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Concept to Creation: Rotoscoping


All images are from Producing Independent 2D Character Animation: Making and Selling a Short Film by Mark Simon. Reprinted with permission.


The art of rotoscoping consists of drawing over live-action to produce your animation. The purpose of rotoscoping is either to animate a scene completely using a live-action reference, or to add animation to a live-action scene while tracking the movement of the camera and the live-action elements. More and more rotoscoping is done these days to produce mattes of elements, also known as rotomatting, within a live-action shot either to remove unwanted elements or to add special effects.

For example, if we wanted to visually remove the legs from the character in Figure 1, we would pull a matte of his legs. The matte would consist of drawing an outline tightly around the outside of his legs. His legs are now the elements that we may remove or add effects to. In order to remove his legs, we would need a clean shot of the background without the character. The leg elements then would be replaced by portions of the clean background.

[Figure 1] Rotoscope template in CorelDraw. The image snaps to the corner of the guidelines, and the crosshairs allow us to line up the images when taping on the animation header strips.

There are a number of different ways to rotoscope, and a few of them produce completely different results. Rotoscoping may be used to create a completely realistic motion, or as a test to study motion. Animators who shoot live-action footage and just use it for research are not actually rotoscoping; they are simply using live-action reference for inspiration.

When you are shooting footage for rotoscoping, set your film or video camera to a fast shutter speed. Accurate movement is what you are looking for, and fast movements with a slow shutter will be blurred.

Rotoscoping always starts with storyboarding and then filming live-action of the shot you need. If you are shooting with film, you will need the frames scanned and saved as digital sequential files. If you are shooting with video, you will need to be able to capture the scene onto a computer or move a frame at a time with your video player. Some software allows you to rotoscope directly within the program. Figure 1 shows a video frame captured in Adobe Premiere, exported as a .TGA file and imported into CorelDraw.

An accurate way to rotoscope is either to paint within a software package or print the frames you need and trace over them on a light table.

To rotoscope with software or to print the frames you need, you should first digitize your video footage. Digital cameras can connect to computers via their firewire connection. There are many video cards that will capture your analog footage through RCA, BNC or S-Video connections. Once youve captured your video into your computer, you can export the video file from your editing or compositing program as individual sequential files. In other words, export the frames as .jpg or .tif extensions, such as roto-01.jpg, roto-02.jpg, and so on. NTSC video runs at 30fps. To cut down your work, you can reduce the video to 15fps. This will be the same as animating on twos (two frames for every one drawing).

[Figure 2] Use the crosshairs to align your rotoscope prints to the peg bars.

When adding an animated character to live-action, it is always best to rotoscope every frame, or the animated character may seem to slide around over the live-action.

Once the individual live-action frames are exported, you need to set up a template in a layout program such as CorelDraw or Adobe Illustrator. In the example from CorelDraw in Figure 2, we placed guidelines half an inch from the top and from the left. We then made two crosshairs and included a reference to the frame number on the bottom. Then we saved the form so that it never changes. Import each video frame into the form and have it snap into the corner of the guidelines (Set the program to Snap to Guidelines). This places every frame in precisely the same position. The crosshairs will help you align all the frames when you tape the header peg strips to the printouts. Print each frame with its own frame number.

[Figure 3] Sample images that have been rotoscoped and composited onto the live-action reference plates. The CD-ROM includes a complete rotoscope animation using this reference footage. Animation by Mark Simon.

The remaining chapter describes laying out and registering your roto-prints and rotoscoping using animation and compositing programs. To learn about other topics, check out Producing Independent 2D Character Animation, published by Focal Press. It can be purchased at any bookstore or online.

Producing Independent 2D Character Animation: Making and Selling a Short Film by Mark Simon. Burlington, Massachusetts: Focal Press, 2003. 432 pages. ISBN: 0-240-80513-5.
