ADOBE AFTER EFFECTS: Forum Expressions Tutorials Creative Cloud

Easily turning opacity on or off over frames

COW Forums : Adobe After Effects

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Scott Green
Easily turning opacity on or off over frames
on Oct 17, 2011 at 8:46:43 pm



I've uploaded a basic diagram to help demonstrate what I'm trying to achieve here.

If I have a piece of footage or a comp that I want to appear for 1 frame, then disappear for a frame showing the frame below, then on, off, on, off... and so on.

I could either make the transparency 0%, 100%, 0%, 100% and so on, copying the keyframes manually but there must be an easier way.

I just wondered if maybe there's an easy way using code possibly to say 'turn on this layer for 1 frame, then turn it off for 1 frame, etc. etc.'?

I really do love good design - http://www.splurj.com


Return to posts index

Walter Soyka
Re: Easily turning opacity on or off over frames
on Oct 17, 2011 at 9:02:31 pm

[Scott Green] "I just wondered if maybe there's an easy way using code possibly to say 'turn on this layer for 1 frame, then turn it off for 1 frame, etc. etc.'?"

Yes -- welcome to expressions. I'll answer your question here, but you can also get a lot of help in the After Effects Expressions forum [link].

Alt-click the opacity stopwatch for your upper layer, then paste in the following code:
frames = 2;
if (timeToFrames() % (frames*2) < frames) 100 else 0;


This will give you a pattern where the upper layer is on and then off for the number assigned to the "frames" variable. As shown, you'll get two frames on, then two frames off.

The math goes as follows:
  • Get the current time in frames (for example, frame 5)
  • Divide that value by "frames" times 2, and return the remainder (in this case, divide 5 by 4, and get a remainder of 1)
  • Compare that value against the "frames" value; if it's lower, return 100% to the Opacity value. If it's higher, return 0% (and 1 is less than 2, so frame 5 will have an opacity on the upper layer of 100%).


Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


Return to posts index

Scott Green
Re: Easily turning opacity on or off over frames
on Oct 19, 2011 at 1:42:02 pm

That works really really, just what I was looking for, thanks very much :)

I really do love good design - http://www.splurj.com


Return to posts index


Christopher R. Green
Re: Easily turning opacity on or off over frames
on Oct 18, 2011 at 3:44:52 pm

I'm rather fond of setting the first few keyframes then using the expression:
loopOut("cycle");

-cg

p.s. and when i say 'few', i mean the first 3 keyframes


Return to posts index

steve agriosi
Re: Easily turning opacity on or off over frames
on Oct 18, 2011 at 7:38:21 pm

I used to use the strobe filter to do such thing.
But the expression idea by Christopher sounds better way.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]