Hi everyone,
when working with GEM (and probably with pd in general), one comes inevitably to the point where input parameters need to be interpolated to make the output looking / sounding halfway good - as a prominent example, using cc's from a midi controller to rotate an object around its axis in GEM will look really ugly (the minimum change will be 360°/128 = a little less than 3 degrees, resulting in jerky leaps). Thomas Grill proposed using pd's built-in dsp filter (lop~ in particular) to do the smoothing, this is a technique which elegance I really admire (although I must admit that I don't unterstand completely how it actually works). It has a serious drawback, however: it interpolates everything, even sudden parameter jumps that would be better passed through unchanged - imagine the following scenario: a geo is constantly rotated by a counter that rolls over at 360 degrees. Now, the lop~ filter interpolates this change that really is a jump by spitting out some values in between 360 and 0 degrees, which will make the result look jerky again when the rollover occurs. I tried to work around this behaviour by filtering these values out or setting the cutoff frequency of the filter during the rollover really high which causes it not to interpolate anymore but ran into timing issues ... to do it the right way, one probably would have to switch over to another lop~-abstraction during the rollover, which seems a bit like overkill to me. Additionally, someone stated on the list that filtering in the dsp domain does require a fair amount of cpu cycles.
So, at the end of this lengthy post:
- is there a possibility to amend Thomas' smoothing
abstraction with a "set x"-message that would cause it to start interpolating from the x-value ? How demanding (in terms of cpu cycles) would that abstraction then be?
- if not: is there an easy-to-implement algorithm that
does non-linear smoothing of yet-unknown parameters and detects parameter jumps? My math is a bit rusty, and googling only yielded stuff regarding the interpolation of _known_ values.
Thank you very much in advance, Thoralf.
How much free photo storage do you get? Store your holiday snaps for FREE with Yahoo! Photos http://uk.photos.yahoo.com