not trails…but kinda like trails…

[Filip Vandueren]

for opacity:

frequency=8; // dots per second
startIndex=1; // layerindex of the first dot-layer

time >= ((index-startIndex)/frequency) ? 100 : 0 ;


for position:

frequency=8; // dots per second
startIndex=1; // layerindex of the first dot-layer

leader=thisComp.layer("solid");

leader.transform.position.valueAtTime((index-startIndex)/frequency)

You could simply use a particle system without gravity or velocity, and tie the emitter’s position to the solid.

If you really need multiple layers, one for each pellet, try the expressions below, apply to one pellet layer, then duplicate the layer as much needed

[Jerry Fines]

wow, that worked really nicely, thanks! Would you know how to do the second part of my problem expression? Where I would like the pellet/dot to fade out over time after it has been dropped?

-Jerry

[Filip Vandueren]

frequency=8; // dots per second
startIndex=1; // layerindex of the first dot-layer

FadeOut= 1.2;

birthTime=(index-startIndex)/frequency;
birthTime>=time ? 0 : linear(time,birthTime,birthTime+FadeOut,100,0);

This works.

You’re probably best off creating a Null-layer with some expression-control sliders, and linking to them for all the variables like frequency, FadeOut time etc. because that makes it easier to tweak.