How to write a Bezier curved path on the fly with one fixed point and one changing

Question

If I have an object performing this CAKeyframe Animation path (it is just an oval shape in the upper region of an iphone..

 UIBezierPath *trackPath = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(20, 100, 280, 150)];

Now imagine that at anytime during this paths travels I want to create a smooth path from its current position at a point in time and some point at the bottom of the screen.

By the way I am assuming that once I have a path I can stop the current CAKeyframeAnimation and add this path to a new CAKeyframe animation, but maybe if this is incorrect you can give me pointers here as well please.

Answer 1

So I said to myself "Self.....it looks like you are going to have to answer this one yourself as nobody even wants to edit it or say that it is a duplicate......"

So I was hoping for some easier or ready made way to do this. From what I have found there is no easy way. It seems the steps are going to be;

1. get the current position of the animated layer
2. calculate yourself with all your own code a nice smooth curve
3. add this path to an animation and animate it.

As for the calculation of a Bezier Curve I am still looking to find some class or code where points can be plugged into it and the two control points are produced for the UIBezier class to produce a curve.

In my case I am going to only animate "out" of my above questioned shape a determined points and thus have ready made smooth curves which I have prepared.

Animating a smooth exit from an oval at any point is very complicated and In my case just not worth it. So I have not done that.