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

elasticIn detail::elasticInEasing elasticIn {} inlineconstexpr Elastic easing with oscillating spring-like motion at the start. The elasticIn easing function creates a spring or elastic band effect that oscillates with increasing amplitude before reaching the starting point of the animation. The motion resembles pulling back an elastic band that vibrates as tension builds. The oscillation characteristics: Multiple back-and-forth swings before the main motion begins Amplitude increases as the animation progresses Creates a "winding up" or "charging" effect More pronounced than backIn's single overshoot This easing is particularly effective for: Magical or fantasy effects: Spell charging, energy gathering Exaggerated cartoon animations: Extreme anticipation and wind-up Attention-grabbing entrances: Elements that need dramatic introduction Game power-ups: Visual feedback for charging actions Playful UI elements: Whimsical, high-energy interactions The elastic effect is more dramatic than back easing, making it suitable for contexts where strong visual emphasis or entertainment value is desired. It's less appropriate for subtle or professional interfaces. Mathematically, this uses a decaying sine wave with exponential amplitude growth. Warning This easing creates significant overshoot in both directions. Values will oscillate well beyond the start value in both positive and negative directions. Ensure your rendering system can handle these extreme values gracefully. // Magical charging effect before an action auto glow = tweeny::from(0.0f) .to(1.0f) .via(easing::elasticIn) .during(45U) .build(); // The glow will oscillate negative before reaching 1.0f // producing a "charging" visual effect See also elasticOut For spring-like oscillation at the end elasticInOut For oscillation at both start and end backIn For a simpler single-overshoot alternative Visualize at https://easings.net/#easeInElastic