• Adobe After Effects Expressions

  Add “Inertial Bounce” Expression to a current Expression

  Posted by Roland R. kahlenberg on September 22, 2011 at 6:46 pm

  Following is the Inertial Bounce Expression Script –
  n = 0;
  if (numKeys > 0){
  n = nearestKey(time).index;
  if (key(n).time > time){
  n–;
  }
  }
  if (n == 0){
  t = 0;
  }else{
  t = time – key(n).time;
  }

  if (n > 0){
  v = velocityAtTime(key(n).time – thisComp.frameDuration/10);
  amp = .05;
  freq = 4.0;
  decay = 2.0;
  value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
  }else{
  value;
  }
  ——————
  I now have the following Expression script in my X-rotation which is linked to the y-rotation on another layer –

  Delay = effect(“Pop-up Delay”)(“Slider”)/25;
  Source = thisComp.layer(“Page 01”).transform.yRotation.valueAtTime(time-Delay);
  ease(Source,0,180,-90,0)

  ——————-

  How do I get Inertial Bounce to work with my x-rotation script. Take note that I can’t apply the Inertial Bounce to the other layer’s y-rotation as that layer should not have the Inertial Bounce effect.

  TIA
  RoRK

  Intensive AE & Mocha Training in Asia.

  Roland R. kahlenberg replied 14 years, 8 months ago 2 Members · 4 Replies
• 4 Replies

• 

  Dan Ebberts

  September 23, 2011 at 1:22 am

  Hmmm…. I don’t think it will work. Because of the ease, the x-rotation will have zero velocity at the times corresponding to the y-rotation’s keyframes. No velocity, no inertial bounce. If you use the y-rotation’s velocity the bounce won’t look right.

  Dan
• 

  Roland R. kahlenberg

  September 23, 2011 at 2:46 am

  Thanks Dan. For my, rotation script, I changed its ‘source’ layer to a proxy layer with KFs identical to the original ‘source layer’. The proxy is of course a Null and I can apply the Inertial Bounce script to its KFs.

  This works but requires the proxy layer to be created and updated manually.

  Cheers
  RoRK

  Intensive AE & Mocha Training in Asia.
• 

  Dan Ebberts

  September 23, 2011 at 3:37 am

  I think you could modify the proxy layer’s bounce expression to point at the keyframed property on the original source layer. That way you wouldn’t have to update the proxy. I haven’t tested it, but it would look like this:

  
p = thisComp.layer("Page 01").transform.yRotation;
n = 0;
if (p.numKeys > 0){
n = p.nearestKey(time).index;
if (p.key(n).time > time) n--;
}
if (n == 0){
t = 0;
}else{
t = time - p.key(n).time;
}

  if (n > 0){
v = p.velocityAtTime(p.key(n).time - thisComp.frameDuration/10);
amp = .05;
freq = 4.0;
decay = 2.0;
p.value + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
p.value;
}


  Dan
• 

  Roland R. kahlenberg

  September 23, 2011 at 10:41 am

  That works very well Dan. Thanks a bunch!

  Regards
  RoRK

  Intensive AE & Mocha Training in Asia.

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