Forums > Jitter

Trail effect

April 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


April 22, 2006 | 5:37 pm

jit.slide will do.


April 22, 2006 | 10:28 pm


April 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:

#P window setfont "Sans Serif" 9.;
#P window linecount 1;
#P newex 179 303 34 196617 % 20;
#P newex 179 282 31 196617 + 20;
#P newex 169 360 76 196617 jit.matrix buff;
#P number 247 252 35 9 0 0 0 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P flonum 128 120 35 9 0. 1. 3 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P message 128 141 48 196617 xfade $1;
#P user jit.pwindow 52 367 82 62 0 1 0 0 1 0;
#P user jit.pwindow 52 283 82 62 0 1 0 0 1 0;
#P user jit.pwindow 52 199 82 62 0 1 0 0 1 0;
#P newex 181 412 41 196617 jit.thin;
#P number 237 225 35 9 0 20 3 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P newex 166 339 27 196617 t b i;
#P newex 189 250 27 196617 – 0;
#P message 207 345 207 196617 srcdimstart 0 0 $1 , srcdimend 319 239 $1;
#P newex 180 385 204 196617 jit.matrix 4 char 320 240 1 @usesrcdim 1;
#N vpatcher 20 74 620 474;
#P window setfont "Sans Serif" 9.;
#P window linecount 1;
#P comment 383 84 55 196617 buffer size;
#B color 1;
#P comment 252 122 30 196617 dims;
#B color 1;
#P comment 393 209 30 196617 sync;
#B color 1;
#P newex 375 187 34 196617 % 20;
#N comlet sync;
#P outlet 375 208 15 0;
#P newex 439 101 27 196617 – 1;
#P message 439 83 20 196617 20;
#P newex 280 59 45 196617 loadbang;
#P newex 317 139 27 196617 – 1;
#P message 317 121 26 196617 240;
#P message 280 121 26 196617 320;
#P newex 280 139 27 196617 – 1;
#P newex 243 164 123 196617 pak dstdimend 319 239 0;
#P newex 135 164 105 196617 pak dstdimstart 0 0 0;
#P newex 104 96 27 196617 t b l;
#N comlet video in;
#P inlet 104 77 15 0;
#P newex 375 166 31 196617 + 20;
#N counter 0 0 20;
#X flags 0 0;
#P newobj 375 121 75 196617 counter 0 0 20;
#P newex 121 189 230 196617 jit.matrix buff 4 char 302 240 20 @usedstdim 1;
#P connect 3 0 4 0;
#P fasten 5 0 0 0 140 185 126 185;
#P fasten 6 0 0 0 248 185 126 185;
#P connect 4 1 0 0;
#P fasten 1 0 5 3 380 160 233 160;
#P connect 11 0 8 0;
#P connect 8 0 7 0;
#P connect 7 0 6 1;
#P fasten 11 0 9 0 285 113 322 113;
#P connect 9 0 10 0;
#P connect 10 0 6 2;
#P fasten 1 0 6 3 380 160 359 160;
#P fasten 4 0 1 0 109 117 380 117;
#P connect 1 0 2 0;
#P connect 2 0 15 0;
#P connect 15 0 14 0;
#P fasten 11 0 12 0 285 79 444 79;
#P connect 12 0 13 0;
#P connect 13 0 1 4;
#P pop;
#P newobj 188 223 36 196617 p buff;
#P newex 188 196 49 196617 jit.xfade;
#P flonum 387 104 35 9 0 0 0 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P message 387 125 42 196617 rate $1;
#P message 251 125 28 196617 read;
#P message 321 125 27 196617 stop;
#P message 287 125 31 196617 start;
#P flonum 230 104 35 9 0.5 0 1 3 0 0 0 221 221 221 222 222 222 0 0 0;
#P toggle 188 104 15 0;
#P newex 188 124 52 196617 metro 30;
#P message 351 125 31 196617 clear;
#P newex 188 151 103 196617 jit.qt.movie 320 240;
#P connect 14 0 25 0;
#P connect 14 0 23 0;
#P connect 16 0 14 1;
#P connect 11 0 14 0;
#P connect 26 0 15 0;
#P connect 25 0 26 0;
#P connect 24 0 12 0;
#P connect 15 0 24 0;
#P connect 21 0 10 0;
#P connect 22 0 21 0;
#P connect 10 0 19 0;
#P connect 10 0 11 0;
#P connect 17 0 20 0;
#P fasten 17 0 10 1 380 426 490 245 352 176;
#P connect 0 0 18 0;
#P connect 0 0 10 0;
#P connect 12 0 17 0;
#P connect 15 1 13 0;
#P connect 13 0 12 0;
#P connect 9 0 8 0;
#P connect 4 0 2 1;
#P fasten 2 0 0 0 193 149 193 149;
#P fasten 1 0 0 0 356 146 193 146;
#P fasten 5 0 0 0 292 146 193 146;
#P fasten 6 0 0 0 326 146 193 146;
#P fasten 7 0 0 0 256 146 193 146;
#P fasten 8 0 0 0 392 146 193 146;
#P connect 3 0 2 0;
#P window clipboard copycount 27;

wes


April 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 http://www.maxobjects.com and search for cv.jit.mean object

cheers,
nesa


April 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?


April 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


April 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


April 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


April 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


April 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!


April 26, 2006 | 11:00 pm

I actually LOVE the jit.wake object. It looks so pretty…



dan
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
http://share.dj

http://gunshowimprov.com


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