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Tracking objects that move off screen in Mocha

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James Williamson
Tracking objects that move off screen in Mocha
on Jul 20, 2013 at 12:13:11 pm

Hey guys. I'm trying to use Mocha to track a few objects on my film, though, when one moves out of the area it stops tracking all the footage, giving me the "One or more selections were not tracked properly" window. Is there any way I can Keyframe the splines and tracked areas to turn off when they leave the screen? I can see on Mocha you can Keyframe, but I'm not sure how to use it, or even if I can use it in the way I want.

I've attached the video I'm using so you can see what I'm trying to do. I'm tracking the black vents on the floor in the grassy area.


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Erik Waluska
Re: Tracking objects that move off screen in Mocha
on Jul 20, 2013 at 6:58:15 pm

The link you tried to post didn't seem to work but I just googled the title of your post and there's quite a bit of info and tutorials out there about this. Here are a couple that may help:

How to track an object that goes off screen

Erik Waluska

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Martin Brennand
Re: Tracking objects that move off screen in Mocha
on Jul 26, 2013 at 6:02:00 am

The youtube clip does not seem to appear, but you can track like this in mocha by simply adding a new spline to the layer, so before the object you are tracking goes off screen, you can stop the track and draw another shape around another area on the same plane and then continue.

Alternatively if you have a long track where the plane is fairly consistent, you can actually unlink the shape entirely from the track:
1. Draw your shape
2. On the left-hand panel click the drop down that says "Link to Track"
3. Choose "None"
4. Turn on the surface (The blue square icon) or turn on the grid
5. Begin tracking

What you will see is the shape will not move, but the surface/grid will start moving along. This is because the shape is no longer linked to the track and information is passing under the shape, providing the tracker with new information every frame.

This doesn't always work, as you need to keep an eye on obstructions, but you can also stop the track and move the shape around then keep tracking. The shape does not control the track, so moving it will not move the tracking, it just gives it the search area to look for information.

Martin Brennand | Product Manager | mocha - Imagineer Systems

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