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Tracking/Rotoscoping a Turning Head in Mocha AE
Tracking/Rotoscoping a Turning Head in Mocha AE
by Peter Campbell on Aug 27, 2017 at 8:54:18 pm


I've been using mocha and After Effects for some time now but recently have been trying to study harder and start doing things "the right way" rather than just winging it whenever I need to do something.

Right now, I need to Roto out someone for background replacement. Before, I would have just done a separate track for each body part, and even though there is a section where the actor completely turns his head, I would just change all the spline points to adhere to it. But now I'm wondering if there's a more elegant way to do that, since with planar tracking and such the original track of his face just gets squashed when he turns and doesnt compensate for the side of his head, obviously.

Do I make multiple masks for each side of his head? Do I do it the way I guessed? For all the research I'm doing right now it's pretty hard to find tips on masking out people that are moving and turning a lot.

Appreciate the responses!


Re: Tracking/Rotoscoping a Turning Head in Mocha AE
by Ross Shain on Aug 28, 2017 at 4:35:19 pm

If the actor completely turns their head, there are multiple ways to handle:

You could mask the head on 1 mocha layer, but do not track the "un-trackable" portion where the rotation is close to 90 degrees. For example, you can track right up to this area, stop the tracker and advance to a frame where the head is now trackable, edit your shape to fit and continue tracking. So the major rotation would be manually keyframed.

Another method would be to break up the masking into 2 separate layers, one for each rotation. Different roto artists use different methods, sometimes depending on the length and speed of the shot.

While the AE Face Tracker and Mask Tracker are cool tools, you would run into similar issues when a head fully rotates.
I find the Mocha tools are a lot more "recoverable" when the tracking does not work and you need to resort to manually techniques. This video might be useful for some users that are unsure when to use Mocha and when to use the AE Mask Tracker:

Hope that helps.

Ross Shain
Boris FX / Imagineer Systems

Re: Tracking/Rotoscoping a Turning Head in Mocha AE
by Peter Campbell on Aug 28, 2017 at 5:32:29 pm

Thank you, that's really helpful! Honestly just getting an idea of what other effects artists do in these situations helps a lot because it's not like the whole industry just throws their hands up and goes "ah well, the body outline changed too much to roto this" haha. Yet, it's just weird that there isn't a whole lot of material out there on the subject.

I was experimenting with the shot and ended up trying something close to the first technique you mentioned, where most of it is tracked but then for certain areas it's pretty much manually keyframed. It doesn't look very pretty when looking at the bezier mask because you can see all of the areas like his ears and jaw just morphing into nose and forehead when he turns profile, but the effect looks pretty good.

I'd still love any other ideas if anyone wants to hop on this thread, I have a lot of roto and head tracking to do on this project.

Re: Tracking/Rotoscoping a Turning Head in Mocha AE
by Ross Shain on Aug 28, 2017 at 6:01:32 pm

You can find the Mocha Getting Started videos here:,product:Mocha%20Pro,product:Mocha%20VR&search=

and more videos tagged by ROTO subject:,product:Mocha%20Pro,product:Mocha%20VR&search=

Ross Shain
Boris FX / Imagineer Systems