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Activity › Forums › Adobe After Effects Expressions › link to value from layer above but hold it at 100%

  • link to value from layer above but hold it at 100%

    Posted by Saudi on May 9, 2007 at 8:23 am

    Hello everybody,

    I am trying to animate a path on a map using “blinking/pulsing” dots. I animated the opacity of the first layer using keyframes. ( 0% to 100% and back to 0%) Then I duplicated this layer a couple of times and linked the opacity to the first layer using:

    thisComp.layer(thisLayer, -1).opacity.valueAtTime(time – .4);

    so they are fading in and out one by one.

    so far, so good.

    Now I want to hold the last layer at 100%, to show the end of the path.
    Is it possible to grab just the two keyframes from 0% to 100% at the last layer.

    How can I do this?

    thanks for your help.

    greez Martin

    Saudi replied 19 years, 4 months ago 3 Members · 3 Replies
  • 3 Replies
  • Lord Scales

    May 9, 2007 at 3:59 pm

    I don’t know this so much, but try this:

    > find the time in which the Opacity of the last Layer go to 100. Let’s suppose it is in 6:21, so…

    o = thisComp.layer(thisLayer, -1).opacity.valueAtTime (time -.4); //value of opacity
    oMax = 100; //maximum value
    t = 6.7; //time when it gets to 100

    if(time < t) o else oMax I think there is an easier way like "when opacity gets to 100%, keep in until..." but I don't know exactly. Lord Scales

  • Filip Vandueren

    May 9, 2007 at 4:40 pm

    Can’t you just keyframe that one layer ?

    I’m not sure I understand:

    Does every layer have just three keyframes 0-100-0, or are they looping/blinkg all the time ?
    When exactly does the last layer need to stay at 100% ?
    When the first layer has completed its cycle ?

    BTW, here’s a different way to do it:

    Draw a Path, use text on Path and fill it with periods …..
    Now use a text animator to animate opacity. You can even add a little bit of scaling.

    No expressions needed, and I think it’s the effect you need.
    Much simpler to change the road by chaning the mask shape, and the spacing between the dots is figured out automatically.

  • Saudi

    May 10, 2007 at 8:21 am

    Hello again,

    thanks for your replys.

    @Lord Scales: I tried to play around with time calculations but ended up in a bigger mess :-). But I think that it is possible to do it this way.Aas u said, there must be an easier way to do it. Thanks for your reply.

    @Filip: I think its to complicated to describe the whole thing. I am triing to animate a path/way on a map. Its a military map and I have the show the movement of the troops. The map was exported from cinema 4d with NULL objekts including position data for each dot. The dots are a bunch of 2D-Layers and just the first dot is animated(opacity) by keyframes. All the Layers under this mother- or masterlayer are connected with expressions like this:

    thisComp.layer(thisLayer, -1).opacity.valueAtTime(time – .4);

    to behave exactly like the first layer (or the layer above), just half a second later.

    Now I want the last dot-layer to “read” just the first two keyframes from the animated masterlayer. (0% to 100%) like “do exactly what the layer above is doing but if opacity ==100 then stop and keep it”.

    I hope u get what I want.

    thank u so much

    greeez martin

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