Elevate your production value with a archetype VFX technique.
Ah, rotoscoping. Scourge of the would-be VFX artist. Time-honored booster of product value.
Put only, "rotoscoping" refers to the process of separating foreground elements from the groundwork of a shot by drawing a series of mattes, frame past frame. While notoriously tedious, the technique can add visual interest to your project. Breaking a shot into individual layers allows you lot both to animate their backdrop separately and add together additional assets betwixt them, providing nearly unlimited creative applications.
Rotoscoping is elementary in theory, but difficult in practice. Due to the frame-past-frame nature of the procedure, it'south like shooting fish in a barrel to finish up with "chattering" mattes whose jiggly edges destroy the effect. And then how do you achieve consistency?
Whether you lot're an animator, motility graphic designer, VFX artist, or videographer, you lot'll probably need to rotoscope at least one shot in your career. In this post, nosotros've gathered the resource you lot'll need to get started with three of the almost popular rotoscoping methods in Adobe After Effects: masks, the Rotobrush, and Mocha.
Earlier we dive into the details, let's offset with some guiding principles from VFX artist Scott Stewart (Iron Human, Pirates of the Caribbean, and many more than):
'Pirates of the Caribbean: The Expletive of the Blackness Pearl' (2003)
Start with keyframes
If you're like me, y'all might be tempted to outset your roto efforts by drawing a matte on the first frame of your shot and so continuing chronologically. Stop that! There'southward a better way.
Rotoscoping is technically a form of animation, so it's helpful to apply traditional animation principles here. An essential concept in both disciplines is the thought of "keyframes," the frames containing the most dramatic movements or poses. Character animators brainstorm a sequence by cartoon the keyframes and then going dorsum to polish out the motion with "in-betweens."
Similarly, roto artists draw their first mattes around the keyframes—simply the beauty of After Effects is that it generates the initial in-betweens automatically! Of course, they'll need adjustment. Once you've drawn your keyframe mattes, manually refine the in-between at the centre of each interval, and then repeat the process until y'all have a result you're satisfied with.
Why is this method amend than starting from the commencement? Stewart says information technology best:
"Consistency! Your mattes will adhere to the motion of the chemical element they were created for in a much more naturalistic and consequent way. In addition, considering of the computer'southward power to automatically interpolate between keyframes, information technology's less work for you. And that'south ever a good thing!"
'Avatar' (2009)Credit: movies.effects
Use as few points every bit possible...
Every second of footage contains at least 24 mattes, and the more points you have on those mattes, the more probable information technology is that their edges will move inconsistently. This is what causes matte chatter, the jiggly edges that make your matte look similar garbage. To minimize this chatter, go back to your keyframes. Generally, keyframes contain the about complicated shapes, which means they also demand the most matte points. Once yous've settled on a number of points, try to move those points in groups to preserve the matte's shape.
...but use a LOT of shapes
Recollect art class in elementary school? You probably learned to draw the human effigy by drawing a bunch of circles, ovals, and rectangles—the bones shapes which make up the course.
The same concept applies to rotoscoping: since the shape of a shin or forearm doesn't change much, by combining a agglomeration of unproblematic shapes in your matte, you can roto complex movements without having to move a bunch of individual points around.
Here'southward an example from Ruddy Giant's Stu Maschwitz:
Rotoscoping: • Isn't the enemy. • Use lots of shapes, with every bit few points as possible • Never use bezier curves with handles • When possible, motility points in groups instead of ane at a time • Preview on a solid color similar to BG • Know when bad roto (like this) is skilful plenty pic.twitter.com/F0YYw7yi97
— Stu Maschwitz (@5tu) Baronial 27, 2018
With those foundational principles in mind, let's open up Afterwards Effects and commencement rotoscoping!
Method 1: Masks
Masks are the oldest (and possibly most time-consuming) manner to rotoscope in Subsequently Effects. They require a meticulous frame-by-frame arroyo, merely if you value control over speed, this could exist the method for you. For a quick introduction, check out this video from Robbie Janney at Shutterstock:
It'southward worth mentioning ane point that isn't covered in the tutorial: while it's definitely possible to use bezier curves with handles in this method, many roto artists advise against it. Returning to Stu Maschwitz's twitter (a gold mine, past the mode):
"Bezier curves are great for static shapes simply terrible to breathing. Non only do they tween weirdly, but (manner more importantly), they are boring to manipulate."
Adobe'southward alternative to bezier handles is a tool called the Rotobezier, which automatically generates curves based on point placement. I personally haven't used the Rotobezier that much, so I'm not sure how much it reduces churr. It seems like the interpolation benefits you'd get could exist nullified if you have to add a lot more than points, but that's just speculation on my part. For details on how to toggle betwixt bezier curves and the Rotobezier, check out this tutorial from Sergei Prokhnevskiy:
Method two: Rotobrush
If yous're looking for a faster roto solution, you might desire to try the Rotobrush, which functions a bit similar the magic wand tool in Photoshop. The Rotobrush uses AI to automatically detect the edges of a selection. From there, you tin use boosted brushes to add together, subtract, and refine edges. This xx minute tutorial from Teddy Gage does a groovy job explaining how the Rotobrush works and how to customize the parameters guiding its algorithm.
Here are a few quick highlights:
The more than contrast in your paradigm, the meliorate your selection will exist. Make sure the Rotobrush is reading your color adjustments by placing information technology at the bottom of the effects stack.
Customize the Rotobrush propagation settings. If your selection keeps jumping around, you might demand to ditch the default settings. Start with the search radius, motion threshold, and motion damping.
Use as few brush strokes every bit possible. Every brush stroke yous make sends information to the selection algorithm, and then if you sideslip, don't try to correct it with any brush strokes. Merely undo.
Method 3: Mocha
You might be familiar with Mocha as a tool for planar tracking and screen replacement, just it's also great for rotoscoping. The plug-in has been bundled with After Effects since CS4 came out, and it uses splines for selections. These take several advantages over the bezier handles in Later Effects masks; mayhap well-nigh notably, they allow you to change the number of points in your selection without dramatically affecting its shape. (Love!) This tutorial from Mocha's YouTube channel covers the basics:
Tech is constantly irresolute, so whichever tool you choose, exist sure to keep Stewart'due south core principles in mind: start with keyframes, use as few points every bit possible, and utilize a lot of shapes. May your mattes be consistent and may their edges never chatter. Go forth and rotoscope!
Have any cadre roto principles of your ain? Call back I butchered my explanation of splines in Mocha? (I probably did.) Let us know in the comments!
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