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Trouble with masking in After Effects

New Here ,
Apr 13, 2020

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Hey, I’m making a stop-motion which requires me to mask-out the rigs, as well as, certain additional elements of the background—such as the line between the green-screen and the foreground created the two different clothes I’m using for each. So, far I’ve been masking, but I only know how to move the mask and create each different vertex manually for each frame. As one would guess this takes a significant portion of time and my project is due this Friday, my question to you would be if there’s so for masking tracking effect or add on I can use to speed the process?

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Trouble with masking in After Effects

New Here ,
Apr 13, 2020

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Hey, I’m making a stop-motion which requires me to mask-out the rigs, as well as, certain additional elements of the background—such as the line between the green-screen and the foreground created the two different clothes I’m using for each. So, far I’ve been masking, but I only know how to move the mask and create each different vertex manually for each frame. As one would guess this takes a significant portion of time and my project is due this Friday, my question to you would be if there’s so for masking tracking effect or add on I can use to speed the process?

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Apr 13, 2020 0
Adobe Community Professional ,
Apr 13, 2020

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The process you are using is called Rotoscope. It's nearly impossible to adjust a vertex for every frame and have the results be smooth. The trick is to set a keyframe on the first frame of a layer, then move forward until the motion changes direction and adjust the mask. You repeat the process all the way down the timeline until every change in direction has a keyframe. 

 

Now you go back to the start and move the CTI (current time indicator) about halfway between the first two keyframes and make any additional adjustments, then split the time difference on either side and check to see if the mask needs adjustments. 

 

If you have a moving camera or a subject that is moving a lot then it is often very advisable to motion stabilize the shot so that the main part of the shot you need to mask is not moving at all. You can then add a shape layer or a solid above the shot, name it Track Matte because that is what it is, set the blend mode to something that you can see through, then animate the mask on the top layer. When you have the mask animated it's pretty easy to put the movement back in the footage and add it to the by simply adding a null, tying the Anchor Point of the Motion Stabilized layer to the Position property of the null, then parenting both layers to the null. All of the motion will return to the frame and the Track Matte will follow the object you are trying to mask.

 

You should also not use one mask for complicated shapes. For example, if you wanted to rotoscope a dog you would create one mask for the body, then another for each leg. Here's a rough tutorial that I did a long time ago that shows that basic technique:

I also use Mocha AE to do what I call advanced corner pin stabilizing so that the object I need to mask is as motionless in the frame and enlarged so I can have a lot easier time doing the roto work and the compositing. 

 

I have some new tutorials and an article coming very soon that covers these techniques in detail. I'll post a link when they are published. 

 

The most efficient technique depends entirely on the shot. Sometimes you can even create a procedural matte using color channels or keying plug-ins and just supplement that keying with a couple of simple mattes. 

 

For specific guidance please post a link to your shot or at least a screenshot of one of the frames and a description of the motion you need to roto. That would help us help you.

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New Here ,
Apr 13, 2020

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https://youtu.be/Sq33x8PflXk

The footage isn't of the best quality, because something was wrong with the render settings in Premier when I uploaded it--this is an After Effects File, I'm just using dynamic link--but you should be able to make out at least fairly well. 

Below, are a few example screenshots of my process. As said, I'm just adjusting the masks (vectors and all) frame by frame.

As you can tell it's less roto-scoping, and more getting the mask out of the way of the figures when they're in the way of the undesired elements of the background intended to be covered. So I'm not sure if you're advice can be applicable here.

   

Screen Shot 2020-04-13 at 9.50.32 PM.pngScreen Shot 2020-04-13 at 10.15.40 PM.png

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Adobe Community Professional ,
Apr 13, 2020

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Can you show me some of the original footage before you applied Keylight? The screenshots help but I still don't know exactly what I'm looking at or what you are trying to mask out.

