Animation Tricks

Animation can be thought of as a "trick". The good tricks are the ones that are not noticed unless they are pointed out. This write-up will describe four types of tricks: design, implementation, economization, and production [BLIN94] as well as tricks to animating characters [LASS94].

Design Tricks

The basic intent of animation is to communicate something. There are four types of design tricks: attraction tricks, distraction tricks, timing tricks, and motion enhancement.
Attraction Tricks

The direction of the viewer's attention to what the designer considers the important parts of the image is one of the most important aspects of designing either still or moving images. This is particularly important for moving images, as they are not on the screen for a long time; the viewer does not have the choice to study it for an extended length of time. One must get the viewer looking at the place where the new action will occur before it is all over. The following are ways of achieving this:

Appearing and Disappearing

Changes on the screen will get the eyes attention. Something changing from existence to non-existence, or vice versa, is pretty dramatic.
Blinking

Have something blink before it moves will get the viewer's attention.
Anticipation and Overshoot

Anticipate actions by having the objects backup a bit before moving in a desired direction.
The See-saw effect

Lead the viewer into some such transformation by "rubbing the transformation back and forth" a bit
Parallel action

To point up the connection between two things on different parts of the screen, attract attention to them by shaking them both up and down at the same time.
Tension and Release

Tension is created by making shapes seem unbalanced, nearly tipping over. Release comes from objects being firmly placed.
Hesitation

Make object(s) pause a little before moving them to their final positions. This builds up anticipation.
Distraction Tricks

Sometimes it is necessary to distract the viewer from something on the screen. This could be a glitch in animation rendering or it might be a short-cut the animator is using to avoid some lengthy or complicated computations. One example is the old switcheroo; sometimes different models are needed for the same object at different points in the animation.
Timing Tricks

These tricks apply to how long you make actions take to occur.
Speed adjustment

If a physical action happens too quickly to see, simply slow down the time scale. This is similar to scaling an object to fit on the screen.
Logarithmic zooms

When flying in to objects that vary greatly in scale, it is useful to animate the logarithm of the distance rather than the distance directly.
When to double/single frame

Double framing is the process of rendering every other frame and recording each rendered frame twice. This makes a motion seem to move faster and is sometimes used to add liveliness to the scene. Single framing is preferable to double framing except it takes longer to render.
Overlapping action

Having various actions overlap in time makes an animation seem more alive.
Motion Enhancement

It is difficult to convey some motions without exaggerating them in some way. For example:
Falling bodies

To give the impression of something falling continuously, put some texture in the background that scrolls as the object is tracked. Another technique is adding some random fluctuation to the position on the screen. This gives the impression of a falling object being tracked by a human cameraman.
Rolling Ball

To show a ball rolling down an inclined plane, add a simple line to the ball. This represents a highlight. When the ball is rolled down the plane, the highlight rotates with it looking just like a mark on the surface of the ball.
The spinning top

This is a problem of spinning a symmetric object. Placing a pair of black marks near the apex of the top (in a "+" shape) gives the asymmetry needed to follow the rotation. Another trick is the use of Gouraud shaded highlights. The number of polygons is small so the irregularities in the image, especially in the