Expression to make an object avoiding another one

[OGlaize]

Hello,

I would like to automate the position of an object "A" in such a way that when an object "B" is getting closer (around 100px of distance), the object A would dodge B.

I don't know if it will be useful but here is a sketch of what I would like to do :

A→            B

----------------------

         A→   B

----------------------

               A→

                  B

----------------------

                     A→

                  B

----------------------

                   B       A→

Thanks in advance !

[Kyle Hamrick]

I can think of ways this would be possible, but unless you're doing a ton of these, I have a feeling it's going to be more successful to animate this by hand.

[OGlaize]

I would like to do this with aproximately 20 objects, so I don’t know wich would be the easiest way..

[Mike_Abbott]

What is the nature of object A's movement? simple X axis left to right as per your sketch above - or something more random?

[Rick Gerard · Accepted solution]

It's going to take some modification of some or all of these techniques demonstrated and explained by expression guru Dan Ebberts:

Proximity Detection

Collision Detection

Elastic Connection

I don't have time to give you the expression but I can give you the idea.

1. Define Layer A and B. If you want to make B move when A gets near then consider placing Layer A above Layer B and using thisComp.layer(index - 1) in the expression you add to layer B so you can paste it into any layer without renaming the layer
2. Decide how you want Layer B to react when Layer A gets close - consider revising he Elastic Connection code
3. If you want all layers to react to all other layers, randomly or based on angles consider adapting the sampleImage(point, radius = [.5, .5], postEffect = true, t = time) method from the Expression Language>Layer>General menu to look outside the layer boundaries for alpha channel changes

The there option, which would work very well if you have 3D layers is Newton 3 . That would be the easiest way I know of to quickly generate collisions between layers.

There may be some other scripts out there that I don't know about. So I guess it comes down to figuring out if you have several hours to devote to figuring out how to modify Dan Ebberts' sample expressions or do you have about $250 to spend on a 3rd party solution.

[Dave_LaRonde]

If you want the motion to be smooth, do it by hand.  If you don't care how the motion looks, code it.

[Mike_Abbott]

For 20 layers I think Kyle and Dave's suggestion is probably the right one. You'll probably spend longer building and tweaking an expression than it would take to keyframe it.

[Mylenium]

What Dave said. Do it by hand. It's just a measly 20 layers, after all.

Mylenium

[OGlaize]

Thanks a lot for all your help !

Have a good week-end.