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Mocha AE Tracking Issue

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Ben Sullivan
Mocha AE Tracking Issue
on Oct 31, 2018 at 12:20:25 pm

Hi all,

Any help would be much appreciated in regards to the issue I am having.

I am working on a project in After Effects and attempting to use Mocha AE. The general idea of the shot is the camera goes out of the back of a subject (so emerging from black) then following him as he sits down at a pc that has a green screen on it and then moving into the green screen which will eventually be the next shot and room. Essentially creating a seamless movement from room to inside the room on the pc screen.

If i start the tracker when the green screen is fully in view I have no problems (other than awful quality ones keylight has been added but thats another issue). Its as soon as I track backwards and my subject begins to take over the frame it throws the mask off completely. Everything I have tried, even going back frame by frame doesn't seem to be changing much.

Anyone have any tips on how to stick my tracking mask even once my subject has taken over the mask or is it simply not possible using Mocha?

Kind regards,
Ben.


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Cassius Marques
Re: Mocha AE Tracking Issue
on Oct 31, 2018 at 4:44:18 pm

Are you masking the subject and subtracting it from the track?

Cassius Marques
http://www.zapfilmes.com


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Ross Shain
Re: Mocha AE Tracking Issue
on Oct 31, 2018 at 8:17:51 pm

If your foreground subject gets in the way of the Mocha track, then you need to add a 2nd layer and mask out the foreground subject. This layer does not need to be tracked, but does need to go above the track layer (in stack order).

Another technique is to find other objects that move on the same relative plane as your monitor, go to the frame just before the foreground subject messes things up and move your search area away to focus on areas that are trackable. This is called offset tracking and is used to solve very difficult occlusions.

This is a good tutorial to watch to learn some techniques:





Ross Shain
Boris FX / Imagineer Systems
https://borisfx.com/products/mocha/


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Ben Sullivan
Re: Mocha AE Tracking Issue
on Nov 1, 2018 at 11:06:41 am

Thank you so much for the response.

I am however still having major issues. The shot itself starts off black, the subject moves away from the front of the camera and reveals the green screen. The green screen itself is fine once he is out of the way but tracking backwards to him completely consuming the screen throws everything off still. I have done what that video suggests by highlighting my actor and then tracking backwards but he still throws it off.

Any help?

Kind regards,
Ben.

"You write to communicate to the hearts and minds of others what's burning inside you, and we edit to let the fire show through the smoke." - Arthur Plotnik


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Ben Sullivan
Re: Mocha AE Tracking Issue
on Nov 1, 2018 at 11:49:53 am





This is how the shot starts and the shot of my subject sat down...

Tracking is fine from the moment he is sat down however working from this moment and going back is when he throws off the tracker.





Any help would be greatly appreciated.

Kind regards,
Ben.

"You write to communicate to the hearts and minds of others what's burning inside you, and we edit to let the fire show through the smoke." - Arthur Plotnik


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Ross Shain
Re: Mocha AE Tracking Issue
on Nov 1, 2018 at 3:57:48 pm

When the guy in the leather jacket is beginning to cover the monitor, you can stop the tracker and move your screen track layer to the edges of the monitor to the left. The other monitor is on the same relative plan and the idea is Mocha's shape based search area gives you a very fluid way to solve offset tracking.

See the attached image, I have shown you some other potential areas to track when he gets int the way.



When he occludes the entire image, there is nothing you can do other than manually keyframe.

Lastly, AdjustTrack module in Mocha is an advanced technique to fix tracks that are close but drift.

If you really want to learn more, check out free Mocha Fundamentals series:
https://borisfx.com/videos/?tags=category:Mocha%20Fundamentals&search=

Ross Shain
Boris FX / Imagineer Systems
https://borisfx.com/products/mocha/


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