XiuXianGame/Assets/Scripts/ThirdParty/StompyRobot/SRF/Scripts/Helpers/SRMath.Tweening.Functions.cs

using UnityEngine;

public static partial class SRMath
{
    /**
	 * 
	 *  These tweening functions taken from https://wpf-animation.googlecode.com/svn/trunk/src/WPF/Animation/PennerDoubleAnimation.cs
	 *  Licensed under the new BSD License
	 * 
	 * @author		Darren David darren-code@lookorfeel.com
	 * @version		1.0
	 *
	 * Credit/Thanks:
	 * Robert Penner - The easing equations we all know and love 
	 *   (http://robertpenner.com/easing/) [See License.txt for license info]
	 * 
	 * Lee Brimelow - initial port of Penner's equations to WPF 
	 *   (http://thewpfblog.com/?p=12)
	 * 
	 * Zeh Fernando - additional equations (out/in) from 
	 *   caurina.transitions.Tweener (http://code.google.com/p/tweener/)
	 *   [See License.txt for license info]
	 *   
	 */

    private static class TweenFunctions
    {
        #region Equations

        #region Linear

        /// <summary>
        /// Easing equation function for a simple linear tweening, with no easing.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float Linear(float t, float b, float c, float d)
        {
            return c*t/d + b;
        }

        #endregion

        #region Expo

        /// <summary>
        /// Easing equation function for an exponential (2^t) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ExpoEaseOut(float t, float b, float c, float d)
        {
            return (t == d) ? b + c : c*(-Mathf.Pow(2, -10*t/d) + 1) + b;
        }

        /// <summary>
        /// Easing equation function for an exponential (2^t) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ExpoEaseIn(float t, float b, float c, float d)
        {
            return (t == 0) ? b : c*Mathf.Pow(2, 10*(t/d - 1)) + b;
        }

        /// <summary>
        /// Easing equation function for an exponential (2^t) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ExpoEaseInOut(float t, float b, float c, float d)
        {
            if (t == 0)
            {
                return b;
            }

            if (t == d)
            {
                return b + c;
            }

            if ((t /= d/2) < 1)
            {
                return c/2*Mathf.Pow(2, 10*(t - 1)) + b;
            }

            return c/2*(-Mathf.Pow(2, -10*--t) + 2) + b;
        }

        /// <summary>
        /// Easing equation function for an exponential (2^t) easing out/in:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ExpoEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return ExpoEaseOut(t*2, b, c/2, d);
            }

            return ExpoEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Circular

        /// <summary>
        /// Easing equation function for a circular (sqrt(1-t^2)) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CircEaseOut(float t, float b, float c, float d)
        {
            return c*Mathf.Sqrt(1 - (t = t/d - 1)*t) + b;
        }

        /// <summary>
        /// Easing equation function for a circular (sqrt(1-t^2)) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CircEaseIn(float t, float b, float c, float d)
        {
            return -c*(Mathf.Sqrt(1 - (t /= d)*t) - 1) + b;
        }

        /// <summary>
        /// Easing equation function for a circular (sqrt(1-t^2)) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CircEaseInOut(float t, float b, float c, float d)
        {
            if ((t /= d/2) < 1)
            {
                return -c/2*(Mathf.Sqrt(1 - t*t) - 1) + b;
            }

            return c/2*(Mathf.Sqrt(1 - (t -= 2)*t) + 1) + b;
        }

        /// <summary>
        /// Easing equation function for a circular (sqrt(1-t^2)) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CircEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return CircEaseOut(t*2, b, c/2, d);
            }

            return CircEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Quad

        /// <summary>
        /// Easing equation function for a quadratic (t^2) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuadEaseOut(float t, float b, float c, float d)
        {
            return -c*(t /= d)*(t - 2) + b;
        }

        /// <summary>
        /// Easing equation function for a quadratic (t^2) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuadEaseIn(float t, float b, float c, float d)
        {
            return c*(t /= d)*t + b;
        }

        /// <summary>
        /// Easing equation function for a quadratic (t^2) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuadEaseInOut(float t, float b, float c, float d)
        {
            if ((t /= d/2) < 1)
            {
                return c/2*t*t + b;
            }

            return -c/2*((--t)*(t - 2) - 1) + b;
        }

        /// <summary>
        /// Easing equation function for a quadratic (t^2) easing out/in:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuadEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return QuadEaseOut(t*2, b, c/2, d);
            }

            return QuadEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Sine

        /// <summary>
        /// Easing equation function for a sinusoidal (sin(t)) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float SineEaseOut(float t, float b, float c, float d)
        {
            return c*Mathf.Sin(t/d*(Mathf.PI/2)) + b;
        }

