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Lars Renklint
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Fade out on every keyframe

Feb 10, 2012 2:23 AM

Another newbie question.

Tried this expression on a layers opacity:

 

d = Math.abs(time -transform.position.nearestKey(time).time);

easeOut(d, 100, 0)

 

The idea was to make the layers opacity go from 100% to 0 on every keyframe.

 

What actually happens is the opacity goes down to 36% in the middle between two keyframes, then goes up to 100 again.

1121 Views   9 Replies   Latest reply: Lars Renklint, Feb 11, 2012 6:22 AM
 
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  • Lars Renklint
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    1. Lars Renklint,
    Feb 10, 2012 5:15 AM   in reply to Lars Renklint
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    Found this: http://library.creativecow.net/articles/ebberts_dan/ae6_exp.php

     

    So if I knew that the keyframes where 1 sec apart this would do the trick

     

    fade = .99;

    hold =.01;;

     

     

    t = time%(fade + hold + fade);

    if(t < fade){

      linear(t,0,fade,100,0)

    }else if (t < (fade + hold)){

      100

    }else{

      linear(t,fade+hold,fade+hold+fade,100,0)

    }

     

    Now I just need to figure out the math for calculating the time between keyframes

     
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  • Lars Renklint
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    2. Lars Renklint,
    Feb 10, 2012 6:32 AM   in reply to Lars Renklint
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    This works good enough, but I would like to find a better solution for the first keyfram.

     

    if(transform.position.numKeys>0);

    {

    n =transform.position.nearestKey(time).index;

    if(n>1){

    p = transform.position.key(n-1);

    fade = transform.position.key(n).time - p.time;

    hold =.01;;

    t = time%(fade + hold + fade);

    if(t < fade){

      linear(t,0,fade,100,0)

    }else if (t < (fade + hold)){

      100

    }else{

      linear(t,fade+hold,fade+hold+fade,100,0)}

    }

    else {value}

    }

     
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  • Dan Ebberts
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    3. Dan Ebberts,
    Feb 10, 2012 10:19 AM   in reply to Lars Renklint
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    If you want it to fade out at each keyframe, doesn't that mean it will always be at 0% after the first keyframe?

     

    Dan

     
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  • Lars Renklint
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    4. Lars Renklint,
    Feb 10, 2012 10:23 AM   in reply to Dan Ebberts
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    Then I have to rephrase it...

     

    What I would like is that the layer should start every new keyframe with an opacity of 100%, and fade away to 0 right before it reaches the next keyframe. Which again starts att 100%...

     
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  • Dan Ebberts
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    5. Dan Ebberts,
    Feb 10, 2012 10:43 AM   in reply to Lars Renklint
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    Try this:

     

    fade = 1; // fade duration

    n = 0;

    p  = transform.position;

    if (p.numKeys > 0){

      n = p.nearestKey(time).index;

      if (p.key(n).time <= time) n++;

    }

    if (n > p.numKeys) n = 0;

    if (n > 0){

      t = p.key(n).time;

      ease(time,t-fade,t,100,0);

    }else

      100

     

     

    Dan

     
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  • Lars Renklint
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    6. Lars Renklint,
    Feb 10, 2012 12:15 PM   in reply to Dan Ebberts
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    Thank you Dan, that was much more accurat then the solution I found. My code actually worked quite well in a simple test, but in a more complex test there were a lot of flickering. Your code works perfect for all but the very first keyframe.

     

    http://screencast.com/t/rPZbB5ljjZbl

     

    Please have a look at this short video and notice the flickering in the beginning. Any thoughts?

     
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  • Dan Ebberts
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    7. Dan Ebberts,
    Feb 10, 2012 5:50 PM   in reply to Lars Renklint
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    Hmmm... it's hard to figure out what's going on. Can you post a screenshot of your keyframes?

     

    Dan

     
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  • Lars Renklint
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    8. Lars Renklint,
    Feb 11, 2012 6:18 AM   in reply to Dan Ebberts
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    fadeOut.png

    In my test comp were the keyframes were in the layers position property everything worked perfect.

     

    In this comp the green solids opacity is controlled by a slider in the midi layer. The green solids position also has an expression that uses the midi-slider.

     
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  • Lars Renklint
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    9. Lars Renklint,
    Feb 11, 2012 6:22 AM   in reply to Lars Renklint
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    Thanks for the suggestion to post a screendump. That made me see the extra keyframe that I didn't notice before. With that deleted everything works perfect.

     
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