Adobe After Effects 7.0 Studio Techniques

Rotoscoping and Paint

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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 frames—the top of a leap in the air, the moment of impact, the kiss—that 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 image—typically one

or all of its color channels—and 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.

Articulated Mattes

I’ve said it before, and I’m saying it again: When animating, or articulating, mattes, keep it simple. All of the

strategies offered here are for setting up and animating your mattes with as few steps as possible. Not only

will this save you time in setup, you’ll have fewer elements to fix if something goes wrong. Each new edit you

keyframe introduces the possibility for more error, and each new point you add to a mask has to be accounted

for on every other frame.

The first question to decide when starting a roto job is whether you prefer to mask in the Composition panel or

in the Layer panel. The advantages of the Composition panel are that you can see the layer in the composition

and that it updates live as you work. This approach, however, does have several potential pitfalls:

• On a large scene you may have to wait for all elements to render and the screen to redraw each time you

draw a point.

• If the layer you are masking has been transformed (and particularly, rotated in 3D, scaled down, or made

transparent), you may find it difficult to edit a mask cleanly.

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You may need to select and lock other layers to be certain that you’re editing the correct layer, particularly

if you’re creating more than one mask.

• The mask you draw in the composition viewer is live by default, causing masked areas to disappear as you

work. This can make it impossible to draw complex shapes.

• You lose the use of selection tools that exist only in the Layer panel.

You may have guessed by now that the Layer panel is generally a preferable place to create masks. Tweaking

mask points in the context of the entire comp is often useful, but I recommend this only as a secondary approach.