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Removing a person from a moving shot

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Rob RhodesRemoving a person from a moving shot
by on May 29, 2010 at 9:34:37 am

Hi all,

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 heard that mocha or something similar can help, but I'm not sure. Anyone know how I can accomplish this?

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Erik WaluskaRe: Removing a person from a moving shot
by on May 29, 2010 at 11:11:22 pm

Check out this tutorial on that very subject. There are some other videos that may be of interest on the right side of the page.


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Viking JonssonRe: Removing a person from a moving shot
by on May 31, 2010 at 6:57:30 pm

I would go with mocha.
But I can think of one other way then mocha to do this I call it "the cheap way".
If I got it right, You should be able to do the following:

Start with:

The footage with no actor. Make a freeze frame.

Continue with:

Track the footage with the actor. Set the tracking to the footage with no actor (the freeze frame)

After that:

Mask the actor (guess You have to animate the mask to get it to look good).

When that is done:

Subtract the mask so You can see the freeze frame.

The goal:

By masking the actor away You should see the freeze frame, the freeze frame should have the same shakes as the footage with the actor.

Then You can:

For example make it look better by pre-compose and duplicate the composition and add some gaussian blur and lower the opacity. Or something.. I'm no pro.

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