• Adobe After Effects Expressions

  Sequenced opacity loss

  Posted by William Walker on June 21, 2018 at 1:22 am

  First of all hi to everybody around,

  I’m guessing somebody must have had a similar conundrum and received indications for it, but I’m unable to find it – early morning/late night in my timezone and I’m busting my brains trying to figure it out on a pressing deadline.

  So I’ve got a wall of about 150 T.V. screens(each playing different video clips) that are supposed to fade out one after another – kind of a sequenced shut down.
  More precisely: Screen A loses 100% of its opacity over 6 frames; then screen B loses 100% over 6 frames as well but it starts doing so a frame after Screen A has begun its fade; then screen C loses 100% a frame after Screen B and so on.
  So long story short the screens are supposed to go off with a slight delay one after the other – and here’s my question – how could I do it using expressions?

  I’m fairly new to using expressions in After Effects and my amazement to their usefulness is only equalled by my frustration when I can’t seem to get a grip on them ☺

  Thank you and all the best,

  William Walker replied 8 years, 2 months ago 3 Members · 4 Replies
• 4 Replies

• 

  Dan Ebberts

  June 21, 2018 at 3:56 am

  What initiates the fade out sequence? What assumptions can we make about the order and position of the layers within the layer stack?
• 

  William Walker

  June 21, 2018 at 7:14 am

  Hi

  The sequence is initiated by the central screen – screen A, set in the middle of the comp and it should occur at precisely 3 seconds after the beginning of the composition. There’s no other special trigger for this action.

  I have stacked the layers according to their switch-off order in hope of making use of the index value – thus Screen A, which initiates the sequence is 1, Screen B – the first to go off is 2, then C is 3 and so on.

  The screens are placed inside the comp in such a way as to encircle Screen A. Bellow is an example of the arrangement – it’s sort of a spiralling effect that I’m after, fading off from middle to the margins.

  G H I
  F A B
  E D C

  Please let me know if there’s any more info that’s needed and many thanks for your help
  Cheers,
• 

  Andrei Popa

  June 21, 2018 at 8:04 am

  This should work
  frameDur = thisComp.frameDuration;
initialTime = 3+(index-1)*frameDur;
dur = 6*frameDur;
linear(time,initialTime, initialTime+dur,100,0)

  Andrei
  My Envato portfolio.
• 

  William Walker

  June 25, 2018 at 5:27 am

  Hello.
  Many thanks for your reply – desolated I didn’t get to answer sooner.
  I will try your solution today and see how that fits.

  We(part of a team working on an animation ☺ ) managed however to improvise an expression to suit our purpose at the time (before I got your reply) – 1st we parented our layers one to another as to create our desired shut-down order. After that we set up a slider control on a null holding values between 0 and 1 to allow us to adjust the delay between the shutdowns. Finally, we came up with this in our opacity:
  parent.transform.opacity.valueAtTime(time-thisComp.layer(“CONTROLLER”).effect(“DELAY”)(“Slider”));
  where CONTROLLER is the null and DELAY is the slider on it.
  We used “Screen A” as the master and adjusted the opacity on it. All the parented layers had the above expression applied onto them.

  Again, many thanks and sorry for not getting back with them earlier :).
  I’m very curious as to how your expression will work so I’ll definitely give it a try today.

  Cheers and all the best.

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