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Unique Snowflake Generator (Generative Expression)

About This Expression

This expression generates a procedural snowflake using a combination of branching geometry, symmetry, and controlled randomness.

Instead of drawing the full snowflake manually, the logic first creates a single arm with small side branches that vary in length and thickness. This arm is then rotated evenly around a circle to form a complete crystalline structure.

The key feature is the use of:

seedRandom(index, true);

by using the layer index as the random seed, every layer becomes deterministic yet unique. When the layer is duplicated, its index changes—causing the expression to generate a completely different snowflake while keeping the same overall rules.

This method mirrors how real snowflakes form in nature: structured growth guided by symmetry, with subtle randomness ensuring no two results are identical.

Expression

seedRandom(index, true);
arms = 8;
radius = 100;
branchCount = Math.floor(random(3, 6));
armWidth = 5;
// Store shape of ONE arm (right side)
armProfile = [];
// Generate one arm
for (j = 1; j <= branchCount; j++) {
 t = j / (branchCount + 1);
 dist = t * radius;
 currentWidth = armWidth * random(0.5, 1.5);
 armProfile.push({x: currentWidth, y: -dist});
 branchLen = random(20, 60) * (1 - t);
 branchAngle = -Math.PI / 3;
 bx = currentWidth + Math.cos(branchAngle) * branchLen;
 by = -dist + Math.sin(branchAngle) * branchLen;
 armProfile.push({x: bx, y: by});
 armProfile.push({x: currentWidth, y: -(dist + 15)});
}
// Rotate helper
function rotatePoint(x, y, angle) {
 ca = Math.cos(angle);
 sa = Math.sin(angle);
 return [x * ca - y * sa, x * sa + y * ca];
}
// Build full snowflake
pts = [];
for (i = 0; i < arms; i++) {
 rotAngle = (i / arms) * Math.PI * 2;
 // Right side
 for (k = 0; k < armProfile.length; k++) {
  p = rotatePoint(armProfile[k].x, armProfile[k].y, rotAngle);
  pts.push(p);
 }
 // Main tip
 tip = rotatePoint(0, -radius, rotAngle);
 pts.push(tip);
 // Left side (mirrored)
 for (k = armProfile.length - 1; k >= 0; k--) {
  p = rotatePoint(-armProfile[k].x, armProfile[k].y, rotAngle);
  pts.push(p);
 }
}
createPath(pts, [], [], true);

How We Use This Expression

Step 1: Create a Shape Layer

  1. Open your composition in After Effects
  2. Go to Layer → New → Shape Layer
  3. Select the shape layer

This expression generates a vector path, so it must be applied to a Shape Path.

Step 2: Add a Path

  1. Twirl open the shape layer
  2. Go to Contents → Shape 1
  3. Click Add → Path

This creates a path that can be fully controlled by an expression.

Step 3: Apply the Expression to the Path

  1. Twirl open Path 1
  2. Hold Alt (Windows) / Option (Mac) and click the Path stopwatch
  3. Paste the full snowflake expression
  4. Click outside the editor to apply

The path will instantly form a complete, symmetrical snowflake.

Step 4: Generate Variations by Duplicating

This expression uses:

seedRandom(index, true);

That means:

  • Each layer index creates a unique snowflake
  • Duplicating the shape layer instantly generates a new design
  • No sliders or keyframes are required

Perfect for creating snowflake collections quickly.

Step 5: Position & Scale Safely

  • Use Transform → Position to place the snowflake
  • Use Transform → Scale to resize it

Avoid editing the path points manually—let the expression handle the geometry.

Step 6: Customize the Snowflake Shape

Inside the expression, you can adjust:

  • arms → number of snowflake arms
  • radius → overall size
  • branchCount → detail density
  • armWidth → thickness of branches

Each change creates a new structural variation.

Step 7: Style the Snowflake

Once the shape is generated, you can:

  • Add Stroke for icy outlines
  • Add Fill for solid or gradient snowflakes
  • Apply Glow or Drop Shadow for depth
  • Animate Rotation for gentle drifting motion

The expression controls structure; effects control appearance.

Step 8: Build Snowflake Scenes

To create snowfall visuals:

  1. Duplicate multiple snowflake layers
  2. Combine with a falling-position expression
  3. Vary scale and opacity for depth

This creates a full procedural snowfall system.

Best Use Cases in After Effects

  • Snowflake generators
  • Winter & holiday animations
  • Background patterns
  • Motion design templates
  • Decorative transitions

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