        /// <summary>
        /// Easing equation function for a sinusoidal (sin(t)) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float SineEaseIn(float t, float b, float c, float d)
        {
            return -c*Mathf.Cos(t/d*(Mathf.PI/2)) + c + b;
        }

        /// <summary>
        /// Easing equation function for a sinusoidal (sin(t)) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float SineEaseInOut(float t, float b, float c, float d)
        {
            if ((t /= d/2) < 1)
            {
                return c/2*(Mathf.Sin(Mathf.PI*t/2)) + b;
            }

            return -c/2*(Mathf.Cos(Mathf.PI*--t/2) - 2) + b;
        }

        /// <summary>
        /// Easing equation function for a sinusoidal (sin(t)) easing in/out:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float SineEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return SineEaseOut(t*2, b, c/2, d);
            }

            return SineEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Cubic

        /// <summary>
        /// Easing equation function for a cubic (t^3) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CubicEaseOut(float t, float b, float c, float d)
        {
            return c*((t = t/d - 1)*t*t + 1) + b;
        }

        /// <summary>
        /// Easing equation function for a cubic (t^3) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CubicEaseIn(float t, float b, float c, float d)
        {
            return c*(t /= d)*t*t + b;
        }

        /// <summary>
        /// Easing equation function for a cubic (t^3) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CubicEaseInOut(float t, float b, float c, float d)
        {
            if ((t /= d/2) < 1)
            {
                return c/2*t*t*t + b;
            }

            return c/2*((t -= 2)*t*t + 2) + b;
        }

        /// <summary>
        /// Easing equation function for a cubic (t^3) easing out/in:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float CubicEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return CubicEaseOut(t*2, b, c/2, d);
            }

            return CubicEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Quartic

        /// <summary>
        /// Easing equation function for a quartic (t^4) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuartEaseOut(float t, float b, float c, float d)
        {
            return -c*((t = t/d - 1)*t*t*t - 1) + b;
        }

        /// <summary>
        /// Easing equation function for a quartic (t^4) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuartEaseIn(float t, float b, float c, float d)
        {
            return c*(t /= d)*t*t*t + b;
        }

        /// <summary>
        /// Easing equation function for a quartic (t^4) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuartEaseInOut(float t, float b, float c, float d)
        {
            if ((t /= d/2) < 1)
            {
                return c/2*t*t*t*t + b;
            }

            return -c/2*((t -= 2)*t*t*t - 2) + b;
        }

        /// <summary>
        /// Easing equation function for a quartic (t^4) easing out/in:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuartEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return QuartEaseOut(t*2, b, c/2, d);
            }

            return QuartEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Quintic

        /// <summary>
        /// Easing equation function for a quintic (t^5) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuintEaseOut(float t, float b, float c, float d)
        {
            return c*((t = t/d - 1)*t*t*t*t + 1) + b;
        }

        /// <summary>
        /// Easing equation function for a quintic (t^5) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuintEaseIn(float t, float b, float c, float d)
        {
            return c*(t /= d)*t*t*t*t + b;
        }

        /// <summary>
        /// Easing equation function for a quintic (t^5) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuintEaseInOut(float t, float b, float c, float d)
        {
            if ((t /= d/2) < 1)
            {
                return c/2*t*t*t*t*t + b;
            }
            return c/2*((t -= 2)*t*t*t*t + 2) + b;
        }

        /// <summary>
        /// Easing equation function for a quintic (t^5) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float QuintEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return QuintEaseOut(t*2, b, c/2, d);
            }
            return QuintEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Elastic

        /// <summary>
        /// Easing equation function for an elastic (exponentially decaying sine wave) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ElasticEaseOut(float t, float b, float c, float d)
        {
            if ((t /= d) == 1)
            {
                return b + c;
            }

            var p = d*.3f;
            var s = p/4;

            return (c*Mathf.Pow(2, -10*t)*Mathf.Sin((t*d - s)*(2*Mathf.PI)/p) + c + b);
        }

        /// <summary>
        /// Easing equation function for an elastic (exponentially decaying sine wave) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ElasticEaseIn(float t, float b, float c, float d)
        {
            if ((t /= d) == 1)
            {
                return b + c;
            }

            var p = d*.3f;
            var s = p/4;

            return -(c*Mathf.Pow(2, 10*(t -= 1))*Mathf.Sin((t*d - s)*(2*Mathf.PI)/p)) + b;
        }

