It's very good, but I think the problem is "too many parameters." In some contexts that's fine (animators are used to it) but in others it might not be ideal. People don't use that spline for font design work; why? The Hobby spline has a tension parameter, which is said to be "very useful" in the paper, but when Apple adapted it for Pages, they left it out of the UI. Was that a mistake, or did they make an informed user experience tradeoff? (Incidentally, I believe tension is in there, as part of the illusion of extensibility, but deeply hidden)

So whether this spline is better for, say, animation, is what I consider a fascinating research question. Hopefully putting it out there will start to get answers.

I can't tell from your online demo if there is any control over the trade off between only dropping curve points where tangentially required verses even distances between curve points. (I'm sure there is some shorter term for that.) I remember a talented animator remarking to me how he had acceleration control with TCB Splines that allowed him to achieve the same curve shapes but with control where curve points are emitted, giving him timing controls for objects in motion. He liked using TCBs for everything.

> Kochanek–Bartels spline

YMMV, but the problem I have is that it generally makes ugly shapes unless you are very skilled/practiced with it and very careful about twiddling parameters, because the control parameters are based on the implementation details of the mathematical tool rather than directly on features of human perception.

There’s basically a mismatch between human-centered goals and the mathematical model of those.

As an analogy, you might think of it like trying to learn how to dance vs. learning how to make a puppet dance by manipulating a control bar with your fingers to pull on its strings. The latter involves more indirection, which makes it harder for novices to get approximately their desired result.

For anyone unfamiliar with this tool, see the image in https://en.wikipedia.org/wiki/Kochanek%E2%80%93Bartels_splin...