public Curve(Keyframe[] keyframes)
{
if (keyframes == null) throw new ArgumentNullException(nameof(keyframes));
keys = keyframes.OrderBy(k => k.Time).ToArray();
empty = keys.Length == 0;
if (!empty)
{
firstKey = keys[0];
lastKey = keys[keys.Length - 1];
}
}
protected abstract float Interpolate(Keyframe left, Keyframe right, float delta);