@redocly/theme/src/core/utils/enhanced-smoothstep.ts

Shared UI components lib

/**
 * Enhanced smoothstep function for smooth interpolation with configurable threshold.
 * Used in active heading detection to create virtual positions for better scroll behavior.
 */
export function enhancedSmoothstep(input: number, threshold: number = 0.4): number {
  if (input <= threshold) {
    return 0;
  }

  const normalizedValue = Math.min(Math.max((input - threshold) / (1 - threshold), 0), 1);
  return (
    3 * normalizedValue * normalizedValue - 2 * normalizedValue * normalizedValue * normalizedValue
  );
}