clipka <ano### [at] anonymousorg> wrote:

>
> Mathematically, "natural splines" are only marginally different from
> what POV-Ray calls "cubic splines": Both are 3rd order polynomial
> splines... [snip]

Thinking back to the v3.62 days, I'm ashamed to admit that you probably
explained this long ago-- and probably in response to a similar post by me! Mea
culpa.

I've been looking at Wikipedia's entries on 'spline interpolation' and 'cubic
Hermite splines', in a (poor) attempt to understand them. But I'm trying! ;-)

My mention of using a 'natural spline' is simply based on its well-behaved use
in other parts of POV-Ray (without knowing its mathematical differences vs.
POV-ray's 'cubic splines'.) I had assumed that a 'natural spline' was somehow
better behaved mathematically than a cubic one... or maybe that it wasn't 3-rd
order...

Since both 'natural splines' and 'cubic splines' ARE both 3-rd order, I'm
willing to guess(!) that the problem is not in POV-ray's mathematical
implementation of the cubic spline, but rather in some kind of co-dependent
problem with the 'difference-ing' operation. Based on nothing but my nutty
intuition ;-)

Post a reply to this message