Rotoscoping and Paint

It's a small world, but I wouldn't want to paint it.

Steven Wright

So, you've gritted your teeth, girded your loins, and opened up the rotoscoping chapter. There's no way to paint an utterly pretty picture, so to speak, of the task you face: Rotoscoping and paint tools are generally a last resort, employed when there is no other way to fix your matte. Rotoscoping is the art (although some would be loath to call it that) of fixing a shot frame by frame, generally using masks. Cloning and filling using paint tools are variations on this task.

To compound matters, After Effects did not gain its fame as a rotoscoping tool. You can get good results with the program, but its interface and tools aren't set up expecting rotoscoping to be your main task, as they are in such dedicated programs as Silhouette Roto or the defunct Pinnacle Commotion.

Although sometimes you just can't get around having to clean up footage by hand in After Effects, it's often not as bad as you think if you follow a few basic guidelines:

• Ascertain that rotoscoping is necessary. Novices and pros alike bite the bullet too quickly, assuming it's time for frame-by-frame work without looking at other ways to break down the problem at hand. Specifically, make sure that these other approaches won't help at least part of your problem:
  • Keying. See Chapter 6, "Color Keying," for more on using luma mattes (including matting footage with itself), color keys, and difference mattes.
  • Tracking. See Chapter 8, "Effective Motion Tracking," for more on the many ways to track in selections. Paint, by the way, is fully trackable.
  • Keep it simple. This is the number-one piece of advice. If you're articulating a mask, do so with as few points as possible. When keyframing that mask, use as few keyframes as possible.
  • Paint is a last resort. It is very hard to re-create realism of any substantial scale via paint tools, and it will always be slower than working with masks. Assume that paint is an option only when you can't achieve a similar result with a mask. There are, of course, exceptions, such as cases in which you can easily track a paint stroke, or when rapidly filling holes in an alpha channel with paint.
  • Review constantly at full speed. Don't waste time heading down the wrong road. Carefully assess your footage via a RAM Preview every few frames, and determine if your approach is working. If it's not, be prepared to switch tactics.
  • Combine strategies. Effective rotoscoping may employ a mixture of keying (whether color keying or a hi-con matte), tracking, animated masks, and paint. Start with the one that protects the most crucial edges, and work your way down to the cruder stuff.

Notes

"Keyframing" is so-called because originally (at Disney, in the 1930s) it was the practice of drawing in the key framesthe top of a leap in the air, the moment of impact, the kissthat would be done by the top animators, leaving lower-level artists to add the in-between frames thereafter. This is the right way to think of keyframing animated masks: Look for the pivotal moments and try to let the computer in-between the others as much as possible.

With these guidelines in mind and a solid grasp of the fundamentals of creating selections (explored in Chapter 3, "Selections: The Key to Compositing"), you're ready to consider some rotoscoping specifics.

Notes

A hi-con, or high-contrast matte, is created by taking luminance data from an imagetypically one or all of its color channelsand raising the contrast to create a luminance matte, typically to hold out areas of the same image. Chapter 6 explores this process in greater depth.