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Mocha Tips: Create Roto Masks With Less Keyframes

April 26, 2018

Learn how to create roto masks in record time with Mocha Pro for simple effects isolation and effects compositing.

Watch this quick tutorial to learn:

  • How to visualize planes
  • Where to split roto
  • How to think like an animator
  • Save keyframes and time

Read along with the video:
Mocha is a vital masking and roto tool that simplifies a lot of the tedious frame by frame animation you’d normally have to use when isolating objects or people in a scene.

Sometimes users will think the best workflow is to draw one large shape and track the entire object, but this is not an effective way to reduce time and you will have to do a lot of manual keyframing.

The key to quick roto inside of mocha is to use planar tracking data to reduce your manual keyframes and save tons of time. If you want to get your shots out the door quickly, you will need to understand: how to visualize planes and separate your layers like a “paper doll or “marionette puppet.

The key is thinking in terms of planar data. Mocha is a texture tracker and it tracks a pattern of pixels moving relative to one another, that is in a single direction, at a time. If you think of your object in terms of low poly models or cubist terms you can see where the planes split.

You need to split the roto based on these planes. For instance, when I track this arm, the forearm and the elbow are a single plane of data, moving together while the elbow to the shoulder is another. If I track those all at once, I might not get a good track at the arm straightens. But by separating the layers, I let mocha do the bulk of the work. Mocha is my roto intern, doing the main tweening animation based on tracking data. After tracking, I will then go through and add inbetweening keyframes to correct the work.

As you edit the shape, you are only correcting the spline points and not effecting the overall tracked motion. So with these 2 layers of animation, mocha allows you to get away with a lot. You save time because you are making less keyframes and your roto moves more correctly because there’s less jittery hand animation as well.

When I am done with my roto work, I can export out the animated shape data to almost any editing or vfx system on the market.

If I am using the Mocha plug-in, I can also view the roto as a matte or cutout with alpha. IN After Effects, we have this nifty “Create AE Masks” button… and if I am accessing Mocha from a Boris Continuum or Sapphire plug-in, we simple close the Mocha instance and have our isolated effect.


Thanks to Pond5 for providing stock footage: pond5.com