this is a pretty standard thing to do in motion graphics and comping software. drawing a line starting at point A going to point B, with variable inputs for speed of movement of leading point of the line, length of the full opacity line, length l of the trailing edge of the line that gets opacity applied.
if a functional sub-comp can be made for drawing a line from A to B then it can be reused to draw from B to C, C to D, and D to E, with the parent level composition calculating the points A, B, C, D and E from the coordinates of rectangle R an triggering the sub-comps the that's that, I just need to solve the opacity masking issue one of two ways I am envisaging.
I'm pretty clear how I'd go about it in other software. wondering for the optimal method to do the animation of 'drawing' a line with a trailing or leading 'edge' that has opacity mask applied. In QC I'd go for animating a gradient image to apply as opacity mask. Not sure how to do that in Vuo, I'm pretty uncomfortable in Vuo applying image effects as opacity masks to other objects as I find the coordinate system unintuitive so far for me.
An alternative method would be to draw ten short lines each length l/10 and set them to step in opacity from 90% down to 0% and have them chase each other.
there's a family simple tool built into Adobe After Effects for 'drawing lines' and applying opacity. but this is only step one of a sequence of effects, unfortunately Vuo doesn't export to an Adobe AE plugin binary (only Motion/FCP X) so I can't combine the very simple AE tools for doing this with the other things I need VUO for. (or QC if I have to!)
Would really like to see Vuo export to BlackMagic Design's DaVinci NLE/VFX application from BMD (which would be a really smart move I think given DaVinci has a good free version of the software). I'd start learning Davinci if Vuo exported to it.
Ideally I can do this all in VUO and export as an app for my video editor so they can render brand collateral effects with variable inputs for certain traits without getting into the weeds. (But OFX plugin or Adobe plugin would be amazing).