Growing shadowesque thing
 

Do any of you guys know how to replicate this effect? It's hard to explain what it is, you have to watch this video to see what I'm talking about.

http://www.youtube.com/watch?v=iUtMSfY8nEQ
At 2:56 it shows up.

http://youtube.com/watch?v=Cusr0QdTpkY
Same concept in this video also.

I need to replicate it for a physics music video. Any replies will help, even if you're going to say it's really hard to replicate.

A physics music video? Sounds like a rockin' party! =D

I can see how it can be done with AE, but it would be time consuming, at least the way I would probably go about it. Take a frame, and create a color solid layer with an alpha mask of the subject, with a stroke as you see fit, at that frame. Animate it to grow over the next, say 6 frames and then vanish or whatever.

Take that layer you've created, duplicate it, move it forward a few frames, edit the mask to reflect the changes in the subject's position, and repeat. A lot. :)

The main work is just creating a mask of the person at that frame. There are probably other ways to go about this, such as a half framerate copy of the video, overlaid behind the greenscreened subject, set to colorize randomly over time, with some sort of posterize time effect?

It can be done, lots of different ways, but it may take some effort! Then again, someone else I'm sure has an easier way to go about it. :)

Carl

I'd love to know an easier way, as well. That's really all I could think of, too.

are you just referring to those trails in the finger snapping video? I think motion has some presets for that, but NOT all colorful. You may want to green screen your performer and copy the layer several times. if there is a slight delay for each layer (drag the layers consistently out of sync) the motion will trail.
Then play with the colors of each layer. Make a background layer of flashing colors. It won't be the same but you will come up with cool stuff through experimenting.

I think I may have a partial answer for you...

If you're trying to apply that effect to a person, you'll have to shoot them in front of a green screen. Once you key them out in AE, apply the Radio Waves effect to that layer. Be sure to select "image contours" as your wave type. Then, you can animate your producer point and things like their frequency and expansion rates. Unfortunately, I can't think of a way off the top of my head on how you'd fill up each shape with it's own color. But I think this can at least get you part of the way there!

Good Luck!