Trail effect


    Apr 22 2006 | 12:03 am
    Sorry for this bombardment of [probably stupid] questions this week, I'm
    still getting to grips with all the jitter objects and the differences from
    GEM that I used to use in PD.
    What would be people's recommended methods to achieve the following be:
    I'm trying to process live footage from a webcam (that is being keyed over
    another video). I've already got it so that the background is removed
    leaving only people in front of the camera. I now want to create an effect
    where when people move around in front of the camera it leaves a trail of
    images (say 500ms cam grabs) following them from where they were standing
    before, that then take a set period of time to fade away. But the longer
    they stand in one place, after they move the longer it takes for the images
    to fade away.
    I hope that is clear. It's difficult keeping that concise when there is such
    a vivid image in my head of how this should look!
    Any tips from you pros?! ;)
    Thanks...again,
    Jonathan

    • Apr 22 2006 | 5:37 pm
      jit.slide will do.
    • Apr 22 2006 | 10:28 pm
    • Apr 22 2006 | 10:50 pm
      Try making you own feedback system with different delays to get more
      of the effect you're looking for. Here's an example using 3D buffers:
      wes
    • Apr 22 2006 | 11:19 pm
      wesley's suggestions are super, but if you want to stick to jit.slide you
      should convert matrix going into jit.slide to float32 type for better
      accuracy/longer trail effects.
      also, you could go to www.maxobjects.com and search for cv.jit.mean object
      cheers,
      nesa
    • Apr 23 2006 | 1:41 pm
      I'm I right in thinking that I should make this conversion by adapting the
      incoming matrix object as so: [jit.matrix 4 char float32 320 240] ? Because
      this is causing the final image to end us as big lines moving up and down
      the window!
      Cheers
      Jonathan
      P.S. Is there an overall intro guide to Jitter I can read somewhere so I
      don't have to keep asking you guys these annoying questions?
    • Apr 23 2006 | 4:01 pm
      On Apr 22, 2006, at 4:19 PM, nesa wrote:
      > wesley's suggestions are super, but if you want to stick to
      > jit.slide you should convert matrix going into jit.slide to float32
      > type for better accuracy/longer trail effects.
      You can also get longer trails without converting to float by using
      jit.wake (which keeps a high resolution feedback buffer).
      -Joshua
    • Apr 23 2006 | 5:58 pm
      almost, you should use float32 instead of char:
      jit.matrix 4 float32 320 240
      checkout jit.matrix help file.
      but, joshua gave you another idea in another post. i knew there was
      something, but couldn't remember: my mind just kept gloping, gloping,
      gloping instead of waking...
      best,
      nesa
    • Apr 23 2006 | 7:34 pm
      Got there just before you had to save me Nesa!
      Thanks everybody for the help on this, converting to float32 has done
      exactly what I wanted, the feedback can now remain on screen for upwards of
      10mins as I wanted.
      Jonathan
    • Apr 23 2006 | 8:46 pm
      ok, but please try joshua's suggestion, jit.wake, maybe you'll find use of
      its other functions.
      best,
      nesa
    • Apr 23 2006 | 9:37 pm
      I did try jit.wake, and I liked the effects it produced, especially the soft
      saturated look. But I couldn't produce the longer time effects with it that
      I needed. But it's still another object I know for the future!
    • Apr 26 2006 | 11:00 pm
      I actually LOVE the jit.wake object. It looks so pretty...
    • May 30 2006 | 12:23 am
      > P.S. Is there an overall intro guide to Jitter I can read somewhere so I
      > don't have to keep asking you guys these annoying questions?
      >
      Yup, the Jitter tutorials in the documentation
      (http://www.cycling74.com/downloads/jitter). Browsing through
      examples/jitter-examples/ can also give you a good idea what Jitter is
      capable of.
      best,
      dan
      --
      ***
      http://danwinckler.com
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