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

circularIn detail::circularInEasing circularIn {} inlineconstexpr Circular easing based on quarter-circle arc for smooth acceleration. The circularIn easing function accelerates following the curve of a quarter circle, creating smooth, gradual acceleration. The motion follows the equation 1 - sqrt(1 - t²), which traces a circular arc. Characteristics: Smooth, continuous acceleration More gradual than quadratic, less than cubic No sharp transitions in velocity Mathematically elegant curve This easing is ideal for: Natural motion: Movements that need organic feel Camera movements: Smooth pans and zooms Scroll animations: Gentle acceleration for reading comfort Subtle UI transitions: Motion with moderate acceleration Circular easings strike a balance between the gentle quadratic and the more aggressive cubic curves, making them versatile for many contexts. // Smooth camera pan auto cameraX = tweeny::from(0.0f) .to(1000.0f) .via(easing::circularIn) .during(90U) .build(); See also circularOut For circular deceleration circularInOut For circular acceleration and deceleration quadraticIn For gentler acceleration cubicIn For stronger acceleration Visualize at https://easings.net/#easeInCirc