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???
On Mon, 2010-03-29 at 13:49 +0200, Matteo Sisti Sette wrote:
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???
Check this thread: http://lists.puredata.info/pipermail/pd-list/2008-06/062878.html
Roman
Roman Haefeli escribió:
Check this thread: http://lists.puredata.info/pipermail/pd-list/2008-06/062878.html
I checked it out (not read the _whole_ thread to the end) but, In what way can the current tabread4~ interpolation, which is discontinuous even in its 1st derivative, be superior to true cubic interpolation? Even at transpositions near to zero, I can't see what's the advantage, nor what it is supposed to minimize.
Hi all-
I haven't looked at Cyrille's interpolator but... tabread4~ uses true cubic interpolation (which perhaps Cyrille's object also does in some other way). The tabread4~ algorithm is to put a cubic through the 4 points surrounding the input point. However, this cubic curve does not necessarily match the next curve over in first derivative.
A workaround is to up-sample everybody by a factor of 2 - this dramatically reduces error, usually by 24 dB.
All described in chapter 2 of my book, http://crca.ucsd.edu/~msp/techniques.htm
cheers Miller
On Mon, Mar 29, 2010 at 02:29:30PM +0200, Matteo Sisti Sette wrote:
Roman Haefeli escribi??:
Check this thread: http://lists.puredata.info/pipermail/pd-list/2008-06/062878.html
I checked it out (not read the _whole_ thread to the end) but, In what way can the current tabread4~ interpolation, which is discontinuous even in its 1st derivative, be superior to true cubic interpolation? Even at transpositions near to zero, I can't see what's the advantage, nor what it is supposed to minimize.
-- Matteo Sisti Sette matteosistisette@gmail.com http://www.matteosistisette.com
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Miller Puckette escribió:
The tabread4~ algorithm is to put a cubic through the 4 points surrounding the input point. However, this cubic curve does not necessarily match the next curve over in first derivative.
Oh I see! I thought it did. I confuded that technique with natural cubic splines :$
Now I remember that in order to compute the coefficients for a cspline you have to know in advance all the points of the table (iirc). But the general formula for csplines doesn't assume equally spaced points...
So now i dubt is it possible at all to find the piecewise cubic that ensures continuity of the 1st and 2nd derivatives by using 4 points at a time? (at least in the case of equally spaced points)
thanks m.
By the way tabread4c~ is not in Pd Extended, is it?
Roman Haefeli escribió:
On Mon, 2010-03-29 at 13:49 +0200, Matteo Sisti Sette wrote:
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???
Check this thread: http://lists.puredata.info/pipermail/pd-list/2008-06/062878.html
Roman
Matteo Sisti Sette a écrit :
By the way tabread4c~ is not in Pd Extended, is it?
no. it is there : http://www.chnry.net/ch/?083-Nusmuk-audio
c
Roman Haefeli escribió:
On Mon, 2010-03-29 at 13:49 +0200, Matteo Sisti Sette wrote:
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???
Check this thread: http://lists.puredata.info/pipermail/pd-list/2008-06/062878.html
Roman
cyrille henry escribió:
Matteo Sisti Sette a écrit :
By the way tabread4c~ is not in Pd Extended, is it?
no. it is there : http://www.chnry.net/ch/?083-Nusmuk-audio
Hi, I downloaded the zip file but Windows tells me he can't open it. Is it something different than a "normal" .zip file?
(it says "linux" but I thought it may include the source code...)
The downloaded file size is about 54k (not 57.5 as stated in the page), so I tried re-downloading it (after clearing the browser cahce) but no luck...
The link works and extracts fine here in WinXP SP3. I used the built-in "compressed (zipped) folders" tool in the explorer shell.
On Mon, Mar 29, 2010 at 11:38 AM, Matteo Sisti Sette < matteosistisette@gmail.com> wrote:
cyrille henry escribió:
Matteo Sisti Sette a écrit :
By the way tabread4c~ is not in Pd Extended, is it?
no. it is there : http://www.chnry.net/ch/?083-Nusmuk-audio
Hi, I downloaded the zip file but Windows tells me he can't open it. Is it something different than a "normal" .zip file?
(it says "linux" but I thought it may include the source code...)
The downloaded file size is about 54k (not 57.5 as stated in the page), so I tried re-downloading it (after clearing the browser cahce) but no luck...
-- Matteo Sisti Sette matteosistisette@gmail.com http://www.matteosistisette.com
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John Harrison escribió:
The link works and extracts fine here in WinXP SP3. I used the built-in "compressed (zipped) folders" tool in the explorer shell.
Crazy.
Internet Explorer breaks downloaded files whenever it takes you more than a few seconds to select the folder to download in. I cleared the browser cache and downloaded the file again, which usually fixes the problem (only if I clear the browser cache), but this time even if it actually and fully redownloaded it it was corrupted again and again so I thought it was actually the file.
How such bugs in a browser can stay unfixed for years is beyond my understanding... (doesn't Bill Gates use his own broser??)
Thanks cyrille for sending the file.
Sorry I don't actually plan to compile it (never compiled a Pd external before), I thought I would just have a look at the source code... But if I do I will certainly send you the binaries