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Hiding Stuff Behind Things

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Diana Jordan
Hiding Stuff Behind Things
on Nov 1, 2015 at 4:07:24 am

Hello, I'm new to the forum and new to After Effects. I'm working in AE CC and Mocha AE. My question is this: How do you hide objects behind other objects?

I'm motion tracking billboards and copying the data to pre-comped layers of animations I made. I want those animations to stick in place of the billboards.

My problem is that there are objects in front of some billboards, like signs and a waving flag. How do I make it look so that my animation is placed behind said objects?

On my first attempt, I motion tracked a billboard in Mocha AE, copied the data, and pasted it onto a pre-comp of my animation. Now the animation is in place.

Then in After Effects, I created a new solid and hit 'ctrl+shift+n' to make a mask the same shape as the solid. I returned to Mocha and copied the data of one other billboard I tracked. Let's call it 'front board' because this billboard happens to be in front of the billboard with the animation.

Back in AE, I pasted that front board data onto the solid so that it's mask would take the front board's shape and motion. Finally, I clicked on the animation pre-comp and applied an alpha inverted track matte.

It worked. My animation is behind the front board, except I'm not done. There's one other sign in front of it. Repeating the steps above with a new solid and mask doesn't work nor does creating a mask within that same solid. What should I do in that case?

Thanks in advance.

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Kalle Kannisto
Re: Hiding Stuff Behind Things
on Nov 1, 2015 at 6:40:09 pm

If the foreground objects are relative simple objects, you can duplicate the layer, mask off all the elements you want to go in front and animate the masks. (If the camera is moving, you may want to combine this with tracking the motion, but that is a more involved matter I won't be able to cover in a few words.)

With more complex objects the masking can be done with the roto brush tool.

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Ross Shain
Re: Hiding Stuff Behind Things
on Nov 5, 2015 at 11:43:00 pm

If you are already using mocha AE for the tracking, you may as well use mocha for the masking instead of applying the tracked data to a solid.

You can create a mask shape layer in mocha AE, link it to a track (or simply edit the tracked shape to be a tight mask) and then in mocha AE choose, export shape.

Select mocha shape data format and paste back in AE.

This might be a useful video to help:

Ross Shain
Imagineer Systems

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