private float CalculateSpringConstant(Spring spring, float duration)
{
float minDuration = spring.SmallestDuration;
if (spring.SmallestDuration == 0)
{
minDuration = duration;
}
var phi = 1 + 0.6f * Std.Log2(duration / (float)MinDuration);
return (minDuration / duration) * 1 / (phi * MinDurationWidth);
}