Easing

Easing functions control the rate of change of a value over time, producing different acceleration and deceleration patterns for animations, transitions, and other time-based effects.

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Overview

The easing library provides 33 different easing functions covering 11 families with four direction variants each: In, Out, InOut, and OutIn.

Family	Description
Linear	No easing, constant speed
Quadratic	Smooth acceleration and deceleration
Cubic	More pronounced acceleration and deceleration
Quartic	Strong acceleration and deceleration
Quintic	Very strong acceleration and deceleration
Sine	Smooth sinusoidal curves
Exponential	Extremely fast acceleration or deceleration
Circular	Circular arc motion
Back	Overshoots the target before settling
Elastic	Oscillates like a spring
Bounce	Bounces at the end or start

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Direction Variants

Variant	Description
In	Starts slow, ends fast
Out	Starts fast, ends slow
InOut	Starts slow, accelerates, then decelerates at the end
OutIn	Starts fast, decelerates, then accelerates again

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Usage

// Evaluate an easing function at a normalized time (0 to 1)
float t = 0.5f;
float eased = Easing.Ease(EaseType.QuadOut, t);

// Use the eased value for interpolation
float value = MathHelper.Lerp(0f, 100f, eased);

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Ease Types

Linear

Type	Description
Linear	No easing, constant speed

Quadratic

Type	Description
QuadIn	Starts slow, accelerates toward the end
QuadOut	Starts fast, decelerates toward the end
QuadInOut	Starts slow, accelerates, then decelerates
QuadOutIn	Starts fast, decelerates, then accelerates

Cubic

Type	Description
CubicIn	Starts very slow, accelerates toward the end
CubicOut	Starts fast, decelerates toward the end
CubicInOut	Starts slow, accelerates, then decelerates
CubicOutIn	Starts fast, decelerates, then accelerates

Quartic

Type	Description
QuartIn	Starts very slow, accelerates strongly
QuartOut	Starts very fast, decelerates strongly
QuartInOut	Starts slow, accelerates strongly, then decelerates
QuartOutIn	Starts fast, decelerates strongly, then accelerates

Quintic

Type	Description
QuintIn	Starts extremely slow, accelerates sharply
QuintOut	Starts extremely fast, decelerates sharply
QuintInOut	Starts slow, accelerates sharply, then decelerates
QuintOutIn	Starts fast, decelerates sharply, then accelerates

Sine

Type	Description
SineIn	Starts slowly with a smooth sinusoidal curve
SineOut	Ends slowly with a smooth sinusoidal curve
SineInOut	Starts and ends slowly with a smooth curve
SineOutIn	Slow middle section with sinusoidal smoothing

Exponential

Type	Description
ExpoIn	Starts imperceptibly slow, accelerates extremely fast
ExpoOut	Starts extremely fast, decelerates imperceptibly
ExpoInOut	Starts imperceptibly slow, accelerates, then decelerates
ExpoOutIn	Starts fast, decelerates, then accelerates imperceptibly

Circular

Type	Description
CircIn	Follows a circular arc starting slowly
CircOut	Follows a circular arc ending slowly
CircInOut	Follows a circular arc starting and ending slowly
CircOutIn	Follows a circular arc with a slow middle

Back (Overshoot)

Type	Description
BackIn	Overshoots the starting point before moving forward
BackOut	Overshoots the ending point before settling
BackInOut	Overshoots both the start and end points
BackOutIn	Overshoots in the middle of the transition

Elastic (Oscillatory)

Type	Description
ElasticIn	Oscillates with a spring-like effect at the start
ElasticOut	Oscillates with a spring-like effect at the end
ElasticInOut	Oscillates with a spring-like effect at both ends
ElasticOutIn	Oscillates with a spring-like effect in the middle

Bounce

Type	Description
BounceIn	Bounces at the start of the transition
BounceOut	Bounces at the end of the transition
BounceInOut	Bounces at both the start and end
BounceOutIn	Bounces in the middle of the transition

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Example

// Animate a value using easing
float duration = 1f;
float elapsed = 0f;
float startValue = 0f;
float endValue = 100f;

while (elapsed < duration)
{
    float t = elapsed / duration;
    float eased = Easing.Ease(EaseType.QuadOut, t);
    float currentValue = MathHelper.Lerp(startValue, endValue, eased);
    
    elapsed += frameTime.DeltaTime;
}

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Summary

Feature	Description
33 easing functions	11 families × 4 directions
Normalized input	Values between 0 and 1
Normalized output	Values between 0 and 1
All families	Quadratic, Cubic, Quartic, Quintic, Sine, Exponential, Circular, Back, Elastic, Bounce

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