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I did a WebGL implementation of Jeschke's model last year.
It did make me concerned about standardizing Diffusion Curves
(such as in SVG).
Some artifact may not be visible in one implementation while
it is clearly visible in another. When rendering images designed
using the original tool by Orzan et al. I get some artifacts
where the artist have left imperfections. Those imperfections
are not visible in Orzan's implementation. Likewise, Jeschke's
model hides other artifacts that ARE visible in Orzan's model.
What makes Diffusion Curves unique is that a small artifact
can have a huge impact on the over all image, as it's spread out
by the solver.
If you're talking about diffusion curves in the idealized sense, you
are right that in principle all boundary points influence the entire
image, but in practice the influence usually tapers off quite
quickly. However, most solvers do have a bit of a problem with
actually converging to a solution, which led me to my thesis
subject. One problem is that all solvers tend to give smooth
solutions that sort of look plausible, so it is not immediately
obvious that something is wrong. In my thesis I describe a potential
solution, by using a fundamentally different kind of solver, but
it's definitely not a drop-in replacement for existing solvers (at
least not yet).