• Adobe After Effects Expressions

  Link position speed to object scale frequency

  Posted by Brad Pickford on November 7, 2013 at 4:14 am

  Hi everyone, hope you can help. I am looking to create an animation of a car. Instead of the wheels rotating they will scale up and down to the pace of the car. So the faster the pace the higher the frequency of the scaling. The scaling only has to be from 100 to 110%. I have looked into taking the position.speed of the layer and trying to use it to run the frequency of a sin wave but not having much luck. Any thoughts would be most appreciated.

  Cheers,
  Brad

  Brad Pickford replied 12 years, 6 months ago 2 Members · 2 Replies
• 2 Replies

• 

  Dan Ebberts

  November 7, 2013 at 6:27 am

  Unfortunately, it’s not simple:

  https://www.motionscript.com/articles/speed-control.html

  Dan
• 

  Brad Pickford

  November 7, 2013 at 2:12 pm

  Thanks Dan. I did look at that earlier but glazed over. I have created a workaround that is working. I am trying to create a delay in a secondary layer to offset its position value, but can’t get it to work. Would you have any suggestions? I need to offset the value of “d” by 2 frames.

  Cheers,
  Brad

  freq = thisComp.layer("controller").effect("sine value")("Slider");
amp = thisComp.layer("controller").effect("max position height value")("Slider");
n = freq.numKeys;
if (n > 0 && freq.key(1).time < time){
accum = freq.key(1).value*(freq.key(1).time - inPoint);
for (i = 2; i <= n; i++){
if (freq.key(i).time > time) break;
k1 = freq.key(i-1);
k2 = freq.key(i);
accum += (k1.value + k2.value)*(k2.time - k1.time)/2;
}
accum += (freq.value + freq.key(i-1).value)*(time - freq.key(i-1).time)/2;
}else{
accum = freq.value*(time - inPoint);
}
d = value[1] + amp*Math.sin(accum*Math.PI*2);

  [value[0], d]

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