After Effects Rotoscoping a person

If Rotobrush does not immediately find a decent edge then it's too much trouble to deal with. Manual roto can be fairly easy if the motion does not take a lot of jerky back and forth motion. The key to good roto is to use multiple masks. Start with the simplest one. In that shot it would probably be just the torso of your actor. I find Rotoberzier curves easier to work with when you are masking by hand. Draw a mask around the torso on the first frame, set a keyframe, move forward in time until the direction of movement on any of the edges of the torso changes direction, and edit the mask points. Then you repeat. When the torso is complete try just the upper left arm or the head. Then repeat for the other body parts. After each section is complete lock the masks. If you need to, feather the masks or use the feather tool as needed. 

Often it is easier if you motion stabilize the footage before you start masking, and it is almost always a good idea to put a solid layer above the footage and set the blend mode to something you can easily see through so you can make the necessary adjustments in the matte. When the entire matte is complete you just use it as a track matte for the footage layer and this will remove the background.

Here is a screenshot of the procedure I am using to isolate a tattoo from an actors neck so it can be removed. I have 2 masks, one that includes the entire tattoo plus a little for feathering, and another that includes just gets me the shadow. I will link these rotoscoped masks to other layers to complete the composite. 

The footage of the guy with the tattoo has been conner pin stabilized and scaled up to make it easier to do the roto. Trying to do this roto job without motion stabilizing the shot and enlarging it would have takes four or five times longer than it did.

Here's a simple video tutorial that I did a long time ago that explains the use of a layer with a blend mode and shows the use of multiple masks. Depending on the subject and the task involved Roto can be extremely time-consuming.

The shot I'm working on in the screenshot has a lot of keyframes because there is an awfully lot of movement by the actor and the shadows change almost every frame. It took me about an hour to do the first pass at the roto and another 3 hours to fine-tune and adjust most of the keyframes for both path and feathering to get this shot to work and it's only 120 frames long. 

It is always easier separate elements in a scene if you do a little planning before you shoot If you shot your spiderman on a concrete driveway with no shadows on the background a very simple garbage matte and maybe the Extract plug-in might be all that is necessary to generate a really good matte.

If you really want to master the art of manual rotoscoping check out this great tutorial by VFX master and friend Scott Squires: Effects Corner: Rotoscoping - Part 1. Be sure to check out the entire series. Scott isn't using After Effects but the technique is exactly the same. Simplify as much as you can and don't try and do everything with one mask.

First, let's clear something up: "Rotoscoping" is a generic term for each and any technique used to separate and isolate items in footage. It's not in any way only referring to the Rotobrush, which more or less is an unfortunate misnomer, anyway, considering how crude and useless it can be a lot of times. That said, yes, your "rotoscoping" technique will involve masking of sorts, whether that be fully manual, assisted with mask tracking or using external tools like mocha. Having grass in an image constitutes having noise and in addition to possibly there also being compression artifacts this is one of those scenarios that can easily make Rotobrush go belly up. Unfavorable lighting with equally dark background shadows blending into your subject doesn't help, eitehr. So yes, study up on how to do it manually and muster up the patience for such a potentially tedious job, though 6 seconds is really not that much and trying to fiddle with Rotobrush may have already cost you more time than just doing it with masks right from the outset.

Mylenium