Add a Slider Control effect to your layer, Alt+click its Slider stopwatch icon, and paste the following expression:
// generate one random number for this layer for use elsewhere
// set the random number generator to remains constant over time, using the layer index as the seed
seedRandom(index, true);
random();
Alt+click the Dash property stopwatch, and paste this expression:
// define lists of acceptable dashes and gaps.
// these will work in pairs -- the first gap value will always go with the first dash value, likewise with the second, etc.
dashes = [100, 150, 200, 250, 300];
gaps = [25, 20, 15, 10, 5];
dashes[Math.round(effect("random")("Slider") * (dashes.length-1))];
Alt+click the Gap property stopwatch, and paste this very similar expression:
// define lists of acceptable dashes and gaps.
// these will work in pairs -- the first gap value will always go with the first dash value, likewise with the second, etc.
dashes = [100, 150, 200, 250, 300];
gaps = [25, 20, 15, 10, 5];
gaps[Math.round(effect("random")("Slider") * (gaps.length-1))];
Of course, you can modify the numbers in the lists to suit the aesthetics of your project, or extend or shorten the lists, but this will allow each layer to pull a separate dash/gap pair from your list of approved values.
Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive | RenderBreak [blog] | Profile [LinkedIn]