime * totalUnits;
// Which bounce are we in, based on current unit
double currentBounce = Math.Log(-currentUnit * (1.0 - bounciness) + 1.0, bounciness);
double start = Math.Floor(currentBounce);
double end = start + 1.0;
//Convert the start and end of the bounce into time
double startTime = (1.0 - Math.Pow(bounciness, start)) / (bouncinessCompliment * totalUnits);
double endTime = (1.0 - Math.Pow(bounciness, end)) / (bouncinessCompliment * totalUnits);
//Create a curve to fit the bounce
double peakTime = (startTime + endTime) * 0.5;
double timeToPeak = normalizedTime - peakTime;
double radius = peakTime - startTime;
double amplitude = Math.Pow(1.0 / bounciness, (bounces - start));
//Quadratic curve to match the start, end and peak
return((-amplitude / (radius * radius)) * (timeToPeak - radius) * (timeToPeak + radius));
}
