• Adobe After Effects Expressions

  Using Slider Control to change keyframes, and then looping those keyframes

  Posted by David Richards on July 16, 2019 at 10:30 am

  Hello,

  I’m relatively new to AE and have hit a stumbling block.

  I am trying to set up a template – the purpose is to be able to drop in images and text in a kind of carousel that could be repurposed and changed depending on circumstances. The various images and text scale up or down over time, all at the same rate, and I want to be able to control the degree of this scaling using sliders.

  In order to do this with the text, for example, I have set up a null linked to the scale parameter of all text layers. I want to ensure that each of these text layers grows or shrinks at the same rate. I have used the expression below to allow slider control of the first two keyframes.

  My problem is that I don’t know how to then loop these keyframes. If I add loopOut() to the end of this expression, the slider values are ignored, and the keyframes loop as if this code didn’t exist.

  Is there a way to alter the value of keyframes using sliders, and then loop these keyframes?

  Thanks for your help in advance,

  David

  if (numKeys > 1){
t1 = key(1).time;
t2 = key(2).time;
sliderStart = effect("Scale Control Start")("Slider");
v1 = [sliderStart, sliderStart];
sliderEnd = effect("Scale Control End")("Slider")
v2 = [sliderEnd, sliderEnd];
linear(time, t1, t2, v1, v2);
} else {
value
}

  David Richards replied 7 years, 1 month ago 2 Members · 2 Replies
• 2 Replies

• 

  Andrei Popa

  July 20, 2019 at 9:50 am

  Try this:

  if (numKeys > 1){
t1 = key(1).time;
t2 = key(2).time;
dur = t2-t1;
sTime = (time-t1)-(time-t1)%dur;
sliderStart = effect("Scale Control Start")("Slider");
v1 = [sliderStart, sliderStart];
sliderEnd = effect("Scale Control End")("Slider")
v2 = [sliderEnd, sliderEnd];
linear(time-t1, sTime, sTime+dur, v1, v2);
} else {
value
}

  Andrei
  My Envato portfolio.
• 

  David Richards

  July 23, 2019 at 10:46 am

  Thank you, Andrei.

  That works exactly as I wished, so I really appreciate you taking the time to reply.

  All the best!

  David

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