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How Rotoscoping Works


New Rotoscoping Tools

The existence of ever smaller, cheaper and more powerful computers has brought us into a great new era in filmmaking. CGI (computer-generated imagery) makes it possible to put nearly anything on screen and make it look at least somewhat believable. And despite the existence of other special effects techniques (some of which we'll talk about in the next section), new graphics software has also brought us new ways to rotoscope that are far less time consuming than they were with physical film.

Some of the concepts are the same, but the media and tools are mostly digital (including the film, the paint and the software). Rather than a physical animation cel overlaid onto a glass table displaying projected film, graphics software often allows you to work in virtual layers, where one layer is the digitized film image, and the others contain whatever animation or effects you want to place in each frame. Then rather than photographing the final product, you save or export it as a new digital file.

Graphics software applications let you do many of the same things you could do with physical film media and equipment. You can paint over each frame of a digitized video using a mouse, trackpad or graphics tablet to create a traditional rotoscoped animation, where you can keep the regular film and animation together or remove the film leaving only the animation. Or you can create complex mattes to composite filmed or computer generated objects into each frame.

Mattes can be created on individual frames using selection and paint tools on the software's tool bar. You can outline using splines (lines or curves that can be manipulated by dragging various points) to make it easier to slightly alter the matte on the next image rather than completely redrawing a new one. Some things can even be handled over multiple frames automatically by the software, which might be able to take the information in beginning and ending keyframes and use that to figure out what information needs to be in the frames in between and generate them. A lot of software can track the position of items from frame to frame to know where to place any composited items that have been added to prior frames. The newer software has become increasingly good at recognizing and properly outlining and masking shapes over multiple frames without animators having to trace exact lines around each and every one, which is a giant time saver.

Modern graphics software also allows you to easily change colors, to morph items from one thing into another, to blur and soften edges with a few key strokes, and to clone (or copy) parts of the screen image from one place to another. This latter tool is useful in things like removing cables and stray boom mics, since you can place other parts of the background (a wall or the sky) over them to make it look like they were never there.

Early software tools that could be used for rotoscoping and similar techniques began appearing in the 1990s, including Colorburst, Commotion and Matador. More modern software that can be used for various levels of rotoscoping includes Adobe Flash, Adobe Photoshop, Adobe After Effects, Imagineer Systems' Mocha, Silhouette, Autodesk's Flame and Smoke, Blackmagic's Fusion and Foundry's Nuke, Ocula and Mari, among others. Some of these are expensive and require very powerful and likewise expensive computers and other equipment. But some, like Adobe Flash and After Effects, aren't outside the realm of possibility for a home hobbyist or independent filmmaker.