How to create outward spiral motion in Adobe After Effects?

Question

I want to create an outward spiral motion in Adobe AE. So how to do it?

I found an expression script for it here but it creates an inward spiral motion and I want outward spiral. And I am not able to reverse it.

shrink=time+1
radius=1000/shrink
angle=time*200
x=radius*Math.cos(degreesToRadians(angle))
y=radius*Math.sin(degreesToRadians(angle))
//z=0 // no depth
z=time*time // with depth
centre=[640,360,0]
add(centre,[x,y,z])

What exactly I want to do?

I want the images to spiral in a circular image from center to some particular points in the circle. And then they stop spiralling and stay at that point. And after a while they shift to left with the whole circular image.

Please help.

Answer 1

That script uses the variable shrink, which paradoxically increases with time. Just make it decrease with time, e.g. by replacing the first line with these two:

var endTime =  123; //how long you want it to take, in seconds
shrink = endTime - time;

Or make the radius the product of the time and a constant, rather than dividing the radius by time, by replacing the first two lines with these:

shrink= time;
radius = 100 * time; //this will grow 100 pixels every second, adjust to suit

Or parent the images to a null, rotate it and scale it up. Then to counter the rotation and scale of the null on each image use this expression for rotation

0 - parent.transform.rotation

and for scale:

100 / parent.scale