after-effects（后效）

After Effects Animation Principles

Implement all 12 Disney animation principles using After Effects' powerful animation tools.

1. Squash and Stretch

// Expression for automatic squash/stretch
s = transform.scale[1];
x = 100 + (100 - s) * 0.5;
[x, s]

Or manually:

• Keyframe Scale X and Y inversely
• When Y compresses, X expands
• Maintain volume (X * Y ≈ constant)

2. Anticipation

Timeline structure:

• 0-10f: Wind-up (crouch, pull back)
• 10-12f: Transition
• 12-30f: Main action
• 30-40f: Settle

Use Easy Ease on anticipation keyframes for smooth wind-up.

3. Staging

Techniques:

• Use depth of field (Camera > Depth of Field)
• Apply blur to background layers
• Use vignettes to direct focus
• Adjust opacity of secondary elements
• Light the main subject brighter

4. Straight Ahead / Pose to Pose

Pose to Pose (recommended):

1. Set keyframes at key poses
2. Fill in breakdowns
3. Use Graph Editor to adjust timing

Straight Ahead:

• Animate frame-by-frame
• Use Onion Skin (Layer > Onion Skin)

5. Follow Through and Overlapping Action

// Delay expression for child layers
thisComp.layer("Parent").transform.position.valueAtTime(time - 0.05)

Or:

• Offset child keyframes by 2-5 frames
• Use parenting with delayed wiggle
• Apply spring expression to end values

6. Slow In and Slow Out

• Select keyframes > F9 (Easy Ease)
• Graph Editor > Adjust bezier handles
• Steeper curve = faster movement
• Flatter curve = slower movement

// Custom ease expression
ease(time, inPoint, outPoint, startValue, endValue)

7. Arc

Techniques:

• Draw motion path with Pen tool
• Use Position property's bezier handles
• Layer > Transform > Auto-Orient
• Apply path from shape layer to position

8. Secondary Action

• Animate main action first
• Add secondary on separate layer/property
• Offset timing slightly
• Secondary should complement, not compete

Example: Character waves → Hair follows → Clothing shifts

9. Timing

Adjust composition frame rate for overall feel (24fps cinematic, 30fps smooth).

10. Exaggeration

// Overshoot expression
amp = 15;
freq = 3;
decay = 5;
t = time - key(numKeys).time;
if (t > 0) {
  value + amp * Math.sin(t * freq * Math.PI * 2) / Math.exp(t * decay);
} else {
  value;
}

Push values 20-50% beyond realistic:

• Larger scales
• Wider rotations
• More dramatic timing

11. Solid Drawing

• Use 3D layers for depth
• Apply cameras with perspective
• Animate Z position
• Use light and shadow
• Consider volume in all poses

12. Appeal

Design principles:

• Clear silhouettes at every pose
• Smooth curves over sharp angles
• Consistent character proportions
• Pleasing timing patterns
• Clean, readable motion paths

Essential Expressions

// Wiggle
wiggle(frequency, amplitude)

// Loop
loopOut("cycle")

// Time remap
timeRemap = linear(time, 0, duration, 0, 1)

// Bounce
n = 0;
if (numKeys > 0) {
  n = nearestKey(time).index;
  if (key(n).time > time) n--;
}
if (n == 0) t = 0;
else t = time - key(n).time;
amp = 80; freq = 3; decay = 8;
value + amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);

Export Options

• Lottie: Bodymovin plugin → JSON
• GIF: Media Encoder
• Video: H.264, ProRes
• Sprite Sheet: Scripts > Render Sprite Sheet