[PD] tabread4~ "broken" interpolation algorithm - was Re: Max Smoother Audio than Pd?

[Matteo Sisti Sette]

Hi,

 > Well, if you use [tabread4~] or any of the many other Pd objects
 > that use the same broken interpolation algorithm
 > (copy/paste programming),

Broken? What's wrong in the tabread4~ interpolation? (note this is not a 
sarchastical question implying there's nothing wrong in it, it's a 
genuine question in order to learn what's wrong in it)
Is it a bug?

Claude wrote:
 > If you use [tabread4] to interpolate graphical
 > parameters for animations, the discontinuities in the derivatives are
 > really obvious.
[....]
 > But IMHO if you're doing piecewise cubic interpolation, it's a bit
 > of a nonsense to have a cubic that goes through all 4 points when
 > it's only being used between the inner-most 2 points

Well using 4 points to interpolate the curve that goes between the two 
inner points should guarantee the absence of discontinuities in the 
first (and second?) derivative; that should be the purpose. Now if there 
actually are discontinuities then there must be some trivial error in 
the equation,  no????



Or am I missing something???

-- 
Matteo Sisti Sette
matteosistisette at gmail.com
http://www.matteosistisette.com