 

I would not do any masking directly on the footage except maybe for a garbage matte for Keylight. I would use a solid above the footage as a track matte. I would also simplify the masks a bunch. It is pretty hard to motion stabilize or track stop motion footage, and you may be stuck with a lot of keyframes, but the way to simplify the process is to figure out how to get the smallest areas that need to be keyframed. I'm not sure what you are revealing with the masks in the bottom screenshot but simplification is the key. Just like me animating the mask on the dog. Trying to use one mask for the whole dog would be a nightmare, but one for the body and one for each of the legs is quite doable. 

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New Here ,
Apr 14, 2020

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https://youtu.be/pOUrcA3kjUo

Sure here you go.

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Apr 14, 2020 0
Adobe Community Professional ,
Apr 14, 2020

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Stop motion is difficult because there are often jumps between frames that trackers can't follow. The procedure that I would use is a combination of masks on a track matte layer working on a zoomed-in portion of your footage. It is pretty easy to create a basic mask that removes most of the garbage using just a few keyframes. Then you can create a simple small mask with as few points as possible and just move those points around. The footage layer should be split so you only work on frames that actually need rotoscoping.

 

The edge of the mask that needs to hide the twisted wires that control your puppets is mostly a straight line so I was able to use a mask with just 4 points and no round corners. To make animating those points even easier I used the Create Nulls from Paths>Points Follow Nulls script that is now available. This attaches a null to each of the simple mask points and allows you to use Ctrl/Cmnd + up or down arrow to jump between layers and then the direction keys to move the nulls and move the masks. 

 

To enlarge the footage and give me a zoomed-in view I applied corner pin and CC Power Pin to the layer. You'll see it in the screenshot. The corners of CC Power Pin are tied to the corresponding corners of Corner Pin, CP is turned off and Unstretch is selected in CC PP. You now have a zoomed-in view of the footage to make it easier to line up the mask points.  This is what that looks like:

Screenshot_2020-04-14 15.37.09_tDaUdp.png

 

With just two masks I was able to create a garbage matte for the first approximately six-second section of the movie that needed roto. There are a couple of parts that still need masks, but they only need to be a few frames long. You can just add them manually and then animate the mask opacity when the masks are not needed. This:

Animate Mask.gif

Becomes this when you use Set Matte to pull a mask from the Track Matte layer after you turn on Corner Pin. I have the layer selected so you can see the difference between the actual masks and the matte created by the layer.

Track Matte.gif

It took me about 18 minutes to get this far. It would take about another 10 to 15 minutes to complete this 6-second segment and move on to the next. This is by far the most efficient workflow I can think of for this kind of roto.  This shot is about 80% complete and ready for applying Keylight. Here's the project file. I used a 720P download of your sample video.

https://www.dropbox.com/s/la2ehsnoyzd1grm/mask%20stop%20motion.aep?dl=0

(note: if your browser adds a .txt extension to the AEP file just delete it)

 

Open up the project and take a look at what I've done. It should help you save some time. After you get the background removed and the wires removed you will have to figure out how you deal with the shadows on the floor. That's another job that is going to take some time.  Let me know when you get to that part and I may have some suggestions.

 

I would strongly suggest that you wrap or paint your wires blue so you can just run a procedural matte on them to remove them in the future. 

 

I hope this helps speed up the process. Using the nulls to animate the mask points saves a bunch of time. Simplifying the masks as much as possible also saves time. Using the Corner Pin / CC Power Pin combination to zoom in on the footage so you can be more accurate with a lot less work also saves time. Using a blend mode to see through the Track Matte solid that is the right color makes it very easy to see the edges when you are adjusting the masks. 

 

If there were more people doing stop motion I might do a tutorial. With regular footage, you can also use AE's motion tracker to pick a point on an edge and let the tracker move the null that moves the path vertex. I do that all the time.

 

Helping you out helped me clear my head on an extremely difficult 216 frame roto and compositing job that has 6 animated masks, clone tool, time remapping, curves and levels adjustments, animated gradients and a bunch of other stuff going on that I have been working on for about 3 days. That's how some roto jobs go, you just have to bite the bullet, set a bunch of keyframes, and put in the time. 

 

 

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