backIn backInOut backOut bounceIn bounceInOut bounceOut byName circularIn circularInOut circularOut cubicIn cubicInOut cubicOut def elasticIn elasticInOut elasticOut exponentialIn exponentialInOut exponentialOut linear quadraticIn quadraticInOut quadraticOut quarticIn quarticInOut quarticOut quinticIn quinticInOut quinticOut sinusoidalIn sinusoidalInOut sinusoidalOut stepped

quadraticInOut detail::quadraticInOutEasing quadraticInOut {} inlineconstexpr Quadratic polynomial easing with gentle acceleration and deceleration. The quadraticInOut easing function provides the most subtle polynomial S-curve. Perfect for animations that need easing but should remain understated. Motion profile: First half: Gentle acceleration (t²) Midpoint: Maximum velocity Second half: Gentle deceleration Creates subtle S-curve This easing is appropriate for: Minimal design systems: Understated, refined motion Fast animations: Under 200ms where gentle curves shine Accessibility: Motion-sensitive users Background motion: Animations that shouldn't dominate Mathematically: Combines quadraticIn for t < 0.5 and quadraticOut for t >= 0.5 // Subtle menu transition auto x = tweeny::from(0.0f) .to(100.0f) .via(easing::quadraticInOut) .during(20U) .build(); See also quadraticIn For only gentle acceleration quadraticOut For only gentle deceleration cubicInOut For more pronounced motion Visualize at https://easings.net/#easeInOutQuad