The ball always go to odd number point on circleA,
                                                                                                            or even number point on circleB.

 

 

 

 

duration: The frames that the ball move up and down until next moving up.
movingTime: The total frames that the ball move up to peak point or move down to ground point.
startDelaying: The frames that the ball start moving later than preview balls.

 

Example
duration: 200 frames
movingTime: 40 frames
startDelaying: 8 frames

 

 

 

We want to move the ball to finish the first duration.

Now, how to move the ball from B0 to A1, or A1 to B2?
We are using Lerp function.
Lerp (a, b, c )                            a: the current point
                                                 b: the next point
                                                 c: ratio number, when it equal 0 staying a, equal 1 staying b.
 

 

We don't want our ball to flash to the point b or a. We want the ball to move to the point with constant speed by frames.
So we need to calculate the ratio c.
For example, current frame is 212

​

So, 212 frame % 200 = 12 frame
Great than 0, lower than 40; the ball is between B2 and A3.
What is the position between B2 and A3?
12 / 40 = 0.3

Then, we can get the ball moving animation by calculating ratio c in Lerp function.
Now, we achieved 1 ball moving, how to make 13 balls moving?
Using transform node with certain angle and detail("","iteration",0) .
However, we don't want 13 balls to move in the same time.
We need to delay the starting time comparing than the preview ball.
Using startDelaying
Current frame is 212, where is the second ball position at?
(212 - 8) % 200 = 4 frames
Great than 0, lower than 40; the ball is between B2 and A3.
4 / 40 =0.1