No recursive expression, right ?

[nicolasg23085032]

Hi,

This expression, put in a NULL.position won't make it move. For the expression is somehow recursive :

newPosition = [] ;

if (time>1) {

    lastPosition = thisComp.layer("NULL").position.valueAtTime(time-thisComp.frameDuration);

    // filter core :

    newPosition[0] = lastPosition[0] + 10 ;

    newPosition[1] = lastPosition[1] ;

    newPosition[2] = lastPosition[2] ;

    }

else {newPosition = [960,540,0] ;}

[newPosition[0],newPosition[1],newPosition[2]  ]

Is there a workaround to create an algorithm of this sort :    position(n)  =   f(     position(n-1)    )   

Thanks !   

[Dan Ebberts · Accepted solution]

An expression can't access a previous result using valueAtTime(). It only has access to pre-expression values. But you can often overcome this limitation by basing your calculation on time. For example, if you want the layer to move right 10 pixels on each frame, you could do something like this:

f = timeToFrames(time);

value + [f*10,0,0]

Dan

[Martin_Ritter]

Everybody would do this with a for-loop, but this is da(m)n clever!

[nicolasg23085032]

Thanks Dan, Thanks Martin,

In fact, my example was purposely basic. What I needed to do was a smoothing of the motion of a NULL to animate another NULL and make it the point of interest of a camera.

I found a workaround ... which is better in fact than the original first order filter I tried to implement :

CreativeCOW

Thanks !