monotonic spline interpolations in Darktable

[Tamas_Papp (Tamas K. Papp)]

@fdw

It would therefore be interesting to know if people are actually doing this.

Yes, they are. See this recent video from @s7habo, who I would consider an expert user. Almost every time he edits a node, he aligns the neighboring nodes to (I assume) avoid the wiggle.

@fdw

while a relatively simple extension to ordinary cubic splines, are seldom covered in numerical analysis courses—even at the graduate level

Yes, I can second this. I work a lot with various numerical methods, read a lot of books on splines, and haven’t seen the cubic version you kindly linked (I was aware of the simple Schumacher scheme only).