Removing a person from a moving shot

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djbobbyrhodes

Well-known member
Hey!

I'm currently working on some very interesting VFX shots. One of them includes a scene where a person spontaneously combusts. In other words, they explode for no apparent reason. This would be relatively easy to do if it were a locked off shot, but it's done handheld. So basically, I've been killing myself trying to track it in AE and trying to find a way to fill in the background after I've removed the actor with some basic rotoscoping..

The shot is like this: actor walks around a bit in the frame. He 'explodes' and then quickly runs out of the frame. Then there is a few seconds of a handheld 'cleanplate' which doesn't do much for me because it's a moving shot. Oh, and bonus points, because I can't cut to a point when the actor is already gone because he throws all of the things he was carrying in an explosive fashion.

I believe mocha or something similar can help, but I'm not sure. Anyone know how I can accomplish this?
 
Difficult to give an accurate answer without seeing the actual scene.

But I would grab a clean plate, then track it over the footage where the guys walks around, you then have something you can use the make a rough junk matte for removing the man.

Hope that makes sense.
 
Lee Wilson said:
Difficult to give an accurate answer without seeing the actual scene.

But I would grab a clean plate, then track it over the footage where the guys walks around, you then have something you can use the make a rough junk matte for removing the man.

Hope that makes sense.
Click to expand...

Hmm. I tried that. But it didn't work out so great. I was left with a hole where the actor was that was filled with a slightly miss matched bg. I suppose I could go frame by frame and adjust the perspective, zoom, etc. I'll try to throw the clip on youtube so you can see what I'm working with.

The only reason I mentioned mocha or maybe it was mokey is because I remember seeing a video where they removed some stuff from a scene automatically. It wasn't perfect, but it seemed easier to fix that up than trying to do it by hand.
 
So you basiclly want to remove his running from the scene and overlay an exploded version of him when he tosses the books? Or is his running supposed to be there?

There are a bunch of ways to remove him with mocha and AE, but I'd just try and cut his running entirely and mask the cut with the explosion/blur/shockwave. You have plenty of footage of the books by themselves. Just chop the running part completely. For the actual explosion you might have to photoshop a bunch of frames to hide his body/etc. You might also have to add in the burnt husk of his body to the "clean" plate at the end. Maybe mask him out when he's standing still and acting like he's exploding and use that short clip as the source frames for the explosion effect (overlaid on the books by themselves). Add some fire/explosion/photoshop work to that. I doubt you really need those frames where he runs off at all.

Mocha certainly can help with some of the tracking and stablization issues that make it hard to paint/photoshop out things. Here's a good example of using mocha to do rig removal.

http://library.creativecow.net/articles/larsen_carl/simple25d_rig_removal/video-tutorial.php

There are lots of other tutorials though. I really enjoyed the roto class at fxphd but I don't think they are re-offering it this term (and it's kind of expensive) it covers a vast number of ways you can use AE to remove things from shots.
 
djbobbyrhodes said:
http://www.youtube.com/v/LpuBfl4A1qo&hl=en_US&fs=1

Here's the shot I'm talking about. Maybe seeing the shot will inspire a bit of genius.
Click to expand...

Based on that, it seems like just a matter of messing with tracking. The camera doesn't move too much and you should have a decent clean plate to work with. It's probably just gonna take some trial and error. Maybe work with a tracker other than the standard AE 2d tracker.
 
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