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Linking a mask path to motion tracking data

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Joe Walker
Linking a mask path to motion tracking data
on Oct 6, 2008 at 2:13:34 pm

Hey all,

I have a mask path that I need to be directly linked to some motion tracking data, so how would I go about setting up an expression for this? I went ahead and tracked the shot and had the motion tracking data fed to a null object, so how do I go about having the mask of another object link up to that data? Holler back.


Joe Walker


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Edu Iglesias
Re: Linking a mask path to motion tracking data
on Oct 6, 2008 at 3:38:26 pm

so you want a mask shape to follow a null object which is receiving tracking data, don't you? if you just want to move the mask it can be done without expressions.

put the mask into a solid and parent that solid to the null with the tracking data. use the solid as an alpha matte over the layer and that's it. but only if you just want to move the mask...


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Pat Rich
Re: Linking a mask path to motion tracking data
on Aug 13, 2009 at 10:30:30 pm

I dont get this solution. I have the null object with tracking data, but i need to parent that data to a mask path...not the layer path. I dont get what is being sugested.


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Keith Neuendorff
Re: Linking a mask path to motion tracking data
on Jan 4, 2011 at 7:32:40 pm

The approach given by Edu does work. To give a bit more detail, I had an existing mask from one frame in the clip that I wanted to apply the mask to but the motion in the clip required that I adjust the mask to match the motion.

I created a new NULL object. I then went back to my main clip and tracked the corner of an object and then applied the tracking data to the NULL object.

I next created a black SOLID and then copied the original mask to that solid and made it SUBTRACTIVE. I then made the NULL the parent of the solid. I mute the solid because we don't need to see it (we will just use it as a matte). I moved the mask on the solid to overlay the correct point on the original clip that was tracked. At this point I can scrub through the composition and see that the mask is following the original clip correctly. Please note that you should make the dimensions of the solid larger than the composition so that the solid can be used as a matte that won't move too far over and expose a part that should be masked.

I moved the solid to be in the track list above the original clip. I changed the matte in the original clip to be an alpha matte using the solid. The lower layers now show through on the masked section.


Keith Neuendorff
Tiny Robot Media
Austin, TX


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Brian Cheng
Re: Linking a mask path to motion tracking data
on May 22, 2014 at 3:15:09 am

Your method does not work if the footage is moving.

Movie Director
Stop Motion Animator (Canon 100D, 24FPS)
Palie Studios


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Luca Dosi
Re: Linking a mask path to motion tracking data
on Feb 27, 2017 at 8:34:26 am

Thank you: this solved my problem. AE CC includes mask tracking but using CS6 I didn't have that feature. And, @Brian Cheng, it works perfectly with moving footage: it actually is for moving footage.


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