MotionKit

Drag Follow

Layer follows its parent with drag and delay, like it's attached by a rubber band.

Expression Code

// Drag Follow
// Apply to Position
// Parent this layer to any moving layer
drag = 0.9;  // Drag amount (0ā€“1, higher = more lag)

if (hasParent) {
  delay = drag * 0.5;  // Convert drag to time delay
  samples = 10;
  offset = [0, 0];
  
  for (i = 0; i < samples; i++) {
    weight = Math.pow(drag, i) / samples;
    t = Math.max(0, time - i * thisComp.frameDuration);
    
    currentParentPos = parent.toWorld(parent.anchorPoint, time);
    delayedParentPos = parent.toWorld(parent.anchorPoint, t);
    
    offset += (delayedParentPos - currentParentPos) * weight;
  }
  
  value + offset;
} else {
  value;
}
Parent this layer to the layer you want it to follow. Apply to Position. Adjust drag between 0 (no lag) and 1 (maximum lag) to control how loosely it follows.
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