Just putting this here for general reference:

The "cubic_spline" type is a Catmull-Rom spline.
So a cubic spline sphere sweep ought to be able to be overlaid on a sor rendered
with an orthographic camera.

Now, there were some old posts by Rune in 2002 where it seems that different
types of spline were given the same name, and which spline you actually got,
depended on which shape you used - prism, spline, sphere sweep, etc.
I don't know if that's still the case.
(It looks like Mark Wagner coded a lot of the spline types.)

This would be something that we need to investigate and document, prior to
delving in a fixing/renaming/aliasing the spline types.

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https://news.povray.org/pan.2002.09.24.02.24.44.755861.210%40gte.net

From: Mark Wagner
Subject: Re: splines
Date: 23 Sep 2002 22:25:37
Message: <pan### [at] gtenet>




On Sun, 22 Sep 2002 19:20:02 -0400, Chris Colefax quoth:

> Fidel viegas <fid### [at] artrecognitioncouk> wrote:
>> Is there any macro that supports hermite curves? Does povray support
> hermite
>> curves? And what are they really good for? Isn't cubic splines enough
>> to create any kind of smooth camera or object animation?
>
> The term "cubic" refers to the degree of the equations used to calculate
> the spline path.  All the cubic splines (Bezier, Catmull-Rom, Hermite,
> Kochanek-Bartels) are just different ways of specifying the inputs for
> the spline, and it's not too difficult to perform conversions from one
> to another.

There's also a "natural cubic spline" type that can't easily be converted
to/from.  POV-Ray 3.5's "natural_spline" is a natural cubic spline.  The
"cubic_spline" type is a Catmull-Rom spline.

--
Mark

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