Apr 22 2006 | 12:25 pm
    hi, I'm using Jitter for the first time in an upcoming project. I was wondering whether anyone could provide me with an explanation of what jit.slide actually does?

    • Apr 22 2006 | 12:36 pm
      Apart from the reference manual page?
    • Apr 22 2006 | 1:35 pm
      Yes, "always consult the manual page" ( the hit single from the new CD by my band, Grazing Zebra).
      I struggled with this too until a light finally went on. It is related to the question, "How far is it to Chicago in miles per hour?" Here is my (more-or-less) plain language description.
      When a jitter matrix passes through jit.slide, it "slides" from the previous frame by an interpolation method that you see in the equation on the help page. The time it takes to slide is determined by the slide up/down values. These values are not in fact time but rate. The further the distance, the longer the time.
      (Jitter gurus correct this next part as necessary) If you have a pixel with a value 0.0 in the starting frame and 1.0 in the ending frame it will take longer to interpolate than te pixel pair 0.1-0.2. Different frames in the same movie with take different times depending on the values of the pixels. Frames that are similar arrive more quickly.
      It's akin to reverberation. If you set a reverb time of 2.0 seconds and play a loud sound it will take longer to decay than a soft sound because the process involves feedback.
      Consider the following two sequences of numbers.
      100 90 81 72.9 65.61 59.049 53.1441 47.82969 43.046721 38.7420489 34.86784401 50 45 40.5 36.45 32.805 29.5245 26.57205 23.914845 21.5233605 19.37102445
      The first starts at 100% and decays by a factor of 0.9. At the 10th sample it reaches approximately 1/3 of its original value. With same decay factor, the second starts at 50% and reaches 1/3 around the 5th sample.
      Cheers, Gary Lee Nelson TIMARA Department Oberlin College www.timara.oberlin.edu/GaryLeeNelson
    • Apr 22 2006 | 1:45 pm
      it makes cells in jitter matrices nostalgic over time.
    • Apr 22 2006 | 2:40 pm
      thanks ever so much! That makes more sense than the reference manual...
      oh yeah, just one more question... What do the 'y', 'n' and 'x' represent in the formula: y(n) = y(n-1) + ((x(n) - y(n-1))/slide)?
    • Apr 22 2006 | 2:55 pm
      take a look at the regular [slide] object first. consider this patch i'm attaching and then consider this process numerical happening to each and every cell in a jitter matrix.
      best, jonathan
      the patch:
    • Apr 22 2006 | 3:31 pm
      On Apr 22, 2006, at 9:40 AM, ed dowie wrote:
      > > Yeah. I read the help file and the reference manual entry, but I > have to confess, didn't quite understand them. Sorry to be really > thick, but i guess i don't really understand the formula: > > y(n) = y(n-1) + ((x(n) - y(n-1))/slide) > > I understand that there is a degree of feedback over time whose > intensity of light/dark is controlled by slide_up and slide_down > controls, but quite how it's done is not quite clear yet!
      Gary Nelson's explanation does as good a job as any of explaining what's happening without making direct reference to numbers. The object is performing the calculation above on each individual plane/cell of a movie; remember that the type of data that the calculation is being performed on is arbitrary - I could be sending it 1-plane matrices (or lists, to put it another non-Jittery way), You'll notice that the help file tells you that the object supports all data types and planecounts. That's what that means.