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

sinusoidalInOut detail::sinusoidalInOutEasing sinusoidalInOut {} inlineconstexpr Sinusoidal easing with smooth acceleration and deceleration. The sinusoidalInOut easing function uses sine curves for both acceleration and deceleration, creating the smoothest possible S-curve motion. Motion profile: First half: Smooth sine-based acceleration Midpoint: Maximum velocity Second half: Smooth sine-based deceleration Creates extremely smooth S-curve This easing is appropriate for: Natural, organic motion: Smoothest easing available Continuous loops: Seamless repeated animations Calm interfaces: Relaxed, gentle design systems Accessible animations: Minimal motion stress SinusoidalInOut is the smoothest InOut easing, making it perfect when fluid, natural motion is the priority. Mathematically: f(t) = (1 - cos(t * π)) / 2 // Ultra-smooth transition auto x = tweeny::from(0.0f) .to(100.0f) .via(easing::sinusoidalInOut) .during(40U) .build(); See also sinusoidalIn For only smooth acceleration sinusoidalOut For only smooth deceleration quadraticInOut For similar gentleness Visualize at https://easings.net/#easeInOutSine