[SOLVED] slow down object with easing out

slow down object with easing out

I have object moving with speed 6.66px per frame refresh (400px/s). I know that target stop point is 2341px away. Frame refresh time is 0.01666667. I want it to start slowing down at some point to keep it smooth and then stop. How to calculate how many pixels away should I start slowing down my speed and by how much?

Here is the code with data I have:

func updateOffset(frameDuration: TimeInterval, speed: CGFloat, duration: TimeInterval, distanceToTarget: CGFloat) {
 self.currentOffset += speed
}

Solution

Found out correct algorithm, this will produce ease-out effect on object:

var speed: CGFloat = 400.0

func updateOffset() {
  speed *= 0.9
  currentOffset += speed
}

to calculate distance it will travel with that speed

func distanceToSlowDown(initialSpeed: CGFloat) -> CGFloat {
  var distance = 0.0
  var speed = initialSpeed
  while speed > minimumSpeed {
    distance += speed
    speed *= 0.9
  }
  return distance
}