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Known Participant
January 24, 2024
Question

Rotobrush

  • January 24, 2024
  • 4 replies
  • 265 views

The rotobrush edge moves when literally NOTHING has changed.  I'm doing some roto of 3d character from a TV show for work, and there's a lot of animating on twos - so there are a lot of frames that are literally identical, yet the rotobrush moves when nothing else does.  Why?  If there's no change from one frame to another why doesn't the rotobrush stay the same?

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4 replies

nishu_kush
Legend
March 28, 2024

Hope the suggestion above helped.

Feel free to reach out. Moving this thread from Bugs to Discussions for now.

 

Thanks,
Nishu

Community Expert
January 26, 2024

Compression artifacts, variable frame rate footage, and noise can foul up a Rotobrush project. I always trim my footage, add some color correction to increase edge detail and contrast if necessary, then pre-compose moving all attributes and trimming the new comp to the layer duration before I run Rotobrush. This even helps with frame rate problems.

 

Give that a try. 

Known Participant
January 25, 2024

A regular mask is 100% unsutiable. I can't go through minutes worth of footage doing frame by frame manual masking just because some of the animation is on twos. And that doesn't even make sense - if the rotobrush tool detects motion, why is it shifting when there is 0 motion?  I don't think it's unreasonable to expect the rotobrush to roto what is actually happening. 

Mylenium
Legend
January 24, 2024

It's the wrong tool and you are working against it. RB works by detecting motion, not static edges. That's a huge misconception most people have and thus of course there are limitations how well it will work with non-smooth footage. That and of course your TV footage would still have differences in the frames e.g. from compression that affect what the tool "sees". Feel free to tweak the settings, but ultimately you may need to use another method like conventional masks to make this perfect.

 

Mylenium