I am not new to using Mocha but I am running into an issue with a scene where the actors hands move beyond the edge of the green screen. The solution seems simple… roto the fingers. Well, my first two efforts failed. So I am trying to rethink my workflow. I have a 15 second clip that has 3 points in time where the hands briefly move into the background. New things I need to deal with in this clip… tracking hands that move in and out of the bottom of the frame. Only small sections of the clip need work. Previously I have done beauty work with eyes and mouth, so every frame needed to be worked and the the eyes and mouth were visible in every frame. The source is a dynamically linked AE comp to a Premiere project.
Get a track for each hand to drive roto shapes. (hand leave frame at bottom repeatedly)
Build roto shapes for each finger.
Link shapes to hand track.
Keyframe shapes to correct motion not addressed by link to hand track.
Dump animation keys and shapes back into After effects.
roto and track each finger shape at same time, skipping a hand track to drive finger shapes.
The biggest issue is what to do with the roto shapes when the hands are not violating the green screen edge?
Should I track every frame of the clip or just the frames where the hands need roto? There are hand violations every few seconds so I have 3 chunks where I need to do work.
Should I break the scene into 3 different chunks that only include the frames where the hands need roto ? And do each one separately in mocha?
Any advice is appreciated and thanks for your help.
Sounds like you should rotoscope the hands as you are planning. Break up the hand roto into separate shapes. Usually better to do each finger individually if the hand is moving quite a bit. You’ll have to make the judgement call on how much to break up the roto. Once done with rotoscoping just those three segments you need, copy the shape data and then paste into AE. Use Edit/Paste Mocha Mask to paste the shape data and create masks. Then as for what to do with the roto shapes when the hands are not violating the green edge, simply keyframe the opacity of the masks to turn them on off when not needed.
I’d recommend importing the entire clip and then just rotoscoping those frames that need it.
There are a lot of good tutorials on rotoscoping workflow in the video section on the site that might give you a better idea on how to solve your shot.
Thanks Chris. That helps significantly with executing my workflow. I just needed a bit of encouragement, I guess, because I feel more confident about doing it right.
As Chris says, This just sounds like you need to do a mix of hand roto and tracked roto. Track what you can, and yes, I’d split it up into groupings of hand layers divided by the splits in the shot where the hands are offscreen. But track what you can and use that for roto, like using the hand track as the main driver for the fingers. But you will still have a lot of manual keyframes that will need to be made on the fingers. Unfortunately, there’s no one click solution for complex roto. We can only give you less keyframes, not no manual work.
You’re going to have your work cut out for you, it sounds like, on this shot. I’d roto fingers individually or in similarly moving groups.