ingo wrote in message ...
>On 2002 02 17, you wrote in povray.general:
>
>> If I knew for certain what sort of cubic spline is used in "prism",
>> I'd be able to duplicate it and add it as another type of pure
>> spline.
>>
>
>If I understand the source right it indeed is a Catmull-Rom spline:

I've looked up some information on Catmull-Rom splines on the Internet, and
it looks like they fit properties 1, 2, 3, and 5 from my earlier list.
Catmull-Rom splines do not, however, have a continuous second derivative.
Since part of the reason I implemented cubic splines the way I did was to
get a function with a continuous second derivative, I won't replace the
existing cubic splines with Catmull-Rom splines.  It should, however, be
easy enough to add Catmull-Rom interpolation to the various spline
interpolation methods.

--
Mark

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