> On the same machine, the instancing version can do a few thousand seed vertices (an order of magnitude more) at 60 frames-per-second, after which it becomes bandwidth saturated.
If you have a powerful GPU you can get even faster results. I have a project that does Lloyd's relaxation using voronoi and for me the using cones with a depth buffer gave the best result.
Real diffusion curve images would multiply that by an order or two at the least depending on complexity of the image (the algo I wrote as well as JFA might have a higher fixed number of iterations but it's fixed so the number of seeds don't matter).
Besides, GPU's have turned more and more general so even if there's optimizations for the triangle rendering the compute case will probably gain even more from more recent GPUs.
Optimizing for GPU's can be funny, and I wouldn't be surprised if the break-point on where the tri-fans are faster is higher than I expect, but at the same time unless it's a tile-based renderer I'm pretty sure there will be a break-point (also tilebased renderers can sometimes fall of performance cliffs in special cases).