I was just looking at that paper too.
I love stippling, and have played with some optimisation based approaches in the past.
This is packing with repulsion strength or radius dependent on image brightness:
The following year I saw this from Mike Wong:
Which also uses iterative attraction/repulsion, but instead of just between the points, it pulls along the gradient of the image brightness, which as you see gives much better contrast and detail, and I’ve been meaning for ages to have a go at implementing a version of this.
I’ve only skimmed it so far, but this new paper from Peter Wonka’s group looks to use something similar but improving it even further - the results really look great:
See also this thread, which similar, but also connects the dots into continuous curves: