lottie-animator（洛蒂动画师）

Lottie Animator - SVG to Motion Graphics

Professional skill to create advanced Lottie animations from SVGs, eliminating the need for After Effects.

When to Activate

Activate this skill when the user requests:

• Animate a logo, icon, or SVG graphic
• Create motion graphics or animations
• Generate Lottie JSON files
• Effects: wiggle, bounce, rotate, pulse, fade, scale, morph
• Entrance, loop, loading animations, or transitions
• Path drawing/reveal animations (Trim Path)
• Character animation, walking cycles
• Shape morphing (icon transitions)
• Replace After Effects workflow

Critical: SVG Understanding

Before animating ANY SVG, you MUST understand its path structure.

See: references/svg-path-mastery.md

SVG Path Command Quick Reference

Path to Lottie Vertex Formula

For C x1,y1 x2,y2 x,y from point (px, py):
- Previous vertex outTangent: [x1-px, y1-py]
- Current vertex: [x, y]
- Current vertex inTangent: [x2-x, y2-y]

Main Workflow

Phase 1: Motion Philosophy (30 seconds)

MANDATORY before any code. Define:

1. Brand Personality: Professional, playful, elegant, energetic
2. Emotional Response: Trust, excitement, calm, urgency
3. Motion Metaphor: Fluid like water, solid like rock, light like air

Example: "Fintech Logo → professional + trust → precise and controlled movement"
Example: "Music App → creative + energy → organic with rhythmic pulses"
Example: "Healthcare → calm + reliable → smooth, slow easings"

Phase 2: SVG Deep Analysis

Before animating, thoroughly analyze:

1. Structure: Elements, groups, paths, viewBox dimensions
2. Path Complexity: Vertex count, curve types (C, Q, A commands)
3. Hierarchy: Primary elements vs. secondary details
4. Animation Opportunities: Independent parts, stroke-based vs fill-based

# Analyze SVG structure
cat icon.svg | grep -E '<(path|g|rect|circle|ellipse|line|polyline)' | head -30

Key Questions:

• Is it stroke-based? → Consider Trim Path animation
• Multiple paths? → Consider staggered entrance
• Complex shape? → Consider scale/rotate instead of morph
• Icon library (Phosphor/Lucide)? → Usually clean, minimal vertices

Phase 3: Animation Strategy Selection

Pro Tip: For complex character animations (walk cycles, run cycles), use Frame-by-Frame technique instead of continuous animation. See references/professional-techniques.md

Phase 4: Create Lottie JSON

See: references/lottie-structure.md

Base Structure:

{
  "v": "5.12.1",
  "fr": 60,
  "ip": 0,
  "op": 120,
  "w": 512,
  "h": 512,
  "nm": "Animation Name",
  "ddd": 0,
  "assets": [],
  "layers": []
}

Phase 5: Apply Professional Easing

See: references/bezier-easing.md

Phase 6: Validate and Export

# Validate JSON structure
python3 -c "import json; json.load(open('animation.json'))"

# Preview
echo "Open in: https://lottiefiles.com/preview"

Shape Modifiers

See: references/shape-modifiers.md

Trim Path (Icon Drawing Animation)

{
  "ty": "tm",
  "s": {"a": 0, "k": 0},
  "e": {
    "a": 1,
    "k": [
      {"t": 0, "s": [0], "o": {"x": [0.33], "y": [0]}, "i": {"x": [0.67], "y": [1]}},
      {"t": 45, "s": [100]}
    ]
  },
  "o": {"a": 0, "k": 0},
  "m": 1
}

Repeater (Radial/Linear Patterns)

{
  "ty": "rp",
  "c": {"a": 0, "k": 8},
  "tr": {
    "r": {"a": 0, "k": 45},
    "so": {"a": 0, "k": 100},
    "eo": {"a": 0, "k": 30}
  }
}

Offset Path (Glow/Outline Effects)

{
  "ty": "op",
  "a": {"a": 1, "k": [{"t": 0, "s": [0]}, {"t": 30, "s": [8]}]},
  "lj": 2
}

Advanced Techniques

See: references/advanced-animation.md and references/professional-techniques.md

Frame-by-Frame Animation (Professional Technique)

The most professional technique for complex character animations. Instead of continuous animation, create multiple "poses" that appear/disappear in sequence using ip (in point) and op (out point).

{
  "layers": [
    {"nm": "Pose 1", "ip": 0, "op": 6, "shapes": [/* pose 1 */]},
    {"nm": "Pose 2", "ip": 6, "op": 12, "shapes": [/* pose 2 */]},
    {"nm": "Pose 3", "ip": 12, "op": 18, "shapes": [/* pose 3 */]}
  ]
}

Timing Formula: Total Frames = Poses × Frames_per_Pose → Duration = Total Frames / FPS

When to Use:

• Walk/run cycles (each pose is a different leg position)
• Complex character animations with drastic shape changes
• When morphing produces ugly results
• Professional sprite-sheet style animations

Layer Parenting (Bone Hierarchy)

Use parent property to create hierarchies where moving one layer moves all children.

{
  "layers": [
    {"ind": 14, "nm": "Shadow", "ks": {"p": {"a": 0, "k": [340, 195, 0]}}},
    {"ind": 1, "nm": "Head", "parent": 14, "ks": {"p": {"a": 0, "k": [88, -84, 0]}}},
    {"ind": 2, "nm": "Body", "parent": 14, "ks": {"p": {"a": 0, "k": [0, -50, 0]}}}
  ]
}

Key Insight: Child positions are RELATIVE to parent. Moving Shadow moves all children with it.

Professional Parent Strategies:

• Shadow as Parent: Move shadow → entire character moves (for walk cycles)
• Body as Parent: Limbs and head follow body rotation
• Joint as Parent: Upper arm controls forearm and hand rotation

Parent Chain Example:

Shadow (Parent for entire character)
├── Head (child)
├── Body (child)
├── Ear Inner (child)
├── Eye (child)
└── ... 13 total children

Path Morphing (Same Vertex Count Required)

{
  "ty": "sh",
  "ks": {
    "a": 1,
    "k": [
      {"t": 0, "s": [{"c": true, "v": [[0,0], [100,0], [100,100], [0,100]], "i": [...], "o": [...]}]},
      {"t": 30, "s": [{"c": true, "v": [[50,-20], [120,50], [50,120], [-20,50]], "i": [...], "o": [...]}]}
    ]
  }
}

Critical Rule: Both shapes MUST have identical vertex count for smooth morphing.

Track Mattes (Masking)

// Matte layer (defines visible area)
{"ind": 1, "nm": "Matte", "td": 1, "ty": 4, ...}

// Content layer (uses the matte)
{"ind": 2, "nm": "Content", "tt": 1, "ty": 4, ...}

Animation Principles Applied

1. Anticipation

"s": {"a": 1, "k": [
  {"t": 0, "s": [100, 100]},
  {"t": 8, "s": [95, 105]},    // Slight crouch
  {"t": 25, "s": [115, 90]},   // Main action
  {"t": 40, "s": [100, 100]}
]}

2. Squash & Stretch (Volume Preservation)

// X * Y should stay roughly constant
{"t": 0, "s": [100, 100]},   // 10000
{"t": 10, "s": [120, 83]},   // 9960 ≈ preserved
{"t": 20, "s": [85, 118]}    // 10030 ≈ preserved

3. Staggered Timing

{"ind": 1, "st": 0, "ip": 0},
{"ind": 2, "st": 3, "ip": 3},   // 3 frame delay
{"ind": 3, "st": 6, "ip": 6},   // 6 frame delay
{"ind": 4, "st": 9, "ip": 9}    // 9 frame delay

4. Follow-Through with Overshoot

"r": {"a": 1, "k": [
  {"t": 0, "s": [0]},
  {"t": 15, "s": [95]},    // Overshoot target
  {"t": 25, "s": [88]},    // Settle back
  {"t": 35, "s": [90]}     // Final position
]}

Common Animation Recipes

Loading Spinner

{
  "shapes": [
    {"ty": "el", "s": {"a": 0, "k": [60, 60]}},
    {"ty": "st", "w": {"a": 0, "k": 4}, "c": {"a": 0, "k": [0.2, 0.5, 1, 1]}, "lc": 2},
    {"ty": "tm", "s": {"a": 0, "k": 0}, "e": {"a": 0, "k": 75},
     "o": {"a": 1, "k": [{"t": 0, "s": [0]}, {"t": 60, "s": [360]}]}}
  ],
  "ks": {"r": {"a": 1, "k": [{"t": 0, "s": [0]}, {"t": 120, "s": [360]}]}}
}

Checkmark Draw

{
  "shapes": [
    {"ty": "sh", "ks": {"a": 0, "k": {"c": false, "v": [[20,50], [40,70], [80,30]], "i": [[0,0], [0,0], [0,0]], "o": [[0,0], [0,0], [0,0]]}}},
    {"ty": "st", "w": {"a": 0, "k": 6}, "c": {"a": 0, "k": [0.2, 0.8, 0.4, 1]}, "lc": 2, "lj": 2},
    {"ty": "tm", "e": {"a": 1, "k": [{"t": 0, "s": [0]}, {"t": 30, "s": [100]}]}}
  ]
}

Heart Beat (Organic)

"s": {"a": 1, "k": [
  {"t": 0, "s": [100, 100]},
  {"t": 8, "s": [115, 115]},    // Systole (Lub)
  {"t": 12, "s": [90, 90]},     // Diastole start (Dub)
  {"t": 18, "s": [105, 105]},   // Refill
  {"t": 45, "s": [100, 100]}    // Rest
]}

Icon Pop-In with Bounce

{
  "ks": {
    "s": {"a": 1, "k": [
      {"t": 0, "s": [0, 0], "o": {"x": [0.34], "y": [1.56]}, "i": {"x": [0.64], "y": [1]}},
      {"t": 18, "s": [110, 110], "o": {"x": [0.33], "y": [0]}, "i": {"x": [0.67], "y": [1]}},
      {"t": 30, "s": [100, 100]}
    ]},
    "o": {"a": 1, "k": [
      {"t": 0, "s": [0]},
      {"t": 12, "s": [100]}
    ]}
  }
}

Icon Library Optimization

Phosphor/Lucide Icons

• ViewBox: Usually 256x256 (Phosphor) or 24x24 (Lucide)
• Structure: Clean paths, minimal vertices
• Strokes: stroke-linecap="round" for Trim Path compatibility
• Scale: Match your canvas to viewBox for 1:1

Recommended Animation Approach

1. Simple icons → Scale + Opacity entrance
2. Stroke icons → Trim Path drawing
3. Multi-part icons → Staggered entrance
4. Toggle icons → Path morphing (if vertex counts match)

Stroke + Fill Combination (Outline Style)

For professional character animations, combine stroke (contour) + fill (color) in each shape:

{
  "ty": "gr",
  "it": [
    {"ty": "sh", "ks": {...}},
    {"ty": "st", "c": {"a": 0, "k": [0.259, 0.153, 0.141, 1]}, "w": {"a": 0, "k": 1}, "lc": 2, "lj": 2},
    {"ty": "fl", "c": {"a": 0, "k": [0.302, 0.604, 0.816, 1]}},
    {"ty": "tr", ...}
  ]
}

Stroke Properties:

Professional Color Palette Example (from Running Cat):

{
  "body_fill": [0.302, 0.604, 0.816, 1],
  "outline": [0.259, 0.153, 0.141, 1],
  "eye_white": [0.902, 0.976, 1.0, 1],
  "shadow": [0.608, 0.706, 0.878, 1]
}

Common Errors

Performance Guidelines

1. Layers: <15 for complex animations
2. Vertices: <20 per shape for smooth morphing
3. Frame Rate: 30fps often sufficient, 60fps for ultra-smooth
4. Modifiers: Avoid nested repeaters
5. Effects: Minimize blur/shadow usage
6. File Size: Target <50KB for icons, <200KB for complex

References

• SVG Path Mastery - START HERE for SVG understanding
• Professional Techniques - Frame-by-frame, parenting, outline style
• Lottie JSON Structure
• Bezier Curves and Easing
• Shape Modifiers
• Advanced Animation
• SVG to Lottie Conversion
• Animation Examples
• Official Lottie Documentation

Final Checklist

• Motion philosophy defined
• SVG structure analyzed (path commands understood)
• Animation strategy selected (consider frame-by-frame for characters)
• Vertex counts verified (for morphing)
• Anchor points set correctly (for rotation)
• Parent hierarchy established (for characters)
• Keyframes with professional easing
• Animation principles applied (anticipation, follow-through)
• Stroke + fill style applied (for outline look)
• Seamless loop verified (if applicable)
• JSON validated
• Preview tested at https://lottiefiles.com/preview