        /// <summary>
        /// Easing equation function for an elastic (exponentially decaying sine wave) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ElasticEaseInOut(float t, float b, float c, float d)
        {
            if ((t /= d/2) == 2)
            {
                return b + c;
            }

            var p = d*(.3f*1.5f);
            var s = p/4;

            if (t < 1)
            {
                return -.5f*(c*Mathf.Pow(2, 10*(t -= 1))*Mathf.Sin((t*d - s)*(2*Mathf.PI)/p)) + b;
            }
            return c*Mathf.Pow(2, -10*(t -= 1))*Mathf.Sin((t*d - s)*(2*Mathf.PI)/p)*.5f + c + b;
        }

        /// <summary>
        /// Easing equation function for an elastic (exponentially decaying sine wave) easing out/in:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float ElasticEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return ElasticEaseOut(t*2, b, c/2, d);
            }
            return ElasticEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Bounce

        /// <summary>
        /// Easing equation function for a bounce (exponentially decaying parabolic bounce) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BounceEaseOut(float t, float b, float c, float d)
        {
            if ((t /= d) < (1/2.75f))
            {
                return c*(7.5625f*t*t) + b;
            }
            if (t < (2/2.75))
            {
                return c*(7.5625f*(t -= (1.5f/2.75f))*t + .75f) + b;
            }
            if (t < (2.5/2.75))
            {
                return c*(7.5625f*(t -= (2.25f/2.75f))*t + .9375f) + b;
            }
            return c*(7.5625f*(t -= (2.625f/2.75f))*t + .984375f) + b;
        }

        /// <summary>
        /// Easing equation function for a bounce (exponentially decaying parabolic bounce) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BounceEaseIn(float t, float b, float c, float d)
        {
            return c - BounceEaseOut(d - t, 0, c, d) + b;
        }

        /// <summary>
        /// Easing equation function for a bounce (exponentially decaying parabolic bounce) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BounceEaseInOut(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return BounceEaseIn(t*2, 0, c, d)*.5f + b;
            }
            return BounceEaseOut(t*2 - d, 0, c, d)*.5f + c*.5f + b;
        }

        /// <summary>
        /// Easing equation function for a bounce (exponentially decaying parabolic bounce) easing out/in:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BounceEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return BounceEaseOut(t*2, b, c/2, d);
            }
            return BounceEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #region Back

        /// <summary>
        /// Easing equation function for a back (overshooting cubic easing: (s+1)*t^3 - s*t^2) easing out:
        /// decelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BackEaseOut(float t, float b, float c, float d)
        {
            return c*((t = t/d - 1)*t*((1.70158f + 1)*t + 1.70158f) + 1) + b;
        }

        /// <summary>
        /// Easing equation function for a back (overshooting cubic easing: (s+1)*t^3 - s*t^2) easing in:
        /// accelerating from zero velocity.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BackEaseIn(float t, float b, float c, float d)
        {
            return c*(t /= d)*t*((1.70158f + 1)*t - 1.70158f) + b;
        }

        /// <summary>
        /// Easing equation function for a back (overshooting cubic easing: (s+1)*t^3 - s*t^2) easing in/out:
        /// acceleration until halfway, then deceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BackEaseInOut(float t, float b, float c, float d)
        {
            var s = 1.70158f;
            if ((t /= d/2) < 1)
            {
                return c/2*(t*t*(((s *= (1.525f)) + 1)*t - s)) + b;
            }
            return c/2*((t -= 2)*t*(((s *= (1.525f)) + 1)*t + s) + 2) + b;
        }

        /// <summary>
        /// Easing equation function for a back (overshooting cubic easing: (s+1)*t^3 - s*t^2) easing out/in:
        /// deceleration until halfway, then acceleration.
        /// </summary>
        /// <param name="t">Current time in seconds.</param>
        /// <param name="b">Starting value.</param>
        /// <param name="c">Final value.</param>
        /// <param name="d">Duration of animation.</param>
        /// <returns>The correct value.</returns>
        public static float BackEaseOutIn(float t, float b, float c, float d)
        {
            if (t < d/2)
            {
                return BackEaseOut(t*2, b, c/2, d);
            }
            return BackEaseIn((t*2) - d, b + c/2, c/2, d);
        }

        #endregion

        #endregion
    }
}