Manually editing a mask and locking it?

Report · Apr 12, 2023

Hi, I am trying to use Roto to mask a scene with a number of people, to apply an effect only to them.

I have used the tool on the first frame, and then I proceed to the next frame, and make a lot of corrections (it seems particularly bad at feet and hands and heads....) and after those corrections I move to the next frame, and I make more corrections. It's taking about 4 minutes per frame, and I have 4 seconds of footage.

However, every ten minutes or so, it will start "propagating", and I see on the layer panl that parts of the previously corrected footage goes blue, then green, then blue again, and when I look back, it has changed something on an earlier frame, and then propagated that, which means all my previous corrections have new errors... So far I have been through the entire thing 3 times, and because the corrections take so long (highlight a shoe and the whole floor is added, then alt-click the floor, and the head is also deselected and so on....), what I really want to do is correct a frame and tell AE to never touch the mask on that frame again, however I can only find freeze, which affects all frames.

How can I lock frames I have worked on so they are not changed without me doing anything?

Report · Apr 12, 2023

When you use Rotobrush, you have to start at the first frame and then start to let it propagate. When Rotobrush fouls up, you have to stop the preview and make corrections. When you reach the last frame, you select Freeze, and everything is frozen from the first to the last. If you have done a good job and the footage is suitable for Rotobrush, everything will be frozen, and the roto mask will be complete.

If you do not have footage that is compatible and Rotobrush makes a lot of errors, you must either split the clip up into shorter sections, add some color corrections, or even hand animate masks or use other tricks to get Rotobrush to work properly. It is always a good idea to trim your footage, then pre-compose the trimmed shot moving all attributes to the new comp and trimming the pre-comp to the layer length before you open the Pre-comp (your nested comp) in the Layer Panel and apply Rotobrush. Rotobrush should always be the only effect applied to a layer, and really, The Rotobrushed pre-comp should be the only layer in that comp. You can then nest it in your pre-comp or pre-composed your Rotobrushed nested layer again, moving all attributes. If Rotobrush takes you longer than just a few minutes to complete, you should probably use the Composition Panel to Pre-render the Roto comp. This will give you a visually lossless movie with an alpha channel and replace every instance of the rendered Roto Comp in your project. This is a good idea because Rotobrush is a resource hog, and it can often cause renders to fail if the shot is long and the comp is complex. After you Pre-render a Rotobrush comp, you can safely delete the rendered comp from the project file to reduce the AEP file size and make your project more stable.

I hope this helps.

If you can post a frame or two of the footage you are having problems with, we can probably make some suggestions for color grading or extra masking that will help speed up the process. I almost never Rotobrush a layer that has not been color corrected, masked, and Pre-composed. There is never a need to let Rotobrush's AE look for pixels that you are never going to need to analyze.

I hope this helps.

Report · Apr 13, 2023

When you use Rotobrush, you have to start at the first frame and then start to let it propagate. When Rotobrush fouls up, you have to stop the preview and make corrections. When you reach the last frame, you select Freeze, and everything is frozen from the first to the last. If you have done a good job and the footage is suitable for Rotobrush, everything will be frozen, and the roto mask will be complete.

This is what I am trying to do. However every now and again when I make a correction say on frame 20, it starts the propagation again from frame 0 and introduces new errors in frames I have already corrected!

If you do not have footage that is compatible and Rotobrush makes a lot of errors, you must either split the clip up into shorter sections, add some color corrections, or even hand animate masks or use other tricks to get Rotobrush to work properly. It is always a good idea to trim your footage, then pre-compose the trimmed shot moving all attributes to the new comp and trimming the pre-comp to the layer length before you open the Pre-comp (your nested comp) in the Layer Panel and apply Rotobrush. Rotobrush should always be the only effect applied to a layer, and really, The Rotobrushed pre-comp should be the only layer in that comp. You can then nest it in your pre-comp or pre-composed your Rotobrushed nested layer again, moving all attributes. If Rotobrush takes you longer than just a few minutes to complete, you should probably use the Composition Panel to Pre-render the Roto comp. This will give you a visually lossless movie with an alpha channel and replace every instance of the rendered Roto Comp in your project. This is a good idea because Rotobrush is a resource hog, and it can often cause renders to fail if the shot is long and the comp is complex. After you Pre-render a Rotobrush comp, you can safely delete the rendered comp from the project file to reduce the AEP file size and make your project more stable.

I have to say this is a little beyond my level of expertise, and I understand that's my problem, I am not competent enough with the tool I am trying to use (generally a PP editor with once a year dip into AE comps).

I had thought instead of animating each frame, I would let RB make a guess, and then edit the results, however it looks like that's not possible. I also followed a few "refine edge" tutorials, but mine just makes a huge blur on the edge of where I drag it, so I've given up for the moment, as I don't have time.

I had already pre-composed, as despite having 25 fps footage, and a 25 fps PP timeline, when I do "replace with AE Comp", RB always gives me a frame mismatch... I have to change everything to 50 frames at some point.

You're notes do look like areas that come up frequently, where I need some more training, so I'll definitely come back here and use them as a list of areas to learn when I do have more time, so I really appreciate you taking the time to answer with such detail.

Thanks!

Report · Apr 13, 2023

Let me try to show the problem anyway, as there may be a quick answer to this one.

In the image below, you can see I am on frame 2.28 (I'm on 30fps not 50 as I stated above)

However the green bar shows it's started propagating again from the start, and this actually messes up/reverts a lot of changes (corrections) I've already made.

I started again, this time going one frame at a time from frame 0, I never ever go back a frame, even to have a look. This time I got as far as frame 4.00 before it started propagating from 0 again and undid most of my corrections.

Report · Apr 12, 2023

The simple answer very likely is that your approach is unsuitable and conventional masks might be a better option. Four minutes for every frame on a four second shot? Yikes! I'd bet you'd do it faster using other methods... That doesn't negate the fact that soemthing is wrong with RB, though, though perhaps even that is in some way plausible in your scenario. if the shot is that complicated then clearly it isn't meant for RB and it's not surprising it acts up.

Mylenium

Report · Apr 13, 2023

I would think it's actually more than 4 mins now... I would completely concede that perhaps I am using the wrong approach, and would be happy to use other masks. Although I am not familiar enough with AE. I was hoping RB would draw a rough outine which I could then refine with brush tools and the like, however doesn't look to be the case.

Report · Apr 13, 2023

I stand by what I said already after seeing your screenshots: This is not a job for Rotobrush. the footage appears quite blurry/ soft and with the talents standing so close the tiniest twitch of a knee will produce a wrong motion detection within the radius. This really looks like manually going through it frame by frame with some good old masks would be much more efficient and safer.

Mylenium