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Roto Brush 2.0 takes very long to freeze (several hours for 23 second clip)

Community Beginner ,
May 26, 2021 May 26, 2021

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I'm new to After Effects so I'm just as new to the Roto Brush but my friend who uses Roto and the tutorials I've seen don't take nearly as long to freeze. It starts off quickly but then slows down usually at the 5% to 10% mark then it's very slow. I think the longest it's taken to freeze the roto was approximately 6 hours for a 23-second clip! I let it go the whole time because I wanted to see how long it would really take. I'm not doing anything very complicated either. I've noticed that it takes longer to propagate than what most have described and what I've seen in tutorials. Here are the specs I'm working with:

MacBook Pro (13-inch, M1, 2020)
8 GB Ram
Mac OS: Big Sur 11.2.3
After Effects CC: 18.2.0 (Build 37)
67% used of 8 GB
aep File size: 46 MB
Duration: 23 seconds

 

1.png2.png


Any help would be so grateful.
Thanks!

TOPICS
Error or problem, Freeze or hang, How to

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correct answers 2 Correct answers

Adobe Community Professional , May 27, 2021 May 27, 2021
Honest answer: Your footage looks less than ideal for Rotobrush. Not enough contrast, many large, uniform areas that due to the underexposed nature of the shot will look even more uniform. Rotobrush thrives on detecting moving details and when there are none, it simply struggles. Chances are that in your case it probably runs infinite loops to figure out what's simply noise (from the low-light shot) vs. actual details. You probably could have spent that time you waited just as well with some maj...

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Adobe Community Professional , May 27, 2021 May 27, 2021
If I was working with that shot the first thing I would do is put that layer in a new comp just for roto. I would then add some serious color correction to separate the edges. You are not going for the final color grade, you are trying to fix the edges so Rotobrush will have something to work with. I would then draw a garbage matte around the actor. I would then draw a second mask, set to subtract, around anything that does not move in the shot. I'm assuming that his legs stay put, but even if t...

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Adobe Community Professional ,
May 27, 2021 May 27, 2021

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Honest answer: Your footage looks less than ideal for Rotobrush. Not enough contrast, many large, uniform areas that due to the underexposed nature of the shot will look even more uniform. Rotobrush thrives on detecting moving details and when there are none, it simply struggles. Chances are that in your case it probably runs infinite loops to figure out what's simply noise (from the low-light shot) vs. actual details. You probably could have spent that time you waited just as well with some majnual masking and mask tracking and got a better result out of it. Again, this simply seems like an unsuitable shot for RB and other techniques would work better.

 

Mylenium

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Community Beginner ,
May 27, 2021 May 27, 2021

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I'm such a noob at video, I never consider that, in fact, I didn't even know what the roto brush was before recording. I decided to do a reshoot of the last remaining layer that needed work and it made a huge difference. Thank you for your input! 😊 

 

Screen Shot 2021-05-27 at 12.37.15 PM.png

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Adobe Community Professional ,
May 27, 2021 May 27, 2021

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If I was working with that shot the first thing I would do is put that layer in a new comp just for roto. I would then add some serious color correction to separate the edges. You are not going for the final color grade, you are trying to fix the edges so Rotobrush will have something to work with. I would then draw a garbage matte around the actor. I would then draw a second mask, set to subtract, around anything that does not move in the shot. I'm assuming that his legs stay put, but even if they did move just a bit, I'd keyframe the roto. Then I would put a white solid below the layer. The comp would look like this:

Prep for Rotobrush.png

Then I would pre-compose the shot and the white layer and run Rotobrush on the remaining image. You'll have better edges to work with, it will take less time to calculate, and you'll get a much better result. Trying to run Rotobrush on that shot is going to require that you babysit it all the time because the edges are so poorly defined. The only way to fix that is with some drastic color correctioin.

 

Then I would render that comp and use the Composition/Pre render menu and use that rendered shot as a track matte for the original footage. 

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Community Beginner ,
May 27, 2021 May 27, 2021

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That is solid advice! I really appreciate your input. I'm a big-time noob at video editing. I reshoot the last layer that I needed and it made a world of difference but I'm going to need to put it on its own comp as you said and do the rest as you can see in the second image the reshoot wasn't perfect but a lot better. 😂 

Thank you so much, Rick! 

 

Screen Shot 2021-05-27 at 12.37.15 PM.pngScreen Shot 2021-05-27 at 12.40.01 PM.png

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Adobe Community Professional ,
May 27, 2021 May 27, 2021

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If your actor was a bit farther away from the background and it was darker or lighter you would not need to use Rotobrush at all. Extract, or just adjusting the color channels may be enough to create a good matte. Roto of any kind should be your last option, not your first. 

 

I'm just about to release a tutorial series about compositing and it will give you solid and efficient workflows for all kinds of compositing tasks including this one. I'm shooting all of the footage for the tutorials on my iPhone and doing all of the AE work without any 3rd party plugins so no one will be able to use the "I don't have a good camera so I can't get good results," excuse.

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New Here ,
Jun 29, 2021 Jun 29, 2021

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Hi sir. Im very intrigued by what U say about those tutorials, can You estimate when it will be done and how to search for them please?

 

Sincerely

Alex

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Community Beginner ,
Sep 17, 2021 Sep 17, 2021

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This is GOAT advice